Control surface horns

[John Hickson]

Hey all, yet another question

I have an ARTF where the aileron control horns angle back on themselves to bring the pushrod holes over the wing/surface joint. Trouble is they are really flimsy so I intended to replace them with something more substantial. But every set I have found dont angle back so the pushrod holes would end up over the aileron and not the hinge point.

I dont have the option to move the mounting location nearer the hinge line as they already sit right on the edge.

I know that ideally you would want them over the hinge line but seeing as I can find any that do angle back, am I safe to assume that whilst not ideal, its OK?

Cheers

[PatMc]

It probably won't make any noticable difference. However if you are concerned you could always move the servo arms off centre in the same direction.

[Biggles' Elder Brother - Moderator]

Hi John,

try SLEC here they do horns that will reach.

Or,...get yourself a small piece of 1 or 1mm GRP sheet (like PCB board, but without the copper, you can get it from EBay and it comes in handy for lots of things) - and make your own. Its very easy.

BEB

[Tony K]

Is it really necessary for aileron pushrod holes to be over the joint? If they are located slightly rearward you will get a bit of mechanical differential, more up than down.

[Steve Hargreaves - Moderator]

Or let them into the control surface so they sit "flat" rather than leaning back at an angle.....these Robart horns are nice but not cheap.....

[kc]

I always mount the horns on small pieces of 1/64 ply chamfered off on all edges to paper thickness ( before fixing ) Just a little bigger than the horn, say postage stamp size. For your purpose it would be easy to thicken one edge to bring the horn into line. ( or make from 1/16 ply and sand thinner at front)    Depending on the surface thickness this might be much better than recessing into the surface as Steve suggested.

I do this before covering so it's near invisible but just a lick of paint before installing would be OK for a ready covered model.

Edited By kc on 14/01/2013 12:32:47

Edited By kc on 14/01/2013 12:35:00

[Bob Cotsford]

Giant Shark do some metal horns with pretty extreme rake

[PatMc]

Posted by Tony K on 14/01/2013 12:05:32:

Is it really necessary for aileron pushrod holes to be over the joint? If they are located slightly rearward you will get a bit of mechanical differential, more up than down.

Depends if it's a low or high wing.

The differential would be wrong for low but OK for high if the holes are behind the hinge line.

[John Hickson]

Its a low wing.

Thanks for all the advise guys I will a look round.

[Engine Doctor]

I very rarely use supplied hardware as its usually rubbish and can ruin an otherwise well built model. Cut horns from either fiber glass , carbon fiber sheet or paxolin sheet then epoxy into the wing with 30 min epoxy . Never had one pull out and you can adjust the position of the holes so that they are excactly where you want them . Once fitted a quick lick of paint and thery match the model exactly. paxolin and g/fiber sheet is available in various thicknesses from maplins or five start products.

[PatMc]

Posted by PatMc on 14/01/2013 13:15:20:

Depends if it's a low or high wing.

The differential would be wrong for low but OK for high if the holes are behind the hinge line.

Actually the wing position isn't the criteria. I should have said that it depends on whether the horns are above or below the wing.
The differential would be wrong for horns above but OK for horns below if the holes are behind the hinge line.

I too usually cut horns from epoxy glass board but cyano them in place. Scrap PCBs from old radios, parts from PCs that have been replaced etc are a good source. Some larger board often have a decent component & copper free area but if necessary components can be cut away or de-soldered & the copper lands peeled off.