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Aerotow from water


oipigface
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Often "Pond"ered that myself. Have also flown off water and often fancied gliding from an aerotow from water. Good luck. I would think 50m of towline would be about right if your stretch of water is big enough for the tug to start its mission from 50m away from the accessible downwind shore.

 

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SilentPilot

I'm a bit worried about the tow line on the top.

Fine off of ground but would there be a tendency to pull the tug's tail into water.

Might be better off with a rear tow coupling... 

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I’ve been looking at the Cularis with its Multiplex Funcub floats and also at a number of websites featuring advice. I’ve decided that the existing floats are too small at 600mm so I’m going to build a new pair 900mm long. Shouldn’t take long, and I can fit a  water rudder to the rear of each of them. The floats are also not far enough apart, so I’ll have to modify the fixings.

Watch this space.

 

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4 hours ago, heli_bee said:

I don’t know how long it took to build that, but I do know it was a very long time. Flies beautifully, but I haven’t heard that it has been towed from water. Hannah Reitsch’s account of the maiden flights of the full-size machine is quite hair-raising.

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Phil.Taylor

Interesting plan - water take-off - water landing too? - and if so, whats the plan for retrieving it from the middle of the pond/lake?

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7 hours ago, Robert099 said:

This is a modified version of the Falke, a German training aircraft designed by Lippisch. The waterborne version was built for the use of the ATC, but doesn’t seem ever to have been used by them.

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19 hours ago, Phil.Taylor said:

Interesting plan - water take-off - water landing too? - and if so, whats the plan for retrieving it from the middle of the pond/lake?

I’m going to buy a boat.

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SilentPilot
5 hours ago, oipigface said:

Eh?

The Venture was the Slingsby licence built version of the Falke.

This float glider looks to have more in common with the Slingsby Cadet than the Venture:

Cadet.thumb.jpg.ab69b00e2aa0035bf579f399eba2bc97.jpg

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14 hours ago, SilentPilot said:

The Venture was the Slingsby licence built version of the Falke.

That was a different Falke. The Slingsby Falke was a motor glider first entering service in 1971. The RRG Falke was a flying wing with added tail feathers to give it extra stability for training purposes. The first Slingsby Falcons (there were three versions) were built 40 years earlier in 1931, under licence from RRG.

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Progress so far. The floats will be 36” long or 75% of the length of the Cularis fuselage. The angle between the front part of the float and the rear is 8 degrees at the keel and about 2 degrees at the edge where a stringer has yet to be fitted, so about right on average.  I have yet to decide finally how to suspend them from the plane, but this float structure is very light so I’m working on the idea that the struts will attach to a rigid longeron between the attachment points, so that the loads absorbed by the floats themselves will be limited.I’m also thinking about how to drive the water rudders, but there are so many options, I’m a bit overwhelmed!

The semicircular tops will be 1/64 ply, and the bottoms 1/16 balsa all finished with glasscloth and epoxy. No paint!


DFECCF1B-4E25-4B01-99BB-60C21F1CD35B.thumb.jpeg.347e91451091d6a8fc7c6ef6734cdb12.jpeg

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  • 2 weeks later...

I know you are all keen to know how this flight of fancy is progressing. When I claimed up above that building the floats ‘shouldn’t take long’, I was almost right. They would have been finished 10 days ago if it hadn’t have been for the decision to fit them with water rudders, which has added complication on complication. Anyway, I’ve made my choices and, apart from final fitting of the rudders, gluing on the tops and covering with glass cloth, everything is done.

I originally thought that I would build floats, fit rudders at the back and then figure out how to make the rudders work. The more I thought about the last part of this, the less I liked it. Driving the rudders from the existing air rudder, or from servos mounted in the fuselage both seemed unsure of success, partly because of the difficulty of keeping things tolerably waterproof, and partly because the floats are unlikely to be sufficiently rigidly attached to the fus to ensure reliable tension on closed loops or pushrods. So I decided to mount the servos inside the floats with a closed loop driving a tiller on the outside of the float, and linked with a pushrod to the rudder’s own tiller. This (I thought) would be quite simple to do, and once it has all been thought out, it is, but getting to where I am now has been a bit of a struggle. The main difficulty has been engineering the rudder system to be watertight. 

I do think that electronics carried in a float need to be watertight (more so than equipment in a fus), and what I’ve come up with is as close as I have been able to manage. It is easy to build a watertight float. All you need is to cover it in glass cloth and epoxy. The difficulty is getting the electronic control signal in, and the mechanical control out. The first of these isn’t very difficult because a wire can always be sealed with silicone. The other requires a watertight bearing. It is possible to buy such things, but the smallest I could find was 10mm id and could only be purchased by the 100! I’ve wound up using a flanged bearing, which can be epoxied or siliconed into a cavity in the float, so that water can only penetrate by running between the shaft and the balls in the bearing. That’s good enough for me, especially since any water that gets in is 16 bulkheads and almost 3 feet away from anything electrical. 
You can see all this in the pictures that follow:
726F250A-B2AE-4C13-BDBE-37C74A2B3698.thumb.jpeg.9c3a8d0d23ba45ef066056cfbf4fee97.jpeg
 

Here’s the view from the front. The thing in the foreground is a plug I’ve made for a nose cone, which will enclose the enormous connector you can see on the left. This is the smallest waterproof electrical connector I could find, and I’m still wondering whether it is necessary. The nose cone will be removable and sealed with waterproof tape, so I could probably get away with using ordinary Futaba connectors. The servos are tiny Emax jobs, which are supposed to deliver 0.25kg torque each. That’s half a kilo altogether, which may or may not be enough to control a plane weighing about 1.5kg. The servos cost under £5 each and weigh 3.5g including wire and plug. The waterproof connectors weigh 8g. 
Here’s the view from the back:6BAF17FB-7AF6-4ECF-ACE0-B4B898331DB1.thumb.jpeg.b701633690537256ed8b9f7e494efd86.jpeg

The photo shows the step, and the V- shaped underside. On the left is a rudder assembly. The oak block will just be glued onto the rear bulkhead. You can also see the output shaft, and the flanged top bearing. I have added a strip of ply along the middle of the keel at the top, so that they form a T-section. At each end of this structure is a small oak block. These are the attachment points for the undercarriage, which do not create any holes through the skin of the float.

Finally, here are some close-ups, to provide a bit more detail:

06ACBCFB-0322-46A8-9F71-28FFE577E71D.thumb.jpeg.07dbfcfc5ecd0b88c39c5852f28548c9.jpeg

Here’s the unfinished output shaft. The bellcrank isn’t fixed yet, and will go across the fus in line with the closed loop. The closed loop I’ve made from 30lb braided fishing  trace. The tiller will fit into a hole similar to the one you can see just above the top bearing. This isn’t finished yet because I’m awaiting delivery of some 4x2mm cf tube to make the final version of the shaft. I need tube so that I can finish all the internal work, fit the skin, and then fit the top part of a split shaft. I couldn’t think of a better way of keeping everything watertight.

B29ADC64-43C7-4E7C-9AE2-D8799BE1EFF5.thumb.jpeg.ae5a89605ebf21f6db9c5396f3143622.jpeg

This is the waterproof connector. Not a lot more to be said. 

8FC024E1-72C2-4188-B2C2-AA094CC1EFEF.thumb.jpeg.548fb35cf68f592addb7ce0317de2395.jpeg

Here’s the plug I made. The nose cones will be moulded in two halves split along the chines.

 

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