Thread: Another UK GIS (Gizzle in Hants)

I had a look at the Raid England website, but nothing of the current one up yet. I see they have "Sneaky Shark" listed at 4.3 m LOA, I though the GIS was 4.73 m long...

Ian

It's good to hear that carbon fibre tubes might be prepared to help out.

I know they supply Anglia Yacht Services with their lug spars for their larger Deben Lugger. They wind extra material to strengthen standard tubes. It does mean they have to buy batches of spars though.

Ian, could the larger standard tube 63.5 mm od form the basis for a mast, stiffness 14.91 KNm2? You could then add additional material using the carbon mesh from the US which comes in expandable sock form?

Carbon Fibre Tubes

Stock length is 3.6m - how long is the Goat mast?

They also do a super tapered 40mm to 20mm section which I used for the Scow yard. Again you could add extra layers.

The 54mm tube would make a super boom.

Brian

Originally Posted by keyhavenpotter

It's good to hear that carbon fibre tubes might be prepared to help out.

I know they supply Anglia Yacht Services with their lug spars for their larger Deben Lugger. They wind extra material to strengthen standard tubes. It does mean they have to buy batches of spars though.

Ian, could the larger standard tube 63.5 mm od form the basis for a mast, stiffness 14.91 KNm2? You could then add additional material using the carbon mesh from the US which comes in expandable sock form?

Carbon Fibre Tubes

Stock length is 3.6m - how long is the Goat mast?

They also do a super tapered 40mm to 20mm section which I used for the Scow yard. Again you could add extra layers.

The 54mm tube would make a super boom.

Brian

Hi Brian, off the top of my head, I guess you could if you re-inforced it enough, though I don't have enough information about the carbon sleeves you and others mention.

The GIS Mast is 4.8 metres or so long.

You need about 35 kNm^2 stiffness at the base for a GIS mast. I dug out an email from Ross Lillistone regarding a birdsmouth mast he made for a Periwinkle (similar sized lug rig), he said it "bent alarmingly but didn't break". He used a lighter timber (Silver Quandong), I think I worked out the stiffness at the base to be 30 kNm^2, so that puts a lower boundary on the stiffness needed for a boat of this size.

To get that 63.5 mm OD 1.6 mm wall standard tube from 14.91 KNm2 up to 35 kNm^2 would need a lot of extra material added. You'd have to add perhaps 2.5 mm more to the bottom metre of the mast, and 1.5 mm more up to two metres. I'm guessing the carbon mesh you could add would need 3 or 4 sleeves to add a millimeter.

So adding sleeve material, you need 4 or 5 sleeves 2 m long, plus another 4 or so of one metre length. I guess you'd do a total of 8 or 9 layers, the longest running 2.5 m up from the base, the shortest running from the base up to about 1 metre, the rest spaced evenly in between, so you've got 8 or 9 layers for the bottom metre or so.

Above about 2 - 2.5 metres, the 63 mm OD 1.6 mm wall original should be OK.

12 - 15 metres of sleeve - maybe you can price that.

All the above is off the top of my head, I'd do more detailed calculations if anyone was thinking of going ahead. I also have no real data for this carbon sleeves/mesh, my guess of 3 - 4 layers for a mm is a complete guess, I'm also just guessing how much stiffness each layer would add. If I had proper data: "We did some proper testing and one of these carbon mesh sleeves added to the outside of a tube of ___ mm diameter adds ___ kNm^2 to it's stiffness". Fill in those two blanks and I could do calculations I'd be more confident in.

Starting with a smaller diameter, you need more material to get the stiffness up to what you need, so it ends up heavier than it would at a greater diameter. The extra material also costs of course, so I don't know if it would make sense on price.

(By the way Brian, it all gets easier at a slightly smaller size of boat that will only be sailed by one person that won't be hiking hard - ie boats like the little "Ruff' you bought recently, or a sailing canoe. At that size of boat, I'd be looking under the closest rowing club boat shed for a carbon oarshaft with a broken blade and seeing if that was stiff and long enough)

Ian

George Isted
Sneaky shark gets line honours in first race of the English raid

George Isted Windy day today so we sailed with a single reef this morning in 13-15kts but two reefs this afternoon in around 20kts. We (again) learnt a lot about the boat and I was much happier with upwind sailing speed and helming over the waves that were stopping us yesterday. We didn't complete the race but had a great 5hrs on the water sailing.



Forgot to say.... Get I'd right and she's a damn quick boat! We just need to work on getting it right more often and for longer.
Yesterday at 05:01 via Mobile · Like · 1

Another great day of sailing on the English raid. Sneaky now back on her trailer ready to go home tomorrow. Lots of interest and positive comments about the GIS from the other raiders. I think we did well in the race today but will not get the results until later.
8 hours ago near Shotley Gate, England

George Isted ‎4th in today's race and a huge improvement in our sailing of sneaky. So pleased we did this event as we got to spend so much time on the water and such a nice bunch of people to socialise on shore. I hope there is an English raid next year.
2 hours ago via Mobile

Another photo from the end of the first day

George wrote "REady for more adventures tomorrow"

Discussion about dyneema for stays .... primarily for a new 12ft storer design was moved here
https://www.woodworkforums.com/f169/1...ml#post1531079

Originally Posted by IanHowick

You need about 35 kNm^2 stiffness at the base for a GIS mast. I dug out an email from Ross Lillistone regarding a birdsmouth mast he made for a Periwinkle (similar sized lug rig), he said it "bent alarmingly but didn't break". He used a lighter timber (Silver Quandong), I think I worked out the stiffness at the base to be 30 kNm^2, so that puts a lower boundary on the stiffness needed for a boat of this size.

So you claim that the birdsmouth mast for GIS is not stiff enough?

I get a bit confused as the numbers are completely different at the wiki:

Originally Posted by WIKI for Lug and Sprit Rigs

A solid round wooden mast of Oregon or similar 62 mm diameter at the base will have a stiffness of about 9 kNm^2.

Mik's 62 mm hollow square section with 12 mm wall in wood will have a stiffness of about 13 kNm^2

The 2.5 inch outside diameter 6061T6 aluminium section with 0.065 in wall will have a stiffness of about 10 kNm^2.

Ian, btw, It would be nice if you could provide how you do the calculations. Then it would be easy for each one to see what effect each mm has on the spars.

I know that a 70mm, 1.65mm wall or 16swg, alloy tube is fine for a 100 sq ft lug sail. So, does anyone know what stiffness that is?

I would have thought that a carbon glass tube of a similar size would also be stiff enough? Possibly it would bend a bit more at first and then stiffen up, as I found will my Scow tubes.

Brian

Originally Posted by engblom

So you claim that the birdsmouth mast for GIS is not stiff enough?

I get a bit confused as the numbers are completely different at the wiki:
******
Originally Posted by WIKI for Lug and Sprit Rigs
A solid round wooden mast of Oregon or similar 62 mm diameter at the base will have a stiffness of about 9 kNm^2.

Mik's 62 mm hollow square section with 12 mm wall in wood will have a stiffness of about 13 kNm^2

The 2.5 inch outside diameter 6061T6 aluminium section with 0.065 in wall will have a stiffness of about 10 kNm^2.
******

Ian, btw, It would be nice if you could provide how you do the calculations. Then it would be easy for each one to see what effect each mm has on the spars.

Those numbers from the wiki are from discussion of mast options for an OZ racer, not a GIS. Smaller boat, shorter mast, one sailor sitting on the rail, so loads are lower, need for stiffness is less.

I will try to put together a bit of a tutorial explaining all this business of GPa's and kNm^2 and so on and how it relates to whether a mast is stiff enough to do the job.

Ian

Originally Posted by keyhavenpotter

I know that a 70mm, 1.65mm wall or 16swg, alloy tube is fine for a 100 sq ft lug sail. So, does anyone know what stiffness that is?

I would have thought that a carbon glass tube of a similar size would also be stiff enough? Possibly it would bend a bit more at first and then stiffen up, as I found will my Scow tubes.

Brian

The alu section you mention above is about 15 kN^2, similar to the 63.5 mm OD/ 1.6 mm wall carbon section from that UK manufacturer. Does that 70 mm OD 1.65 mm wall alu tube stand up unstayed, or is that for a stayed rig? What sized boat - designed for solo sailing or 2 - 3. I'm curious. Also, do you have the spec for John Welsfords walkabout, including mast length if possible, I know he does it in alu?

Thanks,

Ian

One important thing to understand is that stiffness goes at the cube of outside diameter for a thin walled tube, so when you say 63.5 mm OD carbon and 70 mm OD alu are 'similar' in size, there's actually quite a difference between the two. 10 % difference in OD makes a 34 % increase in stiffness, if other things are held constant. Carbon composite is only about 30% stiffer than alu (though it's quite a bit lighter), so the 63 mm OD carbon is similar stiffness to the 70 mm alu.

Another is that with these lightish boats, the need for stiffness depends a lot on the crew's weight. Design a boat for solo use/decide it's a solo boat, and the stiffness spec on the mast can go down a lot.

Hi all,
The English Raid 2012 was simply fantastic, I need to put some words together on what we did each day but there are some pics of the event here..

http://www.flickr.com/photos/53626051@N08/sets/72157630928658910/

I had only sailed Sneaky Shark once before the raid in light airs, my crew Annie had only seen pictures of the boat so it was a steep learning curve!

Will report back again with more info but I'm over the moon with Sneaky!

Sadly I also need to fix a dink in the dagger board as the top aft corner was damaged in the car and split the cedar. Hopefully some epoxy in the crack and a layer of glass will fix it.

Hi folks,
it's all on the blog here Tales of a Weekend Wood-Butcher

And this is a nice pic...

Hope to get some pics of us sailing from the other raiders.

Thanks for the great raid report George! Sneaky looks awesome. Getting to sail the boat intensively for a few days, in a row, shortly after the maiden launch must have been an incredible rush.

Originally Posted by SimonLew

Thanks for the great raid report George! Sneaky looks awesome. Getting to sail the boat intensively for a few days, in a row, shortly after the maiden launch must have been an incredible rush.

It was sooooo much fun! A huge learning curve but having a few intensive days on the water improved my skills and confidence far more than a number of short trips with days or weeks inbetween.

I should be back on her for 3-4 days at the end of next week but with the kids with me so less hooning around and more gentle sails to the beach so we can dig for castles.

If the weather picks up and the dagerboard is fixed I may try for an after work sail one evening.