I have been a little too busy with the havoc in the F16 forum to reply properly to your message. Are you bulding the mast of 4mm ply coated with glass? Do you have any idea about finished weight compared to an alu tube? Why did you choose to strip with ply when you could have bent the ply over a mould and glassed it to shape? Just curious and trying to learn.
I really love your attitude, with the wine and everything. You even have a female co-builder!
The idea is to put the strips I female frames and glass them together whit a layer of BX on the inside. The two halves are then glued together and reinforced from the outside with glass or carbon. The inside of the spar will be filled with a light weight foam (20 kg/m3) I have considered the method of building a box in the middle, making the both ends in solid wood and bend the ply over it. The problem is that for a spar with small cross section you would get a lot of solid wood and very little ply. I definitely hope to end up under the weight of a alu superwing (19kg, the weight of the Sydväst superwing!!!) Don’t start to build one yet, this is only an experiment. But if it works all right it could definitely be a cheap way for the homebuilders. I like female builders…
Hmm, why would you fill the mast with foam? Over time, will not the foam soak up humidity making it heaver? All the litterature I have seen says that foam and wood is a very bad combination, both weight wise and structurally.
If you can build the mast in ply/glass, and come in under the weight of the same section/length in alu, I'll fall off my chair with my jaw dropping to my knees <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> I truly wish you all luck with that goal and really hope you succeed. Would be fantastic.
There are too few female builders! Being stuck with Frode and Omar in the garage several times a week have made this very clear to me <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
Please keep us updated on the project. I am very interested in the results!
Gato, Maybe you allready have answers for this but I'm curious about the foam filling issue, same as Rolf:
from my experience working with foam, poured into tight, confined sealed spaces - it will probably deform the mast shape, unless you provide some "exit holes" for excess foam to get out. It will definitely add rigidity to the mast, but may also lead to damage.
This is much nicer than the F16 forum. Good luck with your projects.
Sorry for taking some time in answering, been away in the workshop for a week, and there is no internet there. The only reason for filling the mast with foam is not having it filled with water when capsizing, there are no structural benefits what so ever, only the problem you mentioned. I am not intending to inject the foam into the mast, but cut the foam to shape with a warm wire and put them inside before gluing the two halves together. In the mast for the mini there will be no foam. As for the weight I am targeting the same weight/lm as an alu spar of the same profile, and so far it looks good. Will try to get up some pics on my page.