wja

I recently picked up a 60” PT Boat and I’m now trying figure out what electric Motors/ESC(s) might be a suitable for this boat. I’m thinking of using 3 direct drive motors with port and starboard engines controlled by an independent speed controller and the middle motor being turned on by a micro switch when the other engines are on full power. Does that sound like a reasonable setup? Would 3 AstroFlight Super Ferrite 40 Marine or Graupner Speed 700 BB TurboElectric motors be sufficient? If so what Speed Controllers would be suitable?
I’m not really familiar RC Boating as my experience is mostly with RC Airplanes so any advice would be greatly appreciated!
Thanks in advance,
Wal

Hookpilot

I've built a 60 inch scale model of a British Vosper MTB. I decided to power it with three large 18V Johnson Electric drill motors, similar to a 900 series motor. Power comes from 3, 3300mAh 8.4 volt battery packs, one for each motor. Power goes from each battery, through a 20A mini automotive blade-type fuse, then to a Proboat waterproof ESC, rated at 50A forward and about 30A in reverse. There are three of these setups, one for each drivetrain. From there, power is delivered to each of the Johnson can motors. The motors turn 3-bladed 1.75" brass props, direct drive. Each motor is independently controlled. I'm using a Hitec 6 channel radio that I've modified using each joystick, left stick is left motor, right stick (was elevator) is throttle for right motor. I removed the centering spring on the right joystick and filed a detent groove in both throttle quadrants inside the xmitter. so I know where "OFF" is. The center motor is controlled with the Flap knob that sits on top of the transmitter. The left joystick, left-right controls the 3 rudders. Left-right on the right joystick fires the torpedoes. The gear switch rolls the 4 depth-charges off the stern.

At 8.4 volts, I'm drawing about 15 amps at full throttle out of each motor. I find that I can run at greater than scale speed (1/2 throttle) on the two outboard motors for abut 20 minutes, keeping the center motor off most of the time. It's a great backup. When the two outboard motors draw down, I simply crank up the center motor and play some more. The BEC circuit on the center motor/ESC powers all the receiver and servos, so I keep that in reserve to get me back to the beach. It works great. This setup really flies when you open up all three motors. I built the boat extremely light. It tips the scales at 17lbs exactly with three, 7-cell NiMH packs onboard. My boat was modeled after a 30-year old Revell 1/72 plastic kit. I just dimensioned up everything 5 times. That worked out to an odd scale of 1:14.6, so I had to hand-build EVERYTHING. If you are doing an Elco boat, there are plenty of hulls and plans out there. 1/16th scale will build out to a 60" boat.

If you put three Astroflight 40s in your boat, it will FLY! I was considering putting Astroflight 25s in mine, but these Johnson motors are really cheap. I got them for $5 apice... My AS geared 25s were $140 each! The Proboat ESCs are great, and only cost $40 each. I've noticed that my motors and ESCs don't even get warm after a run. The motors have internal cooling fans. You can see a video of my boat in action at: http://homepage.mac.com/hookpilot/PersonalPage.html

Good luck with your model. You might want to take a look at John Drain's website. He's in Australia and builds some amazing PT Boats He also sells partial laser-cut kits and components. See his site at: www.pt-boat.com

Mike in Honolulu

martno1fan

sounds great any pics of her and of the build? id love to build one of these from scratch!!.

Stiletto

John Drain's PT boat site is [link=http://www.pt-boat.com]www.pt-boat.com [/link] (without the s on the end)

Hookpilot

Thanks Stiletto for pointing out John's correct web site address.

Martno1fan: There are plans floating around for the Vospers. They weren't available when I originally built the boat in 1969. With the coming of the Internet, I was able to do quite a bit of research on Vosper-Thorncroft and the boats they built during WWII. I found out that Revell went to Herreschoff boatyard on the US east coast to get plans for their plastic kit in 1/72 scale of the Vosper Motor Torpedo Boat. The plans they got were not for a British or American boat, but for an export design built for the Russian Navy under Lend/Lease. The differences are not subtle. the machine guns used were American Browning M-2s instead of Vickers 12.5mm guns, or the .303 caliber Lewis Mark I machine guns. Only the British Type 1 boats were armed with the Oerlikon 20mm gun. the export boat had the same gun. All other Vospers had heavy machine guns. Later on in the war, British boats also were fitted with 40mm Bofors guns, or the 2-Pounder Vickers QF Mark VIII gun. A bigger 6-pounder was planned but the war ended before it was made operational The torpedoes used were also different and the lauch mechanism was a pneumatic air system as opposed to the pyrotechnic cordite impulse charge canister system found on Elco, Higgins and British Vospers. Early Higgins boats also had the compressed air system, but that was also changed over to the cordite canister system too. Engines were the same.

So the boat I built, and the 1/72 kit still sold by Revell is not a British MTB as their kit box cover says. It is a Soviet export version of the Vosper Type 1 built in Herreshoff's Rhode Island yard. Under Lend/Lease agreements, all these boats had to be destroyed at war's end. None remain. Too bad.

Now if you want to really build a boat that you'll probably never see modeled, pick up Squadron/Signal Publications Warships Number 13, Vosper MTBs in action. Larger hobby shops carry their booklets. In there you'll find info on a Vosper test boat called the MTB 510. It was a four-engined monster 100.5 feet long. Vosper Thorncroft built it to test experimental SSS gearboxes. It would make a great model at 1/20th scale and a spectacular one at 1/16th scale- lots of deck detailing, torpedoes, 40mm Vickers gun, 57mm gun, twin 12.5mm Vickers machine guns and a twin Oerlikon 20mm AA gun. I don't know of anyone selling plans for this boat. The Vosper folks are still in business in the UK and they might be willing to let you photocopy some drawings from their war archives. This might be my next project. If plans can be obtained, I'd send them to John Drain and have him laser cut a hull, deck and superstructure frameset. At that size, I'd consider using weed wacker motors with electric starters. At 1/16 scale it would be over 6 feet long!

I have lots of pictures of the rebuild done in 2005/2006, but none from 1969, just one B/W photo taken after it was initially completed in Germany before I shipped it home.

Good luck, Mike in Honolulu

martno1fan

wow thanks for the info Mike ill keep searching for them no doubt soemething will turn up, i remember some 25 yrs ago i once saw an old mtb boat hull with no super structure that some guys were considering doing up.it was in a bit of a mess but still afloat!!.ive no idea what model it was either but the hull looked pretty sound considering it was just moored up for god knows how many years.i too was considering a weed wacker motor in mine but just a single one in a boat 5 ft long or so.if i do do it i will be sure to let you know how i get on.any pics you can post of youres would be great to see.
mart

martno1fan

update,ive received in pdf format some orrigional vosper frames in pdf format,the guy got them from the office where the vosper boats plans are kept.he then put them in pdf just for me and anyone else who wants them.send me an email addy and ill forward them to you!!

Hookpilot

Hi:
I'd like to see those PDF drawings of the Vosper. You can send them to me at:

[email protected]

I'll post some pictures of building my boat. I need to shrink them down to smaller files.

Mike in Honolulu

Hookpilot

Martno1fan:
I'll attempt to upload some pictures of the build. The basic hull and deck were done many years ago and I don't have pictures of the process. The boat went into storage in 1974 and over the 31 years it sat in my brother-in-laws attic, his kids tore it up. I pulled it out in 2005 after his divorce. His ex got the house and sold it. I rescued my boats and went to work rebuilding the MTB. So here's the rebuild.

martno1fan

hi again ive got two 12 volt johnson motors in mind for the boat and im thinking of either 34 inches long 1/24 scale or just going 4 ft which i know is an odd scale .i have two choices as far as batterys go i have two 7.2 battery packs 1800 mah and a 12 volt lead acid type 2300 mah that weighs 2 lbs.would it be too heavy for a 34 inch hull? if so ill go for a 4 ft hull.also i have a speed controller left over from a car its the older mechanical type would that be ok running on 12 volts? not sure what the specs are,maybe worth trying if it doesnt work ill order a 50A esc.heres a link to the motors im looking at[link]http://cgi.ebay.co.uk/Johnson-6-12v-Motor-New_W0QQitemZ250029251854QQihZ015QQcategoryZ140971 QQrdZ1QQcmdZViewItem[/link]thanks for your help in advance .

Hookpilot

I tried many times to upload my build pictures, but keep getting an 'error during upload' popping up. Anybody know what gives? The photos are ~80K jpgs.

Mike in Honolulu

Mac Titanium Powerbook 15"

martno1fan

try emailing me them mate ill put them on for you if you like?my email is [email protected]

Hookpilot

Martno1fan:
I've sent you a bunch of build pictures taken of my Vosper MTB. Thanks for doing this. It's late Saturday night here in Honolulu and I'm going to run the MTB tomorrow morning.

Mike

martno1fan

hi mike here are the pics !!.these pics are of mikes pt boat and im posting these for him so here goes.might take a while!![img][/img]

martno1fan

some more!!

martno1fan

more[X(]!![img][/img]

martno1fan

i need a drink!![img][/img]

cyclops2

On my 8 foot Higgins I wound up using a 41# thrust trolling motor controlled by a Novak Reversing Super Rooster ESC. It took a reversed deep cycle car battery hook up 2 times and works perfectly. Popped the circuit breaker instantly. Timing gears overdrive the props at a 2:1 stepup ratio. It runs for a couple of hours at almost full speed.

You should be able to plane and run beautifuly on about a 25# to 30# thrust motor and a small deep cycle riding tractor battery.

I had to get 5.5" X 5.5" 5 bladed props from the Prop Shop in England to develop efficient thrust and speeds.

Full weight at W. L. is 90#.

martno1fan

thats a big boat id love to see some pics of her!!