Model Boat Mayhem

Dry Dock / Shipyard: Builds & Questions => Submarines => Topic started by: Flying Sparks on September 12, 2010, 08:05:44 PM

Title: Darnell U-570
Post by: Flying Sparks on September 12, 2010, 08:05:44 PM
Today myself and my son Michael went to Old Warden for the last model fly-in of the year and we came home with U-570! We were planning on building a Robbe Seawolf later in the year, then today browsing the second hand stands at OW we stumbled upon U-570 with a sticker stating "Submarine - 130 - TLC required"  O0
We had a good look at the boat and found that the hull looks in good condition but the ancient radio was fitted by a person with 10 thumbs, the metalwork was rusty (push rods etc), most of the deck fittings are broken or loose and the perspex radio box lid must have been cut with a chisel. The single motor and gearbox looks OK. After a bit of haggling we agreed on 100. The TLC bit looks a bit of understatement but as I mentioned the hull and drive train look good.
Now the model is on the bench and we had another look and noticed the sticker on the motor stating that it came from Darnell models in Leavsden. A little bit of Googleing we found that this hull is still available from Models by Design.
The model is quite big at 1700mm long and by the time batteries and things are fitted it will be quite heavy, funny, it didn't look that big lying on the ground with the deck off. I will post some photo's soon.
Now, a few questions for people in the know if you don't mind; Did we pay a fair price? Is the single motor and gearbox powerfull enough for this substantial beast? Should we build it as a static diver? Was it a wise move to buy this?
Any advice/comments good or bad are welcome and no doubt we will have many more questions as we dive deeper into this model.
Thanks

Phil.
Title: Re: Darnell U-570
Post by: Mankster on September 12, 2010, 08:30:38 PM
100 is a fair price for you got. No reason why a single motor and a gear box wont work as long as it has enough go. I would use it as you already have it. Most people would fit 2 motors in a hull this size. Yes static diver, you already have experience building dynamic subs and the hull is big enough for an easy install.
Title: Re: Darnell U-570
Post by: Subculture on September 12, 2010, 09:17:50 PM
Darnell kits used to come with a USE pump (converted steam engine) which was used with air bags. Does the model have this (perhaps you could post a few pics?). Also what workshop equipement do you have? This makes it simpler to advise on the best course of action.

To get these boats to statically dive from a scale waterline usually requires about 1 litre of displacement.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 13, 2010, 03:17:51 PM
Thanks for the replies, all comments are welcome.

Mankster, We will test the motor before deciding if to stay with this setup or not. I don't think Michael will be very pleased if the sub was not a static diver, it's his dream  :-))

Subculture, There is not a pump with the model so we have to buy one. I have a reasonably well equipped workshop, I can weld, drill, braze, forge, cut and drill but as yet no lathe or milling machine.

I need to catch up on submarine technology and I have seen a book by Chris Jackson called Simply Submarines, do you know this book? Or would reccomend a different one?

Photo's to follow..


Phil.
Title: Re: Darnell U-570
Post by: Subculture on September 13, 2010, 06:10:20 PM
Ahh that's good- you don't need a lathe or milling machine (a small lathe is ever so handy though).

I would recommend Model Submarine technology by Norbert Bruggen (also by Traplet). A tough read, but a good one.

Don't bother with the USE pump, there are much better alternatives these days.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 13, 2010, 09:56:44 PM
Norbert Bruggen's book is ordered  :-))

Here are a few photo's of what we've let ourselves in for  :o

As you can see one of the forplanes is missing. Also on the shot of the keel it looks like something else is missing, you can see a pencil mark for the centre line but looks like somthing has come off, any idea what that might be?

Thanks

Phil.
Title: Re: Darnell U-570
Post by: Mankster on September 14, 2010, 04:21:08 PM
I don't think there would have been anything of use attached to the keel, and there is no need to attach anything there either when you rebuild here. Are you going to keep the watertight box or go for a cylider?
Title: Re: Darnell U-570
Post by: Sub driver on September 14, 2010, 05:44:33 PM
Hi.

Looks ok for 100, the holes in the keel are drain holes under the box and for nothing else, this can build into quite a nice model, I would try the motor first prior to removing it and if its ok go with it, as Mankster says are you keeping the box or going with a water tight module ? if you stay with the box you can make a ballast tank in the centre by adding two bulkheads and a separate lid and then use a car tyre compressor to " suck " the air out and store it in the for compartment this is quite a cheep way of getting a static dive sub as the components for this are about 20 quid all in and with your workshop facilities and engineering expertise will be a doddle to do.

I have a scratch built type 1X that uses this system built in 1988 and still a good performer, can send some pics of the interior if you decide to check this route out.

Regards sub. :-))
Title: Re: Darnell U-570
Post by: Flying Sparks on September 14, 2010, 06:12:02 PM
Mankster, My first thought is to keep the radio box rather than a WTC to keep the cost down, but if there is a huge benefit in having a WTC then would could go down that route.

Sub, I like the sound of your idea if there is enough room left for batteries, pictures of your setup will be nice to see.

We will take U570 to the Brockwell dive next month for people to laugh have a look at and give any hints and tips. It's unlikley that any work will have started by then.

Phil.
Title: Re: Darnell U-570
Post by: Mankster on September 14, 2010, 07:29:15 PM
Both systems have their advantages and disadvantages. A WTC generally handles water pressure better, easier and quicker to seal, can me moved from boat to boat to keep cost down if you have more than 1 sub and usually results in a lighter boat as its easier to be efficient with the space within a cylinder.
A box gives much better access to component and is easier to install working periscopes and masts. You can make use of the sides of the hull to form the sides of the box (dry hull) to maximise available space in a hull) No need unhook all the plane linkages and prop joint everytime you want to gain access.
My current project is going to have a hybrid design with 2WTC connected to a central box for the best of both worlds ;)

See you at Brockwell
http://www.facebook.com/group.php?gid=133360626703083
Title: Re: Darnell U-570
Post by: Subculture on September 14, 2010, 07:35:49 PM
Lots of drilling and filing of slots on the deck required to get it looking like a Type VII- I don't envy you that little job! One of the nice things about many of the later (not Darnell) Type VII kits is that they came with photo-etched or milled decks, which saves a lot of work.

A cylinder will not significantly increase the cost, unless you opt for a ready made version. Materials are quite inexpensive, if you're happy to use opaque PVC pipe instead of acrylic, then I find 110mm waste pipe is usually found in skips (unused I hasten to add) and can be recycled into something more fun. A pair of endcaps is not a big deal to rustle up, what is a little more challenging is deciding on a ballast system and how to lay it all out inside the cylinder.

The radio system in that boat looks rather ancient, probably 27mhz (did it come with a TX?). If the servos are a 3-wire type, then they may be compatible with a modern RX if fitted with newer connectors- just observe you have the wires correctly configured. With perfectly decent servos available from Hobbyking for a pound or two it may be easier to just order some new ones.

The ballast system described by Sub Driver works okay. There are a couple of disadvantages to this system, and I speak from experience as I have used it, the air sucked out of the ballast tank is high in humidity, and as you are compressing it in the forward compartment, the cold WTC walls act as a condenser and you end up with a forward compartment with very damp air- any electronics in there can suffer. The second issue with this system is that it maintains an air bubble in the ballast tank, which is vented at the bottom. As the boat dives deeper the air bubble compresses and your boat steadily gets heavier. If you are running with only a few grams of positive buoyancy, this can result in a boat which heads straight to the bottom.

If you only dive at shallow depths it doesn't have much effect, but it does become a problem below about three feet or so. If you fitted a valve at the bottom of the tank (known as a Kingston valve) this would prevent this problem.

One more thing, the ballast tank will require baffling as you have an exposed water surface. This is all covered in Norberts book.

One system you could consider is a water pump in an aspirated main tank, based on 85% of the boats overall ballast volume, and a smaller tank mounted within this large tank using a secondary ballast system, based perhaps on a water pump or a small piston tank (large syringe?) to trim the last 15% of the boats buoyancy.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 14, 2010, 08:13:27 PM
Wow, lots to think about and decisions to be made. We are not rushing into this one as we have a couple of projects already on the go.

I will ditch to radio gear as I have plenty of useable stuff spare. We just need to get another receiver and as I've now acquired a 40MHz module for my 8 channel JR radio, we should not have any worries in that department.

The main consideration is in deciding wether to stick to a radio box or change to a WTC. Hmm.....decisions.

Thanks guys keep them coming

See you at Brockwell.

Phil.
Title: Re: Darnell U-570
Post by: Subculture on September 14, 2010, 08:31:41 PM
Have a look at this link-

http://www.youtube.com/watch?v=N3a7-CSuoIw

From 1:26 to 1:44 is a Darnell Type VII, which was re-engineered internally by Nick Burge for Bernie Woods. The boat started life as a surface runner, and was built by Jim Ward. Bernie purchased the boat, and Nick built a cylinder for it using a compressed air ballast system. I don't know what became of this boat after Bernie died, but it demonstrates what nice models they can be made into.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 14, 2010, 09:01:06 PM
I had a look at your youtube video, nice looking boat with a huge amount of detail.
Thanks

Phil.
Title: Re: Darnell U-570
Post by: hmsantrim on September 16, 2010, 01:57:44 AM
Hi Phil.
            May be just a bit a head of the programme but the weapons fit replacement from here on P 5 & 6.

          http://www.alwayshobbies.com/Boats/Fittings.ice

                                                 cheers Frank
Title: Re: Darnell U-570
Post by: Flying Sparks on September 16, 2010, 08:12:10 AM
Hi Frank, Not to early to gather resources and getting bits for the final fit out  :-))

Cheers Frank

Phil.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 17, 2010, 09:55:17 PM
Norbet's book arrived today, I'm off read and try and digest it now, might take a while  :o

Phil.
Title: Re: Darnell U-570
Post by: Martin [Admin] on September 17, 2010, 10:18:41 PM

Don't want to hijack your thread Phil but who else has built a Darnell sub?

I 90% finished Ulholder ( HMS Uncertain )
Title: Re: Darnell U-570
Post by: Flying Sparks on September 17, 2010, 10:55:55 PM
No problem Martin, nice to see pictures of other Darnell boats as I assume the gubins (technical term) are similar. Is that a can of gas sitting in the middle of your boat  :o

Nice looking boat by the way.


Phil.
Title: Re: Darnell U-570
Post by: hmsantrim on September 17, 2010, 11:01:35 PM
 Hi Phil.
           I had the idea of chopping a mountain bike inner tube and using it as a gasket seal for the perspex hatch.

                 wonder wot the experts think of that.

                                       cheers Frank

              
Title: Re: Darnell U-570
Post by: Subculture on September 17, 2010, 11:19:01 PM
o-ring cord works best.
Title: Re: Darnell U-570
Post by: Flying Sparks on September 18, 2010, 09:06:03 AM
Martin, that looks like an OS carby sitting on top of the cylinder, is this part of a secret form of propulsion??

Frank, we may ditch the radio box and fit a cylinder, nothing is decided yet, thanks anyway.

Subculture, what is O ring cord and where can you get it from?

Thanks

Phil.
Title: Re: Darnell U-570
Post by: hmsantrim on September 18, 2010, 09:09:34 AM
Hi Phil.

              pix here..http://www.jameswalker.biz/group/products/o_ring_cord.html

                           frank
Title: Re: Darnell U-570
Post by: redboat219 on September 18, 2010, 05:31:59 PM
Love your vent valve :-))
Title: Re: Darnell U-570
Post by: Subculture on September 18, 2010, 06:25:14 PM
http://www.polymax.co.uk are excellent for 0-rings, rubber sheet, o-ring cord etc.

They do have a 10 minimum order, so it's best to order up all the stuff you need in one go. As the hatch seal will be one of the final thing you need to do, it should allow you plenty of time to fathom out what you need.

Andy
Title: Re: Darnell U-570
Post by: kazzer on October 13, 2010, 03:13:46 AM

The main consideration is in deciding whether to stick to a radio box or change to a WTC. Hmm.....decisions.

Thanks guys keep them coming

Phil.

It was that awful Darnel box that finally got me to consider a cylinder. I tried to make up one I purchased in bits, but it was awful. I eventually found D&E and that how I got into selling their stuff.  I persuaded them to make the 3.5/2 Sub-driver into an economic kit, and its been very successful. Put a Snort system in there and you've got a REAL submarine. Pm me for details
Title: Re: Darnell U-570
Post by: kazzer on October 13, 2010, 03:23:15 AM
Hi Phil.
           I had the idea of chopping a mountain bike inner tube and using it as a gasket seal for the perspex hatch.

                 wonder wot the experts think of that.

                                       cheers Frank

              

Terrible idea, been there done that - and as I sell Darnell models, I've seen and heard of several people  using the boxes. THEY SUCK!  I told  MBD to not supply them any more, and I believe he took my advice. Get a cylinder! Get a Snort ballast system. You'll love it.
Title: Re: Darnell U-570
Post by: RonP on October 14, 2010, 10:15:16 AM
Phil,
100 for a U-boat is a pretty fair deal as far as I am concerned, you did good but you do have a fair bit of work to do.  If those rubber bellows are still OK then wash them in soapy water (soap, NOT detergent) and guard them with your life, they will be the original SHG bellows and have not been available for some years now and they were the best around for our purposes.
A number of people have run down the original Darnell system but in fact it wasnt that bad if you have patience. The bag was originally forward of centre and this did cause trim problems
as it made the C of G way to far forward, later on he provided two pressure hulls with the bag placed central this was a big improvement. I may have one of the original USL pumps in my junk box that you are welcome to and the bags are STILL available from SHG so you could restore it to original format if you wanted. If you have a little money to spend you can buy one of a dozen ready made modules that will slot straight in. The original single 540 motor will do the job but if my memory is correct the ones Darnell used were 23 turn motors and used a lot of current (around 10 amps) under load so a better solution would be to use a couple of 545 motors one to each prop or for a bit more money you get a lot more motor if you use a couple of Agrachi motors from Ron Dean (Deans Marine) Hope this helps.
Ron Perrott
Title: Re: Darnell U-570
Post by: kazzer on October 14, 2010, 10:57:06 AM

Don't want to hijack your thread Phil but who else has built a Darnell sub?

I 90% finished Ulholder ( HMS Uncertain

Where did you get the gun?  Is it home made?
Title: Re: Darnell U-570
Post by: Martin [Admin] on October 14, 2010, 11:44:17 AM
Where did you get the gun?  Is it home made?

Yes, a poor effort but I was proud of it!
Title: Re: Darnell U-570
Post by: Flying Sparks on October 24, 2010, 04:26:50 PM
Well, I've read Norbert's book and I have a better idea of how a submarine works although I can't claim to understand everything in the book, my eyes glazed over at some of the math. However, it was a good read and will make a good reference book even if some of the electronics is a bit dated.

As for U-570 one of the decisions is made for us (it's a joint project between myself and teenage son Michael. Michael is the brains and chief driving force and I'm the chief sponsor and transport provider) the watertight box is coming away from hull so we will replace this with a cylinder. The ballast system is not decided yet but  it will be either a piston tank or air bag. We had a look at the Engel piston tanks, very nice but a lot of money. If anybody knows where we can find a design we could build our own piston tank to that would be very nice. The ballast tank of whatever type we decide on will be fitted at the c of g to prevent any unwanted trim changes when diving.

For the WTC we can get some 100mm x 3mm acrylic tube on ebay for about 15 and a friend is willing to let me use his lathe to make some end caps.

Lots more to plan design yet but we are getting closer to actually making a start.

Many thanks to all the people who have helped and made many suggestions here on Mayhem and at Brockwell  :-))

Phil.

Title: Re: Darnell U-570
Post by: Subculture on October 24, 2010, 07:13:59 PM
I have some literature on how to make your own piston tanks. It's in German I'm afraid, but the drawings and pictures are largely self explanatory, and I have translated much of the text with the assistance of google (foreign languages aren't my strong suit I'm afraid)

You will need a lathe to make the piston and the endcaps for the tank. You can make a tank for under 20, electronics are extra, but will not be too expensive- a pair of micro switches on a servo can be used, or you can build the servo control board featured in Norberts Book.
Title: Re: Darnell U-570
Post by: Flying Sparks on October 24, 2010, 07:56:39 PM
Quote
I have some literature on how to make your own piston tanks. It's in German I'm afraid, but the drawings and pictures are largely self explanatory, and I have translated much of the text with the assistance of google (foreign languages aren't my strong suit I'm afraid)

You will need a lathe to make the piston and the endcaps for the tank. You can make a tank for under 20, electronics are extra, but will not be too expensive- a pair of micro switches on a servo can be used, or you can build the servo control board featured in Norberts Book.

Subculture

A freind has kindly offered the use of his lathe so we should be good to go and build a piston tank, I think we will buy in the electronics if possible to do so at reasonable cost.

Cheers

Phil.
Title: Re: Darnell U-570
Post by: Mankster on October 24, 2010, 07:57:31 PM
The ballast tank of whatever type we decide on will be fitted at the c of g to prevent any unwanted trim changes when diving.

Many thanks to all the people who have helped and made many suggestions here on Mayhem and at Brockwell  :-))

Phil.



You'll be wanting to set the ballast tank at the centre of bouyancy, not the centre of gravity. With a single ballast tank you will be moving bits of foam about to alter your centre of bouyancy to to match the position of the ballast tank.  The location of the center of Gravity will determine how agile or otherwise your boat will be (COfG forward = more stable/less agile).
Title: Re: Darnell U-570
Post by: Subculture on October 24, 2010, 10:04:02 PM
I would aim to place the centre point of your tank where the number '7' is painted on your conning tower.

Electronics for your tank. Most of the piston tank control boards come from Germany, where this system is most popular. There are various versions, prices tend to range from about 25 to 50, depending on whether you want proportional control or simple bang-bang command of the piston tank.
Title: Re: Darnell U-570
Post by: g4yvm on June 06, 2011, 01:29:02 PM
I wonder if this project was completed?  The photos are very useful to me as a beginner in subs, really good stuff!  As a result of reading it I have bought the book by Norbert Bruggen...

Looking inside the Darnell hull I see why people go for the WTC these days...thats a LOT of bolts to work through to get into the box isnt it??  Very interesting photos of the internals though I do not yet understand what I am looking at.  Is that TWO watertight boxes, a clear plastic ballast tank and a wet hull?  I cant see a piston in the tank so I am assuming it is a total-loss gas powered tank (or using the pump as mentioned in the thread -  drawing wet air back into one of the boxes, which seem to me to be linked via a flexi hose).

That model engine carby...is that an air dump valve for diving?


I can also see that most of the decking flood holes are not cut away.  It looks odd but done for ease I suppose.

D
Title: Re: Darnell U-570
Post by: thegrimreaper on June 06, 2011, 02:42:29 PM
I think David that the system in use on this project is a gas system ala the real thing valve opens to let water into the ballast tank for submerge the cannister in the picture is possibly a can of propelant (the type used for spray guns)when you want the sub to surface you command a rise on the sticks and a squirt of gas enters the ballast tank and because its under pressure forces the water out so as to surface the sub this type of control is primarily used in in the U.S of A
main problems (so I have read ) is you need to keep a count of surface/dive number because if you run out of gas while submerged the boat wont surface

Regard Mark
Title: Re: Darnell U-570
Post by: g4yvm on June 06, 2011, 02:48:15 PM
Mark,

Thanks for that.  It does seem to be a very realistic system, but the scale maneouvre of being stuck on the bottom is one I'll pass on!  The piston pumps seem to be the logical way for a model to work to my untutored eye!

I'd like to see how its all progressed though!

D
Title: Re: Darnell U-570
Post by: thegrimreaper on June 06, 2011, 03:19:33 PM
Piston pump's are good (so I have heard) My Akula uses a ballast tank with a water pump with a pinch valve to dive pumping the water in pressurises the air in the tank when the sub dives the pump stops pumping and the pinch valve pinches the water tube so as to not let the water out which is now under pressure on a stick command the pinch valve opens and the under pressure water exits the tank the sub rising as it do's is a very simple and cheap system which can have its own fail safe built into into

Regards Mark
Title: Re: Darnell U-570
Post by: g4yvm on June 06, 2011, 03:32:58 PM
That SOUNDS very simple to say but complex to make.  any pics?

D
Title: Re: Darnell U-570
Post by: thegrimreaper on June 06, 2011, 07:36:55 PM
I hope this link works.  http://www.servimg.com/image_preview.php?i=984&u=15029581

the picture was taken by myself and shows to the left the water pump on the lower right is the pinch valve with the home made cam that operates from a servo to pinch the tube inside the valve housing the micro switch also operates off the cam to power the pump to pump water to the ballast tank switch is off pinch valve is open to expel water and surfice the boat
Title: Re: Darnell U-570
Post by: Flying Sparks on June 06, 2011, 07:43:30 PM
Quote
I wonder if this project was completed?  The photos are very useful to me as a beginner in subs, really good stuff!  As a result of reading it I have bought the book by Norbert Bruggen...

The Darnell Vllc is myself and son Michaels project. not a lot has happend since my last post. We have slowly been collecting bits, we bought an Engel dive tank and a 9 channel 40mHz receiver. I have also aquired a lathe that I can use to manufacture a lot of components.
We have done some work on the hull, the watertight box has been ripped out and the inside of the hull is being cleaned up. The WTC material is about to be ordered. Photo's to follow.

We will be at St. Albans Dive in on Saturday, meet you there.

Phil.
Title: Re: Darnell U-570
Post by: g4yvm on June 06, 2011, 08:22:23 PM
Ok, see you there.  I'll be in a grey G4YVM tee shirt!

D
Title: Re: Darnell U-570
Post by: Davy1 on June 07, 2011, 09:33:45 AM
I've just been reading through this thread again. Very interesting to see a Darnell model being reborn and could I say 100 very well spent!