Disregarding any class rules...

mixmkr

mixmkr

Well-Known Member
I'm thinking of a winter project to design a new daggerboard. One preference would be to make a shorter one, as at winter pool on KY Lake, there are lots of areas that are sub 4ft in the coves and the water typically isn't clear enough to see the bottom (before it's too late). Basically the shore line depths require you to go out MUCH further in most areas, before you hit 4+ft of depth.

Having no design sense, but I fiberglass and gelcoat a lot, making a fiberglass board won't be an issue, so that seems to be the easiest route.
I also have the ability to slide the daggerboard up from the bottom (if I make removeable/retractable "headstock"), as my Sunfish sits ALMOST high enough on the trailer to do so with normal board. Basically I can have my board all the way in, with my boat sitting on the trailer. So a 10" shorter board should easily slide up from the bottom..
Why>>>??
So maybe I could put on some wings or ballast (I have plenty of lead, etc)??
Realizing the depth of the board works best for sideways slippage, and wings typically are more for "lift"....would those be beneficial or just create more drag??

IOW... if you could build ANY shape or sized daggerboard, is there a better foil shape than what is currently used? I don't class race, so it's not an issue. Something of a "rec" board for winter pool and goofing around.

oh...also a shorter board would be useful for taking/jibing in very shallow waters, without having the boom hit a raised daggerboard...

So... throw me some opinions plz. C'mon design experts.... !! All you hard core racers...what would you ultimately like in a daggerboard??
 
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If you want a better foil shape you're going to have to get into a
study of Reynolds Numbers and how they determine performance
at different speeds. I'd start by getting the current Reynolds Number
for the racing daggerboard and learning why they chose the current foil shape.
You'll also need to learn about Aspect Ratio and basic sailboat design parameters. If your
Dimensional Analysis skills are up to speed you should be able to tell us
if the current racing board is a good match for the Sunfish. Someone here
mentioned that it was originally designed shorter than it should be as a compromise.
Making is shorter yet might be going in the wrong direction. Here's a pop quiz, can
you mathematically explain why the Shadow Daggerboard failed in comparison
to the Berrington Daggerboard for racing?

Putting lead in the daggerboard is kind of like cutting one end off the blanket and
sewing it on the other end. The Sunfish hull if at 125 lbs acts like a Drift Boat hull.
Only the center bottom hull and none of the side chine or bow/stern sits in the water.
This allows for tight and quick turning.

Humm . . if it current daggerboard is made shorter, would a reduction is Sail Area
bring the Sail/Board area ratio back into balance? What is the correct ratio?
Was skipping out of all those math classes really such a good idea?
 
Doesn't take a lot of weight on the bottom end of a daggerboard to help a lot in preventing tipping over... And that is the only reason to put the weight on the daggerboard.
Weighting the daggerboard will reduce performance but might make it easier to sail if you are not good at switching sides when tacking. If not racing... its your call. I'd do 10 to 15 lb on the Sunfish if I weighted its daggerboard.

More than 15 lbs I can guarantee will be annoying for raising the board.
There's no good way to add a second halyard to operate the daggerboard.

I cast 32 lb (appx 11 in fore-aft, 3/4 inch thick, 9 inches tall extension) onto a new daggerboard for a Vagabond 14 to deal with my being slow changing sides when tacking. I have to use an added halyard to pull it up. My resulting board is within 1 inch of what was left of the original (which had serious rot issues and bent like cooked spaghetti when wet)
For me... it turned out to be a great choice.

Shorter board... you can regain some of the area by making the whole length just fit the slot fore-aft.

The slot pretty much limits the foil shape by limiting thickness. So pick a NACA racing aircraft wing "airfoil" and go for it if you want. The limited thickness will prevent you from using the optimal shape. You won't gain much even over the old wooden boards that were mainly flat with a bit of beveling and then rounding.

Can't see much point in the wings.

You need the ability to pull the board up virtually all the way (I'd shape the lead to just be an extension of the board.) for reduced drag when running with the wind.
 
mixmkr said:
So... throw me some opinions plz. C'mon design experts.... !! All you hard core racers...what would you ultimately like in a daggerboard??
Click to expand...
1) One board (in one of two angled trunks).

2) A slug of lead at the bottom of the board. (To still keep the righting-capability of the board).
 
ya know...what's funny is I asked this same question back in early summer. ha! drinking too much lake water I guess!

But I did measure my current '69 board, and it's only 39". So maybe save my resin and fiberglass cloth and just buy one from Itensity. Enough 'projects' as it is, already.
 
Weighted board sounds do-able but the question is, how much weight can you add before
the daggerboard does not float. If the boat turtles and the non-floating board slips out of
the slot will the daggerboard end up in Davy Jones locker?
 
Webfoot1 said:
Weighted board sounds do-able but the question is, how much weight can you add before
the daggerboard does not float. If the boat turtles and the non-floating board slips out of
the slot will the daggerboard end up in Davy Jones locker?
Click to expand...

Tie it to the hull....
 
Just my opinion, but I can't see that weighting the tip of the daggerboard would do much. Sunfish, Lasers and the like are meant to be sailed upright. Keels only have righting moment when they are heeled, and for the keel/weighted board to have real effect, the Sunfish would have to be heeled over too far.

For the idea to work, it would seem that the board would have to be quite heavy. Vipers have a daggerboard with a bulb on the end, but the board is always down when sailing.

If the idea worked, I believe you would see it incorporated into exising classes already.
 
Kind of give you the impression that the Sunfish is close to the optimum design
for what it was intended for. Forbes listed it as one of the 40 best things made
in America. The racing Sail/Board has already taken it faster than it was intended
to go. The next step would be composite materials and I can't see many paying 10K
for a Sunfish. Luckily we have a open Moth class for all the crazy high tech money is
no object racing, or is it flying, I'm not sure. I'll just call it Extreme Sailing.
 
I have a pivoting daggerboard that I could take a photo of if you would like. It is mahogany with stainless steel sleeve. Allows you to pivot the daggerboard in shallower water.
 
sailcraftri said:
I have a pivoting daggerboard that I could take a photo of if you would like. It is mahogany with stainless steel sleeve. Allows you to pivot the daggerboard in shallower water.
Click to expand...
no hurry, but I'm sure there are others that would like to see it too.
 
mixmkr said:
Enough 'projects' as it is, already.
Click to expand...
As I recall, you had some interesting 'projects' set to go this winter. :)

1) My own "motorized Sunfish" is on hold while I finish up three other fiberglass 'projects' next Spring. :confused: The "Ultimate Inspection Port" isn't quite level*, the (winter-bashed) keel repair needs faring and painting, and the bow handle access "port" needs completing.

*Working within the confines of the cockpit "cramps my style". :( Ultimate Inspection Port... | SailingForums.com

2) There's soooo much space "lost" in the Sunfish's cubby. If I had a severe-enough inclination, my next 'project' would to be to create a lightweight fiberglass "drawer", with a notch matching-up to keep it from sliding out too readily. Centered as it is, it would be difficult to get the contents wet, even in a "turtle".

It would save transporting a lot of sailing apparatus back and forth (sunglasses, hat, apple, camera, line, rag, Leatherman, sail tape, trailer stuff, cable-ties), and protecting "chewables" from rodents. Maybe include an upper sheath to "snug" the daggerboard away from UV, collected rainwater, or from blowing away in the wind. :confused:
 
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