Slickest folder ever

[DIY Tri Guy]

Lowering the sail would be the most difficult option. It's as far down as it can go. I'm trying to start the helm balance process by moving the COE forward. I made a new mounting plate yesterday for the pivot point where the mast meets the deck. The new pivot hole is about 2.25" farther aft, which increases the mast angle from about 76 degrees to 84 degrees. I think I can get it vertical if I have to.
I'll see if this makes any difference before trying my next-easiest fix -- moving the leeboard aft. I really want to avoid making changes that will hamper the upwind performance, because this thing pulls like a freight train close hauled. Yesterday I temporarily replaced the 90 sf fan sail with an 84 sf leg-o-mutton for a test. The balance was great, but I felt like I was dragging an anchor. Nowhere near the power of the fan sail.
- Frank

[rapscallion]

Do you believe you will have the same upwind performance if the fansail was vertical?

[DIY Tri Guy]

I can only guess, but I'd say it probably would. I have a suspicion (and I may be the last one to realize this) that there's something you could call an "effective COE" that is not where the actual COE is on a sail. On these fan sails in particular, I suspect that the COE is effectively moving aft as wind speed increases.
Unlike "normal" sails where the max draft is (supposed to be) about 1/3 of the way aft of the mast, I think on these fan sails the point of max draft -- and max pull pull -- is more like 2/3 of the way aft of the mast.
And because the CF mast is so flexible, this may be aggrivated even more in stronger winds. The mast bends farther back, moving the COE still farther aft, and compounding the weather helm. Maybe a stiffer mast would help, but hey, I'm on a budget here!
- Frank

[rapscallion]

Wow, you might be right about the CF moving as much as you suspect. What are you using for a mast now? maybe an old carbon windsurfer mast bought off of craigslist would work. I bought one recently at a very favorable price.

[DIY Tri Guy]

That's exactly what I'm using - an old 500 cm windsurf mast from Craigslist. It's a bit more flexible than I'd like, but it's long enough, it's really light, and it cost me just $50 two years ago. Seems to be in great shape. I'd buy more of them, but haven't seen any for sale since.
- Frank

[dstgean]

Originally Posted by DIY Tri Guy

I can only guess, but I'd say it probably would. I have a suspicion (and I may be the last one to realize this) that there's something you could call an "effective COE" that is not where the actual COE is on a sail. On these fan sails in particular, I suspect that the COE is effectively moving aft as wind speed increases.
Unlike "normal" sails where the max draft is (supposed to be) about 1/3 of the way aft of the mast, I think on these fan sails the point of max draft -- and max pull pull -- is more like 2/3 of the way aft of the mast.
And because the CF mast is so flexible, this may be aggrivated even more in stronger winds. The mast bends farther back, moving the COE still farther aft, and compounding the weather helm. Maybe a stiffer mast would help, but hey, I'm on a budget here!
- Frank

With your mast way up in the bow like you have, your COE will vary quite a bit just sheeting in or easing out the main. Think of your boat a bit like a catboat for a moment. They use a centerboard and a huge rudder to deal with savage weather helm. You can tame that a bit by going with a large balanced rudder, moving the leeboard forward as much as you can stand (until you get a trace of leehelm on some point of sail) or moving your rig aft some. Or a bit of all three....

Have fun, take pictures, and I'm hoping to see it in person in June!

Dan

[DIY Tri Guy]

Great news - raking the mast forward another 8-9 degrees or so seems to have made a real difference. Laura and I took two boats out so I could do some meaningful testing. Both her boat and her skill level are very well-established quantities, and her boat with the 84 sf sail can be hard to catch in light-moderate air. I was able to stay with her in light air and pull away on all points of sail when it got up to 7+ mph or so.
Sorry we didn't take photos, but it was supposed to be a very light air day. However, a few times we really got some excellent sustained gusts, and I probably hit 12 mph a few times. None of the "bad behavior" from the other day was in evidence. The leeboard was easily able to keep me in the sweet spot. So for now, no more mods.
Hope you can make it, Dan!

[edvb]

DIY Tri Guy

Great to hear. Isn't experimenting and getting a positive instead of a negative so much more rewarding! I hope I have the same luck as you this weekend when I finish my sail.

Sooner or later you will be at it again getting the perfect balance with your leeboard set at its best angle. Go ahead bet me! Do you feel Lucky.

[edvb]

DIY Tri Guy

I also found out that moving forward or backward just a couple inches made a big differance in the helm. Try it once and see for yourself.

[rapscallion]

Originally Posted by DIY Tri Guy

Great news - raking the mast forward another 8-9 degrees or so seems to have made a real difference. Laura and I took two boats out so I could do some meaningful testing. Both her boat and her skill level are very well-established quantities, and her boat with the 84 sf sail can be hard to catch in light-moderate air. I was able to stay with her in light air and pull away on all points of sail when it got up to 7+ mph or so.
Sorry we didn't take photos, but it was supposed to be a very light air day. However, a few times we really got some excellent sustained gusts, and I probably hit 12 mph a few times. None of the "bad behavior" from the other day was in evidence. The leeboard was easily able to keep me in the sweet spot. So for now, no more mods.
Hope you can make it, Dan!

That's good to hear!

[DIY Tri Guy]

Thanks for all your support. I sure hope the solution continues to work when the wind gets up over 10-12 mph.
I did try leaning back a few days ago, in the midst of the problem. It did seem to make a bit of a difference, but it's not practical to move my fixed seat fore or aft enough to really solve the problem. Maybe I should make my seating more flexible next time I experiment with oddball sails...
- Frank

[upchurchmr]

Frank,

It might be "relatively" easy to make the seat move fwd or back by using tracks like a sliding seat rowing rig. Perhaps the harder part would be to to have a lock to temporarily fix the position of the seat for that point in time.
I believe you might get an overall benefit in performance, given that small multihulls are notoriously pitch sensitive. I'm thinking day sailing cats where my crew and I have been up at the front crossbeam (light air) to back at the back one with the crew practically sitting in my lap (in very heavy air). Your boat shouldn't be quite that bad, but the principle applies, I think.

[DIY Tri Guy]

I'm sure you're right, Marc. Prior to now, I was able to make everything "fixed" in my boats -- seat, pedals, leeboard, mast step, etc., because I had learned from extensive experience exactly where it all needed to be for a perfectly balanced boat.
But that was when I was always using the leg-o-mutton sails. This new kind of sail rig -- especially one with an adjustable CF -- requires a more flexible design.
My next major project is a boat for the Everglades Challenge (the first leg, at least). Why? Because Laura wants to give it a try! She wanted to try it by herself, in one of my boats. But I insisted on coming along, so now I have to build a "quick n slick" tandem tri. But it will definitely have more flexibility than past designs.
- Frank

[upchurchmr]

Frank,

Great to hear its working out.
Let us know about the ideas for the EC. I bet the conditions in this year would have tested the boat. Reefing and sleeping would probably have caused issues to start. "My guess is your simplicity will be challenged". Please keep us informed.

Buy the way, I am still waiting for the "how to design a good leeboard" article. Also the pictorial on the easy up mechanism have disappeared. Normally I copy anything I really want to look at again, but I missed those.

Marc

[spidennis]

make sure you head over to the watertribe.org forums and look over what the new reefing rules are, plus there's the whole required equipment list to get ready with. Spot Tracker, and plbs, and the list goes on. start on it now so you're not rushed when it's close to the wire. Get a spot now and get used to it!