G'day,
My masts are 47' long with only 3' of bury.
My masts are 47' long with only 3' of bury.
Shows what can be done.
The diameter at the base is 10".At the mast head the diameter is about 6"{not going up the mast to find out excactly} At the base the wall is 1/4" thick. Each mast consists or three tubes of diminishig diameters .I do not know now if the wall thickness decreses with each tube but I would think it does,
So would I. How does the sail pass the diameter changes? Presumably these are faired in, but there must still be a wrinkle.
The sails are slab reefed and fold up like an acordian . When lowered there is of course a substantial gathering of sail at the tack,but it is no trouble to secure the flaked sail to the boom with fitted bungee cord ties.THe good thing is the sail can never get stuck as there is no track.The bad thing is in a breeze it is alot of sail cloth for onr person to handle.I had the same concerns as you about wether or not a sail with a zippered luff pocket would fold the same way but I have seen pictures of James Wharrams soft wing sails with zippered luff pockets flaked nicely. I believe my current masts are about 360 lbs It seems incredible that you can build a mast of similar dimensions at 110 lbs
110 kgs, 242 lbs. The rest is probably the overlaps from the tubes, different righting moments, safety factors and resin/fibre ratios. Any idea where your masts were built?
Do you think it would also be possible to reduce the diameter of the mast section.I know that the carbon feestanding mast on the wiley cat is narrower and taller.
Reducing the diameter is easy enough, but it results in thicker walls, not a bad thing at highly loaded areas such as heel, deck and boom..
Attached is an idea I had for battens for a ballanced lug sail with a luff pocket .The idea was that down haulls could act act on the rings with in the wishbone cambers allowing the wishbones to rotate and the battens to maintain leech tesion when reefed, It might work on a marconi mainsail with a luff pocket full battens and you cup camber idea.
I tried this (halfheartedly, I must admit) on the first Harry. Still got the sails if anyone is interested in trying it. Keeping the tension in the luff was one problem. We are doing similar on the 7.5m wing sailed prototype, but with a solid nose piece. This will not be reefed. The cup camber inducers are a problem on tapered masts when reefed or lowered as they do not fit around the bigger diameter mast as the sail is lowered. . So are pocket luffs with full length battens, as the batten end gets closer to the mast as the sail is lowered. A solution is to have the pocket taper inversely to the mast, with the battens terminating at the pocket/sail interface. Not sure whether this will work.
regards,
Rob
Regards Tim
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