Thread: Is that a 12' GIS I see hull down on your horizon

Originally Posted by woodeneye

There is a square top sail available that fits the Laser standard mast and boom. By the way, the new class legal composite top section is close to being made available. It will solve the problem of bent top sections and performs the same.

125sq ft./11.6 sq m. luff 205in / 530cm same as stock sail foot 107in./272cm. same as stock sail. Features squared off roach [modern design] , full length battens, grid monofilm [basically zero stretch] The sail rolls up into a 9in. roll

$(KGrHqFHJB8FCEbR52ziBQnswsQyWw~~60_3.JPG$T2eC16NHJIQE9qUHsFUkBQnswlqV+g~~60_3.JPG$T2eC16RHJHgE9n0yFlKjBQnswzK4r!~~60_57.jpg

Distributor advises US$675 including sailbag tube and battens.

It is a bit big for the 12 footer, but it might be a fun sail to put on a Goat if anyone wants to put a Laser mast into it. But it might be too big and too likely to bend the lower section if two people hike out hard.

Main problem is that it won't be cheap with carbon topmast plus the fullbatten sail.

The base design problem for bigger, cooler sails on the Laser is the length of the boom and how far that pushes the centrecase back. The boom length and balance really forces square top sails to be very large (or another option would be strangely squat).

My expectation is this big rig on the Laser will be quite "interesting" in stronger winds and chop. Beth has a lot of sail area for her stability - a similar problem but I think gets away with it because the hull is so narrow that drag and pitching from waves is much reduced. But this is mindgaming, not real, and I don't really trust pronouncements like I have just made in this paragraph. Something to look out for when some hit the water.

MIK

Yes, with 2 people hiked hard, bottom section could be stressed, but the bottom section on the std rig doesn't usually have issues, unlike the Radial. Alu sections will still be available, but the composite, while more expensive, will last forever.

As the extra area is due to the square top which flicks off readily, so its not a particularly hard sail to handle, except in upwards of 20kts, and downwind, I expect!

A fairly cheap sail though. If I build the 12, I will probably scale this sail down to fit the Radial spars and do it in a quality dacron. Maybe a cut down boom as well to solve the issue you mentioned, although the CII 12 uses the Laser boom. However, will see what you've come up with first.

Do you think the 12 could be built in a fortnight?

Originally Posted by woodeneye

Yes, with 2 people hiked hard, bottom section could be stressed, but the bottom section on the std rig doesn't usually have issues, unlike the Radial. Alu sections will still be available, but the composite, while more expensive, will last forever.

As the extra area is due to the square top which flicks off readily, so its not a particularly hard sail to handle, except in upwards of 20kts, and downwind, I expect!

A fairly cheap sail though. If I build the 12, I will probably scale this sail down to fit the Radial spars and do it in a quality dacron. Maybe a cut down boom as well to solve the issue you mentioned, although the CII 12 uses the Laser boom. However, will see what you've come up with first.

Do you think the 12 could be built in a fortnight?

Not so convinced that 125sq ft can be disregarded so easily Cherubs (orig 112sq ft) NS14s (100 sq feet) etc have two people to hold up those sort of areas

But I think you have a good plan there with the 12 footer rig ... main thing is to get the CE of the sail in the right spot with a different sail profile. We will have to figure a sail measurement system to account for different rigs. Can you tell me the width of the luff sock on the Laser? I can see a scheme already.

Just deduct an assumed width of sock along with stipulating mast diameters being deducted from the actual measure sail area.

MIK

MIK

Still going on ... worked out some nice things with the rotating mast.

I was a bit hooked up on the era of very simple timber rotating masts from about 1975 to '79. They were tapered both sideways and fore and aft and I was struggling to think about how to make that easy to do.

Then in trying to dig up more information I realised that not too long after that the masts were made in Aluminium tube of constant section from heel to truck.

So that simplifies things enormously. It looks like we will be able to use 12mm thick sides with some infils to allow attachment of shrouds and other bits. Much simpler ... and if the mast is too stiff it could be run through a thicknesser to skim a little off both sides. We can do that until we are happy with the actual behaviour then redesign to bring it back to 12mm thick faces for the stock mast.

Rick is getting very close to assembling the hull. I was dragging the chain by not being sure about which way to go with the mast ... but now a satisfactory direction is worked out it will be fine.

An approximate calculation shows the 4.7 m mast - which is quite short because of the square head on the sail and now because of the deck stepped mast will be about 6kg of pine or fir (oregon)

There are two options for a track ... we have found a plastic track that is available in the USA and Australia/NZ so that is one way, but also I have designed a mast that creates a track by having ply across the back of the mast with a space in front then running a narrow kerf saw blade up the middle of the ply.

MIK

Exiting news! So it is going to be a deck standing stayed mast with a mast track? What has the sail area settled at?

Much looking forward to see the prototype in 3D. The pictures of the pieces layed out in the grass as well as the drawings look very promissing.

Joost

Howdy Joost,

It is a little short of sail at the moment at 6.55 sq m (71 sq ft) and you get another about 3sqft from the mast so it is kindof OK .. but I think I will have to tweak it up slightly. For example the true area of the Laser is a little larger at about 82 square feet if you measure everything.

It would be nice to get another 4 sq ft (<0.4 sq m)

Just did a fiddle to the leach without affecting the square top or the foot to get 6.93 sq m (just under 75sqft) for the sail only.

Dotted line is original profile of sail leach.




You can see the rotating mast area on the left compared to the Oz style mast on the boat. Quite a grunty rig now.

Michael

And link back to flickr so the image doesn't disappear! Storer Boat Plans' photosets on Flickr

As a sail area comparison ... the NS14 has 100 square feet of actual sail area. 9.3sq metres.

Usually the split between main and jib with two people and a six foot beam to hold it up is somewhere between 69% - 74% in the main.

There is now a single handed version of the NS14 which uses the mainsail only with a beam of 6ft to hold up a main of similar size to this boat.

My feeling is that they are a bit underpowered ... and we have reefing anyway .. so it will all still work.

This is not such a good shot .. but i chose it because I was looking for photos of NS14s and found my old one being raced in Northern NSW. #1169 Zazen. But the mast top is the best part of a metre taller than the little boat above.



MIK

Mik, does your sail program do the area calculations?

What material will you use for the fairing of this new mast? Also, I'm not sure I understand how your ply track works. Is the back face of the mast plywood with a slot cut in it with little cutouts in the spacers within the structure to take the bolt rope?

How would an 8 sqm (86 sq ft) rig go? I may have one of those shortly. It may not seem much more but 1 sqm is quite a lot, although the rig I have in mind has the power down low.

It seems to be coming together nicely.

Knocked it together today. Spent two hours and assembled the parts I had cut out and framed in. Here are a few pics (if I can get them to download)

Rick.

BTW, it is pretty sexy looking in real life. The pics don't do justice to how swoopy it looks. It looks like a 49er from the front, and a bit like a Ken Bassett 'Rascal' powerboat from the back. Sorta "Chris-Crafty"...lol. More pics tomorrow if it stops raining and I can pull it outside for a bit.

Originally Posted by woodeneye

Mik, does your sail program do the area calculations?

It doesn't calculate ... the sails are manually designed with the no or little broadseam method that was reasonably common in fast oz boats in the '70s. So I just design it then run round the outside with CAD and it tells me what the area is.

What material will you use for the fairing of this new mast? Also, I'm not sure I understand how your ply track works. Is the back face of the mast plywood with a slot cut in it with little cutouts in the spacers within the structure to take the bolt rope?

It is much simpler now - see the post above .. the fairing has gone - If you can do a uniform section in Aluminium you can do a uniform section in timber.

I'll put a pic up for the slot arrangement. The thing i am worrying about is whether glue ooze will cause a problem.

How would an 8 sqm (86 sq ft) rig go? I may have one of those shortly. It may not seem much more but 1 sqm is quite a lot, although the rig I have in mind has the power down low.

I suspect too big .. but of a bigger consideration is getting the balance right ... might be OK with rake. Also might need a mast extension.

It seems to be coming together nicely.

Rick thinks it looks cool. I think we need to wait for him to get it outside for photos.

MIK

Looks great and you can see it's genes, but that bow and stern swoop are super cool.

Great to see the hull come together. Cannot wait for some pictures from a couple of angles of the boat right side up showing the sheer and the bow and stern sweep. It looks special and fast!

MIK, will the mast now be a square section without fairing of the front part of it?

7 m2 for the sail only for this boat looks just right to me striking a nice balance.

Joost

Here are a few more angles of the progress thus far. Don't look at the messy shop, we are in the middle of a rainstorm and all my 'outside' things had to be dragged 'inside'. No room to maneuver. It was fun to dream a little while standing in the cockpit. It feels fast even standing still!
The build has been no more difficult than an OzRacer MkII, probably easier actually. A little more work than the RV but not by much.

Rick.