Winglet attachment lay-up

[jpolenek]

Don't all those layers of glass, which hold the winglet to the wing, create a noticable hump on the surface and distort the template-based airfoil shape in those areas?

If so, can the foam be sanded down prior to any glassing, in order to compensate for the added thickness, so the end result is a flush surface?

 

Joe

[Waiter]

Yes, they do build up the area locally, but the finishing process (sand and fill) takes care of this. When I finished my wings, I used several long sanding boards to get the wing straight and smooth.

 

One of my sanding boards was almost 6 ft long.

 

Waiter

[Wayne Hicks]

Yes, you can sand into the winglet foam to compensate. However, you really can't sand into the wing because of the previous spar cap layups prevent you from doing that. I've known two people who have sanded into the wingelts to compensate. They both said it wasn't worth it. It takes the same amount of effort to fill-n-sand a near perfect winglet as it does to fill-n-sand a lumpy winglet.

[jpolenek]

What about the fact that the airfoil shape is compromised? I would imagine that builders take great care to make accurate templates and cut the foam as close as possible to the prescribed shape. Not only does the lump of the attachment lay-up distort the airfoil in area where it is applied (by up to 9 layers of glass!), but the filling and sanding process extends that deviation over an even bigger portion of the wing/winglet, to blend it smooth.

If this does not make a noticable difference to the way the plane flies, doesn't it suggest that there's no point in splitting hairs when it comes to cutting the cores since relatively large deviations, like this attachment layup, will mean that wing/winglet won't have the theoretical airfoil shape anyway?

 

Joe

[Waiter]

If this does not make a noticable difference to the way the plane flies, doesn't it suggest that there's no point in splitting hairs when it comes to cutting the cores since relatively large deviations, like this attachment layup, will mean that wing/winglet won't have the theoretical airfoil shape anyway?

Yes, you are correct, but I'm not sure what you mean regarding "splitting hairs".

 

Does mine have a bump or hump, NO, its blended in with filler.

 

Does my airfoil shape (in this area) match perfectly with the template, NO.

 

Is it still an airfoil, YES.

 

Does this mismatched airfoil change the way the plane flys, I doubt you could measure, even with the finest labratory test equipment the impact this has.

 

I would recommend that you do your best when your hot wiring the wing foam. Its been my experience that the better the job on the hot wire, the less filler material will be used later. and the final shape of the airfoil; will closly match the templates.

 

Perhaps the original airfoil template has already taken this into consideration, I don't know.

 

Personally, I don't know of anyone who has done what your suggesting. Wayne mentioned two people that did it, and then indicated it wasn't worth the effort.

 

There are thousands of EZs flying with this construction technique. I'm not aware of any failures or any incidents that this technique was a factor.

 

Given the above statement, I would recommend not replacing a proven technique, with one that has no historical track record.

 

If your an aeronautical engineer, disregard this entire post and do what you think is right.

 

Waiter

[jpolenek]

What's the approximate thickness (ballpark) of that lay-up at its thickest point?

 

Joe

[Waiter]

Thickness! 3/16 inch (WAG).

 

Take a look at the photos on this page, you can see the layups on the upper surface of the wing.

 

http://www.iflyez.com/LongEZ_Construction_Photos_Wing.shtml

 

Waiter

[jpolenek]

Thickness! 3/16 inch (WAG).

 

Take a look at the photos on this page, you can see the layups on the upper surface of the wing.

 

http://www.iflyez.com/LongEZ_Construction_Photos_Wing.shtml

 

Waiter

 

I was just perusing the photos on your site while you were posting this.

 

Looking at your attachment lay-up, it appears different than I expected, based on the [old] AeroCanard plans I'm previewing. I though there would be a thick band of UNI at about mid-chord. Is this area different on an EZ or basically the same?

 

Joe

[Marc Zeitlin]

Thickness! 3/16 inch (WAG).

Way too thick. It's 7 plies of UNI and 2 of BID, for a total thickness of 0.089". Call it 0.09", or 3/32" if you like fractions.

[Waiter]

Marc, That sounds about right. I had in my mind between 1/8 and 3/16, but as I said, that was a WAG.

 

Is this area different on an EZ or basically the same?

The photos on my site are from the original construction of my LongEZ. I don't know how this compares to an AeroCanard.

 

Waiter

[jpolenek]

Way too thick. It's 7 plies of UNI and 2 of BID, for a total thickness of 0.089". Call it 0.09", or 3/32" if you like fractions.

Great. That's somewhat less than I thought it would be.

Thanks for the feedback, guys!

 

Joe