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Jul 21, 2015, 12:45 PM
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Discussion

Balsa Leading Edge vs Skinned Foam Leading Edge


Newbie here. Is there any significant difference between hangar rash, or landing dent resistance, etc. between a separate balsa leading edge on a foam wing versus just skinning a foam leading edge? Or skinning the foam leading edge a bit thicker than the rest of the wing?

A balsa leading edge seems to be some extra effort and I have some idea of why it is done, but not fully and am not sure how well faster alternatives perform.
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Jul 21, 2015, 02:13 PM
San Antonio TX.
sensei's Avatar
A balsa sheeted leading edge won't hold up to any type of abuse, hit and split. a solid balsa leading edge holds up very well and when you get a dent just inject with a little water, heat and with patients the dent can be removed.

Bob
Jul 21, 2015, 04:11 PM
Entropy is happening!
Jim.Thompson's Avatar
As Bob says above.
You have not stated what flying style this model is for though. For example, on my slope planes I use a good hardwood shaped LE strip. While on lighter thermal planes, I use the popular method of light carbon fabric applied to the LE on the bias before vacuum bagging. There are dedicated threads on this subject with several methods of applying the carbon.
I have used a light Baltic Pine or Pauwlonia LE strip on thermal plane wings as well. Quite light enough and very tough.
The hardwood strip LE can be added before or after vac bagging.
Jul 21, 2015, 04:25 PM
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I guess it would be classified as a sport plane. How does the style of flying affect how ding resistant the leading edge should be. Are you trying to protect the leading edge from accidents? Ground rash from belly landings? Does having landing gear make a difference?
Last edited by DKNguyen; Jul 21, 2015 at 04:31 PM.
Jul 21, 2015, 04:33 PM
Registered User
I made wing wing once with a relatively thin uni-carbon piece cut in horisontally about 1/8-1/4" in to the leading edge foam, I gave it away and its new owner DS'd it in to a tree with only minor fractions at the LE as a result. It was quite sturdy I think, possibly 160g/m2 carbon skinned + some thin fiberglass and the leading edge was a couple 140g uni-carbon about 0,3mm thick plate probably, with a kevlar LE overlap.

If you look at some wood planked planes like Tangent (Alpina4m) these are made like this but with some semi hard wood and a little thicker perhaps but still a flat piece cut horisontally in to the leading edge.

Its an alternative at least..

Cheers
Last edited by hallo; Jul 21, 2015 at 05:16 PM.
Jul 21, 2015, 04:37 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by DKNguyen
I guess it would be classified as a sport plane. How does the style of flying affect how ding resistant the leading edge should be. Are you trying to protect the leading edge from accidents? Ground rash from belly landings? Does having landing gear make a difference?
Most thermal flying is done on a flat field with mown grass. Or at least, soft long grass. All of which means that when landing, the leading edge is seldom if ever subjected to damage.
Conversely, some slope sites have very rugged landing zones and some of our so called "lead sleds" are landed hot on any and all sorts of surfaces. As such, a delicate leading edge will be very quickly damaged.
One dynamic soaring site I know has no landing zone as such. The planes are simply ditched into chest high lantana, a common weed here in Australia. They need to be very tough indeed. The vac bagged wings in this case have, typically, Eucalyptus species leading edges, while the hollow moulded wings will have lots of carbon fibre tow in the LE.
Jul 21, 2015, 08:26 PM
Registered User
Quote:
Originally Posted by DKNguyen
I guess it would be classified as a sport plane. How does the style of flying affect how ding resistant the leading edge should be. Are you trying to protect the leading edge from accidents? Ground rash from belly landings? Does having landing gear make a difference?

Well if you have landing gear and your worried about leading edge rash, then your going to have bigger problems to worry about
Jul 21, 2015, 09:31 PM
Registered User
Thread OP
Quote:
Originally Posted by hallo
I made wing wing once with a relatively thin uni-carbon piece cut in horisontally about 1/8-1/4" in to the leading edge foam, I gave it away and its new owner DS'd it in to a tree with only minor fractions at the LE as a result. It was quite sturdy I think, possibly 160g/m2 carbon skinned + some thin fiberglass and the leading edge was a couple 140g uni-carbon about 0,3mm thick plate probably, with a kevlar LE overlap.

Cheers
Thanks. Good to know. This was what I was wondering about.

Quote:
Originally Posted by invertmast
Well if you have landing gear and your worried about leading edge rash, then your going to have bigger problems to worry about
Haha, I suppose so.
Jul 22, 2015, 09:18 AM
The Junk Man
For all of my sport stuff with 1 meter (more or less) spans and wings cut from foam I do not usually bother with wood leading edges. You can, of course, but I have not found it necessary.

I normally use a single layer of .75 or .53 ounce glass (depending on the span) as the primary covering but I also cut 1.5 inch strips of .75 ounce glass on the bias and lay them on the leading edges first, wrapping around from top to bottom. The bias cut fabric is easily wrapped around the leading edge and the final layer over it makes a pretty robust sandwich.

Then I stick the cores in their release paper or mylar "taco" shells and vacuum bag the whole thing.

Tom
Jul 25, 2015, 03:55 PM
Everything is broken
JimZinVT's Avatar
There is a leading edge treatment that some of the DLG guys have used for a while that is both light and ding resistant. A thin slice is taken off the core L.E. and replaced with a solid carbon rod, split lengthwise. I haven't tried it yet myself but from all I've read it is apparently very strong, they've survived some dramatic mid-airs. I don't have a link but it was discussed in the "Zone Foils" thread a few years ago. Here is a quote from Phil Barnes that I saved from that thread:

"We add a split .050" carbon rod to the LEs of the two root panels. This is
for LE durability (don't midair a Zone :-)). To make room for the .050 split
rod, we trim about .025" off the LE of the perfect core. We have a jig to do
that. Just ask if you want details on that jig. That leaves the LE with a
squared off facet. We attach the split rod to the core with little strips of
light glasss and 3M77. The semicircular split rod shape is not really the
exact correct curvature of a LE, but we find that after adding the LE
fabric, that fabric does follow the proper curvature. The fabric just
bridges over what would be improper little dips at the rod/core junction.
Our LE fabric was 1.0oz Kevlar plus a narrower 3/4oz glass strip on the
first wing. While bagging, we added a line of splooge to each mylar LE."


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