Cruisers & Sailing Forums (http://www.cruisersforum.com/forums/)
-   Construction, Maintenance & Refit (http://www.cruisersforum.com/forums/f55/)
-   -   Keel cutting (http://www.cruisersforum.com/forums/f55/keel-cutting-80877.html)

mstrom 26-04-2012 18:47

Keel cutting
 
I have just purchased a DB-1 sailboat the problem is it has a 6.6 " draft has anyone have any knowledge of cutting off say a foot off of the keel? my idea is to weld on some wings just up from the bottom of the keel about 1' up and then when I| am lifted up cut off the keel just below the wings :) any ideas?
thanks

sailorboy1 26-04-2012 18:50

Re: Keel cutting
 
my idea is .............. don't do it!

Ziggy 26-04-2012 19:13

Re: Keel cutting
 
Quote:

Originally Posted by mstrom (Post 939680)
I have just purchased a DB-1 sailboat the problem is it has a 6.6 " draft has anyone have any knowledge of cutting off say a foot off of the keel? my idea is to weld on some wings just up from the bottom of the keel about 1' up and then when I| am lifted up cut off the keel just below the wings :) any ideas?
thanks

Yes. Sell the DB-1 and buy something with a keel you like.

Pblais 26-04-2012 19:39

Re: Keel cutting
 
A DB-1 is a specific boat some people like and would be fun to sail. It is raced as a class too. Cutting the keel would make it suck. You don't just chop off the keel and add wings. There enough boats out there that would have a shorter keel by design and be fun too. Making a boat into a different boat mostly fails.

If you could get a Naval Architect to redraw the keel then find someone to fabricate it the cost is already more than the boat is probably worth.

hellosailor 26-04-2012 19:50

Re: Keel cutting
 
Unless there's a compelling reason...as Ziggy says, sell it and get what makes you happy. Chopping a keel will probably destroy the resale value of the boat.

If you really want to chop it, contact Mars Metal and they can cast wings or a bulb or whatever you want to compensate for the chop.

minaret 27-04-2012 08:10

Re: Keel cutting
 
Quote:

Originally Posted by Pblais (Post 939710)
A DB-1 is a specific boat some people like and would be fun to sail. It is raced as a class too. Cutting the keel would make it suck. You don't just chop off the keel and add wings. There enough boats out there that would have a shorter keel by design and be fun too. Making a boat into a different boat mostly fails.

If you could get a Naval Architect to redraw the keel then find someone to fabricate it the cost is already more than the boat is probably worth.


We did this job once. Everyone in the yard mocked the whole idea, including me, but it actually worked out OK. Can't remember what sort of boat it was, but we removed about a foot from the keel, faired it out, and installed wings. The whole thing was designed by a reputable NA. The wings through bolted to the keel. They thought about a one-piece "shoe" but it was decided that a two piece arrangement with heavy rod threaded on the ends going through the keel and both wings would be stronger. It was definitely a bit of a PITA but actually didn't cost as much as expected. Maybe 10k all told. As I recall one of the primary concerns is the existing keel bolts. Most are J bolts and need a certain amount of "bury" to provide the necessary strength. You don't want to remove too much meat and expose a J bolt, or even come close to it. The owner was quite happy with the result, said the boat actually performed better. Could have been wishful thinking. Less draft + more wetted surface area = slower boat to me.

foolishsailor 27-04-2012 08:47

If you added a bulb to offset the the loss of keel weight you would possibly keep the same righting moment. But how do you deal with all the other changes, you center of effort will change? The wing s minaret spoke of would probably offset some of the righting moment allowing the sail plan to still function, but a foot of keel is a lot.

Do you have money for redesign, as in you are looking for shallow draft but have cash for redesign? You could stretch keel fore and aft with consideration from a naval architect to compensate for the loss and a weighted bulb with wings would compensate for the rest....

...um buy a new boat perhaps? Sorry to be cynical but it is a bigger change than maybe you think it is?

Cheechako 27-04-2012 09:18

Re: Keel cutting
 
I dont see any problem with it. Not sure how you would cut it though! Look at all the designs over the years with widely different keel options.... personally , for the average sailboat.... I think it's more of an art than a science. Look at the old Thunderbird 26 class. These boats have nothing more than a flat steel plate with a bulb for a keel. No foil shape at all. it used to be hard to beat one on the race course too! I doubt Joshua Slocum spent much time thinking about it....

foolishsailor 27-04-2012 09:23

I think slocum sailed a precursor to the thistle which is a precursur to the westsail, and was lucky to get within 60 degrees of the wind?

Not one I would want to base my boats future polars on?

minaret 27-04-2012 10:31

Re: Keel cutting
 
Quote:

Originally Posted by foolishsailor (Post 939959)
If you added a bulb to offset the the loss of keel weight you would possibly keep the same righting moment. But how do you deal with all the other changes, you center of effort will change? The wing s minaret spoke of would probably offset some of the righting moment allowing the sail plan to still function, but a foot of keel is a lot.

Do you have money for redesign, as in you are looking for shallow draft but have cash for redesign? You could stretch keel fore and aft with consideration from a naval architect to compensate for the loss and a weighted bulb with wings would compensate for the rest....

...um buy a new boat perhaps? Sorry to be cynical but it is a bigger change than maybe you think it is?



When we did this job we weighed the piece we cut off as well as the bag of powerplane shavings from fairing and compared that to the wing weight. I believe we actually added quite a bit of weight to compensate for its higher location, as planned by the NA.

Lowcountry 27-04-2012 10:48

Re: Keel cutting
 
Or you could remove the mast and install wings and just fly everywhere you wanted to go, resolving any and all draft issues ;)

hellosailor 27-04-2012 11:13

Re: Keel cutting
 
"Not sure how you would cut it though! "
Sawzall, acetylene torch, plasma cutter, just another day at the office.

The subtleties of retaining performance, or possibly increasing it. Of balance and drag and lift. All that is why most folks would look at a "custom" boat and simply walk away, unless they were in the "money doesn't matter" market and could afford to have a true NA doing the redesign.

You could easily slice off TWO feet of keel, add a tungsten or other denser shoe at the bottom to restore one foot of it while keeping the original weight, but that still leaves all the other matters of balance to deal with.

But then again, there are folks who sail with 20 year old sails that some of us would call hopelessly blown out, and they just love 'em. As they say, "Whatever floats your boat".

zeehag 27-04-2012 11:25

Re: Keel cutting
 
cutting off a foot of keel will only make more problems. there are folks sailing fla with 6'6 draft -- why cant you? isnt difficult.
why didnt ye buy a shallower draft boat?? they are out there.
i think ye goofed in first place if you wanted less than 6'6, shoulda bought what ye wanted-- the market WAS in your favor as a buyer--is NOT in your favor as a seller.

ohdrinkboy 27-04-2012 13:16

Re: Keel cutting
 
There is an article on MarsMetal's website about this. The guy in the article used a chainsaw for the cut.

minaret 27-04-2012 13:25

Re: Keel cutting
 
2 Attachment(s)
Quote:

Originally Posted by ohdrinkboy (Post 940082)
There is an article on MarsMetal's website about this. The guy in the article used a chainsaw for the cut.


I used a sawzall. The lead cuts very easily but clogs blades very quickly. I would think a chainsaw chain would become clogged fairly quickly and be hard to clean and expensive to replace. A dozen sawzall blades was cheap and quick. Shaping with a powerplane goes very quickly as well. Grinding not so much. Some keels are pig iron and can be much harder to cut or shape, depending on the iron/lead ratio. This article shows exactly how we did it.

Capt'n Pauley's Virtual Boat Yard -- Projects Galore!!!: Reducing Draft: Cutting the Keel

And here's an old cruising world article about doing this.

http://www.marskeel.com/fckeditor/us...ng%20World.pdf


All times are GMT -7. The time now is 11:22.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.


ShowCase vBulletin Plugins by Drive Thru Online, Inc.