LIFT STRUT TEST

[EDMO 1078]

Attached is copy of Kitfox lift strut test.  Note that the Kitfox 2 used 7/8" diameter struts.

The thumbnail is large, and when you click it gets larger - someone can resize it if need be - I donno how!

EDMO

Also NOTE:  I don't think there was any wood on the struts for this test!   But, this was a test in tension, and not in compression.

Edited 4 Apr 2014 by Ed In Missouri

[High Country 69]

Thanks for putting this up Ed, I've been thinking about my lift struts lately as I have the original 3/4" struts and am looking for the best way to go. Been thinking about just cutting the tubes about 6-8" from the ends and sliding 7/8" - 1" tubing over the stubs and welding it all back in place. seems to be the easiest way to strengthen them. I think the ends are supposed to be strong enough. what are you guys' thoughts? If I have to build them both from scratch I'm thinking it might be good to add a rod end to both sides...

[EDMO 1078]

I think you should be just fine by splicing the larger tubing over the stubs - you should fishtail and rosette weld, as per AC43-13.

- I had to make new struts and didn't want to cut up the old 7/8 pair because they were good.   My new ones are longer and the fuselage attach fitting has to be at a different angle.

I happened to find some nos aircraft rod ends at a cheap price - and they are 7/16 thread and 5/16 bolt - didn't think I needed the bigger ones, but it wont hurt either, so going to put them on all 4 struts.  Using 1" x .049 wall tubes.

EDMO

Edited 5 Apr 2014 by Ed In Missouri

[TJay 1041]

So do you still have the old 7/8 inch pair? forsale.

[EDMO 1078]

TJay,

     I have them, but since the strut fittings on the spars were located by the builder, there is a very slim chance that the struts would be correct for your plane if your fittings are attached.   Better and cheaper, I think, to cut ends off yours and put heavier tubes on them, making them the exact same length and width.  I don't know if anything about them changed between the KF1 and the KF2 models, or just diameter.  I think that the incidence was changed, so maybe struts changed too.  Mine would be good for someone who did not have their wing fittings installed.

EdMO 

Edited 16 Aug 2015 by Ed In Missouri

[TJay 1041]

yeah I should just make new stronger ones, I wonder how much the stock 3/4 inch ones will really take. Never heard of one failing so maybe building stronger ones is just adding weight again?

[EDMO 1078]

TJay,

    go back and read the strut test again - probably someone with engineering figures like Luke could figure it out, but if a 7/8 held for 15 Gs, (and only quit because a rod-end failed), your struts should exceed your GW by a LOT, IMO, probably more than your spars.

     I never have heard of a strut failure for any of the Foxy Avids....I had to make new ones because mine have to be longer, and a different angle because I raised my roof and wings.

EdMO

Edited 18 Aug 2015 by Ed In Missouri