Unfortunately my aluminum mast is broken… for the second time. It is the mast it selves so luckily it did not went overboard. I can simply have it repaired but then I run the risk of getting the same problem back. Does anybody have any idea’s or experience? I am looking for idea’s on options to strengthen the mast additionally. Or maybe you had a new aluminum mast designed and build? Please let me know! This is one of the UK build F35’s. Thanks, Rik
I got a little ahead in this direction as well. It is not that difficult to get an aluminum flagpole/lightning column of about the right size. Then you need to strengthen it. This is also most likely the way they created the original masts (got this somewhere on this forum) This strengthening can be done with more aluminum.
However I am also thinking about doing this with Carbon. Problem with this, is that Carbon and Aluminum don’t mix for various reasons. But how about taking an aluminum flagpole, strengthen it on on the inside with a carbon rod and isolate the carbon from the aluminum with rubber bands at regular intervals. The same stuff which is use to close the fill the gap between the mast and the deck for example. Would this be an idea?
You should find an Al pole that does not need strengthening. A light pole is stronger than a flag pole. My F40 masts has .25 inches wall thickness. It was made from two pieces, but I don’t think it was for strength, rather that’s all they had. Bottom 20 ft is a straight 10 inch pipe. Top is tapered to 4.5 inches. The top is pushed into the bottom, and bolted in place. Overlap is about 4 ft. Then there is a fiberglass shell to fair out the transition between the two sections which its not structural.
If you really want to stiffen an aluminum mast the carbon would have to go on the outside. There are woven socks/sleeves that can be used for that. They come in polyester and fiber glass, too, which you could use to insulate the carbon from the Al. I don’t think this all is a good approach.
Erik
Erik, this is highly interesting! So your mast (including the lower part which is fitted in the deck and the keelstep) is only 0.25 inch (approx 6.5 mm) thick? There is no additional internal or external tube?
And - pardon me asking - are you using your F40 in rough environments (open sea, 6+ beaufort) or more moderate?
This could imply that the problems we encounter with the Alu masts on the F35’s could be assigned to the (bolting/welding) used for the strengthening.
They are the original masts - I don’t think there is any history of F40 masts failing due to wind/weather. Bridges maybe 
There are different Aluminum alloys, and whereas I think the stiffness is the same, the yield strenth is different. I don’t know what alloy mine are made of, but I suspect nothing exotic and most likely of the 60xx or 50xx series, which are quite common.
Erik
All,
for record sake I think it is good to post how I resolved this. So basically I had three options
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Going for a new carbon mast. This is by far the most expensive solution. See post why I did not went for this.
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Buy an aluminum lighting pole and strengthen it with carbon. Experts highly advised against this. Aluminum and Carbon are chemically not a good combination. Will lead most likely to massive corrosion.
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Buy an aluminum lighting pole and strengthen it with an additional aluminum pipe in the bottom part. This is the one I went for. I bought a standard 12,5 meter, slightly conical lighting pole (Model “Boulevard”
) from a lighting pole vendor with a wall thickness of 5mm. Additionally I bought a 4 m aluminum straight pipe with a wall thickness of 10mm. This pipe was fitting inside the lighting pole.
The weak point in a construction like this is the area where the 4 m pipe ends… This was also the point where my previous mast broke. The issue would be that you go there suddenly from 15mm to 5mm thickness. This should be avoided. This could be resolved by using a lathe to reduce the thickness gradually over say 30-50 cm’s. It is however very difficult to find a lathe which is able todo this. A much cheaper alternative is sawing big V shaped parts over a length of 50 cm’s out of the inner pipe. This is well known trick among aluminum mast builders. So this is what I did.
Have been sailing since then, and everything seems to go quite well. Which makes sense because I have now a mast which is construction wise much better at the original mast.