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[gregk9]

I have now swapped the rudder arms supplied with the brass rudders for straigth arms, as the original ones would not give me equal turn angles. So now after refitting these and also making up some threaded rods to join up the rudders, they are now fully operable, complete with a metal geared servo to cover the loading of 3 rudders on this particular setup.

I have also given the motor setup its first "dunk" in the upstairs  "test tank" and powered the twin 700bb's up for the first time!

Oh Boy !!

Considering the size of the motors, they certanly have some torque, even with a single 12v battery loosly placed in the hull for the test.

I did notice the esc for the motors was getting a little on the hot side, so for now, I've added a small brushless cooling fan motor to the cooling fins to help  keep the temperature below panic level .

The motors? I hear you all ask.................. not a problem, as thery have internal cooling fans as original equipment, plus me drilling air vents in the motor mounts, they didnt even get luke warm, but managed to drain the 12v battery to low volt warning on the esc!

[derekwarner]

Gregk9....you appear to have a linkage glitch here which will cause different rudder positions on axis relative to the rudder servo movement

STDB rudder linkage arm is connected to the third fulcrum point  
STDB to Centerrudder linkage arm is connected to the third fulcrum point  
PORT rudder linkage arm is connected to the second  fulcrum point  
PORT to Center rudder linkage arm is connected to the first fulcrum point   = unequal length = unequal motion to the PORT rudder compared to the STDB & center rudder

A possible solution here would be to use a DUBRO [or similar] Dual swivel ball link between the PORT & STDB rudder connection .....Derek

[gregk9]

thanks for your very keen observations, but after checking all the links prior to fitting AND considering what components i had in stock, this was the best compromise I came up with.

At worst, I am out by 3 degrees !  [wow  wee wow wow].
 When rudders placed at FULL turn.

Its hardly a problem, not for me, the person actually using the boat. Plus when you have to watch every penny I spend these days.
The use of current "stock" has priority over buying more new kit.

If I have a full time job with money to spare in the bank and money was not an issue, id probably agree with you and go and spend like there was no tomorrow, but when you dont know what bill is dropping through your door tomorrow, I have to be very careful.

Mind you shouldn't we all be thinking like this these days ?

[gregk9]

The Transom flap is now fitted and I've bonded in the 3 gas turbine exhausts [made from 35mm plastic film tubes]. I have the exhaust doors ready for final painting too, these ive dropped in place for the photo's. Imhave checked the clearance above the rudder arms and rudders, and there is sufficient space to allow for rudder adjustments or replacement if ness.

[RaaArtyGunner]

Plus when you have to watch every penny I spend these days.
The use of current "stock" has priority over buying more new kit.

If I have a full time job with money to spare in the bank and money was not an issue, id probably agree with you and go and spend like there was no tomorrow, but when you dont know what bill is dropping through your door tomorrow, I have to be very careful.

Mind you shouldn't we all be thinking like this these days ?

Agree
 
 

[gregk9]

firstly appologies for updates, but have been busy with the boat club matters, which unfortunately had to take priority over my own minor projects.

Right!
I have started work again on the superstructure and have today been constructing the main forward mast and the base mounting for the radar.
Following from the plans I have, the mast was made up from a piece of plastic tube, so i could feed the upper navigation light through it. the radar mount I made from rectangular plastic rod, purely for strength and rigidity, not wanting to use wood, for weight reasons. I have fitted some plastic tube bushes in the upper radar support and a small tube piece in the lower section, these will act as bearing supports to the thinner brass tube which will link the radar motor [electric] with the radar unit on the top.

I did however insert a small piece of brass tub in to the superstructure first and bond in with expoy resin, to act as the base for the mast, just for a little added support where its needed. the angled pennant support has been glued in place, leaving the upper fittings to make up and fit once the lower items have fully dried.

[gregk9]

I actually too the boat to my club pool this afternoon to check out the positions for the drive batteries, to ensure they kept the boat in balance for correct planing angle so to speak.

however on its first voyage, the esc burnt out!.

Now, what ampre rating esc's should I be running with twin 700 BB turbo motors, on 12v batteries?

Can anyone assist here, as I did put in one which i believe was labelled to be a 60 amp esc, but its completey melted it.

[Stavros]

Well you should have a esc for each motor,Give Dave at ACTion a ring and he will sort you out with Proper esc's and not those silly cheap and nasty chineese ones !!!


Stav

[craftysod]

I use a Fusion watercooled esc on my big springer,was running on 2 700BB turbo motors,but those motors are power hungry.
Now use 2 600BB turbo motors, get longer run time,and the esc doesnt even get warm.
1 esc and 2 motors,they are many ways to solve the problem

[gregk9]

I am going to refit with twin esc's, i have used the 700 bb's  as they were recommended by several other model boaters who have them fitted to this size perkasa, so was following other people recomendations and due to me limited budget, I'll have to stick with them for a while and just make the most of it.

I have said this before and have to remind certain people again, who dont bother to read earlier posts. My budget is not as big as my enthuisiasm for model boats. I try to make do the best I can. yes, some companies items are far superior but there is no need to rub someone face in it, just because you can afford them and would never dream of going elswhere for parts.
I have used 3 of these types of esc before and had no trouble whatsoever and are still fitted in some of my other boats and working fine.

Advice Is appreciated and I thank those who give this freely.

[TomP]

Hi Gregk9, stick a fuse in line between the battery and the speed controller then if the motors pull to much current it’s just a fuse to replace. I've had the same problem, I should know better being an electrician, and don’t you just love that electrical burning smell!! I had the motor rating at its max current which was 20A so thought a 30A speed controller would be fine, I was wrong and it caught fire, DOH!!  So I put a fuse in line and it was blowing a 40A fuse at full throttle. Learnt my lesson the hard way as usual still I know next time.  Regards Tom

[Mezza50]

Hi all,

I've been following this thread with interest because a have 49" patrol boat running on 2 x 700bb turbo motors, an electronize FR30HX speed controller and a 12v SLA battery. Based upon the comments of others in this thread should I put a fuse between the motors and ESC or fit another ESC. My question is not meant to send this build thread off on a tangent but the issues encountered by greg are of interest to us all with similar size/type boats.

[gregk9]

I have had a response back from the suppliers of the faulty speed controller. Apparently it had been "mislabelled" and didnt have the power out rating it was dispatched as.
SO THATS WHY IT FAILED !

NOT BECAUSE IT WAS A CHEAP IMPORT ! as the majority of people making comment naturally "presumed".

The company has been very considerate and have supplied a "pair" of speed controllers for my inconvenience.

I have to say this is more of a response I would of expected,  any Uk or European company would of simply ignored the emails I sent initially. Let alone send a return addressed jiffy bag to return the faulty component.

[derfledermause]

Good people, may I thank you for this series of very informative posts. I am about to start to build the KD Perkasa kit (all wood) 1/24 scale. Prudance dictates that as this is my first attempt at a vessel of this size, to trawl the model boat web sites for information, hence the thanks for these posts. I have noted the caution that being an all wooden kit, one must be carefull of the weight, if it is to heavy it wont plane properly. I also note that the powering of the vessel must be correct or again, it wont plane properly. The building of the hull and its ancillaries don't bother me that much, but I admit that being a mechanical engineer, electrical and electronic problems fill me with trepidation. I hope that I can follow your example "gregk9" and manage to put the continuing build pictures and text onto this site as you have done.
Again, many thanks to you "gregk9" and "Perkasaman".
derfledermause.

[gregk9]

Many thanks for your comments, dotn worry, this renovation project has not stalled, but I have 3 other projects on the go, this perkasa, a "moorhen" salvage tug [in  this same thread list] and some home based projects on a 1:1 scale!  So I have to spread my time evenly between them all at the present.

Plus, keep my other boats in order, namely my Sun tug, Dusseldorf fireboat and Egrete pusher tug, robbe sea jet,  robbe laser. I do also have a n gauge train layout somewhere in the house [ha ha].

[gregk9]

I have managed to finally get my boat out on to the water for its first trial tests, to see how it performs and also how it handles with the powertrain and battery setup.
First trial went well, A little trim adjust on the rudders, the 45 X props seem to be doing their job ok. but boat seems slow. So tried a pair of 50 X props, boat running faster now, but heavy drain on the batteries.
So, major rethink, I think 2 battery packs may be too heavy, so possibility to drop to a single gel battery.  Im running twin 12v 7 amp/hr units. I do have a 12v 10amp/hr battery I use in my dusseldorf fireboats, so may slot that in and see how it handles then. Ive not yet fully secured the battery trays in, as I wanted to be 110 % certain first.

I will retry with this battery and drop back to the 45x props for this test, but take the others with me as a substitute if needed for comparison.
Pics attached , but not taken under full power as difficult to operate joysticks and camera at same time!





 transom flap works very well, glad i fitted one and also made it with adjustment. I will try  adjusting it next time out as it may need 1 or 2 degrees pos this time as this boat seemed to run too "level", need to lift the bows, but will try battery move first before adjusting the transom flap.

[Stavros]

Well I can tell you straight away what your speed problem is without seeing your MTB !!!!! It is not your Motore or even prop size at all it is simply the WEIGHT of the 12v7amp Batts.Just weight them on your kitchen scales and you will see why.

SOLOUTION    Go out and buy some 12Nv 3700 NIMH batt packs.The weight of these is 660grammes so 2 will weigh 1320 or 1.3 kg NOW your 12v 7amperes weigh 2.6 kg so 2 will be 5.2 kg so in all you will save 4.3kg.

Yes I fully understand that 2 of these packs will cost a fair bit BUT if it's speed you want well I am sorry it comes with a price.I already know this to well as I have a perkassa fitted with a MMB 900 motor and run this on 24v BUT it works.WEIGHT I am afraid is the simple KILLER of speed.Yes I do fully realise that LOA,Hull shape etc etc do add up to speed and you will only be able to get a certain top speed out of a hull,regardless of which motor and prop combination that you use.

The main problem with the stick packs is endurance as they are half the Amperage of the gell cells,but they don't drop in performace  as easy as a gell cell.One thing you might want to try if you go down this route is to go back to a 45 mm prop,why am I advocating this,well it will defo help with the run time as the less work the motor has to do  the less amps it will draw,and remember one thing also with the stick packs she will be lighter so the smaller props will probably be sufficient.Just my Personal thought on the matter

.

Stav

[6705russell]

Problem there is if you do decide to swap the battery to a lighter set-up then you are going to need more ballast to trim it to the waterline again?  Back to square one....

Russ

[nick_75au]

It looks too deep in the water to me, going on the several  Perkassas at our lake, It wont matter even for scale appearance that the waterline is showing, just say if questioned that the boat is at the end of its patrol and has burned off most of its fuel

 Dare I suggest Lipo batteries, the PBs can not output the amps required for any length of time, Ni -XX are now more expensive than Li-po, (15C rated would be sufficient)

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6500

for example

just over 18 Pounds for 14.4 volt 5000 mAH but the correct charger and some form of Lipo low voltage protection will also be required
the closest equivalent from Component shop 12 v 5000 Mah is 40 Pounds.
Total cost would be about 70 pounds, but you would have a charger that can charge any battery chemistry.

My honest opinion, a pair of the battery above (14.4 volts) with a 2:1 reduction on the motor.

I would put a 1.5/2 reduction on the boat regardless of the choice of battery.

With the current set up
At 12 volts the motor should not be drawing more than 12 amps for peak efficiency and the RPM should be 12000 under load
I suspect that the RPM is considerably lower which drives up the amps

Nick

[gregk9]

Great ideas and suggestions guys, but you are all forgetting the one main thing, "Cost". you can't have what you can't afford ! id lurve to go out and buy all the proper kit, but when only doing part time work, you dont get a lot of spare cash left over, so my builds go on a budget.
Thats why i have to try for optimum performance and running time with what i have. if i need more things, i have to budget for months to be able to afford these items.  For example it took 6 weeks to save sufficient to buy the 2 - 50mm props!

The 12v 10 amp/hr battery I have is a mere 8.8 ilbs in weight.

the smaller 12v 7 amp/hr batts are 5.5 ilbs in weight [each].

[nick_75au]

Yes I gathered that from your previous posts, You are probably going to have to settle for a cruiser rather than a speedboat,
As I said definitely the motors need some sort of reduction, this will get the motors working more efficiently, then put the larger props on her, run the lighter battery, when it gets low, bring it in and put the other one in.

Cheers
Nick

[ACTion]

As Stavros says, you can't operate a planing boat this big with sealed lead acid batteries - the clue is in the word "lead". Most of the motor power is being used simply to push along those bricks.
It pains me to see my dear old Fairey Huntsman designs so often condemned to a canal-boat-like performance because the owner wants to run the model for a long time between charges. It's almost cruel! The same goes for Perkie, and you can pretty much guarantee that every model boat club has at least one or the other sailing whenever you go down to watch.
Fair play to Nick, but I very much doubt if gearing the motors and experimenting with different props will get the thing up on the plane. They were designed for I/C engines, and a pair of SLA batteries is a huge burden compared with a tank full of methanol and oil. Ballast and SLAs are for displacement hulls - this is a gas-turbine powered high-speed warship.
Dave M

[6705russell]

I would have to argue that point Dave, my Brave Borderer runs on a 12v lead acid and with the three brushless motors for power it will certainly get to the point where only the back three inches are touching the water, all depends on the powertrain really...

Russ

[ACTion]

I would have to argue that point Dave, my Brave Borderer runs on a 12v lead acid and with the three brushless motors for power it will certainly get to the point where only the back three inches are touching the water, all depends on the powertrain really...
Russ

All things being equal I'd have to agree, Russ - but the scenario is not to change the existing brushed motors as the guy is on a strict budget. My point is that he won't be able to obtain planing performance with his existing combination of motors, SLA batteries and ESCs, irrespective of adding gears and/or changing props. Three brushless motors and their ESCs would be well beyond both his budget and the scope of the question posed - but pretty spectacular and a sight that would do this old model designer's heart a power of good!
Dave M

[gregk9]

the motor setup I have installed WAS suggested by a forum member on this actual site in the first place, so Im not complaining, KIndly remember the pictures posted are NOt at full speed, they were only taken whilst the boat was using the throttle adjustment on the joystick [set at full adjust].  WELl, how else can i take a picture at full throttle, not unless you are fortunate enough to have someone standing around who will do the job for you.  those pics were purely to check its level line and see how the transom flap were performing.
Some people just jump straight in with both feet, I always find it better to read all the story then look back at the pictures on anything i do.

Works for me!

Im not expecting a rocket ship, I know and appreciate that, simply due to my financial budget, but it does not stop me from enjoying my hobby at a level I can personally afford.  its still far better to see the boat out on the water than gathering dust in an attic for several years, whilst funds allow a better drive train. Ive fitted what i can afford and can still get some enjoyment out of the renovation, whilst  my piggy bank develops.