Sprit rig question

Hey all

I have a quick question. Is the traditional square spritsail cut flat or do you put a camber (pocket) in it like one does on a Bermuda (Marconi) sail ?

 

If you take a look at an Optomist dinghy they have quite a large belly shape sown in to the sail. Even if it is flat , it should still work to an extent simply the twistoff at the top.
Itchy

 

Short answer is that it depends on the use and expense tolerance.

Controlled curvature is critical to aerofoil efficiency, and a spriit sail can have some degree of curvature control due to luff, leach and foot tension - also by snotter location and tension.

That being said, it is not as controlled as designing in the desired shape and than using the controls to fine tune it.

Talking to a good sailmaker and determining a budget to make one will help your decision process. There are lots on resources on the web on making your own sails as well (Sailcut etc.). It isn't that horrible, as most appropriate material is panelized and needs sewing/taping anyways.

--
Bill

 

I think a loose-footed spritsail would be able to adopt camber without tailoring, which would be needed for good performance with a boomed sail.

 

Yes a loose footed sail can, but designing in the camber into the sewn sail such that foot tension is not a major factor will have a more predictable shape. Loose footed sails are often over-tensioned on the outhaul, which under cambers the sail.

The main sail on my boat has a fair bit of designed-in camber even though it is loose footed. Doing it this way puts the camber where the sail designer wants it, rather than allowing the maximum camber point to be further aft than desired.

--
Bill

 

Bistros..or anyone with similar experience...Not to hi-jack the thread but I'm interested to know what sort of sailboat you have...or it's rough size and what the drawbacks if any of a loose-footed sail there have been with your rig...Is upwind performance affected adversely or is it enhanced?I've heard loose-footed sails can work well on smaller boats under 25-feet or so...mine's a 20-foot fractional rig sloop right now...I need new sails so I'm exploring going that route.Is there more work and hands-on monitoring of this type of sail when in operation or is it the same or less work handling the rig than a conventional boomed sail..??Maybe you could private message me if possible as I don't want to hijack the thread more than I have..Thanks..Any answers to any of these questions are greatly appreciated.

 

Hey Souljour2000. I started this thread and I certainly do not think your question is a hijack. It is exactly these sort of questions that caused me to start this thread. I've been investigating a Crabclaw rig for an experimental catamaran I'm working up. and I don't want to spend a lot of time and money on an experimental sail plan that I might scrap after the first trial. The crab claw is cut flat.... so for experimenting it is a perfect design. But the look "weird" to me and the spritsail has a nice look to it. I also read an article that claims a spritrig will outperform a Bermuda on all point of sail. So maybe that is the way to go. Thanks for piping in.

Rob

 

If that's the article that claims the sprit is 30% faster than the Bermudan, I've just got to say that it seemed beyond belief to claim such an improvement.

Simply put, if that was true a Hobie 16 fitted with a sprit rig would be faster than a wing-sailed C Class cat or a Tornado, and a Laser with a sprit rig would be competitive with a 49er.

Neither the methodology or the results seem to bear much analysis. Which is not attacking sprit rigs, merely a few of the claims made about them.

 

CT - agree in spades.

Admittedly, for the same area of sail a spritsail or lugger carry more area up top and there could be situations where a Bermudan might be handicapped - close to a bank or some such - but it's difficult to imagine it happening on a regular basis. Of course a well-handled traditional hull and rig will beat a dummy in a racer on most days ...

 

Several year ago, Wooden Boat mag did a report about the various sail configurations. This was a result of some research and testing by the International Agricultural Federation or some such outfit. The purpose of the testing was to discover the best, most economical, and simplest sail that could be used by fisherfolk in third world nations. The peak sprit sail had some promise on those grounds. On certain points of sail the peak sprit peformed better than some of the more sophisticated sail plans. This observation should be taken in its own context; third world, economy, simplicity, etc.

Peak sprits do not perform better than other types on all points. Loose footed sails of any kind have serious drawbacks, They are poor performers on downwind legs unless a whisker pole is used. Loose footed sails need a broad sheeting base for decent trim on points of sail that does not use a pole. Sprits of the peak and/or sprit boom type have a good tack and a bad tack. On the bad tack the sprit interferes with sail shape. This is also a problem with lug sails when the mast obstructs the sail on the bad tack. Yes, the boat still sails in any of those cases but the bad tack is considerably less efficient.

For those of us interested in simplicity and ease of handling, the sprit sail should be considered a possibility. Matter of fact my present dinghy sports a sprit boom rig that is the model of simplicity and convenience. The sprit boom (SB) type has several advantages. Among them are the fact that the sail can be adjusted for beating, running, or reaching with only one tug on the snotter line. The SB sail does not need a vang, the PS type does need a vang. The SB sail does not display the nasty death roll tendency of the PS variety.

To reply to the original question of whether the PS sail needs sophisticated cutting, the answer is " for damned sure if you intend to go any direction but down wind" Sure a bed sheet will make some progress to weather but precious little progress. If you opt for a PS sail have it done by a competant sail maker who is familiar with the type. Way too many good little boats turn out to be dogs because someone opted for flat cut or home made sails.

 

I am doing alot of changes to my Hunter 20..among them is moving the jib tracks..or discarding them altogether . They were ...(per the norm)in the middle of the catwalks and I had toyed with moving them onto the shoulders of the new cabin structure..Now I'm not sure...I have gotten rid of the old pop-top roof and framed out a new coachroof...I have a large steel-framed bimini I want to put over the cockpit to protect me from the brutal Florida sun...so going with just a loose-footed mainsail and a well-cut genoa has appeal...and then just hard-mounted single snatch blocks mounted on the cabin roof shoulders instead of track-mounted ...and of course back-plated for strength......then some cheekblocks to re-direct into the cockpit and maybe that will handle the working jib/genoa...I'm not a performance purist..I rely on weather judgement and judging the weather envelope I can expect vs. what I'd like to do and where I'd like to do it that day....I will have a 5hp motor slung...and a 3 hp backup stuffed up in a locker...I like overall utility for my small boat ...and especially like the idea of that bimini back there...that sun is a killer...and it affects the sailor(s) or crew if they are fried from the sun as much as anything...good judgement is so important..

Anyways...if good or even better (than a boomed main) close -reaching is possible on the good tack...and that almost makes up for the bad tack..then a loose-footer main might be for me...

 

Souljour; I hasten to agree that sailing in the Florida summer sun is a misery. I have often contemplated the use of a Bimini or some kind of protection. Matter of fact I have used a golf or beach umbrella a few times. That works OK untill the wind pipes up at which time the umbrella becomes an unwilling spinnaker. I have used a smaller umbrella on my kayak with some success.

I think that the Umbrella idea has some merit for small boats, they would cost less than a Bimini, be more versatile, easily stowable, light weight too.

I think that it was Bolger who reminded us of an old boatmans saying: "There are three things that should never be found on a yacht; a ladder, an umbrella, or a naval officer."

 

Hey Messabout

Thanks for the info on the sprit rig.

 

There's nothing wrong with a hat, expecially when the Sun is almost overhead, but it doesn't do that for us poor folks way up here. I've used a golfing brolly on a kayak; great for that easy cruise home after a long upwind leg. Until the wind changes direction ...

 

I have cut down marconi mains to make sprit sails. The cut worked OK. Of course I am talking about a skiff not a raceboat.