RC Darby Hydroplane

[Steve D]

I'm back, this time with a history thread.  One thing about moving, you get to clear out stuff and my wife came across a box a photographs of a model I built ~20 years, a Darby Hydroplane.  The pictures chronical the little project quite well, so I'd thought there might be some interest in my posting the build here.  This will be short and quick (as its historic), but it does show some techniques that may be of interest.

 

The idea came from a copy of the MotorBoat and Yachting Manual, but frustratingly, the copy with the lines in seems to have gone missing in the intervening years.  This is the 13th edition, I think the lines were from the 11th edition but I can't be sure

 

 

These turn up on old bookshops (if any still survive) for a few pounds, I'll keep looking, it must be here somewhere.  If it turns up, I'll post the lines, also I can't see my own drawing, so I must have redrawn them on paper...

 

For the history of the boat, it was created just after the war to help get people into small powerboat racing.  It was small enough to build in a single garage and used (I believe) a Ford standard 8 engine, inboard.  This description is from the Oulton Broad Motor Boat Club history page

 

The Club received a boost at this time when Guy Batholomew, a director of the Daily Mirror newspaper, became interested in the racing whilst on  holiday in the area. Keen to revive racing after the war, he commissioned Alan Darby to build six identical single step hydroplanes powered by British Anzani 350cc engines.  These craft were hired at £10 for the season to local  businessmen during the early 1950’s. The idea proved a tremendous success because the following year these drivers went out and bought their own outfits.  The popularity of inboard racing continued into the 1960’s thanks to the Albatross Marine concern at St Olaves who produced a range of aluminium runabouts.

 

The boats were a hard chine design with a small step and must have been a lot of fun to race around the Broads

 

The boats were built upside down by positioning transverse frames on a building frame, so I decided to do the same, the string is to keep everything straight.  Being 1:12th scale, a lot of this build is almost full scale practice

 

 

First 4 frames in place

 

 

 

The frames were made like you woudl a model aircraft, pinned onto greaseproof paper while the glue dries, then mounded on a removable transverse beam which is located in the build frame

 

The stem piece was laminated on a former

 

 

It runs back to frame 6 which is the step

 

 

Chine corners installed here

 

 

Once all the frames were in place, the lower hull ply was added, 0.8 mm thick, you can see the rear hull binds in past the step to frame 3

 

 

The hull can now come off the build frame

 

 

and the upper transom piece and sheer timbers added

 

 

The wood is a mixture of lime and spruce

[Steve D]

Continuation, I wasn't sure how many images a single post can contain.  I should have added that the model is ~25 inches long by 5 inches across the beam

 

Here is the backs hull framing all in place.  Note the small stringers between the main frame, not sure the model needs them but they were full scale practice.  The transvers beams are removed later

 

 

The next picture I have shows the motor and prop tube mounted

 

 

The propshaft runs at a very shallow angle and has a single outer plate support.  The prop is a high-speed prop, in brass, I have no clue where I got is but its right for the boat

 

 

Here is is mounted to the boat, note countersunk screw holes holding the plate in place, I was fussy all those years ago ..

 

 

I believe those are cap nuts, what was I thinking?

 

The steering wheel and rudder were scratch made from brass, shown here painted

 

 

Here is the dash panel in place and the steering wheel mounted.  I think at the time I ntended the steering wheel to move with the rudder servo, at least I gave that bit up....

 

 

The seat is the battery box, works the CofG well

 

Last picture for today, the arrangement of the RC controls and wiring.  The hull has been coated with a 2 part epoxy paint inside and out to waterproof everything and here the inside has had it green final colour coat.  The lower hull has also been planked in 0.5mm walnut strip

 

 

Upper works and RFI pictures tomorrow, very short thread, hopefully of some interest

 

Cheers

 

Steve

[Dancona]

Sublime

[Steve D]

Continuing my little post, below the underside showing the forward fin for lateral stability, the whole painted in high gloss cellulose spray paint.  The demarcation between the paint and varnish with a small walnut trim.  To the right you can see the mountings for the rudder.  The shaft is external but the actuator runs in through a slit trimmed with brass.  The prop shaft is stainless steel running to a two bladed high speed prop

 

 

The deck is built up with cross curved beams, the inner curved beams are the framing for the engine cover.  Note, I had to add a little lead at the front to achieve the correct trim

 

 

More progress on the deck framing and the timber strips of the cowling added.  You will see that I've also added mahogany duck boards

 

 

Th sub-deck is made up from 0.8 mm ply, shown here being glued in place

 

 

With the deck glued and planked in walnut, the inner engine cowling frame is formed from laminated timber strips to fit.  The deck breams have been cut out.  The spine timber supports the cowling cross frames

 

 

The strip wood was added to form the double curvature shape of the cowling.  This plus the rear cowling were covered in heat shrink fabric of the sort used on model aircraft.  The real boat was also fabric covered

 

 

The cockpit cowling has been epoxy coated and painted high gloss white, ready for the dashboard, engine turned aluminium with brass bezels on the instruments (I think the gauge faces were from a model aircraft set).  To the left is the throttle which is connected to the on/off switch with a rod so the boat can be turned on without removing the cowling.  The seat in the foreground holds the battery pack

 

 

And lastly, here it is complete.  Note the tiny rudder

 

 

Steve

[Steve D]

Here are the dress shots

 

 

 

She ran well and got on the step but that rudder was useless so the turning circle was a mile or so, not great.  Really, I should have added a Perspex clip-on rudder for running her to provide some actual comtrol

 

Cheers

 

Steve

[Dancona]

Absolutely gorgeous, I love the way you scaled down the construction from full size practices, there is something very appealing about wooden speed boats !!

 

Cheers

 

David

[Steve D]

47 minutes ago, Dancona said:

there is something very appealing about wooden speed boats

Thanks David, I just rediscovered the pictures so thought it would be nice to show how a drawing in a book can become a working RC boat without too much effort.  It went very fast until I tried to turn it., lucky I was running it on a canal...

 

Makes you want to build a real one....

 

Steve

[Dancona]

27 minutes ago, Steve D said:

Makes you want to build a real one....

 

Funny you should say that, that's exactly what went through my mind............I wonder !!!!