Some trouble shooting with a gaff rig..

[John B]

I have a problem with the gaff on Waione which annoys me. If you look at the photo young Johnny R took in february you can see what it is.
http://www.imagestation.com/picture/sraid15/p7a53920eca332a76826d4d86f597f15f/fde76d3f.jpg
On a run, the gaff rolls and cranks the saddle over, putting an unreasonable stress on the parrel beads.( they shouldn’t be stressed at all) In that photo you can see that we have converted from gaff to balance lug because of it (LOL)( oops... that's a standing lug isn't it.)
I’m aware of it happening in other boats and that the fact that I have a fairly high peak angle is a contributing factor. I’m sure I’ll fix it, but I really want to understand why it happens before I deal with it.
Here’s some background. When I first observed it I reconciled it to a similar problem another gaff boat here had. His boat has a very high peak .His fix was to engineer a fully enclosed saddle which goes right around the mast. I experimented with that but I don’t like the way that this type of saddle adds friction and the “racking” problem you get on hoist and douse. I made a new saddle in the traditional form and it improved ease of hoisting and dousing the sail no end. I extended the link that the throat halyard attaches to on the basis that the extra leverage would stop the gaff from rolling. This is a good thing and it does help.
http://www.imagestation.com/picture/sraid19/pd2b751aaa75fadb94af344e605959d7c/fdc83d9b.jpg
Never the less, It still happens . I have a theory as to why its going on and what to do, but I’d like some input from anyone who has come across it or dealt with it themselves .

[ 04-25-2002, 07:28 PM: Message edited by: John B ]

[sawcutmill]

try lowering the peak on the gaff when going before the wind,this will reduce the friction to a great degree,other than that i dont know what to tell you....if you do lower the peak you will notice a greater surge in speed as the sail will belly up and increase your potential bag effect thus creating a downwind ballon.

[blisspacket]

The only problem I can see from the photo is the powerputter you might impale 'cause he's dallying where you're rallying. I guess I'd try sheeting in some to a)keep compression on the gaff throat and b) force myself to go the faster route by taking a tacking route downwind, rather than just a run. Great photo.

[John B]

Must go and see him( the powerputter) he took a roll of film he told me.. Yeah It was getting close to a gybe at one point but I don't do that unless I have to. ( we were shorthanded for the wind strength that day)

[Thad]

Scary. Trying to think this one through. Sea Harmony has the same type of saddle but I have never seen anything like that threatening. I wonder about her throat halyard tension, thinking that with the throat halyard, tension comes from the clew outhaul. Catboats routinely hoist with the topping lifts and lower the peak when running, but they generally have solid gaff jaws. Does your saddle pivot side to side as well as vertically? I'm thinking it must and shouldn't.

[Smacksman]

Bootiful saddle John.
As I said a while back, the geometry of the gaff jaws is a much ignored detail. I got terrible chews on Emma's mast from the edge of the saddle tumbling over on the run till I re-designed the area.

I'll dig out my drawings and post them - if I can find them - but the nub of it is that the attachment to the throat tackle must line up through the gaff to the throat cringle on all angles of peak and point of sailing. In fact there should ideally be a straight line of force from the crane for the top block of the throat tackle right down to the tack cringle, but that is not easy to achieve.

If the forces are out of alignement then the thrust of the gaff seems to tumble the saddle.

Another common problem is the lack of fleeting in the throat tackle. The quest for ever bigger mains on a given mast pushes the gaff jaws heigher and increases the wringing effect on the throat tackle when off the wind as the throat blocks get closer together.

The other danger is that you can't drop the main off the wind as the jaws/saddle jam. Now bermudan laddies, will say you are not surprised - you have to luff into wind. On a gaffer you CAN hoist and lower the main off the wind if you HAVE to as long as it isn't blowing old boots [ like the great pic above ]. Granted it is easier on the wind but it can be a very useful feature when sailing into a marina or other close quarter work.

All gaff mains need the peak eased off the wind to get rid of the crease that forms from peak to tack. That's why a smack has a peak hardener [ another tackle, usually 3:1 ] on one of the double falls from the peak tackle - it reduces the sweat of hardening up the peak each time you come on the wind. When drudging for oysters, they were up and down wind and tide all day so sails had to be easily handled.

And hauling in the boom has no early effect on the gaff or leach tension as there is no kicker [ boom vang ] on a gaff main. I have tried peak vangs to haul it aft on a run but the lines are a nightmare when hoisting the main and snag everywhere [ the tops'l sheet is bad enough! ] I've also rigged a preventer to the boom but the forces are huge and more likely to snap the boom than gain a lot in leach tension. A preventor works well in a drifter though and helps keep the mainsheet from draggin' in the 'oggin.

I wish I was around for your gybe, John. It must have been 'fun'. I had read somewhere to ease the peak before gybing in a blow to de-power the main. I ended up with the boom on one side and the gaff on the other!! When I peaked up again, the gaff flew across and nearly self-destructed!
I have since found that putting on the topping lift before the gybe is better, especially if you use a double lift like I favour as it traps the gaff between them while you control the boom across. Sorry, I'm waffling off topic again.

I'll come back with a drawing soon.

I shall be interested to hear what your thinking is and learn something from your experience.

Fair winds.

[Ian McColgin]

Before working too hard, I second dropping the peak on a run. The main will set better, you'll go noticably faster, and it'll take that scarey bow out of the gaff as well.

Maybe ease the throat hallyard as well. Let that sail have the power of a sumo wrestler's belly.

I'm also a fan of vanging the gaff for sailing off the wind to let the boom further out. On Waione you will surely need to put a lifting reef in to keep the boom out of the water. If you go that route, you can probably get by with just a new reef clew perhaps half way to the first reef clew, and tweek it up on that. Off the wind who cares if the bunt's not tied.

G'luck

[John B]

Ian, I did get a mini reef in the sail when I got it made. I've never used it and the funny thing is, there doesn't seem to be any tendency to dip the boom at all. Pretty stiff boat. I hear what you say about playing with the halyards, and I do do that in the light to optimise shape. When it blows and you are doing hull speed anyway I'd rather not mess with them. besides, the throat halyard tension on that link( the one that looks like an American football faceguard) exerts a lever action opposing the roll I'm getting in the gaff.

[John B]

How inconvenient, settle down for a quick afternoon tea post and some individual wants some information from me.....

So as I was about to say before I was so rudely interrupted..... there is some information I have withheld in the hope that someone might say" and of course you....".

When I made the gaff from bits of spruce cut out of a mast we dropped a few years ago, I made the gaff in an ovoid shape. Not much, but it isn't dead round. My logic at the time was the niave view that the major bending strain which it had to deal with was in line from the peak halyard/ masthead to the outboard end of the boom.

"Ah "I hear you say, " he hasn't got a round gaff".
What I think is happening is that, like a rat in the doghouse, that bending strain is looking for a way out and its finding it laterally and then it rolls the spar over when it's got a start. I've been trying to stop it by the nice saddle and the even nicer lever arm of that throat halyard strop/link plate( what is the name for that thing?) but I'm pushing the proverbial up hill.

I think I have to rebuild the gaff . It needs more meat along it's sides so that it will bend the way I want it .

You think?

I'll keep you posted.

[Andrew Craig-Bennett]

Umm. Mirelle has smack type wooden gaff jaws, with an oak tumbler, so we don't get the problem, (we get others, particularly halyard getting inside the jaws, and Hollywood type creaking noises!) although I hve sen boats with it. BUT we are making (when we find some good spruce!) a new hollow gaff which will have a saddle.

I am very sure that it has nothing to do with the form of the gaff saddle. Dixon Kemp and Uffa Fox both show gaff saddles designed by William Fife, for the Dublin Bay 25's, smaller than Waione, and for Shanrock III, (bigger!) respectively, and they look just like yours. Fife was known for the excellence of his gear.

Smacksman has already said this, and you are far too experienced not to have thought of it, but are you sure that the throat halyard lower block and the throat cringle are exactly in line at all time?

My own two penyworth is "Are you using a throat halyard crane or a strop?" I very much prefer a strop, for the reasons Claud Worth gives, but also it allows the throat halyard a much fairer lead when running.

Will keep thinking...

[Ed Burnett]

John,

This is not an uncommon problem - I have seen it on quite a few boats but have never heard or been able to figure out a particularly satisfactory answer to it.

I have heard some people argue pretty strongly that a more triangular shaped saddle is better in this regard, but this does not make much sense to me. The reasonalby broad "ears" of your saddle would seem to me to be better at stopping it twisting off the mast.

I don't think the throat halyard is where the problem lies either. When I have watched this happening, it seems that the effect is powerful enough to twist the throat cringle out from under the halyard however it is set up.

Having watched this thread and thought about the problem a bit more, I feel the most likely cause of the trouble is the peak halyard.....

Looking at your picture, it seems that your peak halyard is on a span as normal, however the block sits rather near to the middle of the spar, and thus the peak halyard is mostly pulling the spar up at the middle rather than the end. Now, try to picture all the power out in the leach of the sail (aft of the peak halyard), pushing the outer end of the spar off to leeward. Because the peak halyards are on the aft face of the mast, and the saddle rotates around the centre of the mast, when the sheet is well eased the peak halyard is not only pulling the middle of the gaff up, but is also trying to prevent it from swinging off to leeward. In other words, the halyard is pulling the middle of the spar up to windward and the whole gaff is trying to pivot about its mid point. This pivoting load causes the forward end of the gaff to want to come up to windward. O.K. (nearly there), if you extend the centreline of the gaff to the middle of the mast, this point of intersection is obviously some distance beneath the saddle, the effect of this is that the saddle, in trying to keep the gaff in line with the mast, is putting twist into it.

Points in favour of this arguement are...

1. High peaked sails are more prone to this problem, and this makes sense as the higher the peak, the greater is the separation between the saddle and the intersection of the spar centrelines. The whole problem is much easier to picture if you think about a really high peaked sail.

2. Easing the peak halyard does help, because it allows the gaff to swing off to leeward without causing huge "pivoting" loads described above. You don't always want to ease the peak off though, and at the very least you want to be able to forget about it without the saddle coming off the mast.

So that's my best shot at an explaination - incomprehensible I expect! As for a cure....

Try moving the peak halyard further towards the end of the gaff. You could leave it on the span to try it - just put a lashing on to keep the span shackle further aft. This is going to decrease the angle the halyard has for pulling the gaff up, and will thus increase the compression in the spar but I think it would be worth a go. Judging by the bend in your gaff this is something you may want to do anyway! I think modern sail cloths have lead to much more leach tension in gaff mainsails than used to be the case and the gaff end needs more support to deal with this. You won't see the gaff bending from the cockpit, but if you go forward and sight along it you may get a fright.

I would be interested to hear what anyone thinks about this!

Good luck,

ED BURNETT

[John B]

What a pleasure to get such knowledgable answers from such experienced people. It really helps the thought process.
Each boat has it’s own idiosyncrasies and there’s so many variables with the gaff thrown in. Peak halyard position on the mast , the top panel mast height, spans and the crane for the throat.
I don’t think it’s the throat halyard because even though it’s on a crane( which juts out the same amount as the pivot point at the saddle, as the gaff swings outboard the halyard length must shorten relatively. If anything ,this opposes the roll that I’m getting. The top of the gaff rolls away.

I don’t think its that the attachment for the peak halyard at the mast is too high, because when the sail is reefed the problem goes away or is less obvious, IE the halyard is imposing a more vertical lift onto the gaff,( this is a great thing in a breeze with a couple of reefs in. the saddle doesn’t thrust against the mast so there isn’t trouble with keeping the mast in column).
http://www.imagestation.com/picture/sraid16/p8bc5c1f3b46f09241c1be1a535352419/fdf3231e.jpgI only have one span and I’ve been tuning it to find the optimum position. I really don’t want to add an extra because of the extra fall I’ll have to deal with. There’s enough as it is.

The more I think about it, the more I believe that the problem lies between Ed’s remarks about the force on the gaff/ halyard and twisting force of the leach of the sail… , and the fact that I made the thing oval.
http://www.imagestation.com/picture/sraid19/p06bca19442bf111e8c382486e3209d63/fdc5a129.jpg
I believe that when the gaff swings out and a more complex strain applies to the spar, the gaff bends the easy way as opposed to the hard way.It bends through the narrowest section.

I’ve experienced something similar myself with the jackyard. The first one I made was effectively a plank ( a bit better than that) with the long side in line with the sail. This was bent on traditionally with my approximation of a topsail bend. What happened was that I would set the thing for on the wind by strapping it in pretty tight to flatten it. ( so I would get it to set on the wind.) What it would do is a mini version of what’s happening to the gaff.It would roll over and bend through the narrowest thickness. I fixed it by establishing the sheet position and putting a fairlead onto the trailing edge. It can’t roll now because the sheet won’t let it.

Using this logic, I did the same to the gaff spans and reasoned that if I fitted a track to the underside. IE the head of the sail, that this would stabilise the thing. I think that this has a good chance of success, but that the real problem lies with the fact that the gaff isn’t round. I don’t really want a track.

What a load of fun . I’ve never regretted changing the rig from bermudan. I’ts scared us from time to time, but apart from this little problem we’re fast and doing the right thing by the boat.

After typing this I've just re read the posts again again.

The span. what if i've got the span too shallow?
the shallower it is, the less leverage it exerts on the spar( from a roll moment point of view). I could still keep the positions on the gaff but lengthen the span( it's spectra core so I could experiment with the thing). the greater the angle I can get between the span and the gaff......?
Worth a try.
I 'll try that and Eds Idea of moving the block towards the end and If that doesn't help I'll make a new gaff or beef up that one.

[ 04-29-2002, 10:24 PM: Message edited by: John B ]

[Ed Burnett]

What you say makes sense John, if the gaff is bending at all in the horizontal plane (ie. the easy way with the section you have), any downward load at its aft end (leach tension) is going to result in a twisting moment.

For this to happen, the peak halyard must have a componant of its tension trying to prevent the spar swinging off to leeward. As I mentioned before, the only thing I can think of that would cause this is the fact that the peak halyard block is on the aft face of the mast, whilst the saddle rotates around the centreline of the mast.

The total effect probably results from a combination of these things but moving the peak further out along the gaff should help both.

I wouldn't be in too much of a hurry to throw away your gaff. In all the cases where I have seen this happening before the gaff had a round section. I guess greater lateral stiffness may help but that would be treating the symptoms rather than the cause and there is no point making the gaff any heavier than it has to be!

Regarding the span length, a longer span would share the load rather better between the two points on the gaff. With full sail, as in your first picture, the span shackle has slid pretty much all the way forward so the load is mostly pulling up the middle of the spar. In the picture you posted last night (for me at least), it looks like there is a reef in the main and the change of angle of the peak means the span shackle sits more in the middle of the span. This is better for the gaff I think.

Perhaps when experimenting, rather than lashing the span shackle out towards the end of the gaff (as I suggested before), you should simply slide the forward end of the span aft along the gaff. This will effectively lengthen the span and also move the support aft along the spar.

I would be interested to hear how you get on.

ED.

[Smacksman]

Did I spot sacrificial rubbing strips on your gaff? Do you get the varnish rubbed off the gaff by the after shroud?
If so then on a run the gaff jaws are being levered to windward by the thrust of the main outboard of the shroud. Couple that with the natural force of the gaff 'driving into the mast' and you get a tumbling effect.

I don't think the oval shape is the problem, or at least the only problem. As was said above, my round gaff did the same.

The gaff is bound to rotate axially off the wind as the pull of the cloth/leach is aft and the peak cringle is lashed to the end of the gaff and the lacing/robands on the head are also adding to the twist.

All the above can add up to a tumble of the saddle. I also accounts for split gaff jaws on occasion, I reckon.

I remember taking out a couple of parrell beads and making the parrell strop a snugger fit. That, coupled with a re-design of the saddle/throat tang to a set-up similar to [but not so nicely made] as yours cured the problem.

Is your gaff 'go-faster' hollow?

[Hesp]

You might alleviate that gaff bend by running the end of the halyard to the peak of the gaff. That is - deck, masthead, span, masthead, peak. This distributes the load well, but doesn't allow for smacksmans tensioner.

I think if you can stop the bending you will be okay.

But as Smacksman said, keep it clear of the shrouds.

John

[ 04-30-2002, 05:34 PM: Message edited by: Hesp ]

[John B]

Other people have said this before I know but
Man , this is a great forum.
I'll experiment a bit. It's too much fun not to.

Smacksman, the gaff is basically solid with a vestigal hollow section by default.
If you imagine the nice spruce mast which exploded over the side in 1990 or so, leaving the top 30 ft for a jury rig. And then you imagined John with a skill saw and a zen moment or 5 when he sliced the outside quarters off to make the gaff from, you'd see why I had a wee hollow left. The whole spar plus saddle weighed 20 kg from memory and is 6.5 metres long so it's fairly light. It stays pretty straight on the wind but bends off the wind. It's a progressive bend without a hard spot so I'm comfortable with it.

Thanks to you all for your input into my wee problem. Big racing year next season. 2003. we have a classics regatta in between the challenger series and the cup proper. Last one we had 90 boats from Velsheda to flying fifteens.Nomad was there Ed.
This one there's a rumored 3 J's coming and other classics coming from all around the world.One 30 sq has already arrived from the UK to be restored and raced before being shipped home.
It would really be great to have some gaff boats to race against.... they're a bit thin on the ground out here.

[Carlsboats]

You people know so much about gaff rigs that I have to ask a 'beginners only" question (because that's what I am when it comes to gaff rigs): For the peak angle, how high is too high?
I am thinking about putting a gaff rig into a 19-foot daysailer now under construction (think if it as a cut down Herreshoff Fish Boat) and don't know how high to set the gaff. At one point I was even thinking of taking it all the way up, making it into a gunter rig, a la Herreshoff's Alerion. Then I backed down, and started thinking in terms of a conventional gaff. Based on no experience at all, I assumed that a high peak angle had advantages --better windward ability, less of a dramatic event in a high wind jibe, etc. But it occurs to me that there have to be good reasons for a lower angle... unless one wants to believe that for generations, the people who set their gaffs at lower angles were dummies. I don't think so. So .. is there some rule-or-thumb advice to guide me? Carlsboats.

[John B]

Most of the reading I did left me thinking that about 30 degrees( hey , there's no degrees sign on this keyboard) off the vertical is optimal for a gaff rig which still looks traditional.
I did a lot of drawings on the "looks right/is right" principle and came up with the same. I hedged a bit to 28 and still set a topsail . I'm happy enough with the look ( I agree that a larger topsail and lower gaff looks more traditional)and more than happy with the performance.... The gaff stands very well with acceptable twist when sailing on the wind.

[John B]

Oh, another thought Carlsboats,.
One of the fun things you do with gaff rig is play with that peak halyard. You can dramatically change draught by hardening up or slackening the thing. Your designed 30 degree sail might in fact get set at say 25/27 degrees in the light with a dumped throat halyard and like others have said, get dropped off to 33/35 on a run or to depower.
If you go for gunter or a high peak, you need more room for the spans and to accomodate this tuning factor than you might first think.

[ 05-05-2002, 05:30 PM: Message edited by: John B ]

[Andrew Craig-Bennett]

Carlsboats - there is a magic formula for this:

The gaff should make a 90 degree angle (right angle) with a line from throat to clew.

This is a Claud Worth rule and he is usually right.

If you look at a gaff schooner's foresail, the gaff is very flat indeed, whereas a high peaked gaff goes with a long boom. If you depart far from this rule the sail will be hard to set properly.

[HOWdie]

Just my 2 cents. Kewl pic of a gaffer running all out. Now to the ?, it seems your problem is inherent in running a gaff rig to the extremes. Apart from running vangs or bracing up the sheets it appears that the only other solution is changing rig designs. Sorry not much help.

[John B]

can't agree with that I'm afraid. I'll fix it.

[Art Read]

Andrew... Interesting. I'd never heard of your "magic" rule before, but it sounded reasonable. Just for fun, I did a quick "survey" using the various, gaff sail plans to be found in WoodenBoat's "Fifty Wooden Boats" design book. About a dozen or so... The only boat that exactly matched your right angle rule was the "Pemaquid" Friendship Sloop whose design was derived from historical records. Another "Pilot sloop/schooner" by Geo. Stadel came pretty close. The rest were all peaked up quite a bit higher. Some decidedly so. It's interesting that these two designs derived from "working" boats tend to follow your rule more than the "yacht" designs. Perhaps "yachtsmen" have more time and energy to "fuss" with their rigs than the poor bastards out there trying to earn a living?