SonexBuilders.net

I’ve installed the full size wing tips using #4 screws and nutplates. The installation came out well however there is a LOT of unsupported fiber glass in the tips and I’m thinking I should probably reinforce it some way. I could spend a lot of time fitting foam and fiberglass supports or just install an extra set of wing ribs half way into the tips. The ribs would probably be easier and lighter than fiberglass reinforcement although I hate to see what the price is for an extra set of ribs ;(.

Anyway, wondering what others have done when using the full size, untrimmed wing tips.

The loads would be low out there , are you sure you need it? If you did why not a foam rib glued in place? Have any blue foam left over from a house project?

Purely my opinion, but have we heard of any issues, failures, incidents or accidents resulting from a wing tip?

If not I am thinking the designers knew their stuff and we should not re engineer it....purely my two cents.


Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved

Rule #1 - Build to the plans.
Rule #2 - If tempted to deviate from the plans, see Rule 1.
Rule #3 - If you are still convinced you have a better design and the hundreds of Sonex are built wrong, revisit Rule 2.

That being said, I did go with some mods that violated the rules. Swing back canopy is one.

Appreciate the feedback but I don’t know if this issue is applicable to non-OneX models. The OneX untrimmed wing tip is 20” long, the original tip design was extended to provide sport pilot compliance for “fluffy” pilots. Are the wing tips on non-OneX models this long and unreinforced?

My RV-9A has similar wing tips but probably only 12” long and they ARE reinforced as most RV tips. I know an RV is not the same as a OneX but they are similar. I think many if not most of the OneX builders trim the tips down so when they are folded they will fit under a standard garage door so there probably aren’t too many data points out there regarding full 20” length tips and any problems encountered. I’m not just concerned about total failure and the tip coming off but also concerned about cracking and vibrations.

Anyway, I appreciate the input.

jcondon wrote:Appreciate the feedback but I don’t know if this issue is applicable to non-OneX models. The OneX untrimmed wing tip is 20” long, the original tip design was extended to provide sport pilot compliance for “fluffy” pilots. Are the wing tips on non-OneX models this long and unreinforced?

My RV-9A has similar wing tips but probably only 12” long and they ARE reinforced as most RV tips. I know an RV is not the same as a OneX but they are similar. I think many if not most of the OneX builders trim the tips down so when they are folded they will fit under a standard garage door so there probably aren’t too many data points out there regarding full 20” length tips and any problems encountered. I’m not just concerned about total failure and the tip coming off but also concerned about cracking and vibrations.

Anyway, I appreciate the input.

Sorry, I missed the part about this being a Onex tip. That clearly was an afterthought by Sonex to get the Onex sport pilot legal with a hefty pilot. The Sonex/Waiex tip is just a flat fiberglass plate that caps the wing tip. My 2 cents (and worth every dime) is the tip is probably fine unsupported without a rib. I would be more concerned with not having the spar extend into it. But, Sonex does a pretty damn good job being conservative on their engineering. Looking at other kits, the Sonex is a tank.

WING TIPS-----Thw wing is loaded around 11 LBS pe rsquare foot including the wing tips -------
Talk to Kerry --And build it rer plans ----I wouldn't fly it with 4-40 screws especially if you have the long tips --
Merle Reppert ---ONEX 0049 67 Hours

Merle,
I’m surprised you consider a 1/8” pulled aluminum rivet to be stronger than a #4 – 40 steel screw. The 1/8” pulled rivet has a .125” hollow aluminum shaft with a steel mandrel about .076” diameter compared to a 4 – 40 screw that has a steel shaft .112” diameter. Also, if the steel mandrel happens to break near or below the material surface it is bonding or fall out of the rivet body completely as sometimes happens, it has a lot less strength. I've followed discussions on other forums comparing the strength of pulled rivets to screws and the consensus has been a 4 – 40 screw is an acceptable replacement for a 1/8” aluminum rivet with steel mandrel. Maybe you have had some bad experiences with 4 – 40 screws or perhaps you have some other information regarding strength comparisons?

Plans call for stainless pulled rivets --NOT Aluminum
Merle

Merle,

Before posting alarmist comments like 'I wouldn't fly it', that will be on the internet forever for all to see, could you back up your response with some data? I have yet to do any calculations, but my first assumption is that a solid steel screw will be higher in shear than a tubular steel rivet. My second is that the heads are similar in size so the tension force on the top should be similar, and with the nutplate on the bottom, the tension stress on the bottom would be far less with the screw. Third assumption is that the tearout strength of the aluminum skin would be the failure mode with either fastener.

We have #4 screw kits on thousands of flying RV's at higher speeds (but with less loading area) with not one complaint in 20+ years. I know that builders are using the screws in other areas for pull rivet replacement as well. We selected this combination because of their size being similar to the pull rivets, where #6 or #8 screws just don't look right and seem to draw your eye.

If there is cause for alarm, send me some data as I need to ensure that we are not being unsafe, but this seems like more of a visceral comment like 'I would never drive a Ford'?

Mike Lauritsen
Cleaveland Aircraft Tool