Why have wingtips?

Lazair Parts for sale

Postby Billm » Thu Oct 21, 2004 8:20 pm

Just a dumb question--I don't want to do it but just think about it.
In one of the earlier pieces that I read someone turned his wing tips over to make it look "cool". As I recall it almost cost someone their life when the bird was really unstable in roll and tried to meet the ground the wrong way.
I know that dihedral increases roll stability and that the wingtips look complicated to recover (which I plan to start next week).
Does anyone (Chappy??) know if anyone has tried to lengthen the struts for more dihedral and get rid of the tips?
Just curious but I DO plan to recover it box-stock.
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Postby JPXman » Fri Oct 22, 2004 1:25 am

the wingtips aren't there to increase roll stability, they are there to smoothen the wingtip vortices from such a high lift/low speed airfoil. Vortices cause a lot of induced drag, so if you can minimize the drag with a wingtip like the lazair (and like all winglets on modern commercial jets) then you get reduced drag (free lift) vs. weight (of the wingtip) tradeoffs...

Instead of recovering the wingtips, email Mike McKusick and see if you want to buy his fibreglass wingtip replacements. One piece that slides over the end of the wing and rivets onto the tip rib, real easy install, no messing with fabric,dope, broken internal wingtip parts etc etc...
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Postby Guest » Fri Oct 22, 2004 12:08 pm

You would really hate yourself if you removed the tips and lengthened the struts just to avoid covering the tips. What you would find is closing (capping) the end of the wings and remanufacturing the struts would be far more work than a simple tip covering job. Most anyone can install fabric using an instruction booklet or simply pop on some fiberglass tips.

In the end doing this would surely mess up the nice handling of the plane. You would feel like an ass for the whole thing if you did it. Let's not mention the money and time wasted.

The best thing to do with a Lazair is fix it up lovingly and carefully to the original configurations while adding minor upgrades here and there as needed. Those who highly modify Lazairs always always always do nothing more than screw up a good plane so its unfit to fly and occasionally bust their ass too. Very sad to see any perfectly good Lazair go to the boneyard at the hands of another modification happy idiot. (not saying you are one)

Your post is a good one as it is great to explore the possibilities and ponder the options. Keep in mind that Lazairs have been flying for a long long time. If changes such as this were the thing to do people would have already figured it out and everyone would be doing it now. That isn't the case is it. Most of this stuff has been tried before and in a few cases it cost people their lives.
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Postby Chappy » Sun Oct 24, 2004 12:43 am

Bill,

I would not modify your plane in this manner. The very first Lazairs that were not equipped with rubber pedals had lots of dihedral to help keep them pretty well coordinated in flight automatically. Later Lazairs that did come with rudder pedals didn't need as much dihedral, as the pilot could coordinate (or not) turns. The dihedral now was more to supply stability. Some owner of early Lazairs converted to Peter Lawrence's designed rudder pedals, so we removed a portion of the dihedral (shortened the lift struts). In my plane's case, I could not tell much difference in turn rates or stability. The big improvement is in taxiing, take offs and landings. Wind hitting the aircraft from the side will not have as much to act on, so you don't have to fight as much to keep the upwind wing down.

Turning the wingtips upside-down creates a really crappy handling plane, although it will lower the stall speed some by providing more lift. Because the Lazair all ready excels in the areas of lift and slow stalls, it's a huge mistake to reverse the tips.

Covering the tips with fabric is easy and fun! If you're just not comfortable trying it from scratch, you might search out an EAA chapter were you will find lots of members that are experienced, and probably be happy to help you get started.

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Postby JPXman » Sun Oct 24, 2004 2:07 pm

took a couple of pics of my wingtips yesterday while we were installing external capstrips.
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Postby JPXman » Sun Oct 24, 2004 2:08 pm

back side
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