Aerotow from water

[f3fman]

The ripples DO help you "unstick" from the water, just don't want them to be too big.

 

[oipigface]

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.

 

[heli_bee]

How about a "proper" glider?

https://scalesoaring.co.uk/phpBB3/viewtopic.php?f=7&t=2120&hilit=adler

https://cevans.me/VINTAGE/Documentation/SeeAdler/SeeAdler.html

[oipigface]

4 hours ago, heli_bee said:

How about a "proper" glider?

https://scalesoaring.co.uk/phpBB3/viewtopic.php?f=7&t=2120&hilit=adler

https://cevans.me/VINTAGE/Documentation/SeeAdler/SeeAdler.html

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.

[MAZ]

It now resides in The Wasserkuppe Museum.

[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?

[Robert099]

This  one is  from nearer  home.

https://windermerejetty.org/items/slingsby-falcon-1-glider/

[oipigface]

7 hours ago, Robert099 said:

This  one is  from nearer  home.

https://windermerejetty.org/items/slingsby-falcon-1-glider/

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.

[SilentPilot]

Looks more like a converted Cadet than Venture!

[oipigface]

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.

[oipigface]

53 minutes ago, SilentPilot said:

Looks more like a converted Cadet than Venture!

Eh?

[oipigface]

Spent the afternoon doing some good old-fashioned balsa bashing:

[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:

[oipigface]

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.

[oipigface]

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!

[oipigface]

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:

 

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:

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:

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.

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

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

 

[mtreble]

Yesterday the first test flight of the Cularis with floats was completed successfully on Levisham and ended with a nice landing on the ... er .. bracken?!

I got some photos from my phone:

https://share.icloud.com/photos/06LjS7EfZybPeNmc5EeofzOig

[Andy_B]

Bonkers...................well done JT

[oipigface]

Mark took most of the pictures just after the second attempt at a flight started, and they don’t show the beast at its best. It won’t loop or roll, but it could have been designed to do stall turns. 
We tried the first flight in 5m/s air, which wasn’t quite enough, and I landed at the bottom of Levisham having established that a lot more up trim was needed. By the time I got back from the retrieval, the wind had increased to 8m/s. 10 clicks of up, and it soared out of Mark’s hand with a bit of up elevator applied. 5 minutes of trimming and trying various things and I had learned that the extra 200g or so means that it likes to fly much faster than without the floats. I’ve never tried to fly it with ballast, but perhaps I should. All that drag underneath requires more elevator trim, and turns are much better with some rudder assist, so I’m going to program some in.

[oipigface]

Since the competition at the Bwlch was cancelled today, I spent most of it in the shed, limiting myself to just 5 frames of the snooker.
I’ve now finished fitting the 1/64” ply tops to them, and they are gratifyingly light and stiff. The downside was that I managed to glue one of the bellcranks to the top, so I had to do some surgery to release it, and mend one of the closed loop threads which had suffered under the strain. It was quite easy to open the bottom up for access. 
Most of today I’ve spent working on the water rudders. I’ve been thinking a lot about how to prevent epoxy getting into the shaft bearings, which are flush with the tops, but exposed. The photos show what I decided to do.

First, I covered the rear ends with masking tape, then I cut out a circular piece using the flange of each bearing as a guide.  Then I put a tiny drop of oil in each ball race. The internal shafts are 4/2mm CF tube, and I’m going to glue the external parts of the shafts (which carry the tillers) into them using 2mm rod. Because of this, I didn’t want to get any release agent inside the shafts, so I stuck a piece of rod into each of them, before spraying them liberally -3 coats - with R5.

Half an hour later, I removed the masking tape to reveal two wax encrusted bearings, which I then covered with little circles of masking tape. 
And now I’ve got my fingers crossed that that will do the trick.

I’m almost ready to do the final covering with fibre glass and epoxy now.