2 quick questions re foamies

[paul devereux]

One quick question: there is slight movement of the motor mount- only 1 mm or so side to side and up and down. Will it get worse over time? I have thought about slathering epoxy around the mount where it meets the foam, on the grounds that the airframe will end it's life before the motor wears out or needs attention- would people agree with me doing this?

[paul devereux]

And the second: I've only just noticed the rudder is offset, even though the plane flies fine, straight and level at cruise throttle. Is this unusual, and is it a concern?

[J D 8]

 Foam will flex some, epoxy may react with the foam [depends what type of each]

  Think I would put some silicon sealer around in the space behind the mount, will grip but remain a tad flexible. [ put small blob on some where un seen to test if concerned but I have not come across any foams that react]

 Rudder looks to have a small warp at the top, if it fly's well👌then. 

[Colin Carpenter]

Looks like a Wot 4. The recent thread on the foam Acrowot will give you lots of info re this problem with the marque !! Colin

[paul devereux]

25 minutes ago, Colin Carpenter said:

Looks like a Wot 4. The recent thread on the foam Acrowot will give you lots of info re this problem with the marque !! Colin

It was probably my thread. Yes, it is a Wot 4, which is probably identical to the acrowot. The responses seemed to support the foam acrowot as a good plane generally, but prone to poor manufacture. What I shall do is: buy one, slather it with epoxy, and report back on it's longevity. @J D 8 I like the idea of silicone, but my current theory is that it won't give rigidity- the metal parts are stuck to ply inserted in the foam, so epoxy may act a bit like external ply reinforcement. That's my theory anyway.

Edited May 7, 2023 by paul devereux

[Cuban8]

Just had a look at the Wot 4 foamy kit that my late friend left to me, and there is no movement at all in the foam to mount joint, so I'd say your model needs a little corrective action in that department - it'll only get worse and might fail without warning - seen an engine fall out of a model in flight, not a lot of fun for the pilot.

Rudder mis-alignment is nothing to be concerned about.

[J D 8]

  My old EF 16 was put back together with "Sticks like sh1t" an extra grip silicon from the builders merchant after being chopped to bitts by a nasty Habu. Works very well with foam and is white. Sticks well to metal [ it is only slightly flexible when set] Keeps much of my old series Land Rover together.😅  

   F16 still soldiering on after several years.

 

[Nigel Heather]

The Wot 4 is in a slightly better position than the AcroWot because the motor and mount are easily accessible.  This is because the Wot 4 has a plastic cowling that can be removed to expose the motor and mount whereas with the AcroWot the mount and motor are encased in the foam fuselage - you can get the motor out but you need the skills of a gynaecologist.

 

Also the way the mount is fixed to the foam looks more substantial in the Wot 4, in the Acrowat it is literally just jammed into slots in each fuselage side.

 

With the AcroWot, what happens over time, and accelerated by any less than perfect landing is that the foam around the mount flexes and compresses and the mount loosens and begins to move about more.  As it moves the thrust angle changes which can result in jerky and jittery flight.

 

Would I reinforce an Accrowot if I bought a new one - probably.  If I bought a Wot 4, not sure, I would do a bit more reading because I don’t think the issue is as bad with the Wot 4.  If I were going to secure it I would probably use something more flexible than epoxy, like UHU POR or silicone sealant (most likely the UHU) - my reason, epoxy is hard and brittle, the foam flexes and as it does I imagine that hard epoxy would either peel off or crack.

Edited May 8, 2023 by Nigel Heather

[paul devereux]

19 hours ago, Cuban8 said:

Just had a look at the Wot 4 foamy kit that my late friend left to me, and there is no movement at all in the foam to mount joint, so I'd say your model needs a little corrective action in that department - it'll only get worse and might fail without warning - seen an engine fall out of a model in flight, not a lot of fun for the pilot.

Rudder mis-alignment is nothing to be concerned about.

I think I know what caused the wobbly motor now, I can see the foam has compressed a little. A few months ago I flew it with the wrong memory- the ailerons were reversed. It did a gentle-ish landing on its nose, bending the prop adapter. I thought that that was the only damage- but it must have also damaged the join between the ply and the metal motor bracket, and it has slowly gotten slightly worse

[Zflyer]

It is always the unseen damage that in general causes the problems. You look at the obvious damage and around the immediate area and fix it. Then when you fly you note odd behaviour causing much scratching of head and cinsultatiin with colleagues. Then unexpectedly you find the problem normally hiding, which gives rise to "how on earth".