Tandem Keel Tube Question

[Alan_Cheatham]

The builder of a 2 place tandem machine similar in design to the tandem Dominator has decided to use 2x2 .120" 6061-T6 sq aluminum with a spruce beam insert as a keel tube, is this an acceptable practice?

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[StanFoster]

Alan- I had to epoxy an oak block inside my mast on my SparrowHawk, but in hindsight, and after reading something that I believe was Chuck Beaty saying it could split the aluminum possibly as it swelled and shrunk with moisture changes. That has me doubting this practice, though I have never seen one split out yet.



Stan

[Alan_Cheatham]

Originally Posted by StanFoster

Alan- I had to epoxy an oak block inside my mast on my SparrowHawk, but in hindsight, and after reading something that I believe was Chuck Beaty saying it could split the aluminum possibly as it swelled and shrunk with moisture changes.

Found this post, I think it's what you were referring to Stan.

http://www.rotaryforum.com/forum/sho...8&postcount=11

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[i3 roberto]

I agree also water tramped inside wood can corrode aluminium , nylon , hi density polyurethane ,and small sise aluminium tube inside (jacket) its better election

[cbonnerup]

A better material would be FRP-Garolite of suitable dimensions located at the high stress area(s); low swelling, light, and strong. Tough stuff to mill however. I agree with the tube solution also; depends upon weight limits and section modulus required. However, (2) 2"x1" rectangular pieces would be stronger and just a bit heavier than a 2x2 if 'intimately' (stiffly) joined, but NOT welded.
I've been looking at this conundrum also.

Chris