Rear edge stiffeners ?

[jiott]

One other idea I saw on this forum was instead of the 3/8" tubes he used carbon fiber arrow shafts at midspan hysoled between the trailing edge and the rear spar; an interesting lightweight solution he claimed did the job. Maybe the member/s who posted this quite a while ago will chime in and verify.

[Kahle76]

One other idea I saw on this forum was instead of the 3/8" tubes he used carbon fiber arrow shafts at midspan hysoled between the trailing edge and the rear spar; an interesting lightweight solution he claimed did the job. Maybe the member/s who posted this quite a while ago will chime in and verify.

I used the carbon fiber arrows. You can buy used ones at you local archery shop for next to nothing.

[DesertFox4]

I used the aluminum tubes bonded into the trailing edges in my 7SS. No "scalloping" when shrinking the PolyFiber. Slightly heavier than the carbon rods some use but less chance of galvanic corrosion issues than between the aluminum tailing edge pieces and the carbon fiber. Those near the coasts might consider this type of corrosion with regards to sea water and the reaction between these two materials.
Not an "expert" on corrosion issues but read enough to decide to pass on the carbon fiber rods buried in the trailing edges with no way to inspect for corrosion issues.
Not a quick or simple fix if corrosion does get a foothold in the trailing edges. Anyway, food for thought. I do love carbon fiber but where I can see and inspect it.

[bbs428]

Interesting. I did a search and found in a salt water environment the corrosion can be significant.

"When Eurocopter started to mix carbon composite and aluminum in their helicopters structure and these machines were flown in the North Sea for the oil rig... Within a few weeks they had holes (you read right: holes) starting to develop. If I recall correctly it was less than 2 months!

If you do an Internet search you will find all of this well documented and some people involved with fixing these problems are still today very negative regarding aluminum and carbon.

Nevertheless, it is possible to mix the two with some good design, engineering and care."

Food for thought...

[Kitfox Pilot]

Thanks guys I will get some ordered. I am using oratex.

[Shadowrider]

I will play devils advocate.......unnecessary weight in my opinion but do what makes you most comfortable. Both of our planes we did not use them. We shrunk both wings to 450F and trailing edges are both straight. Wings are tight as a fiddle! When you shrink your wings you go longitudinally and start at the front of the wing so there is not much pulling on trailing edge verus pulling against the ribs. Of course we did a lot of things different than others on here like no rib stitching and minimal finishing tape. On another note this is what drove me crazy about kitfox. Where is the secret menu to order these "must" items? If something is required then include it with the kit!

[Kitfox Pilot]

I will play devils advocate.......unnecessary weight in my opinion but do what makes you most comfortable. Both of our planes we did not use them. We shrunk both wings to 450F and trailing edges are both straight. Wings are tight as a fiddle! When you shrink your wings you go longitudinally and start at the front of the wing so there is not much pulling on trailing edge verus pulling against the ribs. Of course we did a lot of things different than others on here like no rib stitching and minimal finishing tape. On another note this is what drove me crazy about kitfox. Where is the secret menu to order these "must" items? If something is required then include it with the kit!

I had no idea about the little pipes, just ran across them looking at the builders logs. I thought oratex might pull harder since its a tougher material but I guess not if you've done two you should know.

[Dave S]

Harlan,

I believe the instructions to include the aluminum tubes as an option was mentioned in my build manual (early S7); and, at the time I ordered them from aircraft spruce following the demise of skystar.

I see the addition as a way to increase the ruggedness of the trailing edge as well as dealing with the fabric shrinking stress as mentioned in the manual. I have seen way too many OOPS! happen in various hangars with visitors and I would rather see a dent in the perpetrator than the wing if at all possible.

Overall I think it is well worth the trouble but everyone's mileage certainly varies. Regarding weight - I just try to avoid eating too much stuff I shouldn't.

[Jerrytex]

Anyone know the size of this tubing 3/8" OD? What about wall thickness?

Thanks.

[kitfoxrk]

I just looked at the assembly manual on the Kitfox website. Page 8 of the fabric covering section has a note about adding the stiffeners. Says they are optional.

Bob