Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: essex2visuvesi on October 30, 2012, 12:25:21 PM

Title: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 30, 2012, 12:25:21 PM
Just bought a Robbe Seawolf from a member on here which I plan to convert to Static diving

I'm thinking about using a simple rolling pump and Bladder type system where the Lead acid batteries used to live and replacing them with a 3 cell lipo pack located elsewhere

Has anyone tried usin this method before?
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on October 30, 2012, 09:02:56 PM
Yes many times, the system works very well.

http://www.modelboatmayhem.co.uk/forum/index.php?topic=25170.0

I would fit a pressure switch inline with the pump, especially with peristaltics, If the pump sticks on through a fault in the control unit, it will not only burst the bag, it will keep on pumping water compressing the air inside to dangerous pressures.

The cheapest pressure switch are the ones used in the Thundertiger Neptunes, which uses the same type of ballast system. There's a chap in the States selling Neptune spares, he also sells the switcher, pump, bladder etc. So you could purchase everything you need for the ballast system in one hit

http://www.ebay.com/itm/390315372178
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 31, 2012, 07:29:27 AM
Big thanks for that!

I had downloaded the manual for the TT neptune and was going to use that system.... Never even crossed my mind to source the ACTUAL parts from a Neptune lol  :embarrassed:

Anyways I now have a shopping list:-
Control PCB Neptune PJ6174 (http://www.ebay.co.uk/itm/390315372150?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Sensor Pressure Neptune PJ6176 (http://www.ebay.co.uk/itm/390315372178?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Sensor Leakage Neptune PJ6177 (http://www.ebay.co.uk/itm/290600650250?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Motor Mount Neptune PJ6109 (http://www.ebay.co.uk/itm/330602647486?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Motor Set 550 Neptune PJ610 (http://www.ebay.co.uk/itm/330524156582?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Ballast Tank Neptune PJ6110 (http://www.ebay.co.uk/itm/290519261788?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

Prices up quite reasonably compared to other options I looked into which involved buying a bit from here another from there etc and I know its a tried and tested system :)

Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 31, 2012, 09:44:49 AM
Big thanks for that!

I had downloaded the manual for the TT neptune and was going to use that system.... Never even crossed my mind to source the ACTUAL parts from a Neptune lol  :embarrassed:

Anyways I now have a shopping list:-
Control PCB Neptune PJ6174 (http://www.ebay.co.uk/itm/390315372150?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Sensor Pressure Neptune PJ6176 (http://www.ebay.co.uk/itm/390315372178?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Sensor Leakage Neptune PJ6177 (http://www.ebay.co.uk/itm/290600650250?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Motor Mount Neptune PJ6109 (http://www.ebay.co.uk/itm/330602647486?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Motor Set 550 Neptune PJ610 (http://www.ebay.co.uk/itm/330524156582?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
Ballast Tank Neptune PJ6110 (http://www.ebay.co.uk/itm/290519261788?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

Prices up quite reasonably compared to other options I looked into which involved buying a bit from here another from there etc and I know its a tried and tested system :)

Oh and the pump!
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 31, 2012, 10:30:31 AM
Duly ordered along with the pump

next payday will be bayonet upgrade
http://modelluboot.de/Zubehoer/Bajonettver_e.html
or
http://www.piranha-modellbau.de/Preisliste.htm
Not sure what is best.... Pirana is a little cheaper and offer a tech tray as well which is tempting


And maybe later a subtech leveller

All in all that 80 quid bargain has turned out quite expensive lol
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on October 31, 2012, 11:02:04 AM
The original drive system for the Seawolf was a Robbe Navy unit, a 500 size motor geared down about 3:1 I think, although the reduction may be a little less.

Anyway, I think the Neptune motor will work okay. The watertight seal will work well, something that is missing on the original Seawolf set-up which just used a greased stern tube.

One thing you might want to change is that double dog-bone coupling they use. Replace with a straight connector that bolts onto the motor shaft and propshaft. If you don't have a lathe, you can purchase these from Engel (not expensive), they used in the Lafayette and 212 kits.

A few other things to think about before you start glueing things together.

The Seawolf has a most peculiar front plane assembly- with a set of bow planes AND sail planes. No conventional subs I know of have this arrangement, they have one or the other, because hydroplanes induce a surprising amount of drag and noise, so you want to keep them to a minimum. Therefore I would fit only one set according to your preference, bow mounted planes work a lot better than sail mounted planes BTW. If you don't intend to articulate the front planes (and it's not really necessary with a boat of this type and size) I would leave them off altogether, the boat will run faster without them.

The tech rack and hull seal is the Achilles heel of all the Robbe submarine kits. Where the front bolt attaches to the tray is a weak spot that most modellers reinforce with some brass plate. The seal itself relies on axial compression. The o-ring supplied with the kit is especially soft and compliant, because you only have one bolt to compress the seal. When this seal  wears or splits, modellers tend to replace it with a normal nitrile o-ring, which tends to be too hard. This can result in a poor seal and leakage. Silicone o-rings are softer and will work well and can be purchased cheaply from places like polymax.

A better arrangement is radial seal compression, where the seal compresses against the inside of the tube. You can purchase bayonet rings, nicely machined from billet aluminium (I think they all come from the same source BTW). Certainly the Rolls Royce treatment, with the price tag, but you can achieve the same result with a turned plastic ring for beans, but you will need either good bench fitting skills or access to a lathe to make this item.

The Piranha tech rack is a fair old bit of ironmongery. It's certainly much tougher than the original, I'm not sure whether all that metal work will tinker with the radio reception. You could copy it by making some plastic discs and trays using polycarbonate or PVC sheet, and threaded studding from the DIY store. But really the original equipment tray is more than upto the job with a couple of subtle modifications.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 31, 2012, 11:21:30 AM
The motor I ordered is the motor for the pump (I hope), I already have the drive motor from the kit

Thanks for the heads up re the techrack, I do want the bayonet fittings tho.

Building won't start until I have all the parts to hand (Sub kit is in the UK still)

What's the best glue to use? I do have a selection of modelling glues (Humbrol liquid poly etc) and a selection of Expoxy glues (5, 30. 1hr and 4hr) but dont mind buying a specific glue for this model
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on October 31, 2012, 12:38:13 PM
The boat is made up of ABS components with some metal parts. Robbe recommend Pattex Stabilit express, which is modified acrylic adhesive. It's expensive, but you can get other brands which works just as well for half the price.

Staloc adhesives sell a comprehensive range of acrylic adhesives, which have names similar to branded products-

http://www.shop4glue.com/acrylic-sga-methacrylate-toughened-adhesives-66-c.asp (http://www.shop4glue.com/acrylic-sga-methacrylate-toughened-adhesives-66-c.asp)

For instance the Stabilit express equivalent is called Stable-xpress. He, he!

They also do some that don't need mixing, which look interesting (I'm assuming they're anaerobic), haven't tried those yet. I have used modified acrylics however, and I would say they are the best glue I've encountered. Totally waterproof once fully set (24 hours), sticks just about anything, and very, very strong.

A lot of submariners swear by 24 hour araldite. Do not use quick setting epoxies on anything that will be exposed to water, becuase the connection will soften and fail in time. I think the acrylics are better.

I avoid superglues. I find them brittle, and they can degrade some plastics over time. You can use solvent cement on detail aparts, ABS fuses well with itself and some other thermoplastics. I use plastiweld. The problem with solvent welding is that it's sometimes difficult to get a large area of bond, that's the advantage with thick goopy adhesives like epoxy and the some of the acylics.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on October 31, 2012, 02:21:54 PM
Cheers for the insight, I will get some ordered ready, always nice to have just the right tool (or glue in this case) for the job
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on October 31, 2012, 05:35:38 PM
I would go for the super acrylate- http://www.shop4glue.com/superacrylate-10-min-set-acrylic-methacrylate-glue-adhesive-plastic-welder-abs-perspex-grp-metal-108-p.asp

You could ask them about the clear set stuff they do if you want clear joints. You should be able to bond the entire model together with that stuff.

If you want thicken it further, you can mix ground or milled glass and other fillers with it, which will also improve strength. You basically treat it like you would a resin.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: StarLocAdhesives/FiveStar on October 31, 2012, 05:53:11 PM
They also do some that don't need mixing, which look interesting (I'm assuming they're anaerobic), haven't tried those yet.


Acrylics / Methacrylic adhesives are all accelerated slightly by anaerobic conditions so will usualy set between parts faster than in a mixing tub,
They can be formulated to come in different forms, unlike epoxys mix ratios are not very critical , epoxys need part a to be close to part b as the hardener is used up in the cure, with acrylics its similar but different...you only need to trigger the cure to a certain level for it to completely cure ( eventualy, usualy more catylist and the faster it will set but it may vary the strength )


common types are


1/
a bottle of resin containing all the structural components and part A of the catylist  , and a primer containing part B of the catylist ( not a hardener like in an epoxy ) , contact with just a trace of catylist will set the adhesive due to triggering a chain reaction polymerisation


2/
basicaly the same adhesive as above, but the resin is split ( with exact formulation ) between the two parts A and B , then the 2 components of the catylist are split between them, put a drop on both sides of parts to bond and when pushed together the two parts react and trigger the chain reaction , the components are identical in formula other than catylist so dont need blending to get a correct bond strength 


3/
The equal mix type, used like an epoxy , blended well before use, not due to the catylist parts needing to be mixed its due to one side cointaining different blends of monomers or other components that may be seperated for other reasons, for example one may react with one of the catylist components prematurely, they often ( but not always need mixing well, it depends if the parts are different resins or not! )


4/
Products like Stable express are like a type 2, but still sort of like a type 3...they need to be mixed together but not to trigger the cure , the powder has other components, that effect use / performance etc


5/
Anaerobic acrylics like threadlock, they contain the resin and both halves of the catylist ( 4 part catylist system ) , they are very air sensitive as the stabiliser in the bottle needs air present to absorb the free radicals that are trying to polymerise the adhesive, as soon as air is gone the cure accelerates , often formulated to need metal contact as well as abscence of air


6/
Cyanoacrylates, a type of acrylic and not realy accelerated by anaerobic conditions, they set by contact with trace moisture that neutralises the stabiliser , setting rapidly when in a thin layer , if a thick layer is needed you can add an accelerator to cure them quicker 
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on November 29, 2012, 08:49:37 AM

next payday will be bayonet upgrade
http://modelluboot.de/Zubehoer/Bajonettver_e.html (http://modelluboot.de/Zubehoer/Bajonettver_e.html)
or
http://www.piranha-modellbau.de/Preisliste.htm (http://www.piranha-modellbau.de/Preisliste.htm)


So its time to open the wallet and make a purchase.
Does anyone have any experience of buying from these 2 sellers?
Both seem to be highly regarded.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on November 29, 2012, 02:45:07 PM
The first link is reliable. I purchased some peices of Norber a few years back and received them within about three days of purchasing.

Piranha I have not had any dealings with.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on February 08, 2013, 09:17:37 AM

I've been very restrained on this build as I want to get it right first time,

While waiting on delivery of the Bayonet fittings I decided it was time to make a start on figuring out where everything will fit in the WTC


(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/2013-02-08-165annotated.jpg)
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/2013-02-08-164annotated.jpg)


This is layout plan 1.0, a tight fit but everything fits nicely. I plan to make a platform to mount the Front plane servo above the rudder/rear lane servo along with the leveller.  The ballast pump will also be mounted to a fabricated plate


I have encountered a small problem with my chosen Ballast bag, its too wide! and Im worried it won't fill properly.  I'm not sure if this will be an issue or not, but have a backup plan and will purchase one of these bags instead.
http://www.ebay.co.uk/itm/281034213703?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649,
This also has a larger volume so should be able to get away with less static ballast making the sub lighter to transport.  So if anyone needs the ballast bag from a TT Neptune let me know :)


After taking the picture I noticed that the ESC will need to be mounted on its side and not flat as in the photo otherwise it will foul the rudder contol rod.


If I have made some blindingly obvious faux pas, please feel free to heckle or laugh and point :).  This is my first sub so any pointers/recommendations greatly received.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on February 08, 2013, 08:57:37 PM
You can place the bag inside a cylinder. This cylinder should have a few holes drilled in it so it can vent as the bag fills.

This constrains the proportions of the bag, and prevents it shifting position inside the boat. The cylinder can be made out of a piece of plastic pipe (PVC, ABS, acrylic etc.)

The other option is to search for a large syringe and pump in and out of that instead of a bag.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on February 10, 2013, 09:40:22 AM
I had thought of that, I have ordered the larger bag and another member has taken the TT bag off my hands.
The new bag will be a better fit and will be mounted so it cant move about, more on that later.


Tonight the build will start :)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 07, 2013, 09:29:33 AM
Now I have TX working how I want I can start with the build.


Been thinking about servos.  Could I get away with using smaller servos? Current plan is to use Futaba S3003 servos but I have some smaller mini servos from My Trex 500 and was wondering if they would be OK.... gives a bit more room to squeeze all the gear in


These are the bad boys I'm thinking of....
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=13421 (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=13421)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 07, 2013, 10:35:54 AM
9-10 gram servos or larger will be fine. The Robbe boat uses bellows, so low in friction, and it's a fairly modest size, so you don't need a lot of grunt for the controls. The kit dates back over twenty years when micro and mini radio still cost a premium.

The ones in the link are more than adequate.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 07, 2013, 11:27:34 AM
Thought they should be ok, but always best to check... gives a bit more room as I can fit them side by side, rather than staggered as per the instructions
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 11, 2013, 01:10:14 PM
Unemployment does have its advantages..... can actually get some building done


Have started on the tech rack with a few mods
Main mods being a mounting plate for the TT Neptune Dive pump, servo mounts for the rudder and rear dive planes (The instruction suggest double sided foam tape which is something I'm not happy with)
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-11-235.jpg)
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-11-234.jpg)


Also fitted some reinforcement to the front screw mount as research suggests this is a weak point.
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-11-236.jpg)


I did buy a CNC bayonet fitting, but have decided not to use it as it requires quite a bit of fettling of the tech rack to make it fit


Next jobs:-
Cut and fit a plate above the servo mounts to increase strength and mount the ESC.
Make a servo mount that fits to the front end cap for the front dive planes.


I had a change of plan on the battery layout..... I will now be using two LiPo packs of different voltages
A 2cell lipo pack for the drive motor and BEC and a seperate 3Cell lipo for the Dive pump.  Why? the battery pack I had purchased didn't fit too well and after some jiggery pokery th 2packs are a far better (and neater) fit other added bonus is that I had them in the battery stash so no further expenditure was required.



Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 15, 2013, 06:51:43 PM
Custom Front plane servo fitted and working.  These are connected via a Y lead to a leveller and the rear planes.  The leveller only acts on the rear planes
[size=78%](http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-15-238.jpg)[/size]



I will not be gluing the front cap to the Tube, instead i plan to machine a groove into the endcap and fit a rubber o ring to seal it.  This will access to the front servo easier.


Mini servos fitted into custom servo mount with the motor ESC mounted on top.  This design gives far more room and saves relying on double sided tape to hold the servos
[size=78%](http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-15-241.jpg)[/size]


The dive controller board from a Thunder Tiger Neptune above the main drive motor.... A cheap way to get into static diving!  Mounted on standoffs made from 6x6mm evergreen rod
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-15-240.jpg)


I intended to have the dive pump here but it would have put most of the weight at the rear of the WTC


Final pic is the battery area, batteries sit on top (1 x 2600 3s lipo and 1x 2600 2s lipo) with the dive bladder underneath
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-04-15-242.jpg)


Tidying up the wiring is the next mission.... not one I'm looking forward to!



Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 15, 2013, 09:29:20 PM
Better to have the forward vanes on an independent channel. You then use them to regulate depth, especially when near the surface. For a boat like the Seawolf, you could really dispense with them altogether. One point can you get to that servo easily once it's all fitted together, because the model submariners law says the most inaccessible part will also be the most failure prone!

I'd also advise keeping the ESC as far away from the RX as possible. It's an excellent ESC, but they still chuck out a bit of EMI, and on a sub you need all the help you can get with good reception.

When running your cables try and keep signal cables running down one side, and power down the other. Twisting the power leads together is a good, free way of cutting down on any parasitic induced interference. You can also do the same for the servo lines, but not essential.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 16, 2013, 06:39:25 AM
The front servo will have reasonable access as I plan not to glue the forward endcap as per the instructions, but to seal it with a rubber ring like the rear cap.


Thanks for the heads up re the ESC.  I went for the microgyros as it came highly reccomended. I can move it to the other end behind the dive controller.


Not sure what do do with the front planes now


Here is the current TX layout
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Laser6radiocontroller.jpg)




So I'm thinking I should change it to this:-
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Laser6radiocontrollerchanged.jpg)

or have I completely missed the point?
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 08:42:45 AM
That little rotary dial on the top right, does that control a proportional channel? If so, I would use that for the front planes, and keep the layout you have in picture one, but have the rear planes only hooked up to the right hand stick.

Regarding the front cap- sounds like a recipe for leaks to me, as you have doubled the failure points by incorporating a front seal too. Plus it's an area not easily inspected. Don't do it.

Personally I'd ditch the front planes altogether, and remove them completely from the hull. This simplifies the boat, and makes it run cleaner hydrodynamically (fewer control surfaces equals less drag).

Bear in mind that on modern subs, a lot of them have retracating front planes, and small boats like midget subs, Hollands etc. had none at all. You won't miss them. On a very large model, they do have some benefit when running near the surface, but the seawolf is small, so you won't notice.

I would also make every effort to fit the bayonet ring you purchased. The hull seal is the real weak link in these kits in my opinion, and the bayonet ring completely eliminates that weakness.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: sharkbite0 on April 16, 2013, 12:19:23 PM
hi essex
i have glued the front end cap on my seawolf as in the instructions. one less leak to worry about lol
also i have used metal geard micro servos for the dive surface's and moved them to the motor end of the tec plate.that has left a lot of room for me to fit a balleast system later.which is what im planning to do
i will post a pic of my set up later to day when i have the pressure hull opend up and post on here if thats ok with you mate.
regards
mick
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 16, 2013, 12:40:22 PM
No problem the more the merrier!


Maybe I should have moved the servos that end as well! Would have made the control rodding much shorter, but its too late now as the servo mounts are well and truly stuck down!
The servos I used are from my T-Rex 500 clone.  They have a carbonite gear upgrade that is supposed to be almost as strong as metal gears but lighter and quieter.

Already looking at my next subs, but need to find a new job first!
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 01:27:54 PM
Normal bog standard analogue, plastic geared servos are fine for pretty much any sub. Usually most control rods in model subs are the weak link in the chain. If a servo is struggling, it's usually because there is excessive friction in the glanded seals. Bellows offer the lowest friction, but o-ring type seals aren't excessive either provided the linkage is kept straight.

Unfortunately some builders place the servos too close to the bulkhead/endcaps sometimes, and as a consequence, the small arc that the servo arm swings when operated tends to result in the control rods binding against the glands. A simple lack of mechanical understanding.

Money spent on exotic servos is better invested in a leveller and a good quality receiver. Those definitely give you tangible benefits.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 16, 2013, 02:13:40 PM
True, but when they are in the bits box it seems silly not to use them :). My sons RC car has a Digital servo for steering for no other reason than it was in the bits box with the added bonus of being a perfect fit.


I have to agree on the RX thing.... the Corona synthesised RX I am using was recommended by Mike at Microgyros and I must say it seems to be pretty good.  I'll definately be buying more
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 02:29:32 PM
If you have them already, then fair enough. If buying new, then think carefully.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: sharkbite0 on April 16, 2013, 02:31:34 PM
hi essex
pic's as promised mate.
you can see how much space i have on the tec deck almost 10in and the drive batterys sit below the deck.
the ballast system will fit in with no problem (i hope) just need to work out what size ballast bag i will need.
hope it helps mate
regards
mick
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: sharkbite0 on April 16, 2013, 02:37:14 PM
If you have them already, then fair enough. If buying new, then think carefully.

i agree with subculture think carefully when buying new gear but like you essex i had them in the spair's box. lol
 
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 05:06:15 PM
Ballast tank/bag size depends on the waterline you want to operate at.

The Seawolf is not a scale boat, so you can please yourself. Small ballast tanks mean quick dive times. Also bear in mind that a high waterline is not an advantage with a spindle hull, as the props tend to ventilate being near the surface and with no shelf (e.g. bottom of hull) above them, and the hull shape is optimised for underwater unlike say a Type VII with it's shipshape bows. So anywhere between 100-300ml should do you fine.

You can use a bag, or make a cylindrical tank from plastic pipe. if you use a system which maintains a part filled ballast tank, you might want to consider mounting a cylindrical tank vertically, this cuts down slosh to a minimum. If you want an example of why try filling a pop bottle half full. Hold it horizontally and tilt it back and forwards, you'll see the water sloshes alarmingly from one end to the other. Now hold it vertical and observe it hardly moves- the exposed water surface area is much reduced.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 16, 2013, 06:15:44 PM
That's a mighty smart job you have done on that, wish I had seen it before I started mine!


Its interesting that when Robbe updated the Seawolf to V2 they made some good changes to the setup, mainly the method for unscrewing the WTC.  But they then removed the propshaft oiler parts from the V2  :o


I spent ages looking for the parts only to read in the supplement that they have been removed from the V2.... All very odd
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 06:28:45 PM
A glanded shaft seal is better than grease filled shaft, although converting the standard Navy drive may be problematic, as it has a gearbox. Easier with direct drive.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: sharkbite0 on April 16, 2013, 06:53:14 PM
That's a mighty smart job you have done on that, wish I had seen it before I started mine!


Its interesting that when Robbe updated the Seawolf to V2 they made some good changes to the setup, mainly the method for unscrewing the WTC.  But they then removed the propshaft oiler parts from the V2  :o


I spent ages looking for the parts only to read in the supplement that they have been removed from the V2.... All very odd

thank's for the kind comment's. mine is the version 1 seawolf and came with the oil'er and i moded the  unscrewing of the WTC after reading on the forum about the problems people were having mind you my wife bought my seawolf as a present about 5 years ago and it sat in the loft till now lol so its had time for all the bug's to be worked out be fore i started the build. by the way i see you are using the parts from the neptune sub for the static dive in your boat if you dont mind me asking what was the total cost of all the parts you listed please
regards
mick
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on April 16, 2013, 07:00:49 PM
With postage about 80 quid.


I have a spare dive bladder if you are interested? its bigger than the neptune one (I bought a few different sizes for testing purposes).  Ill get the full measurements in the morning
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on April 16, 2013, 07:49:14 PM
An alternative is a geared pump and vented tank system. Should cost about 10-15, less if you have some hose and plastic pipe, and I'm assuming you already have either a spare servo and a pair of microswitches or a extra reversible ESC. If you haven't then add on another fiver!

Simple and inexpensive to build. Doesn't pressurize the internal WTC either.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: sharkbite0 on April 16, 2013, 11:13:26 PM
With postage about 80 quid.


I have a spare dive bladder if you are interested? its bigger than the neptune one (I bought a few different sizes for testing purposes).  Ill get the full measurements in the morning

thanks essex. by the way just to let you know i have had my seawolf in the test tank (the bath)lol.
for over an houre and im happy to report that not one drop of water got into the water tight compartment so im a verry happy camper  :-))
regards
mick
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 05, 2013, 11:32:21 PM
Happy to report mine is now electrically operational


Full static dive system working well


front dive plane servo fitted and working
Twin sealed endccaps held well at the bottom of the swimming pool (approx 1m) for 2 hours.  Not a drop of water inside


I think it could be down to the replacement O rings.  The one in the kit had gone "funny" so it was replaced with an O ring from the "O rings, assorted" drawer in the workshop.
Have to find out what they are as they are very soft and almost tacky in texture.


(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-06-06-328.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/2013-06-06-328.jpg.html)
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-06-06-326.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/2013-06-06-326.jpg.html)


The innards
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-06-06-325.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/2013-06-06-325.jpg.html)


Thunder tiger dive controller, with full water and overpressure protection
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-06-06-322.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/2013-06-06-322.jpg.html)


the underbelly showing dive pump, bladder and drive motor, this should keep the C of G perfect
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/2013-06-06-320.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/2013-06-06-320.jpg.html)


2 lipo packs one running the dive controller and one the drive system both 2200mah but one is 7.4v the other 11.1


on now to the laborious task ove cutting the flood slots.
Does anyone know a quicker way than using a hand file?
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 01:37:12 PM
Well I found the weak link in my setup today  <:(
the glued join between the tech rack and the end cap


Everything was working as it should on the bench so I closed up the WTC and put it in the swimming pool and all was well held it at the bottom of the pool for a minute or so and no water ingress.
tested servos, rods work fine, then I switched on the dive pump and the pressure of the bag filling caused the glue joint to fail :(


Back to the drawing board.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 02:26:32 PM
silly idea perhaps but i was thinking i could inflate the bag eithr partially or fully before sealing the wtc
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 06, 2013, 03:16:33 PM
Go back and re-read my reply in post 23, and don't say you weren't warned. Glue the front cap on, and use the bayonet ring on the stern, or you'll be getting constant problems.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 03:44:45 PM
Guess you're right  :embarrassed:


That means I have strip the rack and shave 1mm off all round as the pirahna bayonet I have has and internal edge to it that narrows the tube opening.... its not just a butt fit like Norberts version.  This should give a better seal but takes quite a bit more work initially.


Its got me thinking tho that if I have to do that, it might be better (and quicker) to make my own rack


or the demell
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 06, 2013, 03:53:54 PM
The o-rings Robbe use for the endcaps are a softer rubber than your average nitrile o-ring. They're about 55 shore, instead of the usual 70-80 shore. As the fixing only uses one bolt, it's asking quite a lot to pinch it up for not just one but two o-rings, and in addition pressurize the internal space when filling ballast- have a care.

The mods may be a bit of fiddling about, but it's a lot less work than dealing with a flooded sub.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 04:41:09 PM

The mods may be a bit of fiddling about, but it's a lot less work than dealing with a flooded sub.


This is true!


I'll fetch the dremell
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 06, 2013, 04:57:48 PM
Good stuff. The tech rack is quite sufficient for the job, so I would only replace it if it is inadequate for housing what you have put into it, which doesn't seem to be the case here. With a bayonet ring in place the rack will no longer be under any tensile stress, so its job becomes a lot easier.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 05:03:19 PM
Well if I balls it up its not the end of the world
I now have a backup plan and a backup backup plan :D


Plan A
Set about current rack with a dremmell and sander


Plan B
Build a new tech Rack from scratch


Plan C
Buy one from Pirahna
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 06, 2013, 05:07:34 PM
I have to say, not mad about the Pirahna rack. The design is  good enough, but it's the choice of materials- all that metal adds weight, in the wrong place, plus it can tinker with the radio signal. They could have made it from ABS or lexan, and it would have been more than strong enough and much lighter.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 06, 2013, 06:41:03 PM
I have been talking to another member on here about having some laser cutting done for a different project so maybe there's an alternative depending on cost.
Got plenty of threaded rod in the workshop.
That's by the by I need to strip the bits off before I start cutting


Well this has certainly been an introduction to model subs :)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Davy1 on June 07, 2013, 10:09:01 AM
Hope you are still enjoying it!
Subs are not very forgiving but are fantastic if you enjoy challenges i.e:
- If it can go wrong - it will.
- Keep it simple and minimise the number of holes.
Many thanks for the postings.
David
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 07, 2013, 10:18:39 AM
not at all..... I already have the next 3 builds planned


A Revell VIIC with the Norbert Bruggen conversion kit
And 2 others in the planning stage
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 14, 2013, 01:55:54 PM
Well the rack has been modded I have done away with the front planes entirely so the servo has been removed for now.  the extra holes in the front cap have been filled with a generous helping of epoxy and the larger central bolt hole had been epoxied with a suitably sized washered nut & bolt to help fill the void.
I have fitted the bayonet rings and glues them in place (again plenty of epoxy).  Once these have gone off fully I will wrap the join in plasterers tape and skim with epoxy
(http://www.locusrite.co.uk/images/tapes/drywall_tape.png)


That should stop the "xxxxx" leaking  {-)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 14, 2013, 10:35:03 PM
Sounds good. Give the epoxy plenty of time to fully cure right through before even showing it the water. You're on the right track now.

If you decide later on you really must have the front planes- and in this model I don't think you'll miss them- you can always add them in via a linkage from the rear cap. Unless you a have A1 access to the front, it's best not to put any seals or linkages there because sods law says they'll be the first to pack up.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 15, 2013, 10:38:06 AM
Do have a minor problem.... the endcap moved (poor supporting on my part  :embarrassed: ) when I glued it to the tech rack so its not square.  Now to figure out how to debond stabilit express
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 15, 2013, 12:01:11 PM
Ooops! Good luck with debonding Stabilit, you'll have to cut it off I'm afraid.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 15, 2013, 12:38:36 PM
Ooops! Good luck with debonding Stabilit, you'll have to cut it off I'm afraid.


That's what I was afraid of! Its in an akward place to get to as well  >:-o


At least I can say hand on heart that the rack is firmly attached to the endcap!
I have sent Mr StarLoc (he seems to be knowledgable when it comes to all things sticky) an email to see if he has any thoughts
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 15, 2013, 04:47:57 PM
Well if anyone knows it will be him. If he suggests anything practical let us all know, the only way know of releasing a resin bond once cured is to apply heat or extremely severe chemicals, either of which will destroy the plastic parts they're bonded to, so only really works with metal parts.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 15, 2013, 05:02:18 PM
It never rains but it pours.... in my attempts to seperate the parts, I have managed to bend the stuffing tube and propshaft, and while attempting to remove the stuffing tube from the gearbox gearbox I have broken the gearbox casing  >>:-(


I did get them separated tho!



Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on June 16, 2013, 10:49:36 AM
As you have knackered the original drive shaft and gearbox, this is an opportunity to upgrade the last remaining part that can be a potential source of trouble.

The original design uses a system designed for surface craft. No shaft seal is present, and it relies on a grease packed stern tube to keep out the wet stuff- not the best solution for a model submarine.

What you could do is purchase a shaft system designed for sub use. The drive set-up used in the Lafayette and 212 will work perfectly in the Seawolf (similar size boat, and prop diameter). It uses a direct drive low RPM (about 5000RPM at 12 volts) 500 size motor on an aluminium mount which screws into the bulkhead, with a 4mm simmering shaft seal. The motor is fixed to the shaft with a direct coupling, and a DU bearing (bronze backed PTFE- self lubricating in water) is bonded into the stern to support the shaft at the other end.

A low friction, easy to service set-up, largely maintenance free, just add a dab of silicone oil or vaseline on the shaft seal now and again.

You may be able to reuse the existing 500, however if it is designed with a gearbox, it will probably be too high revving used direct drive.

(http://modelluboot.de/Zubehoer/Motoreinheit900zk.jpg)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on June 16, 2013, 11:14:23 AM
As you have knackered the original drive shaft and gearbox, this is an opportunity to upgrade the last remaining part that can be a potential source of trouble.

The original design uses a system designed for surface craft. No shaft seal is present, and it relies on a grease packed stern tube to keep out the wet stuff- not the best solution for a model submarine.

What you could do is purchase a shaft system designed for sub use. The drive set-up used in the Lafayette and 212 will work perfectly in the Seawolf (similar size boat, and prop diameter). It uses a direct drive low RPM (about 5000RPM at 12 volts) 500 size motor on an aluminium mount which screws into the bulkhead, with a 4mm simmering shaft seal. The motor is fixed to the shaft with a direct coupling, and a DU bearing (bronze backed PTFE- self lubricating in water) is bonded into the stern to support the shaft at the other end.

A low friction, easy to service set-up, largely maintenance free, just add a dab of silicone oil or vaseline on the shaft seal now and again.

You may be able to reuse the existing 500, however if it is designed with a gearbox, it will probably be too high revving used direct drive.

(http://modelluboot.de/Zubehoer/Motoreinheit900zk.jpg)




You know what! I had exactly the same thought and have just been measuring up!
I have an engel glanded motor mount in the bits box
http://www.engel-modellbau.eu/catalog/product_info.php?cPath=108_189&products_id=1135 (http://www.engel-modellbau.eu/catalog/product_info.php?cPath=108_189&products_id=1135)

Plan is to drill out the endcap and feed the mount through.... the shaft from the old gearbox is bent at the gear end the rest is straight (Tested on a sheet of glass) so can be cut down to fit.  As the motor will now be closer to the encap this shouldn't be a problem.  If not a new propshaft is only a few pounds

I also have a nice slow revving 555 motor that will fit nicely

So the plan is
1 open out the endcap propshaft hole to accomodate the motor mount
2 make a mounting plate to fit inside the encap..... this will give a flat surface to fit the motor mount.  This will also need to be removable for motor maintenance
3 Make up some rails from 5x5mm styrene to reinforce the tail section as the prop shaft tube was part of the structure of the tail section

Thank fully I have all the parts to hand so it'll be much cheaper than a new gearbox

Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on August 31, 2015, 10:27:34 PM
2 years on and I opened the box on this again today.....
I deviated from the plans and started making some mods to the rear end just after the last post.  Now looking at what I did I have no idea what I was thinking lol.


Pica to follow tomorrow
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 05, 2015, 01:54:56 PM
Managed to figure out what I was doing


Pics to follow later today!
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 05, 2015, 06:39:04 PM
The old propshaft outlet was opened up to acommodate an Engel Motor mount
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2769.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2769.jpg.html)


I bonded a couple of M3 screws to the mount then bonded the mount to the endcap
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2770.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2770.jpg.html)


I do still need to run some more Stabilit Express round the outside of the propshaft mount thing, a bit of belt and braces.


A motor mount was then fabricated from plastic and screwed to the motor
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2771.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2771.jpg.html)


The motor then fits to the endcap with 4 nuts.
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2772.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2772.jpg.html)


Test fitting the tail section
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2773.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2773.jpg.html)


I need to glue the prop shaft support tube into the plastic support.  The Kit design had an integrated propshaft/gearbox/motor mount that I manage to break and replacements are stupidly expensive.
Once this is all glued/screwed together I will decide if further reinforcement in needed


Couldn't resist fitting the prop
(http://i532.photobucket.com/albums/ee322/Essex2Visuvesi/Robbe%20Seawolf%20-%20Static%20diver/IMG_2774.jpg) (http://s532.photobucket.com/user/Essex2Visuvesi/media/Robbe%20Seawolf%20-%20Static%20diver/IMG_2774.jpg.html)



Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Martin [Admin] on September 05, 2015, 06:47:40 PM
 
Looking Good!   :-))
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 05, 2015, 06:55:31 PM
Thanks, It's getting there. I think i have now addressed all the weak points of the kit seawolf :)


The problem I have now is that the tech rack has been chopped and changed so many times now that I'm starting to think I should rebuild it.


For now I just want to get it wet tested, so the old tech rack will stay for now, but I  do intend to make a custom rack later on
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 05, 2015, 11:17:18 PM
Should have a good boat there once finished.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 05, 2015, 11:54:30 PM
That's what I'm hoping :)
More work on it tomorrow:-
Refit the bellows and control rods so I can do a wet test
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: salmon on September 06, 2015, 01:27:07 AM
Brilliant work! Looks like a solid solution. Look forward to seeing this finished.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: derekwarner on September 06, 2015, 01:43:29 AM
e2v......yes it certainly appears to be a robust conversion :-))....just one question.....does that orange bonding agent adhere to the whitish synthetic endcap casing?.....Derek
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 12, 2015, 11:33:32 AM
ust one question.....does that orange bonding agent adhere to the whitish synthetic endcap casing?.....Derek


Oooooh yes!!! like the proverbial poo to a blanket.
That's stabilit Express.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 15, 2015, 05:22:34 PM
Neat looking conversion by Pascal.

(http://s9.postimg.org/ns0nr5emm/22012011085.jpg)
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 15, 2015, 05:35:14 PM
Very nice.


Well My WTC is water tight now.
And the dive system works


I am however very unhappy with the tech rack as its been modified, and then the modifications have been modified so it looks messy, so have ordered some more acrylic and going to rebuild it
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 15, 2015, 05:57:35 PM
PVC sheet is very much easier to work, and usually cheaper, but acrylic will do the job.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 16, 2015, 09:24:54 AM
PVC sheet is very much easier to work, and usually cheaper, but acrylic will do the job.


Like this?
http://www.directplastics.co.uk/acrylic-sheet
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 16, 2015, 10:15:07 AM
They do PVC sheet too, and it's cheaper. the advantage with PVC is it isn't brittle, so you can cut it quicker, and no risk of shattering.

Having said that acrylic comes in different grades, and some of it can be remarkably tough.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 16, 2015, 10:17:25 AM
Thanks


Sorry posted the link to the wrong stuff!


Meant to link the Grey PVC
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 16, 2015, 05:02:27 PM
Fairy snuff.

Bear in mind a few pointers. As the rack no longer has to take the load of keeping the hull sealed via a retaining bolt,  it only has to be strong and rigid enough to hold the contents. By the same token, much of the rack can remain inside the boat when the halves are separated, with only the motor and control surface servos needing to be attached to the stern half.

A box section tech rack will be very stiff and rigid, even if made out of of light thin plastic. No need to copy Engel with their over engineered racks. Norbert Bruggen's designs tend to be more elegant, worth blagging a few ideas from.

A box section also offers more space to hold equipment than a plate based tech rack, as you can utilize space inside the box, on the  sides, top and bottom, maximising use of the volume inside. Some builders complain that cylinders offer less space than boxes- but this is usually down to bad layout.
Title: Re: Robbe Seawolf - Static Dive conversion
Post by: essex2visuvesi on September 17, 2015, 12:08:53 AM
My new plan is to go with bulkheads joined with threaded rod. Looks a straightforward way to build and is a tried and tested method.


I can then move the rudder and dive plane servos further back in the hull making the linkages much shorter.
The next question is do I stick with the rubber bag dive system or go for a piston pump?


Title: Re: Robbe Seawolf - Static Dive conversion
Post by: Subculture on September 17, 2015, 07:11:35 AM
Studding will do the job, but personally not a huge fan of that method, because it takes up valuable space and adds weight, often where you don't want it. Also it won't be as stiff as the box section method I mentioned.

A piston tank will offer little advantage aside from speeding up the diving time- peristaltics can be a bit slow, thus they lend themselves best to small volume systems unless you build a large pump.

One disadvantage of a piston tank, if you use a single tank, is a shifting c.g. the error might only be small e.g. one or two degrees of positional angle out, which a leveller can often deal with, but that's still enough to affect the running characterisitics of your sub. To put it into simple terms it's a bit like trying to drive a car that pulls to one side a bit, you can probably drive it okay with careful attention to the wheel, but it keeps you busy.

A pump system won't give you that problem unless you have a unbaffled hard tank or you allow the bag to move about inside.

In terms of accuracy, the system you have is very good.