Thread: Sail Design for the GIS

Originally Posted by Boatmik

Howdy,

I am on the edge of making a simplified sail design available for the Goat similar for the lug designs for the PDR, the discontinued RAID and BETH

I would much prefer if the sail was made with proper dacron. The Goat deserves a sail made in "proper" sailcloth.

The only glitch at the moment is I want to pass the design past Brian (Keyhavenpotterer) as he made the sails for the RAID using a similar design and Dacron.

The sails did look pretty good on his boat and I am wondering if there are any refinements. I emailed him the drawings this morning.

Best wishes
Michael

Mik

I was just wondering if in between bouts of paddling for your life down canyons in the US you have made any progress with this simplified sail design. I need to start looking at the options for getting a sail for my GIS in Brazil and getting it made locally is almost certainly going to be cheaper than importing one. So the simpler the better!

Best

Steve

Steve

MIK sent me the request about the Goat sail and I replied, stressing the value of the profiled battens to the flat cut, yard shaped Dacron sail. I have since made a sail for another boat without the battens and I feel it does not work as well. I think the yard shaping introduces the shape at the head and then the battens help shape the sail in the main body.

There is no reason why MIK could not send me his design for the Goat ( when he is back home and caught up with himself), I can put the numbers in Sailcut4 software and generate the panel layouts for you. Then e-mail them to you.

I used 4oz cloth, 4 to 5oz will be fine, 6oz getting a little heavy. What I would need to know is what width of cloth you can obtain locally then the panels can be laid out to that width.

Just let me know if I can help at all.

Brian

I had a chance to get it together. Bottom edge can be laced or loose foot. The boom will have to be stiffer if it is loose foot.

The sail uses the proportions and allowances of the PDR lug rig, so it will basically be OK, Some photo feedback will allow me to get it really right if any changes are needed at all.

MIK

Good day...

Mik and Brian - Is this the sail I want to order for my Goat?

Chuck tells me DuckWorks is currently looking at 4 to 6 weeks lead time for sails. When asked, he said ordering in January would be better than ordering in February. He said they can make the sail to any spec I want - guess I better get that box boom done and get some numbers re the stiffness.

I have a choice of 3.8, 4.9 or 5.5 white Dacron - what do I want? For half a moment I thought, "Tanbark" but it isn't worth $100 to me...

Loose footed
2 Reef points
Battens?
What else?

The duckworks sail will work fine. If you are mostly looking at using it by yourself and cruising around I would just get their standard sail with the standard reefs.

If you are likely to get into racing it in a kinda serious way, the reef spacing on this drawing is from Joost and Viola's experience. Joost also recommends having the head a bit fuller. However, the problem there is we don't really have a standard for what it is setting at now so don't know how much to change it. The boom makes no difference to the way the sail is cut.

With general cruising around this makes no difference. But if you are planning to compete it could be useful to get a bit more depth in the head.

I would take a blind stab at it and suggest increasing the depth of the sail by an extra 1/3 in section by the yard.

Joost, do you think that sounds right? I don't want to go too far, but this might go some of the distance toward a bit more power up there.

But BobWes ... if not competing hard against other boats the standard sail will do.

Best wishes
MIK

Mik - for better or worse I am planning to race my Goat. I don't know if "competing hard" will describe my efforts this first year but that'll have more to do with my learning curve (sailing the rig) than intentions.

If I am following along (no guarantee I get this right) with the GIS Spars thread - I thought we wanted to have some number for the stiffness of the boom and yard. And I thought having those numbers would be helpful to the sail maker...

Should I be building a yard ahead of ordering the sail?

At a minimum, I'll wait for Joost to comment on the depth of the sail.

Thanks.

It goes back to the same problem ... we want the sail changed ... but how much?

Because we don't have any comment about the Duckworks sail apart from the "top looking very flat" we can only make some steps in the right direction. If we had a figure for the depth of the SAIL as it is then I could be very clear with exactly what was needed.

But I don't have a single figure.

Joost has said it is too flat and Mike McNamara said the first sail he made was too flat in the top too.

So the best I can do at the moment is to make it a bit fuller without going overboard.

A bending measurement of Joost and your yards with the same weight at midpoint would allow a bit of compensation to be made too.

Best wishes
Michael

Originally Posted by Boatmik

It goes back to the same problem ... we want the sail changed ... but how much?

Because we don't have any comment about the Duckworks sail apart from the "top looking very flat" we can only make some steps in the right direction. If we had a figure for the depth of the SAIL as it is then I could be very clear with exactly what was needed.

But I don't have a single figure.

Joost has said it is too flat and Mike McNamara said the first sail he made was too flat in the top too.

So the best I can do at the moment is to make it a bit fuller without going overboard.

A bending measurement of Joost and your yards with the same weight at midpoint would allow a bit of compensation to be made too.

Best wishes
Michael

As for a bending measurement, my sailmaker has asked for measurements based on a 10kg weight at the mid point of the spar. I guess different sailmakers have their own preferences for the measurements, but perhaps when we compile this data for the benefit of the Class, we could easily enough get a range of data, ie. 5, 10, 15kg.

I don't know if it has been decided where this data is to be hosted, but I presume it will be Mick's site?

I guess the solution for those with a Duckworks sail is to stiffen up the yard so it does not flatten out the sail so much at the top. But as mentioned it's only necessary if being raced, and even then it's still not that critical if racing in mixed fleets. Goat on Goat, with the gloves off, it's a whole different ball game!

But as mentioned it's only necessary if being raced, and even then it's still not that critical if racing in mixed fleets. Goat on Goat, with the gloves off, it's a whole different ball game!

Bruce -

I'll be racing in mixed fleets but everything is critical when racing! Since I won't have to worry about racing another Goat (at least not often) there may be some strategy to play here... I figure it will be a bit of an uphill battle bringing a new design to the local races. Maybe I should sandbag things a bit, you know, so the bottom half of the fleet (which in my experienced is more vocal complaining about anything viewed as a threat) doesn't get up in arms right away. Maybe I should use 1" PVC pipe for my yards the first couple of times on the race course...

In the meantime I will work on my boom and yard - and ordering a sail pretty soon.

Originally Posted by woodeneye

As for a bending measurement, my sailmaker has asked for measurements based on a 10kg weight at the mid point of the spar. I guess different sailmakers have their own preferences for the measurements, but perhaps when we compile this data for the benefit of the Class, we could easily enough get a range of data, ie. 5, 10, 15kg.

Howdy, only one measurement is necessary. In the theory the bend is elastic. That twice the weight will result in twice the displacement (movement). All the engineering calcs work on that assumption. The time it starts breaking down is when your spar starts breaking in some way and will result in a permanent bend. If this happens you will start to get a bigger displacement when the same weight is added.

The different weights are probably only to get enough bend to be measurable with different sized spars.

We can put it on my site ... no worries.
MIK

Hello MIK and Bob,

I will try to make some measurements on the spars and the set sail (depth when the sail is rigged) as soon just as the weather clears up a bit here (you might have noticed from Ralph's building tread that we are experiencing some snow and low temperatures right now in the Netherlands).

Hope to have some time (and hopefully the weather will cooperate a bit) to rig the sail and make the spar measurements) over Christmas and definitely before New Year.

I do agree that some more depth in the sail would be nice. If you are racing or cruising a lot one up, I would personally go for 3 reef points allowing you to reef the sail from the full 9.65 square meters to appr. 8 square meters, then to 6.5 square meters (this is appr. the standard Duckworks first reef point) and lastly to the very high reef point when you are caught out badly in sudden high winds.

I normally sail with my girlfriend and together we probably weigh some 145 kg (85 for me, around 60 for my girlfriend) to give you some ideas about the human ballast on board of our GISwerk. The full sail area is fine until 15 knots or so, then it helps to reef down a bit, but I feel that my current first reef (appr. 6.5 square meters) takes away a lot of sail area in one go.

More reef points allow you to set the sail area you really need. One thing I have noticed with the Goat is that less sail area doesn't necessarily slow down your boat (in other words, timely reefing seems to help sailing fast).

Hope this helps.

Best regards, Joost

Originally Posted by BobWes

Bruce -

I'll be racing in mixed fleets but everything is critical when racing! Since I won't have to worry about racing another Goat (at least not often) there may be some strategy to play here...

You got my drift

Originally Posted by Boatmik

In the theory the bend is elastic. That twice the weight will result in twice the displacement (movement). All the engineering calcs work on that assumption. The time it starts breaking down is when your spar starts breaking in some way and will result in a permanent bend. If this happens you will start to get a bigger displacement when the same weight is added.

MIK

Cool, I've always wondered about whether there is some weird theorem at work with bending forces. I guess we can standardise the weights then.

What's the GISSpar unit of deflection to be then? Deflection in
1. mm/10kg or
2. mm/15kg or
3. mm/20kg

No need for a scale to measure. Just use a bucket with 10 litres, 15 litres or 20 litres of water as the case may be.

I've just realised, these measurements are not very friendly for our Stateside mates, but then again, building a Goat is already a lesson in metrification and they are already streets ahead of the rest of the US population

Originally Posted by Joost

I normally sail with my girlfriend and together we probably weigh some 145 kg (85 for me, around 60 for my girlfriend) to give you some ideas about the human ballast on board of our GISwerk. The full sail area is fine until 15 knots or so, then it helps to reef down a bit, but I feel that my current first reef (appr. 6.5 square meters) takes away a lot of sail area in one go.

Have you considered some extra girlfriends, each weighing a different amount?

Colin