Amateur Laser Design modification in keel and sail

[tatria]

Hello I am an Industrial Design Student and did some modifications in a laser boat for my thesis, I would like to know if they will improve the boat's performance. I modified the sail and the keel, you can see the modifications in this page>>> http://www.geocities.com/laser_sailboat/index.swf

Thanks,

Tomas Atria

P.D> if it doesn't work try this one >>> http://www.geocities.com/laser_sailboat/index.html

[DaveB]

Hi,

It might help... but you'd have to take into account the entire boat balance... You've moved the ce fwd without moving the clr. It would likely also be difficult to fabricate such a mast without stress concentration... perhaps a gentle curve would be best... of course you'd have to have an entirely different sail.

With regard to the daggerboard, I don't think having more chord length low is better... it's not the weight that you should be interested in, but the flow over the foil... more chord length is less likely to stall at lower speeds, but also causes more drag... For this reason you might want to have more chord at the top in the boundary layer near the hull, and less at the btm where the flow is faster. The idea with the daggerboard is that it can be raised and lowered, varying the span of foil in the water... so it might be best to keep chord uniform...

Neat topic to be thinking about though...

Just my two cents... might be out to lunch...

Cheers,

Dave

[sorenfdk]

I agree with Dave - you cannot raise and lower the daggerboard, and that is an absolute must. Of course, you could have a longer slot in the bottom, but that would create eccessive drag.

Hinging the mast may be a good idea, but how do you control it?
The hinge is placed at the most stressed part of the masttube, and that is not a good idea. Why not design a maststep with a built-in hinge instead?

[tom28571]

I agree with the others. There are times when sailing a Laser just becomes survival that a bit more balance might help, like trying to bear away in a strong wind at the windward mark or rounding up at the leeward mark. Downwind would be the greatest advantage where the Laser eats most of the sailors. If that blob on the keel represents ballast, That is a no-no for dinghy performance.

The normal Laser daggerboard is a pretty efficient foil for its length and a longer one is a detriment in boat handling. How to mechanically implement the rotating mast and retain good sail shape looks like the most difficult challenge. What you have is pretty near to a windsurfer sail rig.

[tatria]

I agree with you in the keel problem, I think a very deep, narrow retractable keel would be best, similar in shape to the ones used by racer yacht's.

I took some info about keels from this page http://www.boatus.com/goodoldboat/keeldesign.htm and I've read in aerodynamics articles that long and narrow fins are more efficientive and have less drag than short wide ones.

At lower speeds the keel could have a shorter extension and when needed, at high speeds, could reach its max extension by pushing it down. I was thinking in a lock that, by pressing it, could fix the fin at the desired position. Of course it has to be a very simple system that anables fast unlocking to retract the keel when reaching the shore.(I'll have to work on it)

About the sail...I will work on the sail mast to avoid stress problems, a gentle curve is a good idea. The mechanical implementation of the rotating mast it isn't much different to the traditional one. The only variation is the angle, if the lower part of the mast is perspendicular to the base it shoudn't have problems. The hinge problem is the next step, but in this first instance I'm working in concepts that may improve a laser's performance, then I will propose a design that involves all the hinges and mechanisms.

Thanks,

Tomas Atria

P.D: I may have some english errors because I speak spanish, if you don't understand something ask please

[BrettM]

I had to reply here even though I can't see your website. (I get an error)

Not sure if you actually sail lasers but...

As a boat nobody will generally tell you that the laser is a good design. They are tippy, have short aft raked centreboards and rudders and suffer from weather helm. That said, the laser is one of the strongest classes in the world because of simplicity of design and the class association.

If you are going to improve the design - keep it simple. No one who buys a laser wants to spend more than half an hour getting to the water or playing around with rake adjustments and tuning etc.

Brett
(also a laser sailer amongst other things)

[sailgodess]

Hey, do any of you have the dimensions of a laser daggerboard. I need/want to build my own and can't find the dimensions anywhere. I was hoping since you were all talking about modifications that someone might have the actual dimensions. Height at leading edge and trailing edge of the foil is the most important but any others you may have would be great. Thanks

[BWD]

there are ways to try this.
The picture attached shows laser modifications that might really help.
The "football fin" daggerboard won't help.
The system of freestanding mast with a kink at the deck level has been done (By Wylie maybe?) on other boats and preserves boat balance upwind, such as it is. It works because it moves the axis of rotation closer to the CE, like your idea, but without changing the upwind sailplan. It might not be any good on a boat as small as the laser though (esp with the lack of hard chines).
The laser daggerboard case is raked aft, true. But just putting on a more draft stable sail would work better for handling as well as speed IMHO.
Having the sail CE more amidships running could help, and hardening the chines aft would damp the deathroll plus might help more efficient planing.

I have an old laser I have used for 20-some years and if I wanted to improve it, I would put on a fully battened sail. I might even do the chines, but that is probably about it.