As those of you know, the pond has had an episode of weed lately and so thougths turned to making something more weed reistant. I have a few 300x600mm sheets of 10mm thick Blue Styrofoam left over from various things and so I thought of making a skimmer.

BUT I dislike making made-up things and wondered if I could make an all foam Ecranoplan A90, like me other one. Two sheets of foam weight almost nothing…

Could I make it in a single DAY? using 5 min epoxy I thought I might just….

So, cheating already, I cut the foam up on thursday night, and glued the two main wing sides together, and on Friday night I made the ABS plastic motor mount (2 hours shall we say so far). On Saturday, my BSA MOT intervened and then a quick trip to Kingston, so valuable time was wasted..but for the rest of the time I was hard at it.

Below shows the main components, to which I would need a small block for the nose, and a bit of balsa for the tail rudder.

Edited By ashley needham on 28/07/2013 16:24:11

I didnt QUITE finish on saturday..the only thing I didnt manage was the rudder control, as this needed a bit more thought than I previously..er..thought. Remembering that the A90 had a micro servo in the tail, this one uses a normal size one in the body, and a length of aircraft plastic control line to connect both. The flexibility of the control line works well enough to encompass the rather large twisting angle the rudder moves through, due to the extreme rake.

IF I had ALL saturday to work, I recon I could have just made it, including an all-over coat of grey primer (although you cant spray foam, a covering of EZE-Cote resin seals the foam sufficiently well to enable spraying). I took the item along to show the chaps and give it a quick float on the Sunday.

Of interest is; The speed 480 motor, and composite 6 blade prop..made from bolting two 3-blade props together. The motor mount, is the shape it is because the flange with the holes in is sandwiched between the two tail upright bits of foam. The small rudder hinges were bought for, but not used, on the original.

I would be using a C-cell 8.4v Nimh Battery pack, and so the hull is a bit wider than the original (A90) but the rest of the dimensions are sort of the same. If I had more time the nose would have been made a bit thinner perhaps.

Edited By ashley needham on 28/07/2013 16:26:34

Edited By ashley needham on 28/07/2013 16:27:54

So then, after daubing with very snazzy paint, how does it go???

It doesnt go QUITE as fast as the A90, but there is not that much in it! Several other props were tried but the 6 blader worked best. If only I could get that to fit the A90, it is exactly right! I tried the A90 after and I think the battery pack is past its sell by..the second pack I had is demonstrably low on voltage and capacity and I remember the A90 as being a bit faster than it was today.

Still, not bad for a days (or so) work. Not only reasonable performance but endurance too (4700MaHr pack) AND reverse, although this is not to be recomended as the tail gets vey low in water going backwards; However, it is a good brake. Needs more sanding underneath and perhaps a bit shaved off the wing fences. A very creditable first outing all in all. An Ecranoplan within reach of almost anyone!

In retrospect I made it too small.. a 25% size increase would accomodate my 9.6v "c" pack, and the addidtional floatation would probably counter the increased battery weight, and of course there is the extra power. The increase in length would restore the slimness of the fuselage and THEN I would be able to put a 500 motor in the tail without it looking much too large and then there would be a big step-up in performance.? or not, as these things go.

Funny thing is, it looks quite ok on its own, it just looks a bit fat when compared to the original. The original was a nice handy size, but I think I made THAT one a bit too small as well ! You just dont know..it is not until you have built these things that you realise what you should have done. It amazes me sometimes that some of the things I have built actually work at all.

It needs just the font jet nozzles and intakes to finish, and more varnish on the roundels.

Just possibly if I have a free week end I might make a larger one, and then I WILL be giving this one away (just cost of materials perhaps).

Ashley        nb  I put a towing point under the tail, but events Sunday showed that you cant tow properly with an air rudder, just the drag of the string and cork rescue line was too much for it! ANY of my other boats tows that string..with ease

Edited By ashley needham on 29/07/2013 21:16:29