Thread: GIS sail tweaking

Originally Posted by warm beer

As the wind increases, the yard bends more, and my baggy pants upper leech starts flapping. Maybe the sailmaker could cut across the last panel and take in a bit of slack - adding a crosscut to the panel above the top batten pocket?

NO, don't touch the sail! My own sail had this problem and the alu pole fixed it.

The only problem is the weight as it's a 40mm tube with 3mm walls. I really need a carbon one.

Originally Posted by woodeneye

NO, don't touch the sail! My own sail had this problem and the alu pole fixed it.

The only problem is the weight as it's a 40mm tube with 3mm walls. I really need a carbon one.

Bruce, have you checked out your local rowing and or surf rowing club? Carbon or glass composite oar shafts may have a better stiffness spec compared to a windsurfer mast, you might be able to find something of the right stiffness for a yard.

Ian

Originally Posted by IanHowick

Bruce, have you checked out your local rowing and or surf rowing club? Carbon or glass composite oar shafts may have a better stiffness spec compared to a windsurfer mast, you might be able to find something of the right stiffness for a yard.

Ian

Good idea, haven't thought of oar shafts. I have a friend who races surf boats so will ask him. Thanks!

When you talk about making boom and yard more stiff, is it needed to add both vertically and horizontally extra stiffness (1), or only vertically (2)? (Sorry for bad ascii graphics)

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Originally Posted by woodeneye

NO, don't touch the sail! My own sail had this problem and the alu pole fixed it.

The only problem is the weight as it's a 40mm tube with 3mm walls. I really need a carbon one.

Thanks for the tip. I'll leave it alone, and do the boom and traveller updates first to see how that changes things.

Here is the stuff I was thinking of:

60mm x 40mm DF weight .88 lbs / foot kiln dried
I was thinking that the assymetrical shape is a good thing, with the flat side against the mast, tapered to 40mm x 40mm towards the ends.

My calculations show an increase in cross section area of 50% from the standard 40mm round boom, with all the increase in the vertical orientation.

Originally Posted by woodeneye

Good idea, haven't thought of oar shafts. I have a friend who races surf boats so will ask him. Thanks!

It would be interesting to go through a selection of both windsurfer masts and composite oar shafts and get some info on weights, dimensions and resulting stiffness values.

I'd assume most composite oars shafts are larger diameter and stiffer than windsurfer masts. Surf boat oars are presumably stiffer than flat water racing oars? There might be quite a range to close from with something that would work for a yard. One of the stronger surfboat sweeps (is that what you call the big oar at the back?) might be right for a boom or even a mizzen mast for a Goat or a main mast for a OZ racer or the new 12ft boat. I haven't chased any of this up myself as I can get glass composite spars made up quite cheaply over here (and have what I need for the meantime).

Good if you can find some shafts with broken blades lying under the boat shed that can be begged/bought/borrowed.

Ian

Originally Posted by engblom

When you talk about making boom and yard more stiff, is it needed to add both vertically and horizontally extra stiffness (1), or only vertically (2)? (Sorry for bad ascii graphics)

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Option 2: you only really need to add to the vertical dimension/stiffness.

Ian

Originally Posted by engblom

When you talk about making boom and yard more stiff, is it needed to add both vertically and horizontally extra stiffness (1), or only vertically (2)? (Sorry for bad ascii graphics)

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With the boom, the stiffness needs to be more in the vertical direction as the horizontal force is not that great.

The yard is different as it needs to be stiff in all directions, ie a round section. My take on it is the automatic depowering comes from the yard pivoting at the attachment point, so no flexibility is required horizontally.

Originally Posted by woodeneye

With the boom, the stiffness needs to be more in the vertical direction as the horizontal force is not that great.

The yard is different as it needs to be stiff in all directions, ie a round section. My take on it is the automatic depowering comes from the yard pivoting at the attachment point, so no flexibility is required horizontally.

Yes, increase the boom vertical dimensions for more vertical stiffness, but the yard needs to stay as a symmetrical section. Square section might work for the yard, would add nearly 70% to the stiffness compared to same dimensions round. Not use what the downsides of a square section would be.

Ian

Here is some data and a question

My Yard Dimensions (Eastern White Spruce)
Diameters
heel 46.8mm 1.80"
block for halyard 50mm (1.96")
(I placed my block as shown on plans about 1333mm or 52 1/2" from heel of yard.)
1/3rd of way from block to peak 48mm (1.875")
2/3rd of way from block to peak 44mm (1.75")
peak 36.8mm (1.45")

LOA of yard is 3603mm 141 7/8" (11'9 7/8")

I was happy with the yard...the upper part was flexing fine, like a birds wing tip. A little stiffer than Callsign's we think. (see pic) I think Callsign ties off his yard a little further up than I did. The upper part of my yard seems to be flexing the way I want it too...so for a change I am not going to mess with the yard!


3 Goats at the Small Reach Regatta 2012 by Clint Chase Boatbuilder, on Flickr

The question: how do I best and most safely restrict the throat of the sail. I am hesitant to put a hole through the yard there. OK at the ends, but I'd like another way. I think a small eye strap would do it...keep the existing spectra lashing from sliding down. What have others done. Please point me to other threads with these discussions thanks.

I hope to have a boom made in August, hopefully MIK found some time to squeeze in a drawing to his schedule.
This photo shows how straight Callsign's boom is compared to mine...his looks good! You may want to click on it and look at the largest size available.


3 Goats at the Small Reach Regatta 2012 by Clint Chase Boatbuilder, on Flickr

Here is a cropped image

CandC_boomsflex by Clint Chase Boatbuilder, on Flickr

Hey, that cropped photo is a great shot! Calender worthy for sure!

WOW ... it sure is!

I think Christophe uses a saddle (deckeye in USA) and shackles to it. He promised some pics somewhere ... maybe he has done already?

This is very clear and definite method. But I do think a small diameter spectra cord (I've seen 1.5mm) or a bit of kite surfing spectra control line might work just as well with the traditional lashing - out to the end through the hole and turns around the spar itself perpendicular to the edge of the sail.

I'll get onto the boom.

Is the photo yours Clint?
MIK

Originally Posted by warm beer

Hey, that cropped photo is a great shot! Calender worthy for sure!

x2

When I zoomed in to look at the detail Clint described, what REALLY struck me was the big ol' Cheshire Cat grins on both skippers' faces! The heck with eliminating creases; go out there and keep making creases because it sure looks like a good time!

Originally Posted by Boatmik

I think Christophe uses a saddle (deckeye in USA) and shackles to it. He promised some pics somewhere ... maybe he has done already?

Christophe is working and far away from IAZ,P.