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bransom(at)ucdavis.edu
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 Posted: Tue Feb 26, 2008 10:12 am Post subject: bow tip diagonal braces (was structural failure) |
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On the earlier model Firestars, plans called for two crossing diagonal
braces in the bow tip area, aft of the main spar. IIRC, plans called
for these to be tie-wrapped together to avoid chaffing. They chafe
anyway, enf to have worn partway through in mine by 200 hours. As well,
tie-wraps get brittle and can break in 3-4 years. The chafing is from
the 2-stroke vibration, not the 4" wheels. BTW, the plans also called
out an option to beef this area up differently and stronger because it
seemed the most prone to damage in a ground-loop. I believe those who
say these diagonal braces may not be important for flight loads.
I used proseal in a couple other areas where this was a concern, notably
where the steel drag strut braces run right along ribs 2 and 3. Just a
dab in between, right where two members cross each other allows them to
carry their own vibrations and strains without chafing, and Proseal will
never ever unbond.
I might call attention to any new folks that Kolbs are proven in the
area of structural integrity more than most. I don't know of any other
plane where the original designer put his name on the product to the
extent of purposefully exceeding the envelope, in flight, to find what
broke first. That said, it is our responsibility to maintain them so
finding and fixing wear, fatigue, or corrosion is crucial.
-Ben/ KXP
TK wrote:
| Quote: | WhiskeyVictor36(at)aol.com wrote:
>
>
> In a message dated 2/26/2008 12:24:06 A.M. Eastern Standard Time,
> DAquaNut(at)aol.com writes:
>
> To reveal the 5/16 " X. 035 alum tube running from the outboard
> trailing edge to the inside of the outboard end of the main wing
> spar had severed completely .
>
> Ed,
>
> This has happened to many Kolbs, including mine (both
> wings). Basically that tube just holds some tension on the
> trailing edge spar and wing tip bow to help keep them
> in position, so as not to have it bend back during rough handling
> or contact with the ground. It is not to serious and I continued
> flying for awhile, but kept checking on it to be sure it wasn't
> bending back. Finally, I elected to repair mine by using a
> larger, 3/8" diameter tube. The worst part was making the
> decision to cut an access hole in my nicely painted wing fabric 
>
> Bill Varnes
> Original Kolb FireStar
> Audubon NJ
> Do Not Archive
>
Ed, Bill,
How many hours did you have on it when this happened? I haven't heard
of this before and haven't had a problem so far ( keep my mouth shut
or I will ). Having to replace my aileron gap seals after nine years,
not bad for book tape, and I have the wings off to do so. Didn't
notice any problem with this diagonal tube. Have had some pretty
rough landings over the years. Will be keeping an eye out for this on
my preflights.
Terry - FireFly #95
*
*
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WillUribe(at)aol.com
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| Posted: Tue Feb 26, 2008 10:43 am Post subject: bow tip diagonal braces (was structural failure) |
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Hi Ben,
My plans didn't call for tie-wraps, here is a picture of my braces.
Regards,
Will Uribe
El Paso, TX
FireStar II N4GU
http://members.aol.com/firestartwo/Kit1.html
--
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WhiskeyVictor36(at)aol.co
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| Posted: Tue Feb 26, 2008 11:16 am Post subject: bow tip diagonal braces (was structural failure) |
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In a message dated 2/26/2008 1:13:17 P.M. Eastern Standard Time, bransom(at)ucdavis.edu writes:
| Quote: | On the earlier model Firestars, plans called for two crossing diagonal
braces in the bow tip area, aft of the main spar. IIRC, plans called
for these to be tie-wrapped together to avoid chaffing. They chafe
anyway, enf to have worn partway through in mine by 200 hours.
Ben,
I'm glad that you mentioned that. I'd forgotten about that part. When I replaced the long tube that broke, I used a small square piece of aluminum sheet (.032" x 2" x 2") riveting it to the two tubes where they cross (4 rivets).
Bill Varnes
Original Kolb FireStar
Audubon NJ
|
Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.
[quote][b]
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