Main Sail shape question

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Main Sail shape question

Postby Mflyer65 on Mon Nov 16, 2020 12:43 pm

All,
I am trying to get the rigging complete today while the sun shines. I think I have something wrong with the main sail due to its shape. I have the outhauls and halyards pulled up snug and the topping lift pulled up to lift the boom just a little off the gallows. The sale shape suggests to me that I need to lower the boom and topping lift to get rid of the rather deep crease caused by the toppling lift being pulled up, (maybe too much?).
If I lower the gaff I would need to take several inches off the gallows.
What are your thoughts?
Mike
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Mflyer65
 
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Re: Main Sail shape question

Postby TassiePete on Mon Nov 16, 2020 3:31 pm

Hi Mike,

You have to fix the luff first, i.e. the throat halyard needs to be tight. I assume that you mean the peak halyard when you mention the 'topping lift'. The PS, if rigged with gallows, doesn't usually have a topping lift. On my boat I do have a topping lift to hold the boom up when the sail is lowered, because I don't have gallows installed. I digress ...
I'd suggest taking the gallows off the boat, while you are setting up the mainsail:
The head should be snug (not really tight) on the gaff - no crease running along/under the gaff.
Throat and peak go up together, until the the luff is tight. The distance between the goose-neck and the cheek block has to accommodate the luff. The luff has to be tight before anything else. Then, when the peak halyard is pulled up, the leech will get tight and the sail will hold up the boom, but ...
if the foot (out-haul) is too loose, you will get a crease running from the peak to the tack, if the out-haul is too tight the crease runs from the throat to the clew.
(The out-haul and the peak halyard need to adjusted when you are sailing: in light winds the foot is slightly loose, in stronger winds the out-haul is tight to get a flatter sail. Whenever the the out-haul tension is changed, the peak will need to be set to get the crease out.)
Once the sail looks right (no big creases, foot slightly loose, ...), measure how high the gallows can be. Check that you can get the sail flat on the center-line using the main sheet. In a stronger wind the sail needs to be flat and the boom must not come to rest on the gallows when hardening up. Then check again with the main reefed down (first and second reef, one at the time).
Also, check the mast rake. It is easy to get more rake - I have a small block of wood behind the mast in the tabernacle -, but it is not that easy to reduce the rake. Obviously, too much rake will bring the end end of the boom down (a lot). Take the boat out for a sail or two ... then put the shortened gallows back onto the boat, or, install a topping lift instead ;) .

Cheers,

Peter
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Re: Main Sail shape question

Postby Mflyer65 on Mon Nov 16, 2020 5:06 pm

Thanks Peter,
Great explanation. True I did mean the peak halyard. I tightened the luff first and then the peak. I pulled the outhaul for the gaff tight while down after attaching to the throat. I had already tightened the outhaul at the clew. Maybe it is just too tight? I will try your suggestion and remove the gallows and see what positions work. I also have a block of wood 3/4" at the base of the mast between the mast and the tabernacle. Measured I get about 3.5 degrees of rake.
Thanks again for the education and suggestions,
Mike
Mflyer65
 
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Location: Durham, NC

Re: Main Sail shape question

Postby Wayne G on Sun Nov 22, 2020 8:31 am

Hi,
To get the crease out of the main sale I reduced the height of the gallows from the designed 59” to 53.75” when measured from the footwell to the gallows apex.

I reduced the gallows height by estimation so it’s probably a little shorter than absolutely necessary, but when the sail shape looks good, there is very little free space between the boom and gallows.

Before reducing the gallows height I could achieve the correct sail shape by adjusting the peak halyard when sailing. As the wind filled the sail the crease could be removed and the only minor issue I had was the boom would ride along the gallows when going about. Not a big deal, but I wanted to avoid wearing away the varnish and epoxy resin on the top of the gallows and bottom of the boom at the contact location.
Wayne Gray
Orlando Florida
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Re: Main Sail shape question

Postby Mflyer65 on Mon Nov 23, 2020 1:31 pm

Thanks Wayne,
It's reassuring that I came up with almost the same end result as you did once I completed Peter's suggested testing of full and reefed positions. I have 53 inches to the center top of the gallows notch. I ended up removing just under 5 inches from the 2 gallows supports.
I "splashed" my pocketship yesterday! I went to a close, small lake to check out various functionalities, ran the boat out to the middle of the lake under motor power, and fiddled with several rigging and operation items. There was absolutely no wind at all so the boom sat centered and the tiller moved back and forth as a small wave from a fishing boat would pass by while I messed about with lines and reefing effort. It actually worked out well for me to get through all the various setup, launch and retrieve items without fighting the sails but I hope to clean up the few items I need to fix and then try again with wind drive.
I really need a track stop though. Too much of a pain for me otherwise. Another reason for thinking about Peter's laced version instead of the track. I think it could just stay laced when lowering the mast as well?
Thanks again,
MIke
Mflyer65
 
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Re: Main Sail shape question

Postby JonLee on Mon Nov 23, 2020 2:50 pm

I (as many other before me) found a track stop to be outrageously expensive. Instead, I ended up getting a track slide that had a thumbscrew on it: https://www.fisheriessupply.com/race-lite-special-5-8in-sail-track-slide-with-screw-stop-348-ax. This worked just as well. To reduce the chance of losing it overboard (inconceivable!), I have it tied to a short length of spectra, which is in turn tied to a convenient spot on the tabernacle.
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Re: Main Sail shape question

Postby JonLee on Mon Nov 23, 2020 2:51 pm

I should add (since it is that topic of this thread), that I too ended up shortening my gallows modestly.
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Re: Main Sail shape question

Postby JonLee on Mon Nov 23, 2020 2:52 pm

I should ALSO add...

Congratulations on launching your boat!!! Do you have any photos to share?
JonLee
 
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Re: Main Sail shape question

Postby craig on Mon Nov 23, 2020 3:55 pm

Congratulations! Big achievement and I'm glad it went well.

I second Jon's request for pictures when you get a chance ;)
Titania, launched January 2015
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Re: Main Sail shape question

Postby Mflyer65 on Wed Nov 25, 2020 10:36 am

Thanks All,
On my own a bit so no really good pics in the water but here is the start and the dip anyway. I had the trailer built here in the Raleigh/Durham area. It worked out great. Even the rear light framing is a step.
I am making a few more changes and hope to get wet next week if a breeze comes up.
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