PeteWeight in Center board??
Weight in Center board??
I saw a mod where the poster filled his center board w/ concrete. Is the M's center board hollow? Could it be filled w/ lead shot and epoxied on the top to hold it all in? Would need to set up more then a 2:1 lifting system too.
Pete
Pete-
mastreb
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- Sailboat: MacGregor 26M
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Re: Weight in Center board??
Do a search about adding lead shot to the centerboard. There are numerous threads about it. Short answer: Yes, the centerboard is hollow. The right way to do it is to add about an inch of shot and an inch of resin, and let the resin harden before adding another inch. This way the weight of the shot doesn't deform the board. You can add about 50 lbs. to the bottom of the board this way.
Consensus from people who've done it seems to be that while it does contribute a small amount to reduced heeling, it's not nearly as much effect as they'd hoped, and that learning how to handle the mainsheet in a gust is far more effective than increasing the weight of the daggerboard. Consider that the board fills with water when you lower it, and when you do this mod you prevent water from filling at all, so what you wind up with is a board consisting of air, resin, and lead rather than a board consisting of water.
The specific gravity of water is 1.0. The specific gravity of cured resin is about 1.1--close enough to water to factor out. The specific gravity of solid lead is about 11, but given a typical solution to a lead shot sphere packing problem, you can't get higher than 75% packed and it's unlikely that you'd actually get better than 50% packed using incremental resin. Finally, consider that you can only pack about 50% of the board, and you wind up with the following:
11x the weight of water /2 for packing, and /2 again for incomplete fill = 2.5X times water weight. That's not a whole lot of increased lever effect considering that lead and resin don't drain out when you lift it and so create extra work for both you and your board rigging at all times.
The bottom line is that these aren't keel boats, and they're never going to be keelboats, and the sooner you learn to sail a Mac the way it is, the happier you'll be. Took me about a year to learn that.
Consensus from people who've done it seems to be that while it does contribute a small amount to reduced heeling, it's not nearly as much effect as they'd hoped, and that learning how to handle the mainsheet in a gust is far more effective than increasing the weight of the daggerboard. Consider that the board fills with water when you lower it, and when you do this mod you prevent water from filling at all, so what you wind up with is a board consisting of air, resin, and lead rather than a board consisting of water.
The specific gravity of water is 1.0. The specific gravity of cured resin is about 1.1--close enough to water to factor out. The specific gravity of solid lead is about 11, but given a typical solution to a lead shot sphere packing problem, you can't get higher than 75% packed and it's unlikely that you'd actually get better than 50% packed using incremental resin. Finally, consider that you can only pack about 50% of the board, and you wind up with the following:
11x the weight of water /2 for packing, and /2 again for incomplete fill = 2.5X times water weight. That's not a whole lot of increased lever effect considering that lead and resin don't drain out when you lift it and so create extra work for both you and your board rigging at all times.
The bottom line is that these aren't keel boats, and they're never going to be keelboats, and the sooner you learn to sail a Mac the way it is, the happier you'll be. Took me about a year to learn that.
Re: Weight in Center board??
Wow mastreb...Thanks for the great analysis! I think I'll pass on the lead. By the by, I learned to sail on Lazers and own a Lazer II, so i'm pretty good with the sheet! Pete
Pete-
restless
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Re: Weight in Center board??
Restless has 20 odd kg in the cb, together with an anti clunk device. Whilst not converting a 26x to a keel boat, it seems to have added a considerable damping effect to her previous tendency of lurching around at the slightest undulation. A 2:1 lift is sufficient to bring the cb up.
This is a definate mod in my book. The real bummer is getting lead shot at a reasonable price. I made my own with scrap
I also beefed up the lifting eye to account for the physics of leverage with the extra weight. Check out Knot sure for a more extreme approach.
This is a definate mod in my book. The real bummer is getting lead shot at a reasonable price. I made my own with scrap
I also beefed up the lifting eye to account for the physics of leverage with the extra weight. Check out Knot sure for a more extreme approach.-
Erik Hardtle
- First Officer
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Re: Weight in Center board??
Did somebody envoke the name "Knot Shore"...
Yup, I have done it twice on Knot Shore... only because I was being bad once (2-3 foot waves at 22mph and centerboard drops = no more board)
(what the trunk looks like without a centerboard... oops... hhehe)
http://www.macgregorsailors.com/modt/index.php?view=460
Here are some the performance results from my web site. Check out my boat web site for the full mod and pics.
Yup, I have done it twice on Knot Shore... only because I was being bad once (2-3 foot waves at 22mph and centerboard drops = no more board)
(what the trunk looks like without a centerboard... oops... hhehe)
Guess I should officially post it in the Mod section... Oh I did:Pulled up the centerboard line... nothing left on the end except a frayed wire... ok so the board is down. I jump down below and look for damage or leaks.... none... and strangely silent... I don't hear the centerboard slapping the sides of the trunk... most likely because I don't have one anymore.
Yup, it's gone.
http://www.macgregorsailors.com/modt/index.php?view=460
Here are some the performance results from my web site. Check out my boat web site for the full mod and pics.
Ok.. just go back from the sea... er... river trials...
Powering... seemed to do just fine... was doing 17.5 mph for about an hour... hit a few 1-2 ft waves no banging, seems just as before. Boat seemed to sit a little lower in the water.. as if wife was inside the cabin (175lbs) (she wasn't) or the ballast tank was full (it wasn't)
Sailing... (no water ballast) nothing quantitative.. just a feeling... on a close reach with 10-15 mph winds, heeled slowly... not as quick or sudden as it used to.. felt more like a keel boat heeling... got a heel of up to 30 degrees doing 5.3 mph... didn't round up into the wind like it normally would do. Filled the ballast, less heeling... same "keel boat" feeling with it slowly heeling... not sudden heels.
Hitting bottom: it works like a 'boat brake" I purposely went into shallow water while sailing... boat came to a slow stop... just cranked it up a little and it continued along. The new wire connecting to the board does sing a little while sailing... nothing annoying.