Gaff Sail for a Windsprint

Since the propulsion section doesn't have a subtopic area for sails, I'm posting this question here. (Isn't a sail a form of propulsion?)

I need a better "storm sail" for my Windsprint.

Instead of rigging up a lug sail per the original design, I went with a sloop rig. The 76 sq ft main is on what a charitable person might call a boom furler.
The problem? As the main is furled the COE eventually moves to far forward and the boat no longer points upwind at all. I made a smaller triangular sail of 50 sq ft with 2 reef points but still had the same problem. Which I would have realized had I thought more about it.

My intended solution is a Gaff rig sail of about 50 sq ft (10 ft luff, 6 ft foot), with a reef or two. The squareish sail should keep the COE far enough back that I can make headway. And I also plan to carry my "barn-door" style leeboard for extra lateral resistance forward.

My question concerns the cut of the sail. Will the Gaff work satisfactorily if cut flat? Comments on junk rigs suggest that it should. It would be much easier to take a tarp and use its existing grommets on the luff and foot as opposed to cutting and shaping the entire sail.

Any thoughts?

 

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I'd be leery of using a gaff as a "storm sail" because that gaff whipping around might pose a problem on the way up(or down) when its real windy.
I grew up sailing a 20' gaff headed boat and that thing was a ***** if you ever had to drop sail in a strong wind. Could you use something like an adjustable mast step that you could move back? You'd either have to be able to move the forestay attachment back or just lengthen it. Do you use the same size jib when you have to reef the main? Could you douse the jib or use a smaller one?

 

Rough calculations for sail are:
Luff: 10'
foot: 6'
leech: 12'
head: 3.5'
Gaff angle: roughly 30 degree angle off horizontal

This should be a pretty lightweight setup. I handle the downhaul and halyard at the mast and can usually ease off on the halyard as I pull the sail down.

My first reef is dropping my 36 sq ft. jib. Then I start rolling in the main until it becomes useless.
Usual on-the-water weight of boat and payload is no more than 400 pounds so the wind really does a number on it as it starts churning the lake up.

I couldn't figure out if a smaller jib would really help or just add more windage where it hurt the most.
Oh, and redesigning the mast step/partners for now is a no-go. I'm decking over the bow and plan to build a new rudder/tiller so I have plenty to do at the moment.

Really should just build a new one that would have all the "enhancements" I've figured out over the years. Attempting to make a silk purse out of the Sow's ear as the saying goes.

 

Consider a boomed spritsail. It can be reefed without a big change in the COE. Whatever sail you use, have it made by a credentialed sailmaker. Amateur built sails are an exercise in futility unless you can get very lucky.
Yes, a gaffer needs some judiciously applied seam, luff, and foot curves if it is to work as one would hope.

If you want to stay with the Bermuda rig, get to work on a suitably bendy mast. If it bends where and when it should you will not need to reef nearly so soon. A decent sail must be designed with careful regard to the mast characteristics. A competant sailmaker will ask for mast information. If he or she does not, then find another sailmaker.

 

The boat, a Windsprint, is a home built 16' sharpi of "instant boat" fame.
http://instantboats.com/windsprint.htm
First and only boat I've built. Having a custom sail made would cost triple the value of the boat, if not more. So that particular route is a dead end. I've actually made two bermuda sails from tarps. I had no trouble sailing on any point I needed to sail on.

The mast is really stiff. It's spruce and weighs about 22 pounds (19.5'). Heavy but haven't bothered to trim it down. Winds on the lake this year have been stronger than usual so I'm looking for a sail (boom included) that will fit nicely in the cockpit (<7') when not needed. The small main (storm sail) I made works to the first reef, but I lose balance on the second reef, a similar fate the big main suffers rolled up. I must admit, I'm usually on the lake when a boat like the windsprint should be sitting at home, as a couple of guys off a bass boat told me.

So, with that said, is a flat cut Gaff useless? I'm willing to do the extra cutting to get a more airfoil shape, but if the improvement on my boat would be small, I'd rather just leave it flat. And if no one really knows, heck I can try it out and report on the results, but I'd like to have it be useable at least.

 

re:flat cut gaff main --

no,a flat cut sail is not useless--I sailed with a flat cut lug rig for years and it worked just fine for what we used the boat for.As long as you're not racing,or trying to get every last ounce of speed/efficiency out of the rig you'll be ok.

 

I'll take a lot of convincing that your problem in getting upwind is the small change in centre of effort. What are the symptoms?

 

Agreed GGG, the only good way to fix this is to figure out the centers, what has been done, the symptoms and preformance, then reasonable solutions or upgrades applied. Reefing a Bermudian in building winds will help, not hurt windward ability, suggesting the CE is not well located currently. A trisail is the logical storm sail, not a gaff or lug.

GTO, find or draw up a reasonably accurate sail plan for the original rig. Next figure out the CLP. With this calculate the lead, noting everything. A typical Bermudian will need more lead then a gaff or lug, how much is there? You can "play around" with it or nail it, with some fine tuning. It's your call.

 

I built the boat with an externally fixed, rotating leeboard so adjusting the CLR is no problem.
The problem only occurs with a deep reef. It's apparent the sails lose shape and drive so the leeboard loses effectiveness. Otherwise, the boat sails fine and easily out pointed a production boat on one occasion. I'll sketch out a trysail and see if that would work.

Thanks for the replies!

 

GTO; I had no intention of picking on you because of home built sails. I got the impression that you liked to go fast because you persist in sailing in heavy air.

You can certainly sail with flat sails but not as well or as fast as with correctly cambered sails. If you are willing to experiment with polytarp or tyvek sail making then I encourage you to do so. It's cheap and can actually be fun. There is sure enough plenty to learn with such experimentation..

There are some books out there that will be helpful. One is an oldie; Make Your Own Sails by Bowker and Budd. That one has instructions or at least suggestions about broadseaming, luff and leech curves and so on. Another one that is well worth study is; The Art And Science Of Sails by Tom Whidden. It is a goldmine of information about tuning the rig as well as commentary about things like target camber depths and positions, sail twist, utilizing downhauls, outhauls, vangs, travelers and more.