Ekranoplan

[JeremyParticipant @jeremy15845]

The first day of Spring and my A90 had its first run at Black Park. Performance not spectacular, better with the 5.7*3 prop compared to the 5.5*4.5 which, based on my ammeter readings, is oversized for the motor. Next step will be to reduce the depth of the floats and see how it goes then. With the rudder straight ahead, the A90 veered quite sharply to the left which suggested more drag on one side than on the other. That problem may be resolved with the smaller floats.

But for the cost, I would be tempted to try the larger Park 400 motor. tI would fit the same mount and weigh just 20g more. I would have to go with a Lipo to deliver more power and uprate the speed controller. Probably over the top for a fun model.

It's been fun to build and many thanks to Ashley for all his help and advice.

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. Good man !

Looks a touch tail heavy on the move?

The floats can be sanded down to the plan size with no problem. Will improve performance for certain, assuming you still have the original size ones.

As you can see, thedifferent props make a big difference, but fitting an 11V LiPo is the sure fire way for speed, and perhaps a slightly smaller prop then to tame the extra power a touch.

Mine leapt into the air at full throttle on a LiPo, yours may not, so much, as the wings are a bit flatter.

Manouverability at speed ok with the water rudder? If you cant trim the veering off to one side by float sanding or rudder twirling, you could "set" the air rudder a bit, this would affect high speeds and have a lesser effect at low speeds, just what you want !

Well done,

Ashley

[JeremyParticipant @jeremy15845]

Ashley

I took up to 12mm off the floats (more at the front than at the back) and moved the battery a bit forward. Performance much better, approaching but not quite as good as yours on U-tube. It still digs in at the back under full power but my (not very good) photo shows most of the floats to be out of the water. The water rudder works fine and, when centred, the A90 went more or less straight.

Since the run this morning, I have removed all the polystyrene from the forward section of the 'box' which will allow me to move the speed controller and battery a bit more forward. Hopefully, it will then flatten the ride somewhat.

My meter indicates that, at full power, the motor is drawing around 9 amps which is close to the operating limit. If I use a higher voltage Lipo, would I risk overloading it?

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. I only had one go on the pond with an 11v Lipo, and so didnt measure the current draw. In theory I suppose you may overload the motor, but using a slightly smaller prop would load the motor less, as you dont want the full power of an 11v battery, it would be too much…

I think if you can get a bit more weight forward it will flatten off and be a touch faster because of it.

If this does not flatten the attitude at spead, then you COULD glue a thin layer of Blue foam on the bottom of the boat, sanding it to a fine wedge, tapering from nothing at the front to 10mm (or whatever) at the rear… this would add bouyancy just at the back.. ?

The other thing is, if you look closely at the picture of my motor on its bracket..I have bent the bracket a bit so the motor points upwards slightly, to lift the back up a bit… may be worth a go..? My tail plane has a small upwards incidence as well, as seen in another picture where I put a thin wedge in, as the original tail top was parallel to the boat body.

Its all if`s and but`s this experimental lark. It is possible I could increase the performance of mine by trying a new prop, or adding some foam to streamline the bottom, or re-making the rear wings out of foam, or further trimming the floats, or or or ! one day possibly.

Ashley

Edited By ashley needham on 26/02/2012 18:36:55

[JeremyParticipant @jeremy15845]

Battery moved even further forward and the trailing edges of the wings are now well clear of the water. Without a more powerful engine or a Lipo bettery, I think I've gone as far as I can. It's a lot of fun as it is and attracts amused interest at the lake. Link to U-tube video below:

Over and out on this project!

Jeremy

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