Add weight to Eastport Pram centerboard

A few years ago I built a nesting Eastport pram with the sail package.  I've sailed her a few times and have found it kinda tippy.   

I'm now building a pocketship and that has lead in the centerboard.  I wonder if sailing performance of the pram would benefit from a weighted centerboard? 

I am barely going to weigh more than my Eastport Nesting Pram! (only by about 30 pounds).  Is this going to present a problem? (Not finished yet.)  

That was me.  Don't know why it logged me out.

I did just think about the West Wight Potter 19's heavy daggerboard (some few hundred pounds, I believe) which has a winch to hoist it up.  A bit different arrangement than a swing keel, but serves much the same purpose.  
Still doesn't really make them self righting, I'm told.  Might make you wonder what a steel daggerboard shaped like your Eastport Pram's would weigh, and weather that would help any.

Usually, the only weight one adds to a centerboard is to make the thing sink quickly and stay down with the boat tearing along at speed.  This is different than a "swing keel" which is actually meant to be of substantial weight and to serve as both ballast and lateral plane.  Most, but not all, of these which I've seen have some arrangement for locking the thing in the lowered position.

A daggerboard, on the other hand, doesn't really need a lot of weight, it being mostly held down by friction with the daggerboard case, there being no hinge and generally a much more snug fit.  Sometimes they'll float up a little in light air, and a shock cord arranged to pull the board forward or aft will in the case will serve to keep it down.

Given all that, you'd have to add a lot of weight to the daggerboard for it to add to stability like a swing keel does, and it is probably too thin a blade to stand the strain.

If you want to tame your Eastport Pram's tippiness with a bit of weight, I'd suggest starting with maybe 4 one gallon jugs of water lashed securely around the daggerboard case to see if that...what?...15# of fresh water down low tames her a bit, maybe at least giving you a half second more to react to a gust.  I did this once with my Passagemaker, and it did seem to make her a bit less skittish in a stiff breeze.  However, when you weigh twice what your boat does, it's mostly about what you do with your own weight.

At the risk of being pedantic, 4 gallons of water is just over 33 lbs. The good thing about jug ballast is that while the boat's dry you get the ballast effect, but if the boat swamps it's neutrally buoyant and won't make it sink any lower. And on a hot day you can drink your ballast.

And, to be even more pedantic - steel is about .28 lbs/cubic inch and okoume plywood is about 0.0155 lbs/cubic inch, so a steel daggerboard will weigh about 18 times what the okoume one does.

Don't have time right now to calculate the effect on stability.

Laszlo

 

Laszlo's correct, of course, "a pint's a pound the world around" ... and a bit more as it turns out.  I had somehow confused pints and quarts and gotten it into my fuzzy head that there were only four pints in a gallon, plus which, I was thinking that the "pint's a pound" bit was for sea water and made an erroneous adjustment for less dense fresh water.  Mercy, this is how shipwrecks happen!  Mistake + Miscalculation + Mischance = Misfortune.  I was well and truly hard aground there!

A gallon of pure water (not seawater) weighs a bit more than 8-1/3 pounds, so "a pint's a bit more than a pound" should have gotten me to Laszlo's 33# figure.  My sincere apologies to all.  Doing math problems in your 71 year old head late in the evening while your wife is watching television is probably about as dangerous as running with scissors.

My comments about a steel daggerboard were not meant to be taken seriously, but to point out that in a small, lightly built, wooden boat like the Eastport Pram, dense, heavy, awkward things which aren't permanently attached where they belong are impractical.  Even if firmly attached, like a bulb keel like a Star class boat, such things kind of defeat the shole point of a small, light boat for the obvious reason that they are not light.  I should have stated that plainly instead of assuming all y'all would form the same image I had formed in my head of dropping that hypothetical steel daggerboard and watching it pass spear-like through the bottom leaving a gaping hole.  I'll beg your forgiveness for that mistep as well.

What I should have just said plainly was this: small, light sailboats with good sized sails where the crew outweighs the boat by a good margin are going to feel tippy.  Where you put yourself makes much more difference than anything you can accomplish with a weighted fin or a few gallons of water.

Be as nimble as you can, keep the sheet in your hand, stay alert, and reef early!  Here's wishing you more fun sailing your Eastport Pram!  <;-)

Gramps,

What's a little math error among friends? I lost the first carbon fiber mast that I made, a lovely 4 lb, 12-ft hollow tube that I could chin myself on because of a silly math error that ended up putting the internal reinforcement above the mast partner instead of centered on the mast partner. Compared to that getting the ballast weight wrong is nothing.

As for the rest of your post, you'll notice that I said absolutely nothing beyond the weights. I didn't need to. You had said it all with no corrections needed. So stop apologizing for a nice post. You did good.

Laszlo

 

Went out on my local reservoir with our PMD Winklle is some pretty good wind this afternoon/evening, mostly westerly anywhere from SW to NW blowing 10 knots or a bit more for the first couple of hours.  Anyway, I tried lashing down four gallons of water to the daggerboard case again, and it did help steadier her out some, especially in slowing down the reaction to the gusts.

It did make it a bit more difficult to haul her back on the Harbor Freight "flatbed" trailer, mostly where the bottom skids tend to grab the edge of the trailer, but it wasn't all that hard.

Anyway, this confirmed my earlier impressions, and I may continue to do this when sailing solo.  Certainly the best four hours of sailing I've had this summer, which seems to be shaping up to "The Summer of Slack" here in Central Ohio.  <;-)