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Thread: Newbie needs help with small DIY sail plan, trimaran setup.

  1. #246
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Actually, I decided to put the halyard and the down haul through a fair lead(stainless pad eye) on the partner, and then made fast on a cleat up by my cock pit. As long as the partner holds together, I should be ok. If the mast starts rocking around, I will do something different.

    I put the last bit of hardware and rigging together today. I need to change the knot on my robands that secures the loop around the toggle. I was using a bowline, but after flapping in the breeze a bit while I was working on the rigging today, the bowlines started coming loose. I am going to use a double figure 8 instead. I have used this knot many many times while rapelling and it never fails, but yet is easy to untie even after serious loads(my 195lb butt) have been applied to it. I plan to make them all figure 8's tomorrow.

    I put the last coat of varnish on the amas, leeboard, and rudder tonight, and as soon as spring comes back again, I will get this baby on the water!(very cold in Georgia this weekend) If you see a guy struggling on Strom Thurmond Lake in the next month with a Laser Sail on a CLC Rigged cedar kayak, go over and help him out. It will probably be me. I will post pics and maybe videos as soon as I get her in the water!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  2. #247
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Ok, I am finally going to take some leave and try to get this boat in the water first two weeks of April.

    So now I have a sailing technique question - with a trimaran that is not as prone to flipping as a monohull, is it a safe assumption that I can "dump air" by letting the main sheet out and get by without installing reef points in my sail? I eventually plan to sew in some reef points, but I just don't have time before I plan to get this baby in the water for the maiden voyage.

    So what is everybody's "expert" opinion?
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  3. #248
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    With most any unstayed rig, you can always let the sheet fly if the boat gets seriously overpowered. As far as trimarans go, yes, they are a lot more forgiving. The "flip" side is that, if they do go over, they want to stay that way. But I used to let kids take the helm of my bigger trimarans, knowing that they really couldn't mess it up badly even if they tried.
    -Dave

  4. #249
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Thanks for the response Dave! I figured I could probably get away with it. For my first few trips I will go easy and try not to push it in big wind. But once I get the hang of it, I am going to let her rip as hard as she wants too!

    I have not been getting enough work done on the sailrig lately. I had a last minute wedding I had to attend for my son, and now I am on a COVID restriction of movement(thats what we call a lenient quarantine in the Army) since I went outside the mileage limit on leave to attend the wedding. Just a precaution since I was in busy airports. But at least my commander let me go! I am working on some Jeep mechanical stuff that I have been procrastinating too. Next week I have to go visit family so I won't get to work on the sailrig until Friday, next week. I plan to get her in the water the week after next.

    Which leads me to my next question, BATTENS, the sail I have is a recycled/repurposed laser sail that jmanflyer gave me(still amazed at his generosity). I need to make some battens for it. I was planning on making them out of some spare 1/4" thick, 3/4" wide cedar strips that I had left over from building the kayak. I am out of epoxy, so I was planning on just coating them with some "Helmsman Spar-Urethane" after sanding them to a very fine finish to remove any sharp edges or splinters that might tear the sail fabric.

    So the question is, do I make them a little longer than the batten pocket on the sail so they are kind of like a fiberglass tent pole, that would be under compression and form a bow in the sail? or do I make them just long enough to fit snug and not fall out?

    Also, does anyone think the spar-urethane without epoxy is a bad idea for the battens? I just don't want to order more epoxy right now and let it sit after opening it for just a small job. And I like to buy in bulk to save money. But I do want to waterproof the battens.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  5. #250
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Well, I didn't get any responses to my questions on battens, so i made some out of some 1/8~1/4 inch thick flat PVC molding i bought from home depot. I just cut them to length, sanded down the sharp edges, slid them in the sleeves, and then duct taped the sleeve ends to keep them from getting slung out of a flapping leech. I have to attend my Grandfather's funeral this week, so maybe next week I will get to do some sailing. The MISTY SUNRISE is just sitting in the garage, straining against the saw horses wanting to get on the water...
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  6. #251
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    LAUNCH DAY!!!

    I gotta say, this was very exhilarating. According to the windfinder ap on my phone, winds were blowing at 3mph. I forgot to get my GPS out of the Jeep and see how fast I was really going. But it was all my 16 year old son could do to keep up in the kayak going upwind. Going downwind, I ran off a left him. See the pics:

    Assembling on the shore:
    20210417_162809.jpg

    Bending Sail:
    20210417_163211.jpg

    Done!
    20210417_163521.jpg


    DANG IT! The freaking rudder won't stay down, I gotta work on that.
    20210417_163848.jpg

    Heading upwind after getting the rudder to stay down:
    20210417_171225.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  7. #252
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    More pics:

    Heading upwind about to ram my son's kayak:
    20210417_165242.jpg

    Freaking flying downwind:
    20210417_171332.jpg



    Coming about from down wind to put her in irons and drift into shore:
    20210417_171805.jpg

    Yup, this is my parking space... note my rudder fully down now.
    20210417_171839.jpg

    Quietly slipped into the "berth"
    20210417_171859.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  8. #253
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    This is quite possibly one of the best days I have had in a long time. I gotta do some work on the rudder, but other than that, I am stoked! Once I got the rudder to stay down, she didn't need any pressure on the tiller at all to stay the course. I could almost let go of the tiller going up wind and it stayed right on course. After getting the rudder down, it was much easier to steer, and much more responsive. I noticed the leeboard at times bending so far over as to touch the kayak when going upwind. I estimated I was able to sail somewhere between 30 and 45 degrees off the wind when heading upwind. And for some reason it felt like I was going faster upwind than I was downwind. But my wife and son said I was going much faster down wind. I have the whole next week off, so I will try to get on the water some more and post pics and video from the cockpit while underway.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  9. #254
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Excellent. Glad to hear it's working as planned.
    -Dave

  10. #255
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    So I went out today, not knowing there was a small craft advisory issued for area lakes... My plan was to go about five miles up the lake from the dam to a campground, eat some sandwiches for lunch, turn around and come back. Weather forecast last night said 8mph winds from southwest at 8am becoming 15mph from northwest by 2pm. Awesome, I thought. I would catch a tail wind going and coming, because I was going north in the morning, south in the afternoon.

    So I headed out from the beach area at the dam at about 10 am. Once I got out in open water, the wind changed quick. It was blowing really hard, the water changed from a few lazy waves, to some serious 3 foot high waves with white caps nailing me from the front port quarter at a 45deg angle from the port bow. I was getting soaked. After about 30 min, I was almost halfway to the campground when I heard, crack... crack... craaaaaackk. The leeboard was bent way out to port, and there was a small crack on the inward side. I turned around and headed back to the dam beach. When I turned around, I turned away from the wind instead of into the wind, and as soon as the sail swung over, the whole boat took off like a rocket ship. It was all I could do to hold on to the sheet and man the tiller at the same time. The leeboard stopped cracking, but was bent hard agains the kayak hull. I glanced down at my Garmin GPS and it said 8.5mph in just a matter of seconds after turning back. I was putting the leeward ama underwater on almost every wave that was now hitting me from the starboard aft quarter. I got a little scared cause the windward ama was almost 2 feet above the water, so I eased the sheet and dumped some air. I got back to the beach in half the time it took me to get out in the open water. I was holding 6 and 7 mph the whole way back. I wish I would have had the time to video the whole episode, but I was a little busy dodging waves and keep the bow straight.

    Once back on shore, I inspected the leeboard. I could see a hairline crack starting on the inward side. But there was no more loud cracking noise on the way back so I figured, what the heck, lets give it another go. I headed out again and realized quickly that the wind was blowing even harder than before. I got about half as far as i did the first time, and the leeboard gave another loud, CRACK! I was also wondering why it was so hard to steer, I looked back at the rudder and it was also bending waay out to port, like 45 deg from vertical. "Did I crack my freaking rudder too?", I wondered, because it was bending far out to windward like my leeboard. So, I turned around... again. This time I hit 9.3 mph on the way back, and the leeboard was bent even further than before against the hull, splashing water up on me , I was getting cold and starting to shiver.

    By the time I got back to the beach, the leeboard was seriously cracked all the way through, just under the mounting brackets. The eye bolts I used for gudgeons on the rudder were bent, and coming loose from my rudder housing. 1/2" plywood leeboard with 6oz fiberglass reinforcment cracked through, and two 1/4" Stainless steel eye bolts, bent by the freaking wind? Also, my main sheet was worn to a frazzle where I had it routed through a pulley that was attached to the rear of the kayak. It was just a matter of time before it would have let go. It was 11:30 and I was already worn out. I took off my wet clothes, put a jacket on, dismantled the sailrig, and headed home.

    Here are some pictures of the cracked leeboard:
    20210421_114309.jpg
    20210421_114306.jpg20210421_114249.jpg

    This is what the water looked like by the time I got back to the beach:
    20210421_132151.jpg20210421_132115.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  11. #256
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    So tonight I cut off the cracked part of the leeboard, drilled another hole, and also added some reinforcement "stays" to the sides. I plan to leave them tied up until conditions get bad, then snapped them in to keep the leeboard from bending and cracking again. Basically I raised the leeboard up about 3 inches by cutting off the top pieced that was cracked. Probably had too much surface area in the water anyway. Maybe that's why it cracked?

    I will fix the rudder tomorrow and head back out on Friday to test my fixes. Supposed to only be 5mph wind on Friday... we will see if the forecast is dreadfully wrong or not. Oh yeah, I listened to NOAA weather radio on the way back and heard the advisory. 17 to 23 mph winds gusting to 30mph. I am probably lucky I made it back with my entire boat intact. Thats the LAST time I depend on the windfinder app for a forecast. Here are some photos:

    Oh yeah, here are the bent eye bolts from my rudder. I haven't fixed my rudder yet:
    20210421_170843.jpg


    Reinforced leeboard:
    20210421_205450.jpg
    20210421_205501.jpg
    Last edited by Lee.007; 04-21-2021 at 10:32 PM.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  12. #257
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    That was probably about as much stress as the boat will see, so as these things go, that went well. The leeboard had way too much point loading at the bottom end of the bracket without reinforcement there. That's why the crack. Several layers of glass at the top, gradually tapered out like the corner of a sail, would have prevented it. Or a metal plate on each side. Anything to spread out the load. Your solution will do this job, too, but may be more awkward to work with.

    The rudder gudgeons are just too thin and cantilevered out too far to hold up. Standard practice are sets like these. You can bend the tangs to fit the stern of the boat. The picture is borrowed from Duckworks.

    But it sounds like the big stuff all worked -- the boat is fast, you were able to keep it under control, and the major components held together. Good going!

    -Dave

  13. #258
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Quote Originally Posted by Woxbox View Post
    But it sounds like the big stuff all worked -- the boat is fast, you were able to keep it under control, and the major components held together. Good going!
    Thanks for the encouragement Dave! By the way, what is considered fast? And how should I compare the conditions I saw yesterday on a large lake, to conditions I should see on coastal ocean areas?

    You are right, I didn't think about all the other big stuff while I was licking my wounds last night and this morning. The mast held solid as a rock. I was worried it was going to snap, but I kept watching it, especially the scarf joint, and while the mast as a whole did bend a little it never even whimpered. The partner and the step held solid too. The sail didn't rip or lose any threads, and all of my robands held fast. I guess I am a fairly decent seamstress. The only issue with the amas or akas was the fact that I found a couple of small 1/8" diameter holes between the deck and the hull of my ama, and that let a little water in. That was not a structural issue, it was my failure to fully seal the joints. The first time I went out, I didn't get the amas underwater, so it didn't show up as an issue. This time however, I had about a pint of water in the ama when I got off the lake. The kayak hull itself was water tight except for the space around the partner. That let about a half a pint of water in the forward bulkhead cause so many waves were coming over the bow. I buried the nose in several waves, but it popped right up like I meant for it too from my original design ideas. Thats why I put a lot of volume up front. Oh, and the large spacer I had to put between the forward aka and the hull saved me from taking a face full of water from many a wave. But I did get slammed in the ribs from the waves that were hitting me from the front quarter.

    Tonight I am going to fix the rudder with some much shorter eye bolts, to get rid of the large cantilever load like you mentioned. I thought about ordering those gudgeons, but I don't want to bolt anything to the outside of the stern if I don't have to, especially since my rudder is not a flat face. It would take a lot of working to get the angle right. I can't remove the eye bolts in the kayak stern with out some destruction cause they are epoxied into the wood, and they didn't bend, only the ones on the rudder bent. I also cant reach up into the inside of the kayak to get a nut on the back of a bolt, and I am not a fan of wood screws. I prefer thru bolts, nuts, and fender washers to spread the load on the wood. The next boat I build will have a flat enough face to accept those gudgeons, or some similar, more easily.

    I am also going to fill the holes in the ama with some 3m marine adhesive cause I am out of epoxy and tomorrow is my last day I can go sailing while I am on leave, so I want it done right now. I am going to cover the bare wood on my leeboard (due to cutting out the cracked section) with some spar urethane to protect it from the water tomorrow, then later I will sandwich it with some thin aluminum plates like you mentioned. That was an excellent idea by the way! Makes me ashamed as an engineer that I didn't think of it myself. My "stays" do the job like you said, but they are cumbersome and I have to take them loose if I need to raise the leeboard. A metal sandwich is a much better idea.

    Hopefully tomorrow I will have a much more leisurely go of it, and have a hand or two free to take some pics along the way instead of fighting the whole time to keep the friggin thing out of Davey Jones' locker!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  14. #259
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    By the way, what is considered fast? And how should I compare the conditions I saw yesterday on a large lake, to conditions I should see on coastal ocean areas?
    "Fast" is a very relative term when it comes to sailboats. An old displacement boat might be considered fast when it hits 7 knots. The recent America's Cup race saw monohulls doing in excess of 40 knots. My 27' trimaran hit 17 knots a couple of times. Others have pushed that same design to 25 knots. (But that's crazy.) So it depends. A converted kayak such as yours might exceed 10 knots in ideal conditions, but what you saw is typical for a lively downwind run. If you had turned off wind, had the sail trimmed properly, and if the leeward ama didn't bury, you could have seen 10 or 11 knots in 20 plus knots of wind. But as you know, speed in a low-to-the-water boat feels way more than it does in a bigger boat. Like speed sensations on a motorcycle verses in a car.
    -Dave

  15. #260
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Ok, Since I am new to sailing and this was only my 3rd time out on my CLC sailrig, you guys tell me if I am doing this right or not.

    Yesterday I went out and had a fairly decent time. But there was practically no freaking wind. The gentle rocking of my boat almost put me to sleep. I found a national weather service website that has historical data from the weather recorder on Strom Thurmond Dam. Steady winds yesterday were about 2.5 knots, gusts as high as 5 knots, predominately from the north, but varying from North North-West to North North-East. I was able to maintain an average of 2 knots, with some sprints at 3.5 knots while I was sailing upwind most of the afternoon to Modoc Campground, along the GA SC line. Oh, and once I got to Modoc, I had to take a short break on a little island near the Modoc shoreline cause the wind flat died at 6pm for about 30 min. I didn't actually get inside the Campground area cause I was running out of time.

    Then I went downwind back to the West Dam Beach rec area. I felt like I was chasing the wind all day. I just couldn't find a good sweet spot between leeboard height, sail setting, or boat heading, to get a decent speed. Especially when going downwind, which really drove me insane. Isn't it supposed to be easy to go downwind? If I was not pointing directly downwind, I was doing good to make 1 knot of headway, even with the leeboard all the way up to reduce drag.

    But, I did an 8 mile(as the crow flies) round trip in 7.5 hours. After plotting my track from my GPS into my mapping software (see the pic), I noticed I actually traveled 13 miles total with all the tacking. I was having a very hard time pointing close to the wind. Best I could get was about 38-47 degrees off wind when going upwind according to my compass. The weaker the wind was, the more off-wind I had to point. Is that normal? You can also see the track that I did on Wednesday in red in my pic, and my route that I intended to follow in yellow. Data from the NWS recorder said winds on that Wednesday were steady about 17 to 20 knots, and some gusts were up to 32 knots. No wonder I was more nervous than a long tail cat in a room full of rocking chairs! I thought I had gone a lot further on Wednesday. I guess that's just cause every second felt like an hour.

    Anyway, Am I expecting too much from a 17 foot kayak with a CLC Sail rig and 60 Square foot recycled laser sail? I would like to be able to maintain a 5 to 6 knot speed. I think that would be very comfortable in the kayak sailrig. Yesterday I had a really good sail shape. No wrinkles, nice and full. I was able to get a really nice shape by loosening the downhaul a bit. The tell-tale on the leeward side was horizontal, tell-tale on the windward side was hanging straight down. Is that what they are supposed to look like?

    I saw two other sailboats, big yacht types, out on the lake yesterday. One made a couple of slow runs out to the dam, then dropped the sail and went back to the sail club dock under motor power after about 30 min. The other did about the same thing, but she was a smaller boat than the first. I guess they couldn't find the wind either.

    OH Yeah, I forgot to mention, my stays on the leeboard worked like a charm. no flex at all from the leeboard. Of course there was hardly any wind either .

    Map plot of my route yesterday in black, and Wednesdayin red, with my intended route in yellow:
    Map of Plot.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  16. #261
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Hey Lee, you are going through what everyone learning to sail finds. For starts, light air can be tougher to manage than heavier air. Also, when a boat is moving very slowly, the leeboard/centerboard/keel whatever you have is far less effective. The best remedy is to sail, sail and sail some more.

    I will point to one detail -- the telltales will all stream aft if the airflow is perfect. But getting it perfect in light conditions is a big challenge. More generally, when the air is light and shifty, the GPS track doesn't tell you much because it's not paired with information on the wind changes.

    One other point specific to multihulls that you've already observed: these boats will go much faster off the wind than they will go straight downwind. It has to do with the apparent vs. true wind speeds. Off the wind, the boat motion actually increases the apparent wind hitting the sail, creating more drive. Downwind, the boat motion reduces the apparent wind.

    As you gain experience, you'll be thinking about adding gear to allow more precise trim of the sail. But for now, it's mostly time at the helm that's needed.
    -Dave

  17. #262
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Thanks Dave. You always have good advice. I plan to get as much time at the helm as I can this summer.

    And you definitely read my mind about adding gear to allow more precise trim of the sail. I was wondering what you and the experts in the forum would say about me adding a boom to keep the sail shaped better going downwind, especially in light conditions. Yesterday when I was going downwind, the sail seemed like it almost did not want to fill up with air. I guess that is the apparent wind phenomenon you just mentioned. Here are some pics I captured from the video I took yesterday. I can't post the video cause I don't have a youtube account, but I figured out how to screen capture the sail shape. This was going upwind.

    Also, I could match the wind data to the gps track. I downloaded the direction and windspeeds that the recorder on the dam listed. They take a snapshot of conditions every 20 min. But right now I think you are right. I just need more time at the helm to get the feel of how the boat sails, and I also need to learn how to be a better judge of where the wind is coming from. I was trying to watch the waves, but when the wind was slowing, there were more waves from sea-do's and bass boats than there was from the wind.

    Pics from yesterday:

    Downhaul and halyard go through a pad eye on the partner, then over the aka, then made fast at a cleat:
    Tack Rigging.jpg

    2.6 mph / 2.3 kts, woot woot!
    Speed.jpg

    Sail shape at the tack, I was running about 2.2 to 2.6 knots right here, and now that I look at it the windward tell-tale is pointing at the mast. Does that mean I screwed something up?:
    SailShape1.jpg


    Sail shape at the head. I think next time I will put the beehole where the head is attached pointing aft instead of to the side, I think that will help smooth out those wrinkles at the top:
    SailShape2.jpg

    Sitting at port while making a nature call
    20210423_144311.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  18. #263
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I would say that you definitely want a boom, and I would rethink your leeboard mount. Leeboards, rudders and mast steps need to be bullet proof.

  19. #264
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    It looks like that c.board pivot point mounted on the arm is just too liteweight. I'd mount the centerboard pivit onto the side of the main hull...uesing wood blocks to hold it off from the hull- might consider using bungees to hold down the centerboard ( saves weight in the form of lead) and if someone forgot to raise the center board whilebeaching.....it'll allow the board to swing the c.board up to minimize damage
    Last edited by the_gr8t_waldo; 05-03-2021 at 04:23 PM.

  20. #265
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    The biggest problem with your sail shape (too drafty up close to the mast) is simply because you are using a Laser sail. They are designed and built specifically for the large amount of in-use bend that a Laser mast has nearly all the time. There is extra luff round designed into the sail to compensate for all that bend, and when you stick that sail on a less bent mast, all that luff round creates excessive draft and an overly steep luff entry angle. The sail may still fill with wind and look reasonably consistent and crease-free up and down the luff, but the boat will never reach its potential performance with that system set up the way it is.

    A Laser sail is always one of the most common "buy a used sail and stick it on a dinghy" choices, but it is nearly always a mistake from a performance standpoint (possibly second only to using a windsurfer mast on a dinghy because someone found one cheap). Ideally, your boat should have a flatter sail (maximum draft 1' in 10' of chord width or less with maximum draft about 35% aft of the mast). It would be OK to have a fairly steep entry curve off the luff as a rounded entry is more forgiving of trimming errors when fast light boats are moving quickly through various wind conditions, despite maybe being slightly slower than a flatter entry - but not that deeply rounded.

    With that wooden mast, you could possibly re-cut the luff curve to something like 2% draft, but it's a fair bit of work. You would start by removing the luff tape and grommets on the luff. Then draw an imaginary dead straight line (luff reference line) along the luff between the peak and tack corners. Measure at the 1/4 height horizontally above the tack corner, then 1/2 height, and finally 3/4 height. Those will be your horizontal chords and you want to measure them from the luff reference line to an also straight imaginary leech reference line (runs from peak to clew). If needed, you can lay the sail on the floor and pin strings on top to show you these lines. Get out the calculator and calculate 2% of those three chord widths from the quarter, half and three quarter height chords. Typically, those will be fairly small amounts for dinghy sails - a few inches or less.

    At each of the three heights on the sail, you now add the 2% measurements for those chords out ahead of the luff reference line. Then you take a batten and draw your new luff shape from the tack corner at the bottom of the luff reference line, up through the three new 2% marks and then back in to the peak at the top of the luff reference line. If it's not a smooth curve, you can cheat a bit as needed. For a Laser sail, this new curve should be substantially less curvy than the original luff curve was. Cut off the luff to the new shape, replace the luff tape and grommets and you should end up with a sail which works a lot better. with increases in both speed and pointing angles.

  21. #266
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Quote Originally Posted by Todd Bradshaw View Post
    With that wooden mast, you could possibly re-cut the luff curve to something like 2% draft, but it's a fair bit of work.

    Cut off the luff to the new shape, replace the luff tape and grommets and you should end up with a sail which works a lot better. with increases in both speed and pointing angles.
    Thanks Todd, as always, you have excellent advice and insight. So I am wondering if it would be easier to just order some dacron and make a new sail? Is cutting the luff and re-shaping it much easier than designing a new sail and sewing it?

    I have a copy of the PDF that you did some time ago for designing / sewing a poly-tarp sail. The math involved is simple enough for me to grasp. Do the same parameters apply to dacron as it does for the poly-tarp?

    I am certainly open to modifying this laser sail to get it working well, but would a new sail design work better? If so, then I think I would rather keep this laser sail as is and enjoy it for the season, while working on sewing a new sail at the same time on days when the weather sucks and I can't go sailing.

    So, what would you do if you were me? And many thanks in advance for your time and attention. I very much appreciate the entire community here that provides guidance and advice!!

    EDIT TO ADD: Also, what do you think about adding a boom? Will that help the Laser sail without the luff changes, or will it be a waste of time until I get the luff changed or a new sail made?

    --Lee
    Last edited by Lee.007; 05-04-2021 at 02:03 PM.
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    The only thing that would really help the Laser sail would be increasing mast bend. A boom might be able to do that to some extent, though I'm not at all sure that your mast would (or should) bend as much as a Laser mast does. In general, a boom does make most sail shape/trim situations easier to deal with and it offers better performance (especially on downwind-ish sailing angles). It can be a conventional boom, a sprit-boom or in some cases, just a hefty batten sewn into the sail's foot.

    Making a new sail for that boat wouldn't really be an awful lot more work, plus you would end up with new, more stable cloth, whether scratch-built or a Sailrite kit. If you have the energy and interest, it would certainly be an OK option.

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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    So then, with that said, I will make a boom AND a new sail. Boom for now, and then a new sail. And I will keep the Laser sail for the next sail rig I make for another kayak, only get a "bendy" mast for it.

    I looked at sailrite's myriad of sail kits. Since most are for other boats, and none of the ones I saw were what I could find to fit what I want, which one would you recommend to give me 60-70 square feet, work well with a non-bendy mast, With a luff of 15 feet or less? Foot can be up to 10 feet. I really want to stay with a Bermuda rig for simplicity. But I am eager to roll my own if none of the kits fit the bill. Would your polytarp pdf from a few years back work on dacron for a scratch-built? And what weight dacron would you recommend for longevity? I guess I need to dig up my sailmaker's hand book too!
    “If everybody is thinking alike, then somebody isn’t thinking.”
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Sailrite can plot you a kit for just about any boat you can give them measurements for, so it does not necessarily need to be an existing design. Best bet would be to make a measured sailplan drawing showing the lengths of the edges and perimeter shape you want (Luff, foot and leech length). If the basic size and proportions of the Laser sail seem to work well, there is nothing wrong with telling them that you want something with a similar profile, but made for a more normal, less bendy wooden mast. Your sail should be made from four ounce Dacron, which actually varies between about 3.8 oz. and 4.2 oz. depending upon who makes it. There is no good reason to go heavier.

    Adjusting the square footage for sailplan drawings is pretty easy. You multiply all the linear dimensions shown on the plan, like edge lengths, chord lengths, diagonals, batten lengths, etc. by a specific percentage (110%, 120%, 130%, etc.). Then you multiply the original square footage by the same amount, and you do it twice to arrive at your new sail size.

    A sail like this one, for example, when enlarged by 10% (multiply all dimensions by 1.1 - and twice for the sail area figure) would yield a shade under 69 sq. ft. and fit your mast and boom length specifications. Depending upon just how bendy your mast is, you might need to add an additional inch or two of luff round as a bend allowance, but I don't know much about your mast. This plan is for traditional sailmaking, the way those of us who don't own computer design software and plotters have built sails for many years. The cloth panels are straight-sided and shaping is done with broadseams - using variable widths of the seams joining those panels, making some seam overlaps wider in places. Computer plotter equipped companies like Sailrite would build to the same dimensions shown on the plan, but instead of straight-sided panels and variable-width broadseams, their system uses constant width seams and variable width cloth panels (curved edges).

    The traditional plan:
    (Dimensions enlarged to 110% would yield 69 sq. ft.)

    Bermuda-57-sq.-ft.-main.jpg

    Both design methods work just fine and basically yield the same sailshape if you know how to broadseam a traditional sail, which would be the somewhat tricky part for beginning sailmakers, though not impossible. The computer plotted kit would have already figured that stuff out for you. Do not assume though, that the computer is going to make a better sail. When you can hang it up in your back yard using nothing more than a rope from an overhead tree branch and a couple of tent stakes, and the shape looks this good - then you know you nailed it.

    salt bay skiff 016 copy.jpg

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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Whoa! Thanks Todd! I am definitely going to try to do just that. I like that sail shape look. Maybe I can talk the wife into letting me spend some money (warming up the credit card as I type) and get some materials and sail cloth. I am excited to sew my own sail from scratch.

    I have read some about broad-seaming, but have never done it. Are the broad-seams sewn on a straight line tapering from the sail body to the luff/leach, or do you draw a smooth nice curve with a batten or something?

    And if I wanted to add reef points, I am assuming I just space them equally up from the foot to maintain sail shape, and put them at a point so that I have 1/3 and 2/3 of the sail area?
    “If everybody is thinking alike, then somebody isn’t thinking.”
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Broadseams are mostly straight tapers and for 4 oz. Dacron the overlap increase rate is usually about 1/2" for every 30" of the broadseam section's length (the distance from the broadseam curve to the luff or foot). As you approach the luff edge, you usually give it a little bit of flare (increased overlap rate) for the last few (maybe 6"-8" or so) inches. The flare is what will adjust the entry angle on a cross-cut sail. More flair yields a more rounded entry, less flair a flatter entry. The most important broadseam is the one which terminates at the tack corner. That seam usually gets broadseamed at around twice the normal rate (1" per 30", rather than 1/2" per 30"). The shape of the red broadseam curve (showing where the broadening begins) on the plan above is pretty typical for Bermuda and Marconi mainsails. It is established by eye and the sailmaker's experience, rather than by some sort of formula.

    There are also a couple of leech broadseams shown on the plan. These are fairly short, straight, and very slight tapers with no flair. Sticking a couple of them on the leech helps to keep the leech firm and flap-free as the sail ages.

    Reef lines are usually not level with the foot. The aft end is raised a little bit. I'd keep the first reef a few inches below that lower batten pocket to avoid the need to remove the batten when reefing. For a second reef you might want to keep it below the second batten and may or may not need to remove the lower batten during the second reef, depending on whether or not the bundled-up part along the boom will cooperate. My general view of second reefs on dinghy-sized boats is that they tend to be overkill. If it's blowing that hard out there, sailing might not be much fun.

    Battens need to be around three times as long as the leech roach in that area is wide, so a sail like this with a big roach will have pretty long battens. The top one would need to be pretty soft and flexible since it extends so far forward toward the luff. There are some pretty good plastic trim pieces available at places like Home Depot which make good, cheap and durable dinghy battens. On that boat, a fairly big roach is probably a good idea, as skinny multihulls reach really well and can take advantage of the extra sail area.

    A sail like that could also be made fully-battened, though you would want to level them out somewhat. Unlike the tensioned battens which you might see on a Hobie Cat, you would need to stick them into their pockets without tension. The reason for this is that tensioned full battens tend to push forward. On a sail laced to the mast and not having a boltrope in a mast track, this tends to try to push the battens forward and past the mast, which yields bad shape and a constant annoyance. Even without batten tension, this may happen to some extent, so full-width battens on a luff-laced sail may not be worth the bother.

    Confusing yet? As I have often said, sailmaking isn't overly difficult, but to do it well there are an awful lot of tedious little contributing factors which need to be accounted for and juggled.
    Last edited by Todd Bradshaw; 05-05-2021 at 11:26 AM.

  27. #272
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Quote Originally Posted by Todd Bradshaw View Post
    Confusing yet? As I have often said, sailmaking isn't overly difficult, but to do it well there are an awful lot of tedious little contributing factors which need to be accounted for and juggled.
    No Sir, not confusing. Very intriguing and exciting. It might take me the whole summer to finish a new sail, but I am going to do it. I am going to use your plan above and follow your instructions along with my "Sailmaker's Apprentice Guide".
    “If everybody is thinking alike, then somebody isn’t thinking.”
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  28. #273
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    In my opinion, this is the best book on the market for building a basic cross-cut Bermuda mainsail. It's a small paperback, but gets right to the main issues better than any others that I've ever seen. There is a series of them covering different types of sails (mains, jibs, spinnakers, storm sails, staysails and sail repair) and basically memorizing them and putting that information into practice where I could expand on it is what originally taught me how to build sails. I had sailed and been a sailboat dealer before that, but my sewing work had all been from working on hot air balloons. Marino's Sailmaker's Apprentice is monumental and represents a hell of a lot of work, but if I was to hand a beginning sailmaker one book and tell them to go build a sail, it would be one of Jim Grant's little sailmaker booklets.

    https://www.sailrite.com/The-Mainsail-Manual-Book
    book.JPG

  29. #274
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Thanks for the book recommendation Todd. I ordered one yesterday.

    Also, I forgot to mention, in response to your post about the home depot plastic trim pieces for battens - Thats exactly what I used for battens in this Laser sail. But, the pieces I bought had a pretty sharp edges on the corners. They were 3/4" wide x about 1/8" to 1/4" wide, and like 6 or 8 feet long. I cut them to fit the sleeves that I repaired, and then sanded the sharp edges down so they would not chafe the sailcloth. I also rounded the ends to about a 3/8" radius so the end corners would not poke through the sleeves. You don't have a standard go-to at home depot that you normally use do you? Without sharp edges?
    “If everybody is thinking alike, then somebody isn’t thinking.”
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  30. #275
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Mine are white, 3/4" wide by maybe a shade under 1/4" thick and have a shallow groove down the middle on one side. The edges are square, but not really sharp enough to worry about, other than on cut ends. They also make good grain-free lofting battens when lofting out sailplans on the floor prior to building. They seem to work pretty well as a low budget option in any situation where you don't need the forward flexibility of tapered battens. Instances like the long top batten on the sail above leave little choice other than to buy real tapered battens to prevent the inner batten ends from distorting the sail. I don't know whether or not you could taper the plastic stock with a sander as I haven't tried it. I have made a few tapered fiberglass battens using leftover 6 oz. cloth and epoxy resin. I couldn't believe how many layers it took to get reasonable stiffness. It's not really something I would do again.

  31. #276
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I got some time out on the water tonight. I think I found my comfort level, for now. Winds were blowing at a constant 10 knots, gusting to 15 knots at Strom Thurmond Lake while I was on the water. The lee ama was just barely about to go under during a few gusts while going slightly off of downwind, but I was freaking flying. I don't know how fast I was going cause I forgot my GPS, but it felt a lot faster than it did last weekend when I did the same route, and I was hitting about 2.5 ~ 3 knots then. Judging from the sound of the water in my video compared to the videos when I was doing about 2 knots, I estimate I was maintaining about 5 knots, with a few sprints at maybe 7 to 8 knots during the gusts.

    Seems like she wants to go faster, but when I get a good gust she heels over and I slow down cause I think the ama gets more surface area in the water causing drag. Is there a way to make her heel less by straightening up the sail and making it more efficient? Anybody ever tried using foils under the amas to lessen the heel, or do they just cause more drag than they are worth?

    Also still feels like I am not pointing as high as I should into the wind. Same sail issues?
    “If everybody is thinking alike, then somebody isn’t thinking.”
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  32. #277
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Yes, Lee, the sail is the first thing to address here. Your sail needs to be much flatter - this will improve the lift to drag ratio a huge amount. You're getting drive out of the sail, but it's not nearly as efficient as it could be. A simple step before you get the new sail made would be to add a sprit boom. A broomstick would actually be enough to demonstrate the point.

    Fast multihull sails are very very flat. If you rig up something like this and really tension up that line forward -- it's called the snotter -- to flatten the sail out you'll see an improvement, especially to windward. But as Todd points out, you're still working with a sail that isn't a match for your mast. But this experiment would be quick and easy, nothing to lose.

    BTW, the sprit should split the angle at the clew of the sail as shown here. It needs to pull the luff down as much as it stretches the foot out.

    -Dave

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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Wow, thanks for the quick response Dave! So I ordered a goose neck from CLC the other day, should be here next week. I was planning on using it to make a regular boom. I am going to have to research how to rig up a sprit boom and a snotter until I get a real boom made, and a real sail!!

    So my next question is this, if I can get the sail flatter, will it make me go faster without heeling so much? Seems to me if the sail is more efficient, I get more speed out of less wind, and I can go faster before heeling, am I thinking correctly here? Anyway, thanks for the tips!

    Lee
    “If everybody is thinking alike, then somebody isn’t thinking.”
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  34. #279
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Sails with deep draft are generally built that way to provide a lot of power for pushing a heavy or beamy boat along and through choppy seas. They tend to overpower a sleeker, faster hull shape, rather than translating that power into more boatspeed. You will be faster and more efficient with a flatter sail.

  35. #280
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Quote Originally Posted by Todd Bradshaw View Post
    Sails with deep draft are generally built that way to provide a lot of power for pushing a heavy or beamy boat along and through choppy seas.
    That makes me want to ask this: Will the Laser sail be a better choice if I wanted to tow a few friends behind me in kayaks? Seeing as how I would be a "heavier" boat if I was towing something. I keep telling my kids I could probably tow them along behind me so they don't kill themselves trying to keep up in a kayak with a paddle.

    Or is the flatter sail still the better choice no matter if I am towing something or not because of the greater efficiency and my "non-bending" mast?
    “If everybody is thinking alike, then somebody isn’t thinking.”
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