Building materials, covering

jander14indoor
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Re: Building materials, covering

Postby jander14indoor » February 22nd, 2010, 2:55 pm

The Freedom Flight design doesn't have much dihedral does it. Sometimes increasing dihedral a little can get the span under limit if you are close, but not with a flat, or nearly flat wing. Too much dihedral change needed to affect span.

Here's how I'd attempt it.
First, make sure you are fresh and relaxed, this is going to be finicky, don't wait till the contest or you'll be VERY sorry. Make sure you have a good place to work.
OK, ready to start.
Carefully cut off the tip plate. If real solid, consider doing this when you cut off the outer rib later (below). If you used balsa cement, consider dissolving it off. I wouldn't use debonder if you glue with CA.
Make an extra rib, make sure it fits snugly between the spars at one outer rib. Coat the top with your favorite covering stickum and glue it just inside the outermost rib. Leave just enough space between the two ribs to slip an knife between to cut off the outer rib. I'd use balsa cement on ends of the rib to glue to spar to prevent gluing the new rib to the old. Let it dry VERY well, overnight if possible.
Carefully cut off that outer rib with a real sharp knife.
Re-attach the tip plate.

This may all fail, be prepared mentally to make a new wing. Heck, you may want to make a new wing FIRST as a security blanket. Probably easier.

And don't worry! If you are winning contests like Solon at 2:45 plus, you can do it again if you build a new wing carefully.

Jeff Anderson
Livonia, MI

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eta150
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Re: Building materials, covering

Postby eta150 » February 22nd, 2010, 3:00 pm

Just so you know, regionals are on Monday, and the wing is only over by the tiniest bit, if at all. It is also not a freedom flight design, but a leading edge. Thanks, though, because I'm sure that will work just fine if necessary.
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eta150
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Re: Building materials, covering

Postby eta150 » February 22nd, 2010, 3:01 pm

If it is just the tiniest it over, though, do you think a simple sanding and recovering of the tip plate could work?
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leetx
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Re: Building materials, covering

Postby leetx » February 22nd, 2010, 3:13 pm

I would consider sanding the tip plate.

First, be sure you know exactly how much you are over the limit, and where along the wing span. Perhaps the sanding has only be a little bit at only a few spots.

second, are you comfortable sanding the tip plate while it's on the wing? If so, I would do as you suggested: uncover the tip plate, sand at the right places, and recover. You must also be comfortable afterwards to recover the tip plate while it's attached to the wing.

Third, you can also sand the tip plate after you detach it. When I attach a tip plate, I attach it only in 3 spots to reduce the glue weight. In my case, I expect that I can easily remove the tip plate. If this is the case, then I would sand the tip plate after removing it from the wing but keep it covered. I would sand the inside, along the right spots, to reduct the width.

As jander said, if you proceed, be mentally ready. It's definitely do-able.

Good luck.

Greg Doe
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Re: Building materials, covering

Postby Greg Doe » February 22nd, 2010, 8:24 pm

Eta150
My kids had the exact same problem, wing too close to 40 cm. They fixed it exactly as
Jeff Anderson described, but let me add a few specific suggestions. Work on the right wing,
unless you have a very good reason to shorten the left wing. Cut a new tip rib and, and make
it a snug fit. Apply glue stick glue to the top surface of the rib. Install the new rib as close to
the old tip rib as you can, leaving the slightest gap. Glue the new rib in place. Remove the tip
plate. My students only glue the tip plates in 3 places so that they are easier to remove. Cut
off the origional tip rib, and re-glue the tip plate. My girl team did it in about 30 minutes.
At one of our events last year the judges considered the tip plates as part of the wing span.
It's probably best to build your wing with that in mind, unless you know the judges won''t include
the tip plates in there measurement. Good Luck.
Greg Doe
Smyrna, TN

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eta150
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Re: Building materials, covering

Postby eta150 » February 23rd, 2010, 5:30 am

I did build it that way, it just worked out to be longer than I expected
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Re: Building materials, covering

Postby eta150 » February 23rd, 2010, 2:42 pm

THANK YOU ALL SO MUCH!!!
I did the fix, and it worked perfectly. The plane may have lost a second per flight (if anything), and flying on an old piece of rubber with a max altitude of ~15 ft., I was still hitting 2:33 (I got my best times on newer rubber flying to the ceiling of a ~22 ft. gym)!
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Re: Building materials, covering

Postby leetx » February 23rd, 2010, 3:47 pm

THANK YOU ALL SO MUCH!!!
I did the fix, and it worked perfectly. The plane may have lost a second per flight (if anything), and flying on an old piece of rubber with a max altitude of ~15 ft., I was still hitting 2:33 (I got my best times on newer rubber flying to the ceiling of a ~22 ft. gym)!
Tell us how you did it!

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Re: Building materials, covering

Postby Greg Doe » February 23rd, 2010, 10:55 pm

Eta150,
I'm glad my two teams are not in Pa. Sounds like you have it dialed in! Good luck. Let us
know how you place. Our Regionals are this Saturday, but my two schools will be at two different
Regionals, so I'll have to pick one! There should be a lot of events to report on this weekend,
so everyone out there be sure to record the top times, and report them back here.
Greg Doe
Smyrna, TN

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eta150
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Re: Building materials, covering

Postby eta150 » February 24th, 2010, 5:00 am

Yeah, my regional are on monday. I'll be sure to post the results.
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