Twin sheet mainsail(A frame style) - anyone with experience?

[oscarkramer]

The German system is preferred as it is a single line, possibly double-ended, but a single sheet to adjust.

The two-sheet system is a pain and you end up with bad sail trim because it is just too much work to get the triangle correct.

A traveller across the top of the arch would be the best if sail trim is important. A vang will help as well.

[Cpt Mark]

Seems like a lot of the newer boats, Bennies in particular, are losing the traveller all together. My boat has the mainsheet deadended to the aft of the boat,. Horrible location as the mainsheet hits ou in the back of the head. Putting it on top or adding a traveller is a lot of work in order to handle the loads and you have much more loads than I.

The design I finally settled on was taken from a new bennie 38.5? They have a frp arch that bolts onto the boat that holds 2 blocks. I found a company called CarbonCore that makes an awesome laminated product. I went with 2 inch thick material and will fabricate the arch out of that.

[chowdan]

I think I am pretty sold on the German sheet setup. My clutch is a tad small for my existing sheet(old and needs replacing anyways so not worried about ruining the line), but I am going to have it run to both jib sheets with clutches so that I can use the windward sheet for the main.

I don't have great service still so pages load slow, that CarbonCore sounds interesting. Are you going to have them shape it how you want then you layup glass over it, or do they layup the glass? I don't have space to really do a lamination for an arch this size, maybe I could do it in a public parking lot with poly/vinyl, but epoxy wouldnt be possible due to curing times. I really like the idea of FRP arch, but I'm struggling with time constraints, coming into winter now(spaces I have access too are all outdoors) and being able to outsource the build means I can focus on other things at the same time(plus work).

I am also thinking that I'll use a pulley on either side of the arch to similar to how the newer benes are. Harken load calculator for my mainsheet under full sail @ 45knts of wind indicate about 14,000lbs. Obviously I wouldn't be under full main at that wind speed, that'd be insane, but nice to know if I spec something out to this rough area I should be totally fine.

I lean towards a high grade aluminum over stainless due to cost of material, my Atlantic tower is aluminum and the tube size is sch 40 from what I can tell and it has a nice hand feel(holding on). Also feel like I'd be able to find more welders that can work with aluminum in the Seattle area due to the aerospace segments near by.

[Franziska]

Originally Posted by oscarkramer

The German system is preferred as it is a single line, possibly double-ended, but a single sheet to adjust.



The two-sheet system is a pain and you end up with bad sail trim because it is just too much work to get the triangle correct.



A traveller across the top of the arch would be the best if sail trim is important. A vang will help as well.

I disagree.

The double mainsheet is fairly easy to adjust, especially on a cruising boat and gives you the same amount of sail control as a traveler for a fraction of the cost.

Just needs a little bit of practice, as most things new in live need.

We do have an A frame doublé mainsheet and are happy with it.

[Cyrus Safdari]

This video of a Ted Hood design has a twin end-boom mainsheet system with a stationary centered bridle
The centered bridle eye overcomes one of the issue of difficulty in centering the boom with twin sheeting
I think a further improvement could be in making the center eye of the bridle movable , by being able to adjust the bridle legs using swiveling base cam cleats so that the center eye can be raised, lowered and moved side to side
https://youtu.be/gGEpjbie8dI

[wingssail]

Originally Posted by Cyrus Safdari

This video of a Ted Hood design has a twin end-boom mainsheet system with a stationary centered bridle
The centered bridle eye overcomes one of the issue of difficulty in centering the boom with twin sheeting
I think a further improvement could be in making the center eye of the bridle movable , by being able to adjust the bridle legs using swiveling base cam cleats so that the center eye can be raised, lowered and moved side to side
https://youtu.be/gGEpjbie8dI

It seems like 10 ways to rig something that is accomplished easily and efficiently with a traveler. User a German system, and have a traveler on the arch, if you so want an arch, and travel the main up and down simply and easily and so effectively.

[5BTM]

"Adventures of an old Seadog" (YouTube) appears to have sailed from Europe to New Zealand with twin sheets; nothing fancy, no bling no gadgets.

[Bowdrie]

Originally Posted by 5BTM

"Adventures of an old Seadog" (YouTube) appears to have sailed from Europe to New Zealand with twin sheets; nothing fancy, no bling no gadgets.

I've been following him and have paid attention to his sheeting system.
It appears that one of the sheets has a 4:1 purchase and the other a 6:1, perhaps he just assembled it from whatever blocks he had on hand?

[Franziska]

Originally Posted by Bowdrie

I've been following him and have paid attention to his sheeting system.

It appears that one of the sheets has a 4:1 purchase and the other a 6:1, perhaps he just assembled it from whatever blocks he had on hand?

Works the same as any other A frame sheet though.