ADVICE NEEDED: Adding weight to keel FOLKBOAT
wondering if I can brainstorm the boatbuilding / shipwright community.
I have: 1982 Fiberglass FOLKBOAT 26foot sloop, fractional rig, FULL KEEL
5800lbs displacement. 2900lbs ballast.
Problem: boat is little tippy. Needs weight down low - ie in keel
Have redone everything on her, stipped out interior, redone the all electrics from scratch, redone rigging, redone all brightwork, every single fitting resealed and every thru hull redone. These little boats have proven themselves offshore. I love this little boat, she really grows on you. Have taken a few good spankings in her already, only proves to me It is worth trying to fix this problem in my opinion, the question is what is the best way?
This summer, by adding 350lbs of lead shot in 5lb bags distributed low down in bilge lockers and hull lockers, I have steadied the boat enourmously. She is no longer tippy when climbing aboard. She sails better to windward, etc etc. I realize that in adding yellow cedar and mahogany to the cabin roof, I have made her just a little too top heavy. in the cabin.
Any ideas you could provide as to how to add weight to the keel permanently, so I can remove the temporary shot bags would be appreciated.
Idea#1: bolt on 350 lbs of shaped lead to near bottom of full keel. Something in lines of a torpedoe shape. Simple, easy, but how does this affect water dynamics and sail performance?
Idea#2: take the bottom of the keel apart, strip the fiberglass back and remove concrete (i have not sampled the fiberglass with a core at the base and assume it is a mix of steel and concrete or something like that), weigh it and replace with 350lbs extra lead. Seal her back up. Very time consuming I assume, big job, not sure if this is doable in a few weeks say.
Thanks in advance for any input
Well, I'm no marine engineer but it occurs to me that the shot bags should be secured so that they can't shift. I am picturing in my mind a knock down. The shot bags would fall to the lowest point and cancel some of the keel ballast in trying to right the boat. Again I'm no expert but I would love to hear what others with more experience in this area would have to say. I also realize that many successful ships have relied on shiftable sandbags for ballast- perhaps I'm dead wrong.
You have 2900 lbs of ballast in a boat that dispalces 5800 lbs. that is a 50% ballast ratio. that is huge. You don't need any more lead.
The folkboat originated as full keel wooden boat, a very traditional design. This type of boat always shows poor initial stabilty due to their narrow water line and veed hull shape. It is very normal for them to rock a bit as you step on the side deck. Also since thay depend largely on the keel weight for stabilty they commonly heel to 20-30 degrees, that is normal.
Think of how much heel you need to have before the righting force of the keel comes into play. They do get very stiff beyond this, you will just have to get used to it.
A more modern vessel, has a flatter bottom which increases the intial stabilty so typically they have a lower ballast ratio, 40% might be more common now.
We have some very beautifull wooden folkboats in our club, I was admiring a couple today.
While a folkboat is a rather tender design, adding such additional ballast may also put more stress on the rigging than it was designed for. The greater the righting moment, the less give the boat has for the rigging, and the stronger the rigging needs to be.
I would definitely consider consulting with a marine architect about this, especially if you're looking to open up the keel and add the weigh internally or bolt it on externally. The keelbolt fittings may not be up to the task of supporting that much additional mass and may need to be strengthened to be able to handle it.
IMHO, I would go with adding the weight by re-building the keel with lead ballast rather than trying to add it externally, which will add underwater surface area and slow your boat considerably, as well as possibly increase your draft a bit.
The shot bags, while you're using them, really should be secured so they can not shift in the event of a knockdown or roll over. In the case of either, unless they are secured, they are potential missiles... and could cause you and your boat a lot of damage. They could also prevent the boat from righting itself or slow the righting process, to the point where the downflow through the dorades and such would sink the boat.
You should probably should have consulted with a marine architect about the negative effects of the weight you've added by adding the cedar and mahogany to the cabin roof prior to doing the modification, and may want to ask their advice regarding it now.
Definitely consult a marine architect or designer. Having read two books on the subject already (and seriously contemplating going through Westlawn - money being the current holdup), I know that boat design is NOT an easy thing. It takes considerable planning and thought. Lack of such leads to easy disaster. Bear in mind each boat was designed around specific parameters and considerations (as well as knowledge of boating) - by doing things like adding additional weight up higher you may create a much larger problem than envisioned (btw, there is a calculation to determine how much extra one *could* add without severly affecting stability) in the original design.
The bottom line is, your craft may not be able to handle what you'd like to do so have your plans checked by a competant marine architect.
/s/ Jon C. Munson II
350 lbs equals about two people's weight and the addition of the weight improved the boat enourmously. So just leave the shot in the boat, but secure it like everybody said. Spread it around a bit to distribute the weight and go sailing. Don't tear the keel apart or bolt anything to it.
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