Backstays and mainsails

I am in the process of doing a preliminary drawing for an 11 metre cruiser/racer. I want to incorporate a roller-reefing, fully battened mainsail. However, this brings about the problem of the upper sections of the sail overlapping the backstay(s). Mine is surely not the first to encounter this problem - indeed I have looked at a number of sailplans which seem to incorporate this exact overlapping situation (see attached file). I find it difficult to believe that the sail simply drags itself across the backstay(s) every time the boat comes about.
Suggestions - alternatives - explanations - help!!

 

well actually..

yes!
Sorry could not see your file but The Dashews are big fans of the big roach mainsail. A miss-calculation was originally responsible for their discovery that the sail tacked just fine. Their site is here check out the Q+ A section.

I believe their response is " re-inforce it!". Also if you dont get an ans in the Q+A post to Steve Dashew and he will get back to you.

Hope this helps

PS now go and vote for a racing sailboat design here!

 

I'm sorry that you still can't see the forum images Paul - I just spent some time today looking at a dedicated server on a different network partially with you in mind though, so in the next month or so hopefully I'll finally have them fixed for you. (I'm very very happy with our existing host and network though, other than this one problem for which I cannot find a solution, so making a switch is difficult.)

P.S. Off topic, but if anyone else experiences problems with broken images appearing, please let me know. So far it only affects Paul, and we've tried everything and cannot narrow it down. I'm still curious though, and would like to know if anyone else has any problems with our forums.

 

Thanks Paul. Shame you were unable to view the image - it can be found at www.aerodyneyachts.com/html/default_sail_plan.html
I couldn't find the Q&A section of Dashews web site, but their later designs certainly illustrate what I was talking about. I'm amazed that there isn't something a little more sofisticated than allowing the sail to simply drag itself across the backstay(s). I would have thought it would results in rapid wear and tear - especially where the battens are located.
However, Since my initial post, I have decided to make some alterations to my rig design. With swept back spreaders easing some of the burden from the backstays, I believe that I can successfully run twin backstays to the top of a strong radar arch which is located at the vessels transom (and if necessary from there to the aft corners of the boat). This will give sufficient room to allow me to include at least some roach in the main.
Any thoughts?

 

Paul - Had another look - found the Q&A section @ Dashews....lots of info - thanks...

 

I remember reading somewhere, about an Open 60 I believe, that the skipper had to reef the main before tacking because of the extreme roach. However, I don't see the amount of roach on the Aerodyne as being a problem. It should easily glide over the backstay except maybe in very light conditions. As for wear, a long distance cruising boat (the purpose of the Aerodyne), will often remain on the same tack for days so it wouldn't be as much an issue as for an around the buoys racer.

For another solution to the extreme roach issue check out the wing mast version of the Next 47 at www.nextgy.com. They've eliminated the backstay altogether by sweeping back the spreaders to an extreme - which introduces a new set of problems.

 

After my last post I looked up what the Dashews had to say about mainsail roach. The following is from Steve & Linda Dashew, Offshore Cruising Encyclopedia Second Edition (Tucson: Beowulf Inc., 1999), 99.

"To minimize chafe... We found that a piece of PVC pipe, slipped over the end of the backstay and held in place with a hose clamp, takes care of chafe from the backstay, reducing friction when tacking and jibing...(the PVC pipe is on only the upper portion of the backstay, where the roach overlaps)."

They go on to say "To protect the sail,... UHMW plastic is sewn over the batten pockets... The UHMWPVC (sic) combination allows the sail to blow by the backstay in relatively light airs."

As for how much overlap can be used they write "On Sundeer's mainsail,... we went to a 28-inch (711mm) overlap. When the first of the Sundeer 56s went into the water we went really aggressive, to a 32-inch (812.8mm) overlap..."

 

3 things

1) James - I was just heading to my copy of the encyclopedia to type that same paragraph out !

2) so heres a favourite (related) ocean cruising quote instead
" We only gybe on Tuesdays and Thursdays as we like to keep the weekends clear"

3) Jeff - as you know I can get the images at work and I keep a copy of Opera handy that with some messing around lets me get to them at home. - so please don't worry too much about it - you have enough on your hands with the great site!

Cheers

Paul

 

(Running) Backstays

What about using running backstays instead, like old cutters used? I have never sailed on a boat with these, so have no idea if they are a complete nightmare when tacking, presumably only the windward one is kept taut, and the slighly swept back shrouds stop the mast falling forwards too much when both running backstays are eased during tack/gybe?
Anyone any thoughts on this?

 

For an example check out Oswald Berckemeyer's designs at http://www.berckemeyer-yacht.de/. Many of his designs forego the backstay and use runners in conjunction with swept-back spreaders.