SCORPIAN

[zipper]

Im glad your happy with the Scorpian Andrew, they are also good for combat except you fly past everyone.

Glenn

[ding]

Andrew, I love the idea of spreading the batteries across two enclosures. I think I might end up using that idea

[thevon]

steve that's one problem with the Bee (responding to your other thread) they have the bays precut for batteries and servos, so it's harder to customise it! Eg I would like to put the servos a bit further out, so the horn isn't right at one end of the aileron. Same with batteries. I guess you could cut bits out of your old Bee to fill the existing holes, and then cut new holes!

[thevon]

During this wind - less week I took the Scorpion into the shed for some TLC ; looked at the elevons and decided that I couldn't live with the amount of slop and twist. There's too much slop in the GWS servos, and as Glenn predicted, there's a lot in the curved plastic control rods. Also the thin ailerons, narrow near the root where the horn is, are too twisty. So I luanched into a partial rebuild. Ripped all the covering off, removed the servos and ailerons. I'll put a pair of bog standard servos out in the middle of the wing, and stiffer conventional ailerons. I have used 3M90 liberally under the tape and under the Monokote - seems really good, but hard to apply as it tacks up so fast. Very rubbery and tough. I wrapped the ailerons in bi-di tape. Also decided to experiment with silicon hinges. I'm not sure that there's any advantage, but it will be interesting to see how they hold up.




Not far from finished. A long way from looking as smicco as a Sean build but about as good as I've ever done.



Hard to see, but there's silicon between the trailing edge and the elevon. Below is the outer corner.

[GotrekGurnisson]

Is that silicon as in a bead of silicon glue? Will that hold up?

[ding]

What is the advantage of a silicone hinge over a tape hinge? The really positive thing about tape hinges is there is no leakage from the top to the bottom.

[thevon]

Silicon is widely used for moulded planes, where they cut the aileron free from the main wing - there's info about that on RCG etc. I used it on the Minij as recommended, and it's truly awesome, incredibly strong. But in that situation the aileron is a perfect match to the TE, so you use masking tape along the top to hold them together at the right gap, approx 2/3 mm and run a bead into the gap, spatula it to fit the shape and let it set. If you use too much it's too stiff. On composites, it grips unbelievably well and is very rigid, making a rubbery sort of hinge and yes, one benefit of it is that it fills the gap.

But on foamies it's different - the tape hinges work well - I'm just experimenting. The silicon's fiddlier than the tape, takes a lot longer waiting for it to set, and it doesn't stick as well to the Monokote unless you rough it up a bit, and there's the risk of the Monokote lifting. One possible advantage is that when hit, the aileron might absorb the shock or even tear the silicon, rather than snapping.

When tape hinges get older they can get sloppy and have up/down wobble .... maybe the silicon won't? But if do them well, tape hinges are great.

[zipper]

You need tapered elevons for two reasons
1: With them thicker at the root you will find that they will slow the plane down on up elevator,especially in the turns.
2: The reason they are wider at the tip, is that there is no built in twist to the wing when it is cut, so the elevons makeup for it, if they are straight then you might find that it flick the other way in a tight turn and wont recover as quick if hit in combat.
It will be good to know how the silicon hinge goes, I think it would work better if there was a sub spar on the trailing edge to stop some flex which might lift the covering.
Keep us posted on how it goes.

Glenn

[thevon]

It's finished. But the extreme makeover has certainly added weight ... it's now 800gm. It took a lot more lead in the nose to counteract the bigger servos, which are mounted much further aft ... also the steel control rods ... also the plugs of EPP glued into the old holes, and some spackle/PU smeared on to fill bumps ... it all adds up!

I took the photos on really low res and it makes the finish look messy but it's actually pretty smooth.





The elevons are really stiff (absolutely nil slop). I used short servo arms, s/steel bike spoke control rods, and long horns on the elevons so that the servos can work over their full range, but at low elevon throws. That way it should have finer trim control and less slop. It previously had small horns and I had to cut the rates back a lot.

I also used electrical insulation tape on the LE this time, instead of Clearshield.

Took it to a park around sunset for a test/trim flight and it seemed promising ... now just gotta wait for some wind ...

[sean]

Hey Andrew, looks good, once again amazingly fast work! The finish looks nice and smooth. Why the frown? ;D

[thevon]

I was just mucking around with sticking bits of Monokote on, using acetone to prime them ... cut out these using paint tins ... the smiley way looked silly but the frown looked more striking!

[callun]

Maybe it caught site of the Drongo and the duck! ;D