Vosper 60ft MTB No.71

[Ray Wood 3Participant @raywood3]

[Ray Wood 3Participant @raywood3]

Hi All

The saga starts 20 years ago when my wife and I had a look round a Portsmouth Navy day and seeing the preserved MTB 71 afloat in one of the basins, I spoke with one of the guys on board about making a model he kindly sent me an excellent drawing with the lines and sections . Now having a grandson of 11years old I had a good excuse to build the model at 1/2" to the foot, so the model is 30" long and took roughly a year to on the water. Powered by 2X 400 size brushed motors turning opposite handed 25mm 3 blade props, with a Perkins 50 Amp speed controller and a 3 cell 2200mh Lipo battery, this gives a good scale planing speed for about 10 minutes. The interesting and different features are the twin transom hung rudders and the double diagonal planking from 1/64" ply, photos of the build in "Ray's Boats" album. Now its been on the water, crew flags and numbers to complete

Regards Ray

[Ray Wood 3Participant @raywood3]

Hi All

Here are the twin rudders, protected by semi circular plates to protect them from backing into the jetty.

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Ray. That's a good speed for such small conventional brushless motors!! I like the speed 400`s, a fast little engine.

​The stern looks very…startk..in the picture, almost as if it has been made much too deep. Obviously this is how its meant to be, but it does look odd?

Ashley

[Dave MilbournParticipant @davemilbourn48782]

Ashley

If it wasn't that deep then the rudders wouldn't reach the water…..

DM

[harry smith 1Participant @harrysmith1]

Hi All

Ashley, look odd and you the maker of odd boats!!!

I thought you would love it!!

Canabus

[Ray Wood 3Participant @raywood3]

Hi Ashley

I did try it this way up as an airboat, but it wasn't as fast

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Pilloried for making serious comments….what is the world coming to !!!

Ashley

(Ray, you should have tried bigger props….)

[Dave MilbournParticipant @davemilbourn48782]

"Pilloried", Ashley, or perhaps just "light criticism"?
Nah – "taking the mick" is most like it!

Ray
A very tasty little model. What adhesive did you use to put the second layer of 1/64" ply on top of the first?

Dave M

[Ray Wood 3Participant @raywood3]

Dave/Ashley

Here is the real one at Duxford

Gorilla wood glue, it dries fairly fast

[Dave MilbournParticipant @davemilbourn48782]

Ray

I see no rudders….

Dave

[Ray Wood 3Participant @raywood3]

Dave

It was used as a houseboat for years and lost her bits, only a cosmetic external restoration and paint job, they have fabricated new torpedo tubes and gun tub, hence the different colours. I nipped up to see her at Duxford before Christmas only to find out she was moved to a new location near Portsmouth for a new Coastal Command Museum ? but not been confirmed yet. I reckon Harry would put some big brushless motors and X50's to get her moving

Regards Ray

[Dave MilbournParticipant @davemilbourn48782]

Thanks for that, Ray. I'm bound by international treaty not to make any further comments about Harry's choice of power plants! He does have the luxury of a test pond the size of a small Scottish lough, though.

If you're interested then these days I would be looking at either one chunky 28mm brushless motor for that model – or two 22mm or even 18mm types. I think that perhaps 3-blade 25mm props might be a wee bit oversize for the Speed 400's, which is why you get a drop off from planing after just ten minutes. Have you put a wattmeter into the boat to measure the current each motor is taking? The golden rule with 400 motors is not to exceed 10A.

Dave M

[Ray Wood 3Participant @raywood3]

Thanks Dave

I fly Aeroplanes with brushless set ups hence my use of 2200 lipos giving 11.1volts, but have yet to put one in a boat ! I'm not sure how often the MTB will be used, but I will invest in Wattmeter at some stage.

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Ray. Speed 480`s would fit in place of the 400`s and give a decent percentage power increase. The JP ones are rated to 9.6V as well so scope for more voltage to be applied. 25mm props certainly ok for this motor.

​I will make it my new years resolution to try the wattmeter on ALL my boats and then I can give a definitive answer on the amperage thing. Certainly the Alvis (speed 400/25mm props runs well on 7.2V 3700 mAhr Nimh's, for a good long while without meltdown. Wattmeter this Sunday!! and notebook.

​Ashley

[Dave MilbournParticipant @davemilbourn48782]

Sorry to our UK colonies. A 'lough' is an Irish lake; the proper term for a Scottish one is 'loch'. One can't be too careful these days.
DM

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