Summer Breeze Sail/Dagger board placement

by Kevin
(Az)

I am preparing to build a David Beede "Summer Breeze", I intend to make two changes.

First is to place a single sail, Sloop, perhaps using the originals Lugs mast location.

Second is to install a Dagger board box instead of using a LeeBoard.

My Question: Can I place a Sloop type rig in place of the lug in the original mast position?

If not where?

And second: After determining the placement of the Sloop rig where should I place the Dagger Board?

I assume that one affects the other.

Thx in advance,

Kevin

Comments for Summer Breeze Sail/Dagger board placement

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Aug 04, 2022
 why a sloop?
by: LR

Late to the party again. But maybe someone else will be interested.

Why a sloop? In what way will it be improved? Since it's your boat, of course, "looks cool" is a legitimate reason, but I doubt if you'll get a large performance enhancement. A larger, single sail might be easier.

If you add a jib, and you're putting in a daggerboard, you could move the daggerboard a bit forward from where the leeboard is now. If you move it too far, make the rudder a bit larger.

You can find a brief discussion of this stuff here:
http://www.jimsboats.com/15jan22.htm#Sail%20Area%20Math

Suggest making the daggerboard out of a bunch of boards glued edgewise, with alternating grain directions, covered with glass and epoxy. Plywood daggerboards can be on the weak side, though I suppose if the daggerboard breaks, instead of the trunk, you're better off.

Consider using a nice foil section, which will allow your daggerboard to develop much more lift before it stalls. This may be helpful at slow speeds. The following section is very close to an ellipse, 45 percent of the length of the foil, with two tangent lines. For your boat, I'd thicken it to as much as 12.5 percent, since the Reynolds number is much higher than in the model airplane tails this foil was designed for.
https://m-selig.ae.illinois.edu/ads/afplots/ht08.gif
I suppose, with 12.5 percent thickness, plywood may be strong enough. Especially if you make sure there is a fair amount of material with the grain running along the length of the rudder, a fair distance away from the center. Two layers, or even 4, of 1/4" luan, with those thin face plies, would be fairly fragile unless the grain in the thicker core was parallel to the length of the board instead of the face grain. It would be easier to make a nice shape, though, if making it of glued up boards. I'd try a drawknife, which is so fast it's almost like a power tool. Just be careful.

You may be able to adapt the techniques here:
http://charlesriverrc.org/articles/construction/markdrela_airfoilshaping.pdf
http://charlesriverrc.org/articles/allegrolite2m/tail_sand.pdf
Note that the tail airfoil shown is a thinner version of what I think you should use.

caveat: I've only used the technique to make balsa wings. I've evaluated the thicker foil using Xfoil, but have not tried it yet. Some guys who tried a 7 percent version for the fins in their RC sailboats liked it a lot.

Your rudder, if you're feeling ambitious, would also benefit from this kind of foil.
http://charlesriverrc.org/articles/allegrolite2m/tail_shaping.pdf

Good foils are probably a lot easier than most other things you could do to improve upwind performance.
Jan 25, 2018
 glad to help
by: Leonard S

Glad to help Mike, I have never sailed a day in my life, I have always wanted to build a wooden boat.

I have been a power boater for years, so when I decided on the boat to build I thought it would be nice to finally learn to sail.

Haven't even launched it yet, but I have sure learned a lot about sailing during the course of the build.

Cant wait to get on the water, (under sail)
Nov 15, 2017
 in answer to CE, behind or in front of the CLR?
by: Mike

You were quite right to point this out.

The comment "Sail Plan" by Mike, was incorrect, I have now altered it, apologies for any confusion it may have caused.
Nov 14, 2017
 CE, behind or in front of the CLR?
by: Anonymous

In the index under center of effort, an center of lateral resistance is says that a sail should always carry some "weather helm" and says to achieve this to have the CE behind the CLR.

This article suggests the opposite?

I don't understand, I am new to the sailing game can someone please explain.
Jan 14, 2017
 Sail Plan
by: Mike

I am not a naval architect, there are formulas for working out C of E and LR but they can be complicated as there are so many variables.

My gut instinct is to go for trial and error.

The position of the centerboard and mast position need to be established first as they will need major structural changes if you wanted to alter them.

The sail plan can more easily be changed by using cheap poly tarp or shower curtain material as trial sails.

I would put the centerboard roughly in line with the position of the lee boards.

Then to find the centre of lateral resistance of the hull, put her in the water and find the point where if you push her sideways she doesn’t turn in either direction.

The centre of effort of the sail plan wants to be slightly behind this.

A rough rule of thumb for mast height for a Bermudan rig is 25% longer than the hull length.

The mast may need to move back depending on the size of headsail wanted.

You might find some of the information here useful gmatkin/therules.htm.

Personally, I would leave the mast as in the plans but rig her with a balanced lug, it will give you more sail area without the complications of the bermudan rig.
Jan 13, 2017
 Thanks
by: Kevin

Those are great pics.... gonna help me a bunch! Thanks!
Kevin
Jan 13, 2017
 Summer Breeze
by: Michael

Here are some photos you might find interesting  https://www.flickr.com/photos/23438966@N07/albums/72157603844285468/

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