Adding weight to daysailer centerboard

I hope someone can help me with a basic question: Should I add weight to a fiberglass only centerboard?

I have a 17' LOA beamy (7'6" beam) Harpoon 5.2. It has a very light centerboard which is fiberglass only, no added ballest. Draft with centerboard down is 3' 8" vs. 5" with it up. Hull weight of 565 lbs.

These boats, if capsized, like to turtle. The way I imagine it, with no real knowlege in this area, adding lead or other ballest will give me advantages such as:

Less heal for a given wind,
slower to heal - more reaction time,
Less possibility of capsize, easier recovery
Less possibility of turtling

I will have to account for the added weight with the lifting mechanism, trailer will have no trouble with weight.

Am I thinking about this the right way? How much weight must I add to get significant benefit?

Any insight will be greatly appreciated!

 

Harpoon 5.2

If you haven't already, talk to other owners before considering any major mods.Here's a site that may help:
Boston Whaler Harpoon Sailboats
Address:http://www.ruach.net/Harpoon.shtml Changed:8:44 PM on Thursday, October 12, 2006
-----------
Is the mast sealed or does it fill up with water when the boat first capsizes? If it isn't sealed I'd consider that.
Adding weight is probably the last thing you'd want to do but try to talk to other owners.
---------
Hobie Waves use a little football shaped buoyancy pod at the top of the mast but another alternative is a pocket at the top of the sail with foam for added buoyancy-will look better than the wave solution and not negatively affect the sail appreciably. I think some inland lake scows use the pocket system.

 

If you sail on open water then I would reconsider the idea of stopping the boat inverting. Its a very important safety feature. If you lose contact with the boat on a windy day then if its on its side it will blow downwind faster than you can swim, but a boat that inverts won't. That could easily be the difference between getting home and getting washed up on the beach a couple of days later...

 

Turtling

That's something to consider but the hull shape of the 5.2 doesn't seem to me to offer much to hang on to upside down-I'd hate to be stuck at sea with that as the only thing to hang on to. I doubt- but don't know for sure- that it would sit up high enough at 90° to blow away very fast and it would allow righting.
But I'd sure do a lot of research-particularly with other owners.....

 

mast flotation is good idea

Thanks for your replies,

I have been thinking about mast flotation, I will try to figure out something here, maybe like the bouyancy pod you mentioned. I have not thought about the question of sealing the mast, this is very interesting.

I have asked the centerboard weight question on the harpoon website, no one has aparently tried it yet. They have voiced the concern of making the boat non-standard for racing, but I don't race it in any serious way, I'm not too concerned about this.

What I'm wondering about is if I'll see a significant reduction in the heel for a given wind, and possibly slow down the speed at which the boat picks up heel in a gust with a realistic amount of weight. I will be limited by the physical size of the existing centerboard in how much weight I can add. My general thought is to drill/route out some of the fiberglass, add steel or lead, and fiberglass it back up. I would try to get the weight as close to the tip of the centerboard as possible.

 

You can prevent turtling by putting a flotation panel into the head of the sail: http://www.mcscow.org/rigging/float.htm.

It's easy to provide a pocket that can hold a piece of closed-cell foam, and it doesn't take a lot of volume due to the leverage of the mast. The foam can be left out for light air performance, and put in when conditions dictate. It's not much weight aloft, and the performance penalty is minimal. I don't think it would cost very much for a sailmaker to add pockets to your existing sail.

You don't get any more beamy than an Inland Lakes scow, and these are used by boats as big as the 28 ft E scow. So I'm sure they would be effective on your Harpoon.

 

It beats the **** out of having nothing to hang on to. I know from last Sunday's experience that in 25 knots of breeze even a boat as narrow as an International Canoe will blow downwind faster than I can swim in sailing gear until it goes inverted.

 

---------------
TC, I doubt weight added to the existing board would make much difference and it's generally not a good idea to mess with a structural design w/o competent guidance -like from a marine engineer. If you were to route out a 1" X 6" X 12"
section at the bottom of the CB you'd only gain 29 pounds; twice that wouldn't be very significant either. For reference, the Bongo a 15' "modern" keel boat has around 100 pounds in a bulb at the bottom of a retracting board. Bethwaite's "high performance" Skud 18 uses a retracting board(keel) with 300 pounds of lead on an 18 footer.
-----------------------------------------
GGG & TC-I'd imagine the 90° performance of a 100lb. 17' IC would be substantialy different than that of a 565 lb. 17' 5.2 . Personally, I would check out the performance of the boat at 90° in the conditions you mention by jury rigging up some masthead flotation. It would seem to me that if the boat is manageable and doesn't blow away too fast being able to right it would trump letting it turtle.

 

how much weight?

Tom,

The sail floatation shown from Sequel Sails looks good, unfortunately I wasn't able to find a web site for the company, it looks like their domain may have expired. I wonder if they are still in business?

Doug,

Point taken - 30 - 40 lbs added may not be significant

I wonder how much weight it would take to make a significant difference. Maybe you have to define a significant difference as something like adding another crew member - from (2) 150 lb crew to (3) 150 lb crew up one foot above the waterline (at the rail) is equivelant to x lbs 3 feet below the waterline.

Anyone know how to ballpark that?

 

5.2 + lead

TC, these are rough ballpark figures. If you add 150 lb.s on the rail of the 5.2 you're adding 562 ft. lb. of righting moment(boat level).
If you added weight to the BOTTOM(just for illustration) of a new board/keel (like a bulb) here's the approx. amount you would have to add to achieve the same RM at three different angles of heel:
1) 15° ---add 472 lb. absurd and impractical
2) 25° ---add 253 lb.
3) 35° ---add 176 lb.-probably too much heel for this hull design.
---
# 2 might be practical - with a lifting daggerboard type keel- but would entail serious structural redesign of the board and the trunk.
The daggerboard/bulb combo could be made deeper reducing the weight required a bit.
You could make a "swing keel" which is just a heavy centerboard but it's CG would be higher than the daggerboard/bulb combination and would require more weight for the same RM at the angles shown. The structual redesign is not just necessary because of the angles above it is necessary for the trunk and board/keel to be strong enough in the worst case scenario -a knockdown. The trunk MAY already be strong enough if the board is designed to support a couple of crew on it for righting the boat as is. Your maximum crew/stowage capacity would, of course, be reduced by the amount of extra weight added including any structural reinforcement necessary.
===============================================
I don't recommend you consider doing this at all without the input of a NA/marine engineer!
===============================================
I'd test the righting characteristics of the boat with flotation near the top of the mast and make damn sure you and your normal crew can right the boat and that it won't get away from you in the process. That wouldn't cost much at all. Assuming that works well I'd use the floatation pocket in the sail like the scows do-and forget adding ballast. Good luck and keep us informed about what you decide to do and how it works out.

 

Don't know if it's possible, (surely not allowable on an strictly class racer), but may I suggest a better solution than weight adding to centerboard may be extending it about one more feet deep... it will not compromise floating level, nor total weight, even end-speed.
It will help you better,as it will need less effort to turn hull back from capsizing.
cheers
Solrac

 

Thanks Doug for those RM calcs - That was the info I needed to think it through. And thanks to all for the good ideas

I guess the mast floatation is a definate, and I like the simple design of that scow model.

I'll let you know if I make any changes in the centerboard!
TC