Aquabird - Electric Build - Page 4 - RC Groups
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Oct 28, 2012, 02:05 PM
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There is no need for plastic fairing. The water never reach that high.
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Oct 30, 2012, 05:27 AM
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Trevorh's Avatar

Pushrod waterproofing

Since my wife underwent shoulder surgery on Thursday, I have had no time at all over the last few days to do any work on this model. However, this has allowed my subconscious to mull over the water ingress problem and I did get an e-mail out to some fellow builders asking for their ideas.

Many thanks to all who responded to my plea. Almost all the responses involved re-locating the servos. Whilst I can't argue with the sense of this, I am stubborn enough to be reluctant to give up on the current arrangement just yet. I'm presently thinking along the lines of the picture below, using the finger of a rubber glove to form a gland. As long as this seals well around the trailing edge, I would think it should be okay since the end of the 'finger' is well above the waterline so the seal to the pushrod hopefully won't be under any pressure.

However, I normally don't bother with servo hatches so I would want the gland to have a long service life. This makes me a bit unhappy about using rubber. Can anybody think of any other suitable items that could be adapted to make such a gland, preferably from a more durable material (neoprene perhaps)? I am wondering about the bulb from an ear- or eye-dropper, or maybe a finger stall

As always, all suggestions welcome.
Oct 30, 2012, 06:21 AM
eye4wings's Avatar
Baby's feeder bottle top?

I suppose you have no concerns about balance yet... but Laddie's solution does move a little weight forward.
Oct 30, 2012, 03:17 PM
DFC~ We Do Flyin' Right
Vapor Trails's Avatar
Originally Posted by eye4wings
Baby's feeder bottle top?
I call them nipples
Oct 30, 2012, 04:47 PM
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Trevorh's Avatar
A couple of fellow builders (thanks Scott & Tim) steered me towards the model boating community. Could these be the answer, perhaps?

I'm not sure that the wide end of the bellows is quite large enough to accommodate the clevis but I might be able to reverse the pushrods i.e. fit the clevis end to the servo and the Z bend to the aileron horn.
Oct 31, 2012, 06:23 AM
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Trevorh, I feel you might be setting up your self for the failure. It will be extremely hard to make your arrangement water proof. Other concerns I have are. The pivot arm between the hinge and the clevis attachment bracket is too small. The aileron will be too sensitive. The trailing edge is weakened as well. You have no access to the servo. Can you tell us why you chose this arrangement?
I am asking these questions because I really want to see you succeed.
Oct 31, 2012, 12:08 PM
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Trevorh's Avatar
Laddie, please feel free to ask the questions. We all have our usual ways of doing things and it is good to have them challenged from time to time.

All my reasoning was on the basis that the underside of the wing would be exposed to splashing but I hadn't realised that the trailing edge would actually be on the water during taxiing. Entirely my fault this - I had watched the videos on Youtube a while back so should have noticed the taxiing attitude.

The general location of the servos was governed by considerations such as keeping pushrods as short as possible and getting the drive point closer to the centre of the aileron without needing servo extension leads. As for the linkage arrangement, I generally try to make control linkages as inconspicuous as possible so putting them on the topside of the wing would be a bit of a last resort.

The depth of the trailing edge allows a maximum hinge-to-clevis distance (i.e. effective horn length) of 11mm. I agree this is shorter than ideal but I checked the servos carefully and they have no detectable free play either in the gear train or in the bearing so I took the view that this was just about acceptable, given the benefit of a rearward facing pushrod exit being less vulnerable to water ingress than a downward facing slot. This last bit of the argument has of course now been shot down!

As for access, I gave up on servo hatches 12 years and 1800 flights ago and since then have only had to remove the film from one wing bay to replace a servo.

Relocating the servos is still an option but the last thing I want to do is rip the servos out and then realise that I didn't need to, so I have ordered some of the transom pushrod bellows and will have a play with them before giving up on the present arrangement.

Incidentally, on the subject of aileron sensitivity, what aileron deflections do you recommend? I haven't spotted any guidance on this on the Traplet plan.

P.S. Robin, I haven't really thought about balance yet. I've deferred choosing a motor until I have a better idea of the likely all up weight so I have some flexibility there. Also, one of the joys of building a non-scale model for a change is that I can leave the firewall positioning until very late in the build so the motor can be pushed forward a bit if need be.
Nov 01, 2012, 03:23 PM
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At the widest points, here are the deflections. The ailerons 1/2" both ways. The elevators 3/4" and rudder 1".
You did not asked, but I am enclosing the picture showing inside of fuselage.
Nov 02, 2012, 05:36 AM
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Trevorh's Avatar
Thanks Laddie. With a root chord of 2.25in, an aileron deflection of 0.5in amounts to just 13 degrees. I must admit that is less than I expected.
Nov 07, 2012, 05:27 PM
What could possibly go wrong?
nickchud's Avatar

Excellent contributions all round.

Move the servos Trevor - you know you will eventually

Nov 08, 2012, 11:32 AM
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Trevorh's Avatar
Mary's recovery is progressing well so I have managed a bit of time in the workshop to do a trial fit with one of the transom bellows. I took the wing along to our club night last evening and shared the issue with a number of other modellers. Quite a few people instantly recognised the bellows as 'those things the boat builders use' and I was heartened by the fact that all the people who examined the setup seemed to think it should work.

Of course, they may have just been being polite. . .

Anyway, now that I feel that I at least have a solution, even though it may not be the final solution, the wing has been set aside while work on the fuselage gets underway. Hopefully by the time I return to the wing in a month or two's time, I should be able to weigh up the pros and cons of re-locating the servos a bit more objectively.
Nov 08, 2012, 11:44 AM
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Trevorh's Avatar


Since there won't be a .45 i.c. motor throbbing away up front, I have cut the fuselage sides from 1/8in balsa instead of Liteply and downsized the longerons from 1/4in sq to 1/4 x 1/8in basswood.

The front of the fuselage side has been extended forwards to allow for some flexibility in the final location of the firewall. Also, because I won't be using the plastic/fibreglass cowl, the front section of the sides have been made deeper so that the underside of the fus can be faired into the wing more easily.

Laddie, I have noted the need to close off the rear section of the wing bay. I will have to work out how best to do this since, with the built up wing, it isn't so easy to flatten off the top of the centre section as is shown on the original foam wing.

Nov 09, 2012, 07:40 AM
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You are right, the drawings are showing it flat, but I made the change so it is not flat. Take a look at the picture. You can see the bottom of the former and the balsa sheeting is following the contour of the balsa wing.
Nov 09, 2012, 11:21 AM
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Trevorh's Avatar
Nothing to do with the Aquabird, but I just had a good example of how the obvious solution to a problem can hide in plain sight.

Our club has recently started holding indoor flying sessions in a rather small school hall. To limit the stress on my dodgy back, I have been in the habit of taking a pasting table along. However space is very limited at this venue and I have felt a bit guilty about taking up so much room. Having done several abortive mental searches of the house and garage looking for something about half the size, some days later, the obvious solution finally hit me. Remove four screws - job done!
Nov 09, 2012, 11:27 AM
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Trevorh's Avatar
Laddie, did you have to add any lead to the nose of the Aquabird to balance it? I'm about to cut out the fuselage formers and was pondering where best to position the top hatch for battery access. Ideally it would extend back to F4 to give full flexibility but this would necessitate beefing up the over-wing structure between F3 (the leading edge bulkhead) and F4. If, as I suspect, the battery is definitely going to have to go forward of the cg then I can get away limiting the hatch to between F1 and F3 which would be better from a structural viewpoint.

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