Building Shesha, a Hunter Valley GIS, Australia

[woodeneye]

Hi Ian

I have indeed looked at windsurfer masts. As you have indicated, the relative stiffness for other than use with a windsurfer sail is difficult to determine. Vendors seem to quote IMCS values, but it doesn't appear to a standard as I cames across a website that tested masts against their quoted IMCS data, and none of them met their advertising claims.

I think if you are buying new, the way you went is the best way, but at least you will have received a spar that came close to meeting your specs. The windsurfer mast route would, I think, be very hit and miss, so could be an expensive way to go if you find out the mast doesn't suit your requirements.

I have picked up and handled some quite light fibreglass spars that are used for Walker Bay and Access dinghies. The stiffness of these feel about right to me for a yard, but I hazard a guess that they would be quite expensive as I think they are fully imported. While not as light as carbon, they are half the weight of wooden and much stronger, so if people have an opportunity to buy an old fibreglass rig for not much money, this could be a good way to go.

I agree with you about the WS masts for booms. I think they are fine for a boom with a laced on sail which allows for some bend, but are not a proposition for a loose footed sail where a stiff boom is required.

[BobWes]

I suspect they're too flexible for a boom...

Okay, I am confused a bit...

Without going back to the Spars thread to check before posting...

I thought that the long and the short of the Spars thread was that stiffness of the boom was a non-issue and that the key element was the stiffness of the yard.

Again, without checking Dabler's site before posting, if I remember correctly, he only requires information re deflection of the yard.

Did I miss the entire point of the Spar thread (heck, that might not even be the title of it)? I seem to recall a rather convoluted discussion that went back and forth but the bottom line was, the deflection of the boom is not a critical factor.

So, what did I miss? Has the discussion evolved past my recollection - admittedly, that is quite possible?

[woodeneye]

Hi Bob

Ideally the boom should be stiff if you have a loose footed sail. However, I have put up with a somewhat bendy boom married to a loose footed sail for quite a while. No real issues that were ball-breakers, but the gap between the boom and foot became quite large in a breeze due to sheeting and vang tensions.

Yes, sailmakers do require information about the deflection of the yard, but unless they really know how a lug sail works, it may not work in all conditions. My sail was nice but simply horrible with my bendy yard in anything above 10 knots. A stiff aluminium yard has fixed the sail completely and given me more control over the sail, especially the fullness above the throat which is adjustable at the peak.

We think that the new versions of the McNamara sails may account for the distortion that occurs in higher winds because the sailmaker has actually sailed the GIS and was surprised how much the yard did bend. However, we've not had any conclusive reports from those GIS's with McNamara sails about how they perform in a stiff breeze.

Ian has gone the carbon route, with a stiffish tapered yard, so we are looking forward to his findings to increase our knowledge of what the ideal sail/spar combinations might be.

I think what I might do shortly is rig up my old bendy yard in a breeze and take some pics to show how the sail shape went to rubbish in a decent breeze, and a comparison with how it looks with the stiff yard. In my case it was chalk and cheese. With a bendy yard I had a rag, but with a stiff yard I had a foil!

[BobWes]

Thanks for the summary, Bruce.

I should have reviewed the thread before asking the questions.

Having done that, I see I was mixing boom and yard features...

So, what I am gathering is, build/buy/steal the stiffest yard possible - regardless of how the sail is cut and built? I thought the sequence was: build a yard, measure the deflection, provide that data to a knowledgeable and experienced sail-maker, and that sail-maker would cut/build the sail to match the yard. But that's not what field testing is showing, is it? Or is it?

I am beginning to look for a sail-maker in the Michigan area although Duckworks remains a viable option if they have been working with Mik on improving the cut and build quality of their sails (I'm not imagining that comment, am I?).

Friday is my last day at work. And then I;ll be busier than ever... finishing packing up and getting ready for the road. Lots to do and many miles to go before I can get back to the task of finishing my Goat and sailing her. But I am looking forward to my new adventures.

[woodeneye]

Hi Bob

All the best for your retirement! Lucky you

If I were you I'd go with the Duckworks sail unless your sailmaker is really experienced and does a lot of balanced lug sails and is prepared to do the extra work. My guess would be that a lot of lug sails get made for people who don't really care what the sail does and wouldn't know a good sail from a bad sail. This type of person doesn't provide feedback to the sailmaker so they churn out the same sails for everyone. It's more than simply altering the curve of the yard edge.

Duckworks, or maybe the McNamara sail from the UK...

[BobWes]

Bruce,

Given that thought, I should order a Duckworks sail and provide feedback through this forum and directly to Chuck. And that makes more sense than finding a local sail-maker who may or may not appreciate lug rigs.

While my original plans for the first few months of retirement had me on the road enjoying my new-to-me camper and the Gulf Coast, I may find myself in Michigan before the ice melts. I am getting anxious to build the mast and yard (have a couple of different design ideas I want to try). If either of those ideas work, I will probably build another boom, too. Even if I do not build another boom, I realized last night that I need to re-measure the deflection of the boom as there are at least two parameters that weren't correct when I measured it last January.

Lots to do! Gotta get back into it!

[IanHowick]

Hi Bruce, another question on your current set up with both downhaul and vang - do both of these need to be on a traditional (4 to 1 ?) pulley system, or can they work with a cascade set up? I know you changed back to a traditional pulley system when you first changed things, but then you changed the geometry again, I'm just wondering what the latest on this is.

Thanks,

Ian

[Boatmik]

Bruce will answer soon.

As you know a cascade is cheaper and often more efficient, but needs some space to operate.

If the line is coming to the back of the centrecase some of the cascade could be there - one some rigging setups I've done on Oughtred boats we have put a wider cover over the top of their long centrecase so the cascades could run underneath..

But you need enough slack in the system that the boom can be raised too high before the downhaul and vang are pulled on without running out of cascade space.

MIK

[woodeneye]

Bruce will answer soon.

As you know a cascade is cheaper and often more efficient, but needs some space to operate.

If the line is coming to the back of the centrecase some of the cascade could be there - one some rigging setups I've done on Oughtred boats we have put a wider cover over the top of their long centrecase so the cascades could run underneath..

But you need enough slack in the system that the boom can be raised too high before the downhaul and vang are pulled on without running out of cascade space.

MIK

That is exactly right MIK, the cascade ran out room so I went back to the traditional set-up. Cascade systems offer a lot of power for the buck provided the blocks have space to work.

Ian, as MIK suggests, the cascade could be put somewhere else, such as alongside the cb case. I'm currently using a traditional 4:1 system.

[woodeneye]

Bruce,
Given that thought, I should order a Duckworks sail and provide feedback through this forum and directly to Chuck. And that makes more sense than finding a local sail-maker who may or may not appreciate lug rigs.

Yes exactly. I don't think you'll be sorry about that decision Bob. The Duckworks sail was always pretty good, and now that it's had some more work done to it with MIK's input, it will be even better.

[Boatmik]

And I am looking for further feedback on new sails so we can improve it more.

Going back to the spar bend - it depends on how you want to use the boat. If considering racing and regattas (as Bob is) then to look at the stiffer spars makes sense. For a more forgiving boat (maybe) the original spars are better with the exception that a bit more beef in the boom for loose footed sails makes sense.

MIK

[BobWes]

Yes, I am looking forward to racing a bit and participating in distance events (Texas 200, Tip-of-the-Mitt, Florida 120, and others) which may not, strictly speaking, be races. But I do want to improve the performance - right now that probably means honing my skills more than wringing more out of the boat.

I will be ordering a Duckworks sail, probably by late January. This means I need to build my yard and measure the deflection so I can provide that data to the sail maker. I contacted my niece in Austin, Texas this afternoon. My Goat will be stored there for a few months this winter. I made arrangements with her and her fiance to use their shop and tools to build the yard when I take the Goat there in mid-January. They even called around to source 6mm and 4mm okoume plywood for me - it is available in the Austin area. So, things are looking up and I am getting excited about finishing out my boat.

Mik, if you get a chance would you comment on what I should features, data, etc. I should specify to Duckworks? Seems to me we did this about a year ago but circumstances kept me from ordering. A late January order ought to deliver a sail by early April - just in time for ice-out on small Michigan lakes.

[Boatmik]

Hi Bobwes,

I would go with the standard sail - we are working it up so will be fine. The standard yard will work OK and a stiffer yard will give you more power for sailing hard two up. Best of all worlds I think

MIK

[woodeneye]

Today I built my new boom, all from timber sourced at Bunnings.

It is made from three 3600 x 66 x 12mm lightweight Meranti. Here you can see it under construction. One of the planks was split down the middle with a Japanese rip saw to make the two top and bottoms 31mm wide. The sides were epoxied to the outside edges of the top and bottom, which made it finish 55mm wide. Infills are Paulownia

The sides finished up 65mm max, tapered on both ends. It is 55mm wide along the entire length.

I managed to get 2 coats of 205/207 epoxy (wet on wet) on before I ran out of light. I'll have to get the third coat on in the morning after a wash down and light sand, and then that will be it.

Haven't weighed it but it is quite light and a lot stiffer than my old boom.
Attachment 156992Attachment 156993

[woodeneye]

Completed boom with 3rd coat of epoxy drying. As this was 207 hardener, it won't need to be varnished.
Attachment 157079

Here is some interim data. When complete I'll post it to the WIKI.

Summary:

Material - Superlight Meranti 3600x66x12mm (Bunnings) and Paulownia infills
Finished Length - 3600mm
Finished width - 55mm
Finished depth - 65mm
Front taper - 20mm to zero over 800mm
Rear taper - 20mm to zero over 1000mm
Weight - TBA (approx 2.6kg)
Flex - TBA (substantially stiffer than previous pine version which broke)