Author Topic: RAF airboat, 16th scale possible build  (Read 1597 times)

Offline tghs

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RAF airboat, 16th scale possible build
« on: September 20, 2020, 08:18:34 PM »
years back I found the good clear photo of this boat,, purpose built from "spare" parts, fairy swordfish floats, hawker tail and walrus engine.. not enough info in the photo to work up a good set of plans,, the other day stumbled on 2 other photos, not clear but do clear up enough to get as set plans together.. thinking that my 1/16th HSL whaleback could use a running partner,, at 1/16th it will be in the 34" range, looking at brushless electric motor hidden in the engine nacelle ,, but it would leave room for a very detailed dummy Bristol Pegasus engine,, now looking for a good dimensioned engine drawing.. this would be very cool project for a scale radial engine project as you would be able to use it without the fear of crashing from the sky..
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Offline Vixen

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Re: RAF airboat, 16th scale possible build
« Reply #1 on: September 20, 2020, 08:30:19 PM »
Hello tghs,

An interesting waste of Her Majesties resources, but idle hands will always find something to do.

I have the Bristol works handbooks for several different Marks of the Bristol Pegasus (it's a long stroke Mercury, or is the Mercury a short stroke Pegasus) Either way, I could scan the Pegasus GA drawings from which you could build a detailed dummy engine.

Stay safe

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #2 on: September 20, 2020, 08:47:29 PM »
that would be outstanding!!! it's just to cool of something not to build a model of,, I have found drawings for the floats, tail fin and close enough for the engine nacelle,, on the whaleback side of things a photo showed up that shows a whaleback with something besides a solid black hull,, it also operated out of Egypt as the airboat did, a very good candidate for the finish of my model. folks are trying to work out the colors..
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Offline Vixen

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Re: RAF airboat, 16th scale possible build
« Reply #3 on: September 20, 2020, 09:40:29 PM »
I'll look out what drawings are in the handbooks over the next few days. I will also check which Mark of Pegasus they fitted to the Walrus and see what I have nearest. I can scan the handbook images and send them to you. PM me with you e-mail address as the files will be too big to post on the forum.

Check out my ' Mercury revisited' topic for detailed photos. The Mercury and Pegasus were almost identical, except for displacement.

Stay safe

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline Vixen

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Re: RAF airboat, 16th scale possible build
« Reply #4 on: September 20, 2020, 09:50:07 PM »
That was easy. The Pegasus VI P (pusher) was fitted to the Walrus 1 and II. I'll have a look and see what handbooks I have.

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline Vixen

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Re: RAF airboat, 16th scale possible build
« Reply #5 on: September 21, 2020, 11:04:02 AM »
Here are some photos from my last visit to the Yeovil FAA museum showing the Walrus engine installation. Note the exhaust stacks and the tin plate baffles between the cylinders.







Here is a cutaway and the dimensioned installation drawings. You need to ignore the the exhaust ring, it's for a normal puller engine





Finally some details of the tin plate baffles to aid the cylinder cooling. They are installed the other way round on the pusher engines





That should get you started

Stay safe

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #6 on: September 21, 2020, 11:49:13 AM »
that will help greatly,, good shot of the air directing baffles,, read a rescue report where a walrus was unable to get airborne after landing and picking up a raft bound aircrew,, all they could do is taxi in the direction of home,, after several hours a RAF boat located them and towed the final miles.. at arrival the engine was found to completely salt entombed due to the constant sea spray and hot engine.. in those conditions the baffles most likely hurt more than helped..  it does look like the "airboat" employed a ring exhaust pipe..
« Last Edit: September 21, 2020, 11:53:28 AM by tghs »
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Offline AVTUR

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Re: RAF airboat, 16th scale possible build
« Reply #7 on: September 21, 2020, 11:58:53 AM »
If times were better I would suggest you pay us a visit at Bristol RRHT and have a good look at manuals, engines and bits (OK, I know you are in North Carolina). However at present no one is allowed in to RRHT, not even the volunteers.

A little bit of trivia: The flying test bed for the Pegasus (piston engine) was the Hawker Harrier! A lot of work was done developing the cowling and exhaust ring.

AVTUR
There is no such thing as a stupid question.

Offline Vixen

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Re: RAF airboat, 16th scale possible build
« Reply #8 on: September 21, 2020, 12:18:12 PM »
  it does look like the "airboat" employed a ring exhaust pipe..

The ring in your photos is unlikely to be an exhaust ring. It is on the wrong side of the cylinder heads, the exhaust ports point towards the propeller. The ring in the photos is on the inlet side. I would make a guess that it's a conduit for the 18 spark plug leads to keep them as dry as possible.

At 1/16 scale your model engine will be only 3 to 4 inches in diameter.

Mike
« Last Edit: September 21, 2020, 03:11:11 PM by Vixen »
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #9 on: September 21, 2020, 05:18:13 PM »
about 3.25" diameter for the engine, floats 23" LOA, around 27" LOA, width will take some photo calculating to come up with a value,, not a big model but a nice size.. enlarging the photos shows Y pipes off the ring structure between the cylinders and robust fittings joining the ring sections,, the quarter stern view shows an open pipe off the ring facing aft and down,, does look like exhaust smoke cloud there,, this must have been something they fabbed up,, not having the advantage of a enclosed cockpit and airspeed the noise level would have extreme,,(when I was a Coast Guard coxswain our back up boat was 30ftr open cabin, you rested your butt on the 671desiel cover, if you wanted to have  decent radio comms you had to throttle down near idle)  the fairey swordfish used a ring cowl collector some the mechs would of had experience, maybe stole parts..  a sound simulator on this model might be needed!!!(need a fingers in ears emogi)
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Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #10 on: September 21, 2020, 11:11:07 PM »
did some rough copy machine drafting just to get a feel what this boat would look like in 1/16th,, not to bad, big enough not to be a cork on the water but still easy to transport, considering the whaleback's hull is just under 48"..
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Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #11 on: September 24, 2020, 09:42:50 PM »
the swordfish floats did not look exact in shape,, some surfing around and I think they used a set of floats from a Fairey III, it would have been an older aircraft type at the time,, the shape of the float is dead on,, some photo measuring will shorted things about 1.5 inches.. it should be an easier float to make.. Fairey III in the photo, the plans are for the swordfish..
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Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #12 on: September 26, 2020, 06:47:14 PM »
With the floats sorted out it was time to draw up a profile plan, yes I still "draw" plans,, 24" LOA going to call this little beasty the "Nile delta water bug"  have planned out how to make a good dummy engine, turn or mill masters for the multiple of nine parts(cylinders cast around aluminum tube) the block will be turned and milled aluminum in case bearings need to mounted for the propeller shaft that will pass through the fake engine..  Looking at the drawing I think it needs a Vickers machinegun mounted somewhere..
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Offline crueby

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Re: RAF airboat, 16th scale possible build
« Reply #13 on: September 26, 2020, 07:19:33 PM »
What a neat project!  Is there any information on how well it actually worked?

Offline tghs

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Re: RAF airboat, 16th scale possible build
« Reply #14 on: September 26, 2020, 08:09:39 PM »
not a great deal of info, its top speed was about 15knts, not as fast as you would expect,, the aircraft floats most likely didn't work like a flat bottomed airboat not trapping a wedge of air under them,, without the lift from a planes wings the thrust may have pushed the floats deeper into the water,,  the builders most likely thought it would be faster than the 36knts of the whaleback launchs..but all in all it was a inventive effort...
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