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Getting Ready for SHTP 2021

You have that u-bolt through the stem where you can attach a bobstay. I'd do that to take most of the upward load, and attach the sprit as far out as you can, leaving as little on deck as you can get away with. Look at most Minis - they rely entirely on a bobstay and sidestays to support the sprit; in fact it hinges up at the headstay when not in use.

Then rig the tack line so you can ease it from the cockpit and go see how far off the wind you can sail. Get as much bang for the buck as you can.
 
BobJ said:
You have that u-bolt through the stem where you can attach a bobstay. I'd do that to take most of the upward load, and attach the sprit as far out as you can, leaving as little on deck as you can get away with. Look at most Minis - they rely entirely on a bobstay and sidestays to support the sprit; in fact it hinges up at the headstay when not in use.

Then rig the tack line so you can ease it from the cockpit and go see how far off the wind you can sail. Get as much bang for the buck as you can.
Click to expand...

Yeah, I've been thinking about making a bobstay. I'd feel better about the loads on the deck with one set up, too!
 
Philpott said:
Do I detect a change of format? Race to Hanalei - Race Back with just a bit of time to recover in between. This means you get two races for the price of one. The Singlehanded Sailing Society continues to offer the best deal on the water.
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Once Upon a Time, Jackie.....

There was a Singlehanded Race to Hawaii, and at the Awards Dinner, the clever Race Committee, who had figured out how many spouses, friends, s.o.'s and hangers-on would be doublehanding back to California....distributed...

Singlehanded Sailing Society
Hanalei 1-2

t-shirts. I didn't do the race that year, but I was at the awards dinner and I remember a few people who got those t-shirts. I bet there are others on the forum who remember, too. If I remember rightly, the shirts were maroon. Gosh, maybe they were sweatshirts!

Terry McKelvey and Heli got a pair of them. Who else?
 
After working the real job all day I dashed out and did some quick epoxy work on the trim tab and the asymmetrical spinny pole.

Here are microballoons in epoxy for fairing the trailing edge of the trim tab, and the piece of red oak I put into the inboard end of the spinnaker pole. The pole got to me with a slot cut out of it, so that will be filled with sliced-up bits of carbon in epoxy. The whole thing will get a sanding to remove the paint and then a wrap or two of carbon fiber tape. That will change the diameter of the tube, so I'll have to duplicate the wraps up where the support point will be. I could have cut that part out, but I want to retain all the length of the tube that I can!

assy-pole-trim-tab.JPG


The oak will get tabbed in there, and I might sandwich it between some aluminum. It will get drilled for a fast pin.

I decided to do it this way 'cause this is pretty similar to how one of the Forte carbon poles have their ends done.

image_bowsprit03.jpg

CTA_bow04.jpg
 
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Round one of microballoons-fairing/sanding is done and the trim tab is better. It's far from perfect. Should I do another round of fairing? I'll never get it perfect. --- Probably. ONE more round.
 
Which NACA shape did you choose? A NACA 12% profile is fairly forgiving as regards stalling as it has a relatively blunt nose. It's not difficult to create a shape from by plotting a template onto some paper, spray-glue that to some masonite, cut out female profile with band saw or sabre saw, and keep shaping until the trim tab matches your template across the length of the tab.

http://airfoiltools.com/airfoil/details?airfoil=n0012-il

This assumes you have a fair bit of time available...

- rob
 
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tiger beetle said:
Which NACA shape did you choose? A NACA 12% profile is fairly forgiving as regards stalling as it has a relatively blunt nose. It's not difficult to create a shape from by plotting a template onto some paper, spray-glue that to some masonite, cut out female profile with band saw or sabre saw, and keep shaping until the trim tab matches your template across the length of the tab.

http://airfoiltools.com/airfoil/details?airfoil=n0012-il

This assumes you have a fair bit of time available...

- rob
Click to expand...

I used NACA 0015 for the rudder itself but the trim tab? I had a half inch s.s. rod for the backbone of it. I had a buddy weld a 1.5 inch s.s tang, edgewise to the rod to provide the resistance to torque, and glu'ed a 1/4 inch fiberglass rod opposite that, to form a rounded leading edge and give it at least a bit of balance. I glued some lastafoam to the tange on both sides and then when everything settled, went after it with 80 grit sandpaper and a wood rasp. Not very scientific! As foils go, it's pretty fat! It's a tich over half an inch thick and about 2 inches, maybe 2 1/4 inches in chord. It's got two layers of 6-inch glass tape in epoxy over it all. It's some sort of reasonably smooth, at least.
 
Well, I got a nice surprise today. I was out front in the yard / workshop and my neighbor walks up to the end of the driveway. I see him walking by with his wife and little girl, pretty often. He says to me...

"Do you want some carbon fiber?"

HUH? So I drop the piece of starboard PTFE that I'm shaping and he puts a box of stuff down on the end of my driveway. OH MY GOD.

yards and yards of heavy 3-inch woven tape. A huge spool of linear roving. 30 feet of carbon tubing weave...and a bottle of epoxy and a bottle of catalyst!

I thanked him profusely...about 5 x and offered to give him something for it but he just brushed it off. Said that he used to make bamboo bicycle frames, but was out of it, now for years. This was the last of his stock that he'd bought off of ebay. So I just repaired the slit in the end of the carbon fiber assy pole, and made a reinforcing sleeve at the midpoint. I laid some 6-inch strips of the tape lengthwise, forward of the midpoint of the pole and then got two wraps of heavy carbon tape around the pole that overlapped those. Everything was wrapped with plastic wrap, and then blue painters tape went around all that for nice even pressure all 'round. That pole was already crazy strong, now it's insane.

Today, I also got a piece of shaped UHMWP under the shoulders of the eye bolt, at the end of the pole, which should limit the bending back-and-forth. I shaped a couple of pieces of starboard and PL-Premium'ed them to the side of the pole opposite the eye bolt that will hold the tack block for the assy. I'll put a small eye strap through it all, with a couple of machine screws and that will work for the bobstay. The difference between the load distribution of the eye bolt and the bobstay padeye is rather large, but I think it's all plenty strong enough. The eye bolt has a rated break strength of 1500 pounds, so a 600-700 pound load should be just fine. i can't see this kite pulling more than that in any wind I care to have it up in, so I think I'm good to go.

While I was at it, I also worked on the bottom of the rudder, fixing the lowermost trim tab bracket in place. It's now bolted down, now that I've let the wood in the rudder dry for over a week. Everything is sealed with epoxy, and there's some structural "fairing" ...if you can call it that, done with sawdust and epoxy. I'll be reinforcing the bracket with carbon fiber, since I now have oodles of it!
 
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I'm adding some structure to the bottom of the rudder, to the bracket that supports the weight of the trim tab. This is not doing the surface flow that exits the back of the rudder, any favors, but I'm paranoid about it breaking.

The assy spin pole is nearing completion! Today I'll probably wrap a few winds of 3-inch carbon tape around it for the bow bracket tube.
 
AlanH said:
I'm adding some structure to the bottom of the rudder, to the bracket that supports the weight of the trim tab. This is not doing the surface flow that exits the back of the rudder, any favors, but I'm paranoid about it breaking.

The assy spin pole is nearing completion! Today I'll probably wrap a few winds of 3-inch carbon tape around it for the bow bracket tube.
Click to expand...

The bow bracket loop around the assy pole came off this morning. I could've done a better job, it took a lot of sanding on the inside to get it to fit, so I wrapped it 3x more. Once that sets up it'll be about 6 wraps thick of pretty heavy 3-inch tape. Should be bombproof.
 
Progress continues.

the bracket at the bottom of the rudder that supports the trim tab is almost done.

trimtab-brackete-attached.JPG

and the essentially completed assy pole got a couple coats of paint, today. Note the reinforcement in the middle.

spin pole paint.JPG
 
Look what arrived in the mail, from The Sail Warehouse in Monterey. ...."find the Wildcat", taken from the ramp.

stormjib-3.JPG

and....

stormjib-2.JPG

stormjib-1.JPG
 
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I am getting tantalizing close to "done" with the trim tab! The whole thing is MUCH less friction that the last system. I have a good feeling about this!
trimtab-rudder-top.JPG

Some details... Here's the trimtab shaft bearing at the bottom. It's made out of two 1/4 inch pieces of starboard (the plastic product..)

trimtab-rudder-bottom-detail.JPG
 
More detail shots... Here's the "middle" bearing. I was going to use the aluminum and sintered bronze pillow bearing I got from McMaster-Carr, but in fact the wood bracket is not quite level, not quite perpendicular to the trim tab shaft. The pillow bearings are self adjusting, but I've been leery about having three dissimilar metals so close to the waterline, so I just used a spare piece of UHMWPE that I had not used, earlier. The shaft is still very low friction.

trimtab-rudder-middle-detail.JPG

Top detail, showing the nifty pillow bearing. Sitting on the rudder is a stainless steel shaft coupling. A Stainless tiller for the system is currently out of the picture, setting up with JB Weld - steel dust reinforced epoxy. I had some inspiration about how to make a tiller system from wood, and since I had the time and the scrap wood, I made what you see here. The set screws, which jam down on the s.s. trimtab shaft are just stainless machine screws that I put on the grinder wheel, and flattened the tips, somewhat. They look a little funky, but the system works!

trimtab-rudder-top-detail.JPG

I just took this one to show the s.s. shaft collar, which prevents the whole system from bouncing up and the lower shaft "jumping" out of the lower bearing. $5.25 at the hardware store, totally worth it.

trimtab-rudder-top-underside.JPG
 
The s.s. "tiller' is made, now. It's JB-Welded together. It should, at most see 25-30 pounds of load. I can't see it getting more than that, the windvane simply can't generate that much force, so JB Weld should be plenty strong enough. And if it's not, I can just put on the wood one! It's a backup!
 
DONE!.... time to put it on the boat and test it. It's heavy, but the One Design class rudder is even heavier. Some of the stuff at the top is a little on the crude side, but whatever!

DONE-rudder-and-trim-tab1.JPG

DONE-rudder-and-trim-tab2.JPG

DONE-rudder-and-trim-tab3.JPG
 
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