Thread: GIS Yawl

Originally Posted by CCBB

Good measurement...60" it is on the plans!

Mizzens are too much fun. I was surprised the wind on the bow didn't overpower the mizzen.

Some other feedback from MIk from Texas 200. When seawater gets into the mast tube for the fwd position, if the mast fits the step tight, the water may not drain out and fill the tube. I plan to leather the mast to keep it from chafing. I will add a plywood ring around the partner, and use a canvas boot cinched around ply ring and mast to keep water out.

Attached is a more up to date plan with some notes added. I was able to pull the mizzen aft and move it closer to centerline of boat, about 5 1/2" away, but I'd go 6" minimum. Other notes on plan.

Clint,

I like the adjustments to the Yawl Rig you have made. Keeping the water out of the front mast step is more of a maintenance issue than a sailing issue. Bigger drain tubes will help. When we finally got the mast out, it was stuck after 6 days of sailing, there may have been as much as a ½ gallon of water trapped in the front mast box. With the new aluminum tube design you have invented that amount of water will never accumulate in the mast step. With my forward box full of water I was carrying about an additional 4 pounds of weight in the front of the boat. With your new design that will never happen.

My mizzen placement does tend to be left handed. With the mizzen moving closer to the centerline the boat, it will be more neutral on both tacks.

Moving the mizzen aft will help the boat track better. I have not felt any undue pressure on the rudder with the mizzen located where it is on my boat. So moving the mizzen back a little will help the yawl rig track even better. My concern is how to tie the mizzen sail tack down. I tie my mizzen tack down to a pad eye just behind the mizzen. That means it’s between the mast and the transom. So with moving the mizzen mast aft, the tack will need to be secured in a different way. The tack downhaul is the only thing attaching the mizzen to the boat. In the event of capsize; the downhaul is the only connection between the boat and the mizzen mast.

We had the mizzen mast slip out of the lower step during a hard and long pounding to windward a few weekends ago. We noticed the mizzen swinging around after we got to a little island for lunch. I believe it was more of an issue of the mizzen downhaul was not tight enough. Another idea might be to add another 20mm of timber the lower partner. That way the mizzen cannot bounce out of the lower partner as easy. On both Texas 200 events we never had this happen and it has only happens once. So this event is rare.

I think the adjustments you have made will fine tune the rig and make it even better.

Best wishes

Originally Posted by CCBB

The mizzen is 2" and the sprit is 1" square with roundovers. I feel like 2" may be a little flexi for a hollow...feel free to add 1/8" if going hollow.

Thanks, Clint.

I'm thinking of getting a two piece fibreglass mizzen made on a tapered mandrell, probably about 55 mm ID/60 mm OD at the bottom, tapering to about half that at the top. I could look for a windsurfer mast, but if I get one made, I'll be able to get it optimised for stiffness at the bottom. Should be reasonably cheap in fibreglass, carbon probably isn't worth the 5 time price for the weight saving at this size.

Other ideas: (good or bad?)

Put the mizzen step on top of the aft tank and the partner near the top of the transom inside face. Partner with a half round cut-out and lashing to hold mast in place. Needs the top of the transom to be strong enough, but I think mine is.

Saves cutting a hole into the aft buoyancy tank and should make it easy to drop the mizzen and put the whole thing away if I want.

Leave the main mast step/partner as is. My centreboard slot is wider at the top, extended forward from standard, so I can angle the centreboard more than standard and move the CLR back at least 6 inches, which should have at least the effect of moving the main mast forward.

I'm curious to hear your thoughts.

Ian

I'm thinking of a later design, SOF folder, kind of a sailing canoe but with a transom, a bit like a slightly bigger version of Dave Gentry's Ruth, but on the concept that Keyhavenpotter and John Welsford are working on with their Nautilus - good sliding seat rower plus fast sailing canoe plus room to sleep inside, so I'd be able to use the mizzen mast as a stowable main mast for this design.

John, Thanks for your comments. I will be going to you now for GIS expertise, so having your feedback is great.

Ian, Did you already make your aft tank? Good...even more fun to cut a hole...I'll likely convert a local Goat into a mizzen version. I will cut the tank open, build the step, then scarf the tank back in place. Easy with a grinder, spokeshave, a little ply to double up the scarf underneath if any at all. That is what I would do. I think the glass mast is a fine idea. I have to say I picked up a carbon mast on a boat with a lug about the size of the gOat...it was striking how much lighter it was than even a birdsmouth with spruce and light scantlings. Glass fiber would be fine for a mizz.

Cheers

Hi Clint, (or John Goodman), do you have a weight for your (I presume hollow birdsmouth at about 2 inch OD?) wooden mizzen mast?

I just got my fibreglass mizzen, it's wound on a 50mm dia tapered mandrel, 2.5 mm wall at the base going down to 1.5 mm wall and 25 mm ID at the tip. Stiffness about 30 % more than a solid 50 mm diameter wooden section.

Looking at the numbers for strength and stiffness for fibreglass versus wood, I think I could have spec'd it a bit lighter, perhaps 2.0 mm wall at the bottom down to 1.3 mm wall further up, stiffness would be about the same as the wooden stick, but ultimate strength of the glass mast would be a lot higher as it would bend a lot further before it would break.

Weight about 2 kg, I could have done it in carbon at about 1.3 kg for about seven times the price but saving 600 - 700 g didn't seem worth that much money.

It's sleeved in the middle so it comes apart into two 1750 mm pieces so I can keep it stowed up the front of the boat, decide if I want to use it just before launching.

I'm going to see if I can manage the balance with the mizzen by just moving the mainsail a bit further forward on the mast, and angling the centreboard back a bit. (My centreboard case is a bit wider than standard at the top so I can adjust things a bit more than normal)

Ian

Ian, I have no idea what mine weighs. I still need to get a scale for the shop. When I do, I'll report out.

Cheers

Ian
I just ran out in a rain shower to weigh my mizzen mast thinking I may have a weight you could use, wrong. As it turned out my finished birdsmouth Sitka spruce mizzen mast = 3302 length, 50.8mm down to 28.575mm weighed in at a whopping 3.95kg. I think I could have made a solid stick and it wouldn’t have weighed any more. It must be all those coats of clear coat and varnish. To get down to 2kg I’ll have to go back to the drawing board.

Rod

Hi Rod, it's great to have the data point, thanks for taking the trouble.

I can figure out theoretically how heavy a 50.8 mm dia, wall thickness 20% of OD 3.3 metre long tube from spruce (density 480 kg/cu m?) should weigh, it should come in not much more than 2.2 kg, a solid stick of 50.8 mm calculates as 3.3 kg or so.

I suspect the difference is in the blocking and the weight of epoxy that goes into a birdsmouth spar, it must be quite a high proportion of the weight especially at these smaller diameters. Also as you say the epoxy and varnish you put on the outside to protect it adds up.

Again, in theory a hollow mast should save 40% over a solid one of the equivalent stiffness and strength, but perhaps there is nothing in it at these smaller diameters.

I'm curious if Clint can get any data on all the birdsmouth spars he makes once he gets a set of scales for his workshop.

These mandrel wound fibreglass spars represent pretty good value for money - my two piece mizzen mast cost about $150 inc tax for nearly half the weight of a wooden one, to get one done in carbon would have cost $800 +, for a weight one third of the wooden one (1.3 kg).

Ian

Edit and correction: I got the tape measure out and a more accurate set of scales, my fibreglass mizzen is 3400 mm long, it weighs 2000 g without the joining sleeve, with the joining sleeve it weighs 2250 g.

I'm going to step it on top of the aft tank, with a partner on top of the transom, so I'll cut 300 mm off it so it's effective length is the same as on Clint's plan.

Well, my Goat is painted. It has been a haul. I WILL sail my bumm off this season. Very happy with the finish. I was going for really nice, but not nec. yacht finish. This skiff will get used. NO VARNISH!


006 by Clint Chase Boatbuilder, on Flickr

I think I will name the boat Flicker. Not 100%. She has character now with the paint, so the name should come more easily.

I still need to make my oars. Actually, I have a pair of GIS oars that were for somebody but they have not been picked up.

Originally Posted by CCBB

Well, my Goat is painted. It has been a haul. I WILL sail my bumm off this season. Very happy with the finish. I was going for really nice, but not nec. yacht finish. This skiff will get used. NO VARNISH!


006 by Clint Chase Boatbuilder, on Flickr

I think I will name the boat Flicker. Not 100%. She has character now with the paint, so the name should come more easily.

I still need to make my oars. Actually, I have a pair of GIS oars that were for somebody but they have not been picked up.

I think Flicker is a fine name. I've already told you I like your paint scheme. The white maybe be too bright, and the dark thwart too hot... but - as you say - maybe not in Maine. Time will tell. Nice job! Time to start thinking of posing her for next years GIS calendar!

Originally Posted by CCBB

Well, my Goat is painted. It has been a haul. I WILL sail my bumm off this season. Very happy with the finish. I was going for really nice, but not nec. yacht finish. This skiff will get used. NO VARNISH!


006 by Clint Chase Boatbuilder, on Flickr

I think I will name the boat Flicker. Not 100%. She has character now with the paint, so the name should come more easily.

I still need to make my oars. Actually, I have a pair of GIS oars that were for somebody but they have not been picked up.

OH HAPPY DAY!!!

The interior is Brightsides Seattle Gray. I have painted a couple dories with it and it is really lovely even in bright sun.

I'll get some hardware on this weekend.

Howdy.

I always find the discussion about painting interiors of open boats or decks of bigger boats in white interesting.

I've sailed on bigger boats with pure white decks and never found it a problem. The brightest things are the sun and the water. And then when it is overcast or dusk the white decks are really nice.

Michael

Clint, I hope you're GIS build is progressing well. I have two yawl-related questions for you, one for each end of the vessel.

1) What are your thoughts on a square section mizzen mast? Would that be incompatible with the sprit's snotter set-up? My main mast is square and I do appreciate the lightweight construction method. It's not a deal-breaker for me; if I have to do a round mizzen I can live with it.

2) Do you think the forward main mast step is essential? Or is it technically correct but undetectable by recreational sailors? [John G. and/or MIK's experience with the set-up might be invaluable, but as the designer of the Yawl variation, I wouldn't want to ignore your opinion.]

The other yawl sailor will chime in here:

Originally Posted by davlafont

Clint, I hope you're GIS build is progressing well. I have two yawl-related questions for you, one for each end of the vessel.

1) What are your thoughts on a square section mizzen mast? Would that be incompatible with the sprit's snotter set-up? My main mast is square and I do appreciate the lightweight construction method. It's not a deal-breaker for me; if I have to do a round mizzen I can live with it.


2) Do you think the forward main mast step is essential? Or is it technically correct but undetectable by recreational sailors? [John G. and/or MIK's experience with the set-up might be invaluable, but as the designer of the Yawl variation, I wouldn't want to ignore your opinion.]

1. I am building a Jim Michalak, Hap's Cut and it has a solid square mizzen mast. If you can build a light weight mizzen mast using the same technique as the main mast go for it. A solid mizzen mast is too heavy for a GIS. My GIS mizzen is a birdsmouth and it has performed well in every condition I have sailed in. (Thanks to Clint, he made it for me)

2. I have played with sailing in yawl configuration with the mast in both front and normal locations. The front step is a must for the long distance cruising I do. That extra few inches of separation between the mizzen and main mast helps the boat track and stay on course. The front mast step's only drawback is that it pushes the boom/tack of the sail closer to the front of the very narrow bow. Mik and I had no trouble with him in the rear of the boat and me way up front. When reefing by myself I can feel the transom get pretty light as it lifts up in the waves while I am tying the new tack in. ( I weigh 205 lbs) Here is a picture of Mik and I tying in a reef in 20knots of breeze and "flat" water during the Texas 200.

I found that with the main mast in the normal position the mizzen can cause more weather helm with less sheet tension. Off the wind it sails about the same but when close hauled the mizzen becomes less effective and pushes the boat into irons easier during a tack. We found releasing the mizzen just before "banging" the tack made the boat roll over to the other tack nicely. Get the main powered up then slowly sheet the mizzen in. With the main mast in the forward step we could be a little more lazy when tacking.