Ivan writes:- "When I first read that some modellers were using silicon as a hinge to fasten ailerons and elevators to their pride and joy I thought, “Poor demented sods! What will these new upstarts to the hobby come up with next? They must be absolutely stark staring barkers”
OK! So I admit that I am one of the world’s leading cynics who once said that only wimps and weirdoes would go in for power steering, central locking and electric windows on cars.
Well! Can I help it if most of the world’s drivers have turned into a load of wimps and weirdoes?
Anyway back to these silicon hinges ~ About four of five years ago I saw this type of hinge on one of Carl Baker’s models and after having a chat with Carl about the pros and cons of using silicon for this purpose I decided, a little apprehensively, to give it a whirl.
At the time I had a rather old and well worn Hatchling in need of a new tailplane. (V type). (The Hatchling was one of several own design models that Ian Webb and I had been making for a while)
This was the ideal model to experiment on because the model was nearing its sell by date and it would be no big loss if things went awry, or, as some of our more eloquently spoken members say; ‘Tits Up’
Following the instructions Carl had given, I found it a reasonable easy job to do, a bit messy because I used an old silicon cartridge that had been originally used for a building job and the hole in the cartridge nozzle was on the large size for the recommended 2mm wide bead and I ended up smoothing the surplus off with the first thing that came to mind, my finger, the finest universal tool in the world.
I was reasonably pleased with the result although one side of the elevator was a bit on the stiff side. This was because I’d been over generous with the silicon and the silicon hinge was a little on the thick side.
Since then I have used silicon to hang ailerons and elevators on numerous models; in fact, there has to be a special reason for me not to use it these days like on centre hung control surfaces (as apposed to top or bottom hung).
The following are some of my thought and tips on the use of silicone for hinges. I want to stress that they are only my own opinions and are not intended to be some definitive instructions/advice
The complete control surface is sealed so that no air can pass between wing and aileron or tailplane and elevator ~ makes for a more efficient overall performance
I’ve found silicon extremely easy and quick to use (it may take one or two attempts to master the right technique)
It is weather proof and long lasting and doesn’t seem to be affected by the normal range of temperatures we get on our slopes.
I have never used silicone hinges on any power plane or on these suicidal self destructing dynamic soaring models so I can’t make any comment about its suitability for these types of models (A possible adverse effect of fuel on silicone hinges etc.)
I’ve only used silicone for top/bottom hung control surfaces ~ I would think centre hung ailerons/elevators would be a bit messy and may prove difficult to hold the control surface at a neutral position while the silicone cures. For this reason I wouldn’t recommend silicone for centre hung aileron/elevators ~ I’d like to know if anyone has tried this and what the outcome was..
There is one major drawback with silicone and that is no other adhesive, at least not in my own collection, will stick to a surface that has had silicone on it even if all visible traces of the silicone have been removed. If you stick aileron/flap servos in a wing with silicon; you’re stuck with it ~ you would have to use silicone again after any maintenance to the a servo (Say replacing stripped gears)
An unrelated experience is worth a comment at this point :> Ian Webb and I used to use the old fashioned Simonize (a non silicone car polish) to shine up fibreglass moulds prior to applying gel-coat and glass (several coats of Simonize acted as a release agent) On one occasion the cloth we used to polish up the simonize must have been used by Ian’s wife to polish furniture (many furniture spray polishes contain silicone)
This resulted in the epoxy gel-coat forming areas of round circles with volcanic like rims round the edges. Some people call it ‘Fish Eye’ or ‘Orange Peel’ effect ~ It can be a sod to eradicate
How do I apply the silicone?:
With a top hung elevator/aileron taped in position (See photos) ~ hold the elevator in the up position { about 9mm or 10 mm of up ~ this is not critical}
There is one major drawback with silicone and that is no other adhesive, at least not in my own collection, will stick to a surface that has had silicone on it even if all visible traces of the silicone have been removed. If you stick aileron/flap servos in a wing with silicon; you’re stuck with it ~ you would have to use silicone again after any maintenance to the a servo (Say replacing stripped gears)
An unrelated experience is worth a comment at this point :> Ian Webb and I used to use the old fashioned Simonize (a non silicone car polish) to shine up fibreglass moulds prior to applying gel-coat and glass (several coats of Simonize acted as a release agent) On one occasion the cloth we used to polish up the simonize must have been used by Ian’s wife to polish furniture (many furniture spray polishes contain silicone)
This resulted in the epoxy gel-coat forming areas of round circles with volcanic like rims round the edges. Some people call it ‘Fish Eye’ or ‘Orange Peel’ effect ~ It can be a sod to eradicate
How do I apply the silicone?:
With a top hung elevator/aileron taped in position (See photos) ~ hold the elevator in the up position { about 9mm or 10 mm of up ~ this is not critical}
In the opened ’V’ gap, run a 2mm bead of silicone down its full length . ~ I know what you are going to say! You’re going to say that anyone who can run a smooth accurate 2mm bead of silicone down the full length of an elevator/aileron with a bloody great big sod-off mastic gun like the one I’ve got, is a better man the ‘Gunga Din’
Not to worry! After you’ve run your hit and miss, thick and thin, 2mm silicone bead down the length of your aileron/elevator; take your index finger, and run it down the length of the ‘V’ so that it forms a nice smooth continuous radius at the bottom of the gap (over the underside of the tape)
The reason I use my finger is that it forms just the right radius curve (if I hold the control surface at the correct angle to the wing/tail,) and it feathers the edges of the silicone nicely up the sides of the ’V’
Now make sure that there is no surplus silicone at the ends of the ’V’ that will impede the control surfaces down movement ~ clean any such surplus out with something like a lollypop stick
When you’re happy with the silicone, bring the elevator/aileron back to its neutral position (hold with a strip of tape if necessary. Then run your (Clean) finger up and down the tape ~ this makes sure that the silicone is flush to both top surfaces (Wing and aileron)
Leave overnight ~~~ if you find the control surface movement is restricted or too stiff, peel off the silicone and try again ~ you’ll soon get the hang of it ~~ .
If you haven’t tried a silicone hinge yet, It’s well worth a shout; but start on something small like a tailplane."
I have also found on the Internet useful articles on silicone hinges
- Basic Article with diagrams on hinges - http://www.rc-soar.com/tech/silicone.htm
- This video is also quite instructive - http://vimeo.com/30175374
- Again another good article showing how to do a hing on the Aldij model - http://www.howe2wash.co.uk/SMSA/howsilicon.html
- This article shows you how to do a silicone hinge for a mouldie where there is a bottom or top hinge with hollowed out surfaces - http://www.southernsoaringclub.org.za/a-siliconehinge.html