Thread: Building Shesha, a Hunter Valley GIS, Australia

Originally Posted by Boatmik

If the vang and downhaul don't go down to the same point - to avoid the problem of the lines wrapping around the mast there is some hesitation in the movement of the boom when it is trimmed through big angles until you adjust the vang and/or outhaul - requiring adjustment of one or both - there are very high loads at deck level - so those points need to be strong.

I thought a lot about this when rigging my Scow and the best method I could think of was to lead both vang and downhaul to the base of the mast.

I wanted all the tension from the 6:1 downhaul and 4:1 vang to be kept within the mast and not pulling on the hull or deck. That is all the tension just going up and down the mast and no where else.

So, the mast sits on pad with eye bolts bolted through it. The eyes allow the small blocks to be fitted just with a rope loop. It so easy to pull screws out with the loads applied.

The pad it's self was just screwed into the centre keel.

Attachment 158944

Brian

Hoped you would drop by and add to this Brian!

Thanks!

MIK

Hi Brian

I would think that the Goat's deck is hugely stronger than the scow's deck, and I definitely would not consider attaching the downhaul to that deck! There is a lot of merit though in attaching the loads to the base of the mast, and I will go down that path now that I know how well the downhaul and vang work together.

If I pass my controls through a ss eye in the deck, that will eliminate much of the binding and likely that would be an improvement over the scow's arrangement too. I say this because I can see from this pic that as the boom swings, you will still get similar binding against the mast as I'm getting as the pivot point isn't central.

The other advantage is that all the blocks get moved to under the deck.

Thanks for that.

Attachment 159052

Sailing on Grahamstown Lake yesterday was a bit challenging. Lots of boats capsized due to the gusty wind that was swinging through 120 degrees.

As we were sailing close to a weather shore, the water was flat. We recorded some gusts of 20 knots, so I had some nice planing rides in the Goat.

There was the inevitable capsize, which was too bad as I was leading the fleet at the first mark, when hit by a gust just as I gybed. It had it's funny side, as I won the "Caught the most fish award"!

Another first happened yesterday. I can confirm that the Goat can plane upwind! I managed it several times on the flat water. The trick is to get the boat absolute flat while planing on a close reach and then come up into the wind gradually while hiking like mad to keep it FLAT, and she maintains the plane beautifully for 15-20 seconds or so, or until the pressure collapses. I'm guessing that when I was able to get it right, the wind was no more than about 12-15 knots. If there is too much pressure, I can't hold it flat enough.

I must get that hiking board made before the end of this summer!

[ame="http://www.youtube.com/watch?v=ZIm3-DXlaYQ"]YouTube - Catch fish with a GIS![/ame]

Check out some more video taken yesterday!

http://www.oztayls-shesha.blogspot.com/

That's a terrific video! What fun.

Did you gybe at the mark or before the mark? I find at the mark, there is a rotational force that seems to capsize as you head up. Being a scaredy cat i always try to gybe before the mark if it's fairly square. Broad reach to opposite tack upwind - not easy!

your waters must be very healthy - all those fish!

Did the others sailors have anything to say as they sailed by? At least a "thanks for that" is customary.

Brian

There's always lots of banter if anyone capsizes. There was plenty after I won the start, but they got back at me at the top mark.

The funny thing was I had been practicing gybing a lot before the race and am quite confident. I didn't have enough speed up as I rounded and the gust hit. I should have just bore away on starboard and gybed once I was planing. Stupid.

Water quality is excellent as the Lake is our main water supply

Howdy,
Not big enough. Better luck next time!

Planning upwind is a bit tricky in non trapeze boats.

The instructions for the Taser are

Boat dead flat
Jib sheeted wide
Main played to keep the boat flat
Only in smooth water or there is too much drag so you have to point too low to maintain speed
Centreboard half up - might be less up in the Goat.
To avoid the drag "hump" and get free acceleration, speed has to be around 8 to 9 knots. Maybe a little faster in the longer goat.

Mik

Yes, the Taser instructions would hold true for the Goat. The conditions for doing this are very rarely ideal. The most important one is for the water to be dead flat. With the wind on Saturday coming off the weather shore and being so gusty (0-20kts were recorded), the water surface was almost like glass and only tiny ripplets for what were in fact "bullets" on occasions.

When the wind gets up over 12 knots and I'm by myself, I've been pulling the board up by 15-20cm on the beats. If the boat is moving nicely it doesn't seem to hurt upwind performance by much at all.

I wrapped some rubber tape around the foot of the mast, so those very loud creaks that where happening as the mast foot shifted by a mm or so have now disappeared. You may remember some of them were loud "cracks" which could be a little disconcerting. With the rubber tape at the base, the mast doesn't move in the step at all, so I need a little tug now to free it when removing.

The mylar tape around the mast where the boom contacts and at the partner has worked a treat to quiet everything down. I've also applied some to the top of the mast where the yard rubs. It is wonderfull stuff and very tough and resistant to abrasion.

Boat is now completely creak and groan free!

That's interesting regarding planing upwind. An MG14 will plane upwind in about 15 knots, which is fringe trapezing breeze upwind. As long as the hull was flat she would plane.

Even when teh boat wasn't planing their was minimal turbulent wash around the transom.

Originally Posted by tpb03

That's interesting regarding planing upwind. An MG14 will plane upwind in about 15 knots, which is fringe trapezing breeze upwind. As long as the hull was flat she would plane.

Even when teh boat wasn't planing their was minimal turbulent wash around the transom.

That's pretty good considering the crew weights to be overcome!

As Mik says, it’s hard for a non-trapeze boat to plane upwind. The Goat seems to have the right hull shape to do it though. With its light weight and 105sf of engine it has the power to make it happen with one-up in lower wind speed registers, but adding another 70kg body means that your next opportunity to plane upwind will be at about 25-30kts. The trouble then is that holding the Goat flat upwind is pretty well impossible just hiking on the rail. Likely too the water isn’t going to flat enough either.

My brother in NZ will be coming over in April. By then I’ll have the hiking board made so we’ll see what we can do, although we would really be pushing a number of components way past what the designer had in mind! I don't really want to break it.

Howdy, I use the creak as the mast moves over during a tack as a reference to straighteners up on the new tack.

MIK

Planing upwind can be easier with two people.

Double the wind gives four times the power, righting moment is doubled, but displacement only goes up by less than half.

MIK.

Originally Posted by woodeneye

Boat is now completely creak and groan free!

Apart from those transmitted by the skipper

That was good information on the righting moment vs displacement. Thanks Mik. Will give it a crack when the next 20kt southerly comes through and the water is flat near that shore.

If there is a fair bit of wind heavier crews can plane upwind in somewhat rougher water than a light crew.