I figured that since I spend a considerable portion of my life thinking about this it warranted its own post.
Here is the problem. The Duo 660 is set up for unstayed, rotating, carbon masts. But I want to be able to throw out the sail for downwind sailing, so I need a boom.
Puget sound wind is often out of the North. Puget sound is mostly a North-South body of water, so
usually you are beating to the wind or on a run.
The conventional answer is to use wishbone booms.
Then I lose most of the benefit of rotating masts (can't be used to furl or reef).
Also need to install sail track: risky or expensive on carbon masts
This is my fall back position if nothing better comes along
Freedom yachts used rigs that used sails that wrap around the masts (read no sail tracks) but still had wishbone booms. I think they must have used topping lifts but cant quite figure out how they rigged the snotter, or why the wishbone wouldn't just bang into the mast. Not to mention reefing.
I hate (I should stay dislike) the Bermuda rig. The presence of the boom vang and topping lifts give away the issue here. I suppose its feature is that you have controls (of various levels of effectiveness) to influence all areas of sail shape. The bug is that you have to use all those controls. Besides I don't think it a good option for an unstayed masts.
I thought about trying to design a 3-D wishbone that could freely rotate about the base of the mast but curve up and around the sail to engage the sail clew like a conventional wishbone. But this entails some complex and likely heavy bearing hardware. And I'm not sure I could ever trim this right in a breeze since the downforce on the leech would likely be limited to the weight of the boom (which I would be trying to keep light). A regular wishbone accomplishes this by pushing off the mast.
My latest thought is to use softwing sails, perhaps junk rigged?. This is sexy, but not sure if it would be too heavy. And I still lose the rotating masts, but wouldn't have to deal with sail tracks. Of course there is expense to consider as well. The idea would be that no boom would be required because of the battens. But then how to reef?
You can see why this leads to sleeplessness.
Hi Esteban
ReplyDeleteI read your latest entry with interest , especially so since i was faced with a similar quandary. Before I comment further could I ask what general principle you were thinking about. For example , pocket luff sails, furling round the mast, or a conventional set up, boomless. Also, as a matter of interest, what are you using for masts, if I can ask.
You can contact me direct if you like , contact details should be available through the forum.
regards
Bryan
Hi Bryan,
ReplyDeleteOf course you can ask. I want to stick with carbon masts, since that is what is on the plans. That said, exactly how these come together is an open question. Bernd's plans call for two tubes epoxy bonded together but adding a sail track would be problematic (I think) .
Other than being pretty committed to carbon everything else is open. There are so many pros and cons to consider. I really would like soft wing sails or at least pocket luff sails but I really do think I need a boom. I'm reading up on soft wing sails now, if I can convince myself that I can afford the weight and complexity this would be my favorite. Once I get some of this reading done I'll do another rig post hopefully I'll have my thoughts better organized.
-Esteban
Hi Esteban
ReplyDeleteyou could use fibreglass (as opposed to cf) masts and save a lot of $$$ without adding much weight. We have got great spar makers here , but there must be some in your neck of the woods , surely. Personally, I would not attempt to build my own masts. If I was going through the whole procedure again, then with hindsight I would use a more or less standard set up, making sure the boom heights are adequate for head clearance (sitting, at least). One thing with the biplane rig, is you have to watch out for 2 sails coming across when you tack or gybe. With my boomless set up it is harmless , but I get reduced performance except hard on the wind.
I would also use mast tracks, and you can get uv treated plastic stuff, and also cf or glass ones. Attaching them is pretty easy= epoxy, and some glass overlap for the cf and glass track, and sealant for the plastic stuff.
The other benefit of going to a more or less standard set up is you can get a sailmaker to understand exactly what you need- this is a bigger deal than what you might think. Check out Whirlwind Sails in San Diego (Chip Buck) . He will make exactly what you need, and you will find that his prices are most reasonable. I would use him again, even though we have got good sailmakers here. i dont know what you were budgetting , but I reckon Chip would do you a couple of mains in 6 oz dacron for not much more about US$ 1000 each.
The other thing I would mention, regarding setting up the boat for the masts , is that you might organise an adjustable or movable mast location , because it is very hard to get the c of e exactly right with unstayed masts. With stayed masts of course you can address this with the rigging, and, with a normal central mast with fore sails, you can fine tune the boat with the right selection of foresail/ main for the conditions of the day.
Anyhow, you've got plenty to work on in the meantime. Keep up the good work, I enjoy checking in on your progress each week
regards
Bryan
Hi Bryan,
ReplyDeleteThanks for the input, I have poked around a New Zealand spar maker C-Techs website. The prices were eye watering until I figured out the prices are in $NZ. Still a big investment. I had not thought about adjusting the position of the mast. Seems like a heavy lift from a design and execution standpoint. It might be easier to adjust rake. Would have to be very careful of the bearing set up. I need to settle a philosophical question for myself which I think revolves around risk. I could go the low risk route, conventional as you say (sail tracks etc) or I could take some risks and try for a soft-wing sail or a 2 ply lungstrom. Its too easy to get lost in the details of these options, I first need to consider how many resources (effort, time, money and risk) I am willing to spend on the rig. Its one of those things that I don't think there is a right or wrong answer. But I do need an answer.
Also thanks for the recommendation on the sail maker. I was going to try Polysail (link is on the usergroup). I was thinking about doing a post on suppliers I have had reasonable luck in finding things. Of course the post would be the the style of this is where I've found stuff. My experience is generally that if your careful to know what you are ordering you generally get the right thing.
Thanks for following along and chiming in its good to have someone with experience that is willing to share onboard.
-Esteban
Hi Esteban
DeleteI understand what you're going through. Your project is similar to mine, though yours is a lot bigger.
I dealt with C Tech, they are very close to me, and they were great. I was only ordering the cf front crossbeam from them for a start, but they showed me some "cosmetic seconds" they had in stock in their masts that were nearly exactly what I needed. So the prices were really good, and also they made up the bearings and attached them, and supplied the receiver tubes, plus I got some various pieces of flat plate for backing plates etc, and glass tubing for my bow net attachments. They were great to deal with , so you would have no worries if you were going for the top$$ version for your masts.
You could also try Killwell in Rotorua. They are similar to C Tech ,but they do a wider range of products. Maybe a conventional epoxy glass lay up, which would be more economical.
The other idea , which again, I originally considered for my boat , and which would work for yours, I am sure, would be Bernds gunter rig style. Which means you could use a straight, untapered lower section, in other words a tube of the correct wall thickness and strength, to which you glue and glass on the sail track. I can also show you methods I learned about for using glass tube for the sailtrack which you rout the slot in, once attached on the mast. I know there are manufacturers of fibreglass tubing in the USA.
I guess a lot comes down to time and effort vs $$$.
If you do go the conventional sail method, Chip Buck is your man, for all odds. If you were going to try something like the split junk rig like Mike did with the red little tri, you could sew up your own pretty easy. We just bought a new sewing machine for making some sunshades and sail covers for NZ$ 300 that would absolutely eat any weight of sailcloth or polytarp fabric.
Plenty to work on. Keep up the good work. (I reccomend a practise run with your rudder blade)
regards
Bryan
Bryan,
ReplyDeleteGood input. I'm working through options and am planning to do a post once I have some of these thoughts organized, your suggestion of a glass mast is definitely making the list of options. If that one wins out your expertise on mounting a sail track will be much appreciated. I won't be going with the gunter, not because I have anything against it, I'm just committed to a bi-plane
-Esteban
Hi Esteban
Deleteall good.
Re: gunter rig- I meant biplane gunters- I dont see why they would behave any different than when on a single rig. Benefits: shorter masts, easier to make ( non tapered ) easier to lift into position. Negatives- dont know, other than the sail making- maybe you could sound out Bernd on the idea. I certainly wouldnt try to talk you out of the bi plane rig- I still really like it on my own boat
regards
Bryan
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