( Cap Strips ) 2024 T3/T4 versus 6061 T6

[Donny Morley]

Just wandering if I could use the 6061 T6 for main spars as well, as this is also used for the rear spars.. I can get this local, and cheaper than anywhere. Or would it be better to make the rear spars out of 2024 . Trying to understand the most significant differance.. Any thoughts on this would be great.. Thanks and best wishes to all ..Donny..at dadknowsbest@hotmail.com

[Gavin Chester]

Bobs strength calculations are based on using the materials as per plans . there are thousands of flight hours on the design . you will not go wrong by sticking to the plans, This way you will not need to be a test pilot every time you fly.

[marcusofcotton]

Definitely not okay to use 6061 for main spars, not enough strength. Should be able to use 2024 for the rear spars but why would you want to??? It is more susceptible to corrosion, costs more, and you have a cheap local source for 6061. Anytime I go to second guess an engineer (and I do), I like to start out with lots o' studying.

Mark J

[Donny Morley]

Thank you very much Mark, for your input in helping me to understand more about the differance in material. I was thinking of how to beafup in any way I can. I'm sure you understand. This is for my Grandson on floats.. I think I will just keep it simple. Sounds like a ( plan )

[Donny Morley]

Thank You Gavin for your responce. I understand what Bob has illustrated in his plans.However, regarding the use of differant materials in the cap strips for making the front and rear spars, still eludes me. I guess I mainly wish to understand the significance between the front and rear spars that requires the use of a differant alloy. Any higher understand in this regard, would be most helpful to me, and much appreciated. Thank's very much

[X'N]

My guess the strength isn't needed for the rear spar so he went with a less expensive material.

[Enewton57]

2024 is stronger than 6061. Bob designed the main spars with 2024 because they take the majority of the load through the wing strut. The rear spar has less load and the 6061 was adequate strength for it.

[mswain]

2024 is stronger, better strength/weight ratio and more fatigue resistant than 6061....all of which are important in the main load bearing structure of the wing. I think X'N is right, Bob chose 6061 for the rear because 2024 was not needed, so the lower cost material prevailed.

I can get 6061 around town, but I could not get 14' lengths from any supplier.....I had to get the rear bar stock from Wicks.

[marcusofcotton]

Donny, since you are talking about floats, make sure you do the float plane fuselage reinforcements outlined in the newsletters for same.

Mark J

[Donny Morley]

I am sure glad you guys are here, and such a great help. Thanks Brothers...