Thread: GIS Lugs’l Design (and eventually, build)

Originally Posted by Boatmik

I remember Todd saying (and it makes complete sense) that it is a good aim to have a seam coming in to meet the throat. That becomes a really useful place to put some broadseaming - if you are doing broadseaming.
...

I'm kinda sorta doing broadseaming. With traditional broadseams, one gradually increases the overlap of two straight edges. In effect, one of the two edges can be considered the baseline, or reference, and the other describes a curve away from that baseline. What Sailcut does is determine precisely what that curve is. The corresponding edge of the adjacent panel is left straight by the program and when matched to the curved edge, the draft is defined just the same as in broadseaming. The difference is that one may choose to leave the ever-increasing overlap of a broadseam in place--hence "broadening" the seam. But if one chooses to trim the excess to maintain a uniform seam width, one ends up with a curved cut edge just like Sailcut defines.

Personally I dont' like roach on lug sails - I really like the simple shapes of the traditional sail.

No roach for me. I'll either revert to a straight line leech, or cut a touch of hollow. I just haven't yet found my original source reference on that recommendation yet.

Finally (for tonight), here's a shot of my sewing practice project. More details on my blog (linked in my signature).

Hi,

I think this shape is looking much better. As you say, you still have all the adjustment and spar bend to flatten the sail.

Also confirming that you do need a decent amount of reinforcement down the luff as there are huge tensions there. From what you mentioned in an earlier post, you were doing this. I have 5oz cloth and this is only doubled along the luff, but it's not enough so I'm going to get some extra taping sewn on. (Yesterday I had the luff vibrating like crazy as it has stretched a bit)

Originally Posted by woodeneye

Hi,

I think this shape is looking much better. As you say, you still have all the adjustment and spar bend to flatten the sail.

Also confirming that you do need a decent amount of reinforcement down the luff as there are huge tensions there. From what you mentioned in an earlier post, you were doing this. I have 5oz cloth and this is only doubled along the luff, but it's not enough so I'm going to get some extra taping sewn on. (Yesterday I had the luff vibrating like crazy as it has stretched a bit)

Howdy,

In the bottom third you can design in the flatness you want, but if the sail is set up loose footed, you can just add the depth you want by easing the outhaul. This has found to be important for good pointing.

If a laced foot you would need a fair bit of depth designed in that area as well as there is not as much of an option for easing it out - and lots of foot round.

The leach will need about 50mm of hollow, but check with your books.

MIK

Originally Posted by Boatmik

Howdy,

In the bottom third you can design in the flatness you want, but if the sail is set up loose footed, you can just add the depth you want by easing the outhaul. This has found to be important for good pointing.

If a laced foot you would need a fair bit of depth designed in that area as well as there is not as much of an option for easing it out - and lots of foot round.

The leach will need about 50mm of hollow, but check with your books.

MIK

Good points MIK. The loose foot is very flexible in that respect and a lot less work and cheaper to make.

Originally Posted by Boatmik

Howdy,

In the bottom third you can design in the flatness you want, but if the sail is set up loose footed, you can just add the depth you want by easing the outhaul. This has found to be important for good pointing.

MIK

Mik,

These were your recommendations a year ago. Do they need updating?

10% draft for upwind in rough water or when you are looking for more power
14% when reaching with flow attached to the sail
5% in very flat water and good wind strength upwind for higher pointing
0% when running with the flow stalled around the sail or upwind in strong wind and flat water

Brad

Howdy Brad,

Those are just general guidelines. I think if they need any refinement, you are the guy who knows now after all your practice!

With a sloop rig the mainsail must be a bit flatter along the foot when going upwind.

Actually Brad, if you feel like it I would be really happy if you wrote something for the WIKI about using vangs etc on lug rigs - and how you gradually improved your setup until you started to be kinda OK in solo sailing. (and then what happened sailing in the fleet!)

Would you be happy to do that - no pressure! Brian was the main person that instigated the discussion of these bits, but you are the guy that has experienced the before and after comparison.

MIK.

Originally Posted by Boatmik

Howdy Brad,

Those are just general guidelines. I think if they need any refinement, you are the guy who knows now after all your practice!

MIK.

I thought the GIS guys were getting everything figured out

I really don't have much time in the OZ, maybe 30 hours, so I definitely don't have anything optimized. There are three things I've done that have helped significantly.

First I moved the sail tack closer to the mast. I started at 400mm but the boat points higher now that I've moved it to 300mm.

Next I installed a Laser style mast mount wind indicator, before that I tried tell tails at different locations on the sail but couldn't get them to perform satisfactorily due to turbulence from the mast. I now compare boom angle to apparent wind angle, since the end of the boom and wind indicator are in close proximity, and the boat seems to point well with the boom angle about 10 to 15 degrees lower than the wind indicator angle. When I have good speed upwind I sheet the boom in to about 6 inches inside the transom corner.

Third I installed a compass, seeing a compass in an 8' Puddle Duck got a few chuckles at Sail Oklahoma but they can be a valuable tool when racing. Using the compass I kept making adjustments to sail trim and sheeting angles until I could consistently tack through 90 degrees.

In good breeze I set the draft at 8 to 10% and forget it. In lighter wind I try to use your guidelines. I only use the vang when reaching or running and give it a good tug to reduce sail twist but with 6:1 purchase it doesn't have enough power to get the yard and boom close to parallel.

I'm sure I could get more out of the boat If I had someone to do two boat testing with but it's hard to gauge any performance gains at this point.

Brad

If all goes according to plan, this stuff will be transformed but my two hands, one sewing machine and a yet-to-be-determined amount of beer into a GIS Lugs'l.

That's 16 yards of 4 oz. Dacron surrounded by the supporting cast of tapes, thread, rings, tools and plans. Most of these goodies were sourced from Duckworks Boat Builders Supply, with some augmentation from Sailrite.com. I can't say this is the most economical way to go about it, but the materials here were a little less expensive than buying a Duckworks sail. And I will love it more (like it or not!).



I'm a little crazy. Let's just get that out there. But a significant cost driver were these brass rings and liners. They will be the basis for the major lashing points, peak, throat, tack and clew. These will be handsewn, so not only did they cost more money that necessary, they will take more time than necessary. And they will be overkill. My future GIS will see inland lakes and an occasional dip into protected Atlantic waters such as the New York Harbor, and the Long Island Sound. Maybe Callsign will badger me and humiliate me into sailing up in Maine, but there will have to be some serious spirits involved (arrr!). But I digress...



Along with MIK's plans, I've been collecting various tips, advice, and lessons learned from the great members of this forum (Wooden Boat Forum too...). Thanks in advance for the support I know I will receive from this great community of sailors. My goal is to join the ranks this year with my own Goat worthy of the company. Click on the blog link in my sig for additional pics of my new goodies.

Ciao for now...

Originally Posted by davlafont

maybe callsign will badger me and humiliate me into sailing up in maine, but there will have to be some serious spirits involved (arrr!). But i digress...

aarrggh scurvy dogs we will drink rum!

Subtitle: "I'm doin' it mom! I'm makin' a sail!"



What's is this a picture of? Why, it's my makeshift pseudo-loft in operation of course! I've cut out all the panels using a plywood drafting board and my metric ruler and tape measure. The full details are on my blog, but here's some feedback:

Just like MIK's plans give measurements to a tenth of a millimeter, so does SailcutCAD. It took no time at all for me to realize how innacurate I was going to be, and thus how relaxed I could be. I cut each panel individually and they will all be assembled soon.

It was fun working with Dacron and I really got a sense for how big this sail is really going to be. I'm not really sure where I'm going to store the thing once it's all stitched up, but I may as well figure that out now since I'll be making spars pretty soon. Really.

At some point, I should probably visit a real-live GIS in person. I think the first Goat I ever meet should probably not be my own... So a shoutout to Alzuger: start thinking about when you're going to launch this spring!

Dave, it's great to see someone else using Sailcut4. I think it's a great resource for all lug sail sailors. Lots of fun and so much to learn about sail shaping.

Just checking, I see you are about to assemble the sail. Have you obtained the correct double sided sail makers tape? I guess Sailrite would be your supplier. Impossible to sew without it - cheap tape will clog your needles.

I used the corners of the actual sail panels to draw all the patches, luff re-enforcements etc.

You will be so proud when she drives your dinghy along. My sail was a simple flat panel dacron sail, but I have properly shaped designs just waiting to be made.

When you get to sewing, the main issue is controlling all that cloth, and feeding the machine. Two people will be best.

Good luck

Brian

Yes, yes, double sided tape from Sailrite is in effect.

I stitched the first three seams last night and will post updates tonight after stitching some more. The tape from Sailrite did make the needle gummy, but I was able to get by cleaning after each seam.

Two people will be needed tonight as the panels are getting longer! Stay tuned...

This is the second of three seams sewn yesterday. Only one hiccup with tangled thread occurred. I was either a sticky needle from the double stick tape, or it was a bobbin that was not very tightly wound. I address both and things went well afterward.