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

  1. #456
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Hey guys, finally got some video that I didn't do myself. I can't remember who it was, I think it was upchurchmr that was asking when I was going to get some video of me sailing by. I sailed across the lake yesterday and met my family at the beach. They brought the dogs and a good time was had by all. My wife and kids did the videos, except for the one where I mounted the action cam on my tiller arm. Oh, yeah, it was cold as crap yesterday. My new wetsuit barely kept me from freezing. I had to wear an external wind breaker over my suit when the sun started going down, well, it was cloudy most of the day.... 45 to 50 deg F, with 12 mile an hour winds is not good for a wetsuit. I think if it was above 50 I would have been ok. Enjoy:

    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  2. #457
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Did you get the wet suit completely wet?
    It won't keep you warm until it is soaked, and your body heat makes the water in the suit warm.
    A dry wet suit is not much use.

    Pity there was so little wind.

  3. #458
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I got my legs wet, but the not the torso. I think I still would have been chilly. There was enough wind that the legs were drying out. It wasn't that bad, my feet are what got the coldest. I have wetsuit boots, but they were filled with water. I need to get me some velcro straps to cinch them down, maybe keep the water out.

    You are right about the wind though. It was gusting up to 12 mph, but was only steady at about 5 to 7 mph. Towards the end of the video you can see me moving at about 6 mph out in the lake, but when I was coming into the beach I was on the leeward side of a peninsula. The trees were totally blocking the wind and I pretty much just paddled into shore. I really wish my camera was working the last time I went out when the winds were freaking scary. You guys would have gotten a kick out of watching me almost nosedive and swamp my boat. Oh well, I am sure I will nearly wreck the boat again in the future!!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  4. #459
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    A wet suit can't be kept dry, unless you never get in the water.
    Its made to suck up water.

    You need a "dry" suit to keep dry. Completely different thing and lots more expensive (or used to be).

  5. #460
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I dont' mind the suit getting wet. But when the wind blows hard, and the temp is 45 and dropping, the wind dries the suit and cools me down to far. I am going to go out again to test the suit in slightly warmer, but not hot, temps. I want to go when I know the weather is going to be above 50 deg F, but less than 70 deg F.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  6. #461
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    So I went out again today. Nice day, almost too warm to be paddling. Why was I paddling? Watch this video:

    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  7. #462
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    So this is what I did when the wind died. Yeah, I was a little disgusted. I had no wind for about 3 hours:

    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  8. #463
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I put some stays made out of some fairly non-stretchy rope from lowes today. Trying to get ready to use my jib on the water on monday. Winds are going to be super light, so good time to try the jib again, and probably going to be good to have the jib so I don't have to paddle. I have some questions though:

    1. How much tension is too much / too little and how do you know?

    2. I noticed my mast still wants to bend a little. Is this normal, or is it because I am using rope instead of metal cable?

    3. Is it acceptable to use rope? Or should I use steel cable? And what size should be big enough if I use steel cable?

    4. Do I need to use turnbuckles, or can I just do a trucker's hitch and tension the ropes that way?

    I'll try to post some pics tomorrow when the sun comes back up. Got dark on me tonight.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  9. #464
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Twangy tight is best. But big box rope won't get you there. But it's still way better than no shrouds.
    -Dave

  10. #465
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Stainless steel stays are gradually being phased out by this new rope. Stretch and strength are equal or better than metal. You would only need the 1/8" line.
    https://duckworks.com/amsteel-blue-1...-spectra-line/

  11. #466
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Twangy tight. Got it. Is that western acoustic guitar twangy, or southern banjo twangy? Just kidding. I understand what you are saying. I have some old tie-down rope that came with some kayak tie-down kit that is pretty non-stretchy - I think it is dyneema. The stuff I bought at lowes is pretty non-stretchy, just as much as the old kayak rope. I have never seen this stuff at lowes before, and figured I would give it a try. I am using it for the shrouds, Jib halyard, jib sheet, If it doesn't do me any good, I will order some of the good expensive stuff Gary sent the link for.

    Ok, so this weekend I did quite a bit of work. Mounted severaly pad eyes on the aka's and boom to allow a sheet for the jib to work and for a boom vang. I also made a "anti mast rotation" mechanism. My mast has been rotating around recently since I put the boom on, and the partner is getting more loose around the mast due to a little natural wearing from the friction of the mast. I also found a slick compas on the amazonian walmart and mounted it in a very nice spot. Check out the pics:

    Todd, Dave and Gary take a look and tell me if the clew of the jib needs to be further back behind the mast the jib is kind of slack in this picture. Normally it is a few inches further back:

    20220220_161011.jpg

    20220220_160522.jpg

    Here is the boom vang I made. Holy crap, talk about a rock solid boom that don't move at all now. I had no idea how solid the vang makes it. My boom had been rising up when I would try to tighten the halyard or down haul. Now I bet I will be able to shape the sail even better:

    20220220_160605.jpg

    This is the anti rotation mechanism I made. I have a 3/8" Eye bolt all the way through the mast. The eye slides down over a bracket that is screwed into the partner. No more rotating mast causing my gooseneck to slip out of the boom:

    IMG_20220220_151035.jpg

    And lastly, my sweet compass! I was having a hard time with the compass on my gps. The 1 to 2 second lag on updating the screen when i changed course was irritating me. Now I can find the wind, and then just glance down at the cockpit and instantly know my heading and be able to quickly figure if I am at my prime angle to the wind or not. Sorry about the sideways picture.(interweb difficulties):

    20220220_160636.jpg
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  12. #467
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    I am going out again tomorrow since I have the day off for presidents day. I will try to remember to report back on how the additions improved or degraded performance.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  13. #468
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Holy efficiency batman. I went out on the lake today. Winds started out about 5 to 6 mph. I was hitting 4.5 and 5.5 mph. The Jib made a HUGE difference. Now that I have the mast tied down with some shrouds, and a boom vang on the boom, the mainsail shape is freaking near perfect. Nice and flat, hardly any wrinkles at all, smooth curvature. I started off with the jib tied off too far forward and to far out from the center line cause it looked kind of baggy. But it was still getting me much better speed than the mainsail alone. After I got across the lake, the wind died down to almost nothing. I could barely feel a breeze on my face. So I beached the boat, took a break, and re-configured the jib so that the tie off point was closer in, and further aft. I think it made a big difference. I got back in the boat, and there was not barely a breeze. But, I was still hitting 2 miles an hour! Even when the water was so placid and looked like glass, I was still making 1.7 to 1.9 mph. There were two other boats on the water. After I got back on the water and headed back across when the winds had died, they dropped their sails and powered back to the sailing club marina, one was about a 30 footer, the other a small day sailer about 20 feet. I never had to paddle today!

    EDITED to add: I forgot to mention, this is just a storm jib. Thanks to jmanflyer!

    Don't believe me? Check out this video:
    Last edited by Lee.007; 02-21-2022 at 09:51 PM.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  14. #469
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    If that doesn't convince you, this one should. Check out how glassy the water is due to no visible wind, but yet I was still scooting across at 2 mph!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  15. #470
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Glad to see it's all coming together for you, Lee. Trimarans can be really good at getting a lot out of really light air.
    -Dave

  16. #471
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    It certainly is coming together Dave. This boat has been a great training resource for me, along with all of everybody's expert advice. Cant wait to build my next boat and get it dialed in!!
    I only wish I had put the Jib on earlier. When I was adjusting the set of the Jib, every little adjustment I made definitely made differences. It was pretty easy to see the change in speed based on the small adjustments, so I was able to dial it in pretty quick. By the way, will a normal Jib work even better than a Storm Jib?
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  17. #472
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    There's an optimal amount of sail for a given wind speed and direction. Go with more or less and the boat won't perform as well. So will a "normal" jib work better? As always, it depends. That small jib you have looks pretty good. You might actually find that you don't get much more out of a bigger sail. But it's always fun trying.
    -Dave

  18. #473
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Well, I didn't mean a bigger jib, just a regular jib instead of a storm Jib. But I believe in the "if it ain't broke, don't fix it" philosophy. I am going to try and get back out on the water soon. If the storm jib works, then why change it, right?

    My neighbor came over today while I was out adjusting the jib sheet. Turns out he is a well seasoned catamaran sailor. He gave me some pointers on speed. He told me I could adjust the angle of attack on my leeboard to generate some lift in the windward direction, thereby reducing leeway. I did some internet research, and found a site that said to do that you need to measure your leeway angle by towing something behind you tied to the centerline of your boat, and use a protractor to measure the angle. Then you set the leeboard angle of attack at that angle. But, you need two leeboards to do it. When you tack, you raise the windward leeboard, and drop the leeward leeboard (maybe thats why its called a "lee" board hmmm?). Anyway, I don't have two boards, and it would take me a few weeks to make one with my current work and school load. So, what about an adjustable leeboard, that I can rotate to port and starboard depending on which tack I am on? Do y'all know of anybody that has done this before?? I could make another leeboard, but if I am going to spend time cutting more lumber, I want it to go into my new boat I want to build. And yes, I plan to put two leeboards on my next trimaran, and make them adjustable So I can measure the leeway angle and set them at the correct angle for a given wind speed. Cause I think different windspeeds probably cause different leeway angles. What do you guys think?
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  19. #474
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Hey guys! Long time no hear. I know, but, I've been busy becoming a grandfather. My oldest son and his wife made me a grandfather two weeks ago. And yes, that little girl already has us wrapped around her finger.

    But anyway, I am going to try to head out again tomorrow. Winds are going to be about 12 to 15 mph, and I am trying to talk my sons into going with me, towed behind in kayaks. Maybe get some close up video of the boat while under sail. My only worry is that it might be too much wind. But we shall see.

    I put some amsteel shrouds on the mast. Thanks for the tip on Amsteel Gary!. They are super strong and rigid. No stretchy stretch like the crap from Lowes. I bought 600 feet of 7/64"diameter for 130 bucks. The website said it is supposed to have a tensile strength of 1100 pounds. I swapped out everything with it except the main sheet and main halyard. That small diameter line might cut my hands. Can't wait to see if it makes a difference on the jib's sail shape. I'll post back and let yall know how it goes.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  20. #475
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Well guys, I survived my first capsize yesterday. Wind was blowing a steady 18 mph, and according to the weather station gusting up to 30. I thought with my son tethered in his kayak to the windward aka I would have enough righting moment to keep me from flipping. And I did. And it worked. Until it didn't.

    Even with him tethered, I still had to hike out on the windward ama to keep from burying the leeward ama. The wind was picking up, and the gusts were getting stronger. I was hoping to get across the lake and let the wind die before we would have to head back by dark. I had pulled Noah, my son, up to the rudder so he could adjust the hieght of the tiller pin to enable me to hold the tiller up higher. During this process he lost his paddle. The wind and the waves were beating us together like crazy. I gave him my paddle so he could go back and get his, and told him I would turn around and catch up to him has he was retrieving his paddle which the wind had blown about 30 yards behind us by the time we got the pin changed. We had been heading up wind, and I figured I would turn with the wind, keeping the wind in my sail as I headed back down wind so I would not have to let the boom cross over. As I was about half way through the turn when another gust hit me and shoved the leeward ama down to Davie Jones's locker. I tried to counter it and hike out more, but I wasn't quick enough. I was on the windward ama and the wind flipped the boat so fast it kind of threw me into the lake. My son saw what happened, and paddled back to me. After gathering my wits, I told him to push down on the leeward ama of the now capsized boat. We both pushed down, and I got it to where I could get my feet up on it, but it still wasn't enough to right the boat. I was scared the mast had dug into the bottom of the lake. Noah decided to go ahead and jump in and stand on the ama with me(kudos to Noah, I had a wetsuit on, he didn't, and the water was frigid). Between the two of us, and the wind blowing against the now windward ama, we got her flipped back right-side up. I dragged myself aboard, and quickly put her in irons. After resting for a bit. I sailed her back to the ramp, with a fully swamped cockpit. I think the extra weight of the water gave me some ballast to keep me from flipping again.

    So, if Noah and I are going to go out in winds like that again, "...we're gonna need a bigger boat." I have never seen the lake like that. The waves were literally long swells like you see at the beach, but coming at us at a faster rate that what you see at the beach. I should have listened to my intuition and not gone out. But, I am hard headed and only learn by experience.

    So Sorry guys, no video for this trip. My cell phone, GPS, and some good 5V batteries are currently being used by Davie Jones to call up the Kracken!
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  21. #476
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Congratulation on both of you surviving. Seriously.

    When you have a chance to calmly think about what happened and why, you will be able to review old comments and see where there were good suggestions.

    Experience is a bitch, but a great teacher.

    Some of the best tri's in the world have gone over just like you.
    Even when you build a bigger/ better boat, nature can humble you.

  22. #477
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Now you will start to think about rigs that are easy to reef.

  23. #478
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Thanks Gary and upchurchmr. I know exactly what happened and why. I had too much sail up, and not enough weight out for the 30mph gust that hit me. Oh, and as I went around the bend of the turn, I was more focused on sailing back to my son in the kayak, than I was about shifting my weight to windward. As I settled down on the drive home, I realized that I didn't get to windward fast enough, because my dumbass was sitting on the leeward aka as I went around the turn(the windward aka became the leeward aka, duh). I knew better, but when I realized my mistake, it was too late and Poseidon decided to show me who owns the sea.

    So, Lessons Learned:

    1. Never be distracted when the wind conditions demand your extreme attention to detail and situational awareness. I never should have gone out in that kind of wind while I was trying to keep track of where Noah's kayak was behind me and making sure the tether line wasn't getting tangled up in the rudder.

    2. TIE EVERYTHING DOWN. I was kind of in a hurry at the ramp. I just through my little bag that normally holds my GPS, keys, wallet, phone, etc., into the cockpit as we were shoving off. Usually I have it tied to the inside of the cockpit somewhere. Yesterday for some reason I did not. Luckily I had put my wallet in the car yesterday. But my phone and my favorite GPS are on the bottom of the lake in over 20 feet of water.

    3. Make all adjustments at the ramp / dock before you head out. I was in a hurry to get away from the ramp because the wind was blowing me towards the dock before I even got my sail up. I didn't tidy up the halyards or the down hauls for the main or jib and I had a spaghetti mess of lines around my feet in the cock pit. What's worse, I had tightened the main sheet up way to much while I was at the ramp to keep the boom from swinging. This prevented me from hauling the sail all the way to the top of the mast, and I spent 15 minutes trying to find something on the mast holding it up while the wind was blowing closer and closer to the dock. I finally figured out it was the main sheet pulling the boom down almost too late. I thought I would just get out in the middle of the lake and put her in irons and straighten everything up. But I was in the thick of it before I got 20 yards from the ramp, and its hard to go fishing when you are up to your ass in alligators.

    4. Never get in a hurry. See number 2 and 3.

    5. Know your boat's limits. This one is probably hard to know without experience, some naval architect knowledge, or going over like I did. But, I should have noticed that all the other sailboats on the water yesterday were heading in, as I was heading out. Most of them were healed over just about with the lee rail under.
    Last edited by Lee.007; 03-20-2022 at 09:40 PM.
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  24. #479
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Hey guys! I took some leave this week and got to get on the water twice. But only one counted. The first was a warm day with nice winds. I am currently compiling a video from that day. Watch it until the middle, and you will see a surprise. In the beginning of the video, I am going down wind trying to learn to fly wing and wing. I got the jib to stabilize for a little while, but it seems that the sweet spot has a VERY narrow bandwidth. Stray a little too far to port or starboard with the tiller, or loosen one end of the jib sheet even slightly, and that freaking jib starts to luff like a mad man. Is this normal behavior for a jib when you are trying to fly wing and wing? The last part of the video after the surprise just shows me on a starboard tack with the jib nice and tight, and then landing at a secluded beach I found.

    Looks like the video is going to take all night to compile. I will post it tomorrow. Take a look at it and let me know what errors I am making when trying to go wing and wing.

    So the second day I went out, I got to the ramp and spent an hour waiting for the winds to die down enough for me to launch. They were blowing 18 and gusting 25 mph. I checked 4 different forecasts and NOAA before I left, but the atmosphere made liars out of all of them. I bought an anemometer so I would know exactly what the winds were (learned my lesson from the capsize event with my son). So I waited. At about 5pm the winds had died to 5 or 8mph. So I launched. I only put the jib up. Kept the main rolled up on the boom. I was having a heck of a time keeping the boat straight, oh, and the freaking winds picked back up on me. The freaking whitetop waves were nearly enough to capsize me. I just don't understand how these waves can be so big on a lake. Well, not that big, maybe 3 to 4 feet, but their period is only about 15 to 20 seconds so that just keep pounding and rolling you. I knew the forecast said the winds were supposed to die throughout the evening, so I tried to hang on. About 30 min later, I still was not even out of the cove where the ramp is, and the winds had not died at all and the jib was acting like a pissed off kite. I stood up, grabbed the mast with one hand, and rolled the jib up with one arm around the mast, and the other trying to roll the jib. I tied it off with a bungee, and then started to paddle. It took me another 45 min to keep the boat in the wind, not broadside to the wind and waves cause that was dangerous at this point, and paddle to the ramp. It took every ounce of strength I had to make the short 300 meter trip back to the ramp. It was a constant battle to keep the boat pointed in a direction close enough to the wind so I didn't get flipped by the waves, and still keep it pointed close enough towards the ramp. I knew worse case scenario I would just let the wind blow me up the cove to the shore line, steer myself to a decent spot if I could, and wait it out. There was one point in the shore line that was a rocky peninsula, so I would have to paddle/sail away from that or risk being smashed to bits on the rocks, but the rest was sandy. When I finally got back to the ramp my shoulders and back were screaming. I think I sat there in the boat a good 5 minutes before I got out to go get the Jeep and the trailer. Once I got to the car, I got my anemometer out and checked again. It was a steady 15mph with higher gusts. The highest one was 19.5mph. I packed up the boat, drove home, and slept like a baby that night.

    Soooo, I am learning that my boat's max limit is about 10mph winds. Anymore than that is no fun. If there are whitetops, it is at least 15 mph. Now I know when to stay home, and when to go to the lake. Assuming the forecasts are correct that is....
    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  25. #480
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Here is the video. Let me know how to be better at flying wing and wing:

    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  26. #481
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Ok sailors, so whats the best way to control a jib????

    I don't know if you can tell from this video, But running a jib is very stressful for me under some fairly strong winds. I was on the other side of the lake yesterday and a storm started trying to organize itself. Winds started picking up, so I sprinted for the ramp on the other side of the lake. I didn't want to get caught in 3~4 waves and 13~20 knot winds and capsize again. After each tack, I spend a good amount of time trying to decide where I am going to put the jib sheet, figuring out how much tension to keep it from luffing, etc. Unless y'all have some good advice, I think I will just roll up the jib when the winds pick up. But under light winds(less than 6 to 8 knots), the Jib is a dream.

    What is the best way to manage a jib? Here is the video from yesterday when I went out in some moderate wind(but not too strong) :

    “If everybody is thinking alike, then somebody isn’t thinking.”
    “You’re never beaten until you admit it.”
    - General George Smith Patton

  27. #482
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Any possibility of substantially increasing the jib luff tension? There is an unusual (and quite undesirable) amount of jib luff wobble going on in the last two videos. It tends to create excessive amounts of jib draft (especially in heavier air) and a constantly changing jibsail shape, which is pretty much never a good thing.

  28. #483
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Quote Originally Posted by Todd Bradshaw View Post
    Any possibility of substantially increasing the jib luff tension? There is an unusual (and quite undesirable) amount of jib luff wobble going on in the last two videos. It tends to create excessive amounts of jib draft (especially in heavier air) and a constantly changing jibsail shape, which is pretty much never a good thing.
    Todd, THANKS! I was wondering why it just didn't seem to want to settle down. There was like a very narrow sweetspot between too much / not enough sheet tension, and pointing too high or too low to the wind. I will try to increase the luff tension, both with the forestay turn buckle and the jib down haul. Or should I worry about one and not the other? Seems like when I have tightened up the jib downhaul, the forestay loosens. So I tighten up the forestay, and now the luff is loose again, rinse and repeat for 30 min until I start cussing like a drunken sailor on liberty in tahiti. And of course there is the frustration of not yet having enough experience to know how tight I should make the forestay and backstay out of fear of breaking the mast or the deck where I have it attached to an eye bolt(screw) that is going into the epoxy from the end pour.

    But I did notice last Saturday that the mast was much better behaved after adding the back stay. When the seadoos and 500hp speed boats go screaming past me, the mast use to flop and sway quite a bit in the waves. I didn't notice nearly that much sway at the top this time out. You can actually see the backstay flexing and relaxing in the last video. I was originally thinking the two side stays with their attachment points about 6 inches aft of the mast would create enough back tension, but obviously they were not. So I cut my boom, which was too long for the sail anyway, so it would swing inside of a back stay, and added a back stay. I am using the amsteel rope suggested above for shrouds by the way. I loop them through a stainless turn buckle up to a double figure 8 knot that forms a loop, pull tension through the loop, and then getting that last bit of tension with the turn buckle. But no matter how tight I get them, the leeward shroud always gets slack in it under wind. I looped a bungie cord through it to keep it from slapping around and loosening the turn buckle. When it is on the windward side, the bungie flexes with the shroud tension.

    Is there a better way to tension the shrouds, fore, aft, port and starboard? Or am I doing as best as possible given the limitations of my rig setup? ( I really need a little bit bigger, more capable boat to satisfy my aspirations )
    “If everybody is thinking alike, then somebody isn’t thinking.”
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  29. #484
    Join Date
    Oct 2002
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    Default Re: Newbie needs help with small DIY sail plan, trimaran setup.

    Some diagrams that may help.





  30. #485
    Join Date
    Jun 2000
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    Madison Wisconsin
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    10,432

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

    I'm really not aware of any situations where a sagging jib luff is a good or desirable thing. It creates excessive draft, screws up the sail's designed and intended shape, and the "shape" that it does create is totally unstable and constantly changing. When we design and cut a jib luff, the final luff shape is not straight. It has some convex shape added to create draft and also some concave shape subtracted to compensate for a certain amount of inevitable luff sag. The final luff generally comes out as a shallow S curve, concave in some areas, convex in others. A saggy luff tosses all that work and planning and predictability out the window.

    A jib downhaul can at times make up for lack of good jib halyard tension, but its main function is usually to move the draft forward when desired. Tensioning it tends to gather the sail's luff round into a crease along the luff, flattening the sail. This would be something that might be desirable if you are sailing in high winds or trying to point as high as possible. It's essentially luff tensioning more than normal, and for a specific reason. The same sort of thing can be done on a mainsail using a tack downhaul or a Cunningham - gathering luff round up close to the mast. It may even make a vertical wrinkle in the sail, just behind the luff, which may not look pretty, but can be pretty effective at times.

    So step number one would be to get the forestay tight and leave it that way. It needs to be solid enough to support the jib. The jib downhaul can then be used for a bit of sail shape fine tuning. The exception to this would be something like the system on a Hobie 16. In that case, there is a fixed-length wire built inside the jib luff and the jib luff is not attached to the forestay. The forestay is basically just there to hold the mast up when the jib is not hoisted. In use, the jib halyard is tensioned so much that the forestay is slack and the jib's luff wire is taking all of the headstay tension - and providing a nice tight jib luff.

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