Sonex wing tips

[Brett]

Have any builders used screws instead of rivets to fix the fibreglass wing tips to the Sonex?

The reason I ask is that I live, and will be flying right on the coast and was interested if it would be a good idea, whilst checking for corrosion at 100 hourly inspection to pull them off. The wing tip allows quite a good visual look down the wing, with them removed. Good idea , Bad Idea? What's everyone's thoughts on the matter?

-Brett

[Rynoth]

Probably a question for Sonex, but I bet it would be fine to use screws. The wingtips are non-structural and can be attached with aluminum rivets, so I'd think screws could do just as good a job.

(Note, the tail tips ARE structural and must be attached per the plans)

[peter anson]

Hi Brett. My feeling is that you won't gain much. Corrosion is more likely between the lower skin and ribs or the lower skin and spar or rear spar. A small hand-held USB camera/microscope will get you a look in a couple of bays, but to get much further you probably need a good steerable boroscope at many thousands of dollars. If you park it in a hangar you're not too likely to have problems. Chris Dearden and Steve Nelson have had a Xenos hangared at Goolwa on the South Australian coast for 5 years. Why don't you ask them for their thoughts?

Peter Anson
Sonex 894

[eppre]

I plan on using screws and nut plates. I may want to install lights later.

Can't see why that will not work.

[SonexN76ET]

Be careful with any extra weight you add to the wing tips. The more weight you have out on the wingtips the more likely you are to spin your aircraft in a stall. Also the spin will wind up faster. Nav Lights/strobes, landing lights, fairings all add weight. Nut plates and screws add up pretty quickly. I have read reports of builder's who used nutplates on their wingtips and regretted it later on as being unnecessary. I put landing lights on my wings in the outboard panel inside of the last two ribs. I can remove the landing light and inspect the inside of the wing and I can reach the wiring on the nav/lights and strobes. I used aluminum rivets on the wingtips. So far, this has worked out well for me.

[Brett]

Thanks for the replies everyone . I will probably just do what Sonex recommend and use Ali rivets. By the time I start to feel I need to worry about it all and have a look, it's not really a big job to drill a few rivets compared to building a whole plane.

[DCASonex]

For what it is worth, I have found the Avex non-structural aluminum rivets like Zenith uses for their entire structure to be very good for riveting Fiberglass. As the mandrel is pulled, these immediately form a bulge and then pull that bulge down to clamp the material, but they do not expand their shanks inside the material. To my way of thinking, this makes them unsuitable for aluminum to aluminum, as the joints can move slightly after riveting, but this same characteristic makes them ideal for riveting into fiberglass that cannot withstand much shank expansion pressure,

Zenith uses the countersunk heads into non-dimpled holes and with a domed recess into the head of the puller which forms the countersunk head into a dome. Nice part is that the resulting dome is a bit smaller than the standard domed head. Either that or the standard domed head works fin into fiberglass, Their aluminium bodies are at least as strong as the fiberglass, and they are easy to drill out when necessary. My experimenting with these rivets came about after an abortive start with a Zenith CH650 kit before the folding wing problem became known. Mothballed and then dumped off that kit and built a Sonex, No regrets on that, but the rivets for fiberglass where the only good thing to come out of that experience.

David A.