MAINSAIL to MAST Attachment ?

What started out as a personal interest question - could easily evolve into a Model Yachting magazine article - depending on number and quality of responses. I would be interested in hearing any/all wanting to contribute to the responses here or via PM to me.

Given I have used both a “jack line” on trailing edge of the mast, as well as mast “ties” I am curious how others have faired with either/both - or a different method.

In addition to a jack-line on back of mast, the possibilities are to “tie” the sail to mast with very fine line, some have used light weight nylon cable ties. I’ve heard of thin Velcro strips, using a bolt-rope in a groovy mast ala “real” boats, stainless clip rings, slide sail on mast using a “sleeve” of sail material, bra hooks to wire set inside a slot on rear of mast, and probably even more ideas that I haven’t seen or thought of.

What works for you?
Which ones have you tried?
Which ideas were discarded and why?
Boat class ? (since some have rule limitations or one design rig/sails)
Is leading sail edge (luff) close to mast - or about how far away if you leave a slot?
Ease of changing out sails - or do you replace entire rig?

A nice paragraph or two would help to formulate a tech article - but a response on what you use and why you find it acceptable. In some cases, I have a hunch you use what the sail-maker provided.

Thanks for your responses.

Dick, the method I like best for attaching the main to the mast is: glue crimp sleeves on the aft edge of the mast, run a solid stainless wire through the luff, cut out windows in the sail material at the crimp sleeve locations. Clyde

I have this posted on my website, because it is something of a passion with me… and since you did not mention any class, that requires any specific mast design or type… I will assume that anything goes…

THE BEST way, to attach the mainsail to mast, is via a boltrope and sailtrack in the mast. PERIOD.

The airfoil shaped mast is ideal, but the IOM class requires a round tube. For this reason, Graham Bantock and myself have both created a round mast with a sail track. The round shape is THE worse aerodynamic shape (square is better than round believe it or not), and you need all the help you can get to make the leading edge entry of the relative wind onto the mailsail as smooth and turbuence free as possible. The sooner the RW is travelling smoothly across the sail, the closer the sail is to reaching it’s full potential.

YOU WILL HEAR… old wive’s tales… about the dreaded “S” curve… causing the sail to not “hinge” out properly… and that sail area being wasted when the boom swings out to go down wind… NEVER lose sight of the fact… that these are MODELS… and as such… they can accelerate to hull speed within their own length. Once there, all the sail in the world will not make the boat go any faster. EVEN if this were a concern… and it is not… the next thing to consider would be the legs of the course… which are almost always… (almost) an odd number of legs with the one more being upwind. In some cases… the track is a simple windward leward, and they are even… but even taking into account the amount of distance covered prior to the start… the boats still spend 51%+ going upwind. If I was going to have an advantage, I would want it to be going to weather.

Pointing ability is directly affected by the airflow onto the mainsail, and more and more I am hearing from skippers that have returned to using a mast with a sailtrack over using a carbon tube or or other similar spar and are pleased and recognized the improved performance of their boat. You will also find that a good aluminum mast is extremely close in weight to a carbon mast, and in some cases even lighter. Carbon is great oooooooohhh… gotta have it that “turbocharged” was back in the 1980’s… right before the Andretti’s brought a normally aspirated car to Indy and blew everyone off the track.

If ANYTHING else worked… you would see it on full sized race boats… and YES… there are other methods used on full sized boats… but consider the percentages. Also… if it was not a better method, you would not see myself and Graham make a better spar with a sail track for the IOM’s :sly:

As long as we are at it… for the record, wind tunnel testing has proven beyond ALL doubt… that lowering the tailgate of an empty pickup truck creates MORE drag, than leaving it up… so laugh away at the guys on the highway that think they are saving gas. The tailgate actually helps create a pressure bubble in the back of the truck bed, which deflects the airflow up and over the bed of the truck giving it a smoother profile. It is an extremely small amount, to be sure… but the same thing here… WHY THROW away performance? The sailtrack mast and boltrope main, will not help you as much as a lower performance version (slugs, rings, ties) will hurt you.

Don’t throw away performance.

Larry -

I posted a bit of an ammendment that I thought of reading Johns reply on WINDPOWER forum - that being classes allowing rotating masts.

In that case, I specifically agree with your above views… and rotating a mast that is foil shaped will further smooth the wind over the leeward part of main. Since it is fact that multihulls can often sial under just the side area of a wing “mast” (not sail) the ability for creating this extra lift also seems to be an area of additional performance - IF - the class allows it !

Thank you for your comments.

I have raised my eyebrows a bit about your adamant position on bolt ropes for model boats. It seems to me that a bolt rope attached to a model sail should not be captive within the hem or cover as it usually is in full sized sails. I use a mast with a sail track such as a Goldspar. I use round beads sewn to the luff at frequent intervals. That is a fussy operation but is entirely do-able. The distance between the bead and the luff is adjusted such that the leading edge of the sail will be just slightly inside the sail track. I will argue that such a system is as effective, possibly more effective, than a bolt rope.

A rotating mast is essential to best performance whether the mast is round or streamlined.

I also raised my eyebrows a bit about your adamant position on bolt ropes for model boats - if the mast is not allowed to rotate.

My diagrams show that with the sail track centred on the boat, the airflow around the leeward side of the mast is disturbed and will worsen as we go further offwind - effectively flattening the sail, which is wrong.

The rings method of attaching a sail to the mast allows the sail to “rotate” to the leeward side of the sail presenting a more efficient foil.

Given no rules, perhaps the method the full size lasers etc use, with a sock over the mast would be the most efficient.

Just look around at what mast/sail systems the hang glider people think is efficient.

“Pointing ability is directly affected by the airflow onto the mainsail” ???

“You will also find that a good aluminum mast is extremely close in weight to a carbon mast, and in some cases even lighter” ???

“If ANYTHING else worked… you would see it on full sized race boat” So why do they all have carbon masts?

I have added just another OPINION.


The first thing to address would be…

What is a rotating mast? :confused:

Uhh…well… it’s a mast that… uhhh… huh huh… rotates.:slight_smile:

Ok… what is rotation? This is not addressed. Period. Depending on your rig, your mast may or may not rotate.

But Larry… the class rules say that I can’t have a rotating mast… Ok… how do you tell? Does your mast rotate? did you do it on purpose? Does it rotate on it’s own? Guess what… if the mast is not secured akin to a radio station antenna… it may well rotate… or twist…whether you mean for it to or not. If you have ever tied a load onto a car or truck… you probably found that unless you really knew what you were doing… there was still movement in the object. So… does your mast rotate? Probably. :cool:

Again… go carry a half a sheet of plywood in 10 kts of wind and come back and tell me if there is enough force to twist your mast around.

remember… FA=M The amount of reserve power in these boats is enormous… I had hold of one of my J boats, sitting in a 100 lb aluminum rowboat, with 450 lbs of crew (2), and a 95 lb Endeavour II… and holding it along side, she hit hull speed IN TWO LENGTHS HAULING A ROWBOAT @ 550 lbs, and the entire Woodlawn club saw it… we left a curling wake…

My diagrams show that with the sail track centred on the boat, the airflow around the leeward side of the mast is disturbed and will worsen as we go further offwind - effectively flattening the sail, which is wrong.

By the time you are off a beat, the airflow is not coming over the mast to get to the sail, and remember too… that even before you get to a full beam reach, the RW is deflecting aft because of the forward movement of the boat. You are dealing with deflection lift… NOT pressure imbalance at this point. The T-38 was the first a/c to fly from AoI alone (angle of incidence) and the only one with an ATC waiver for the 250 kts limitation below 10k because of it. and if anyone mentions Bernouli I will have a “teppicfresser” moment…

and… as pointed out above, you probably have some deflection in your mast. Rig your boat, grab your spreaders and give a tug… yoink… the mast twists… I bet… on a 72" spar, you could twist it 30 degrees, and not permanently bend it. (i.e. it would spring back)

I would have to ask in return though… if you are concerned about this phenomenom… what happens to the airflow on the lee side of the mast on a round shaped spar? That’s even worse!

Why are there carbon masts??? someone asks… didn’t specify full sized or model… so take your pick. Carbon carbon carbon… I want carbon… make sure that if you get a carbon mast, it is light… my shaped 72" aluminum mast is 4.6 oz and you will be using the most un-aerodynamic shape available…UNLESS… you can get a carbon airfoil shaped mast… which IS available… and wait till you see the price… anyway… carbon masts work on full sized boat because the savings in massive… it doesn’t work on models because you are already dealing with such a minute amount of weight. On something such as a Victoria, sure… the tapered carbon tube is far better than the aluminum tube that comes with the kit.

If you can sail your boat ounces won’t matter

If you can NOT sail your boat ounces won’t save you

Think MODEL… this is not a full sized boat. It can tack in 1 second and therefore stitch a course to the weather mark that a full size boat cannot begin to approach. IOM’s can tack and not even lose 25% of their speed.

The bottom line here is obvious too… if you don’t like it… DON’T USE IT… I am just putting it out there for you to see… AND CHOSE… don’t believe me… think I am nuts… don’t have a clue… OK!!! not a problem, you are NOT alone… there are a lot of guys out there that don’t believe me… If you think round is better… knock yourself out…that is what makes it great… you can do anything you like with your boat.

My job is to bring the best available hardware I can manage to make the boats go fast… I do this 7 days a week and have a lot of time and a FORTUNE invested. I just want to help you go fast, it is that simple. If it didn’t work… I would not recommend it… I would say… I DON’T KNOW… it should tell you something… that considering this is my full time employment… if it didn’t work… I would not be willing to put my name on it.

It doesn’t matter to me which is better… what matters is getting it to the racing skipper. If Easter eggs and gardenhose would make a better boat… buddy… I would use them.

I have many, many skippers that call me and thank me…

I have NEVER had one switch back. * EVER *

If you don’t believe me… about using a sailtrack mast… because I am a bozo…talk to Graham Bantock and ask him why he had his IOM round mast made (Groovy) with a sailtrack… if he isn’t out winning ANOTHER National Championship he will be glad to talk with you… and I bet it is the exact same reason I had mine made (albeit with a different internal design for shaping)




“By the time you are off a beat, the airflow is not coming over the mast to get to the sail, and remember too… that even before you get to a full beam reach, the RW is deflecting aft because of the forward movement of the boat.”

How about getting one fact correct - because of forward movement of the boat, the apparent breeze moves FORWARD - hence fast boats like multihulls have sails trimmed tight even when (appearing) to run offwind.

“The T-38 was the first a/c to fly from AoI alone (angle of incidence)”

Are you trying to say that no aircraft is/was capable of flying upside down?

Oh Golly… considering I had 10,000 hours PIC before I was thirty years old and spent 25 years in the cockpit flying everything from fighters to heavy jets… as long as we are getting facts straight an aircraft flies upside down by deflection lift, sailing in reverse.

“airflow deflecting aft” says the same thing as the RW moving forward, which is really a reduction of AoA… again… same thing.

Are you trying to say that no aircraft is/was capable of flying upside down?

Are you just trying to insult me?

Like I said at the bottom… if you don’t believe it… DON’T USE it… if you don’t believe me, that is perfectly fine, I have no problem with it at all.

Sorry about hijacking your thread, Dick.

Larry; A mast will auto rotate if there is a couple. Attach the shrouds forward of the pin centerline and the mast will rotate. The sail itself may constitute a couple but the shrouds will resist if not appropriately placed. You seem to infer that the mast will twist in torsion. True, but only a miniscule amount.

M does not equal FA if you are referring to Newtons equation. M=F/A

Help me out with the physics guys. A 550 pound boat (mass) is moved 24 feet in two seconds. How many foot pounds of force is that?

This is a friendly argument. No offense intended, so don’t take it that way.

Hey - no problem - that’s the whole purpose of these forums - to discuss and debate ideas. I had answered Larry on Windpower before I got here, but for benefit of keeping both threads somewhat similar, I will repost the basics here regarding “my feelings” about the question “what is a rotating mast?”

Sorry for redundency to those who also read more than one forum.

From my big boat experiences…

[i]A rotating mast with a wing/foil shape, full battens in the main and honest rotation with leading edge into apparent wind had much more ability to provide the horsepower to drive the boat.

To me, any mast with a back-stay from masthead crane to aft deck really doesn’t rotate. I would agree it might twist - but is dependent on amount of back-stay tension. Any mast confined in a “tabernacle” or pinned at it’s base really doesn’t rotate. On the other hand a fore-stay, single set of side shrouds mounted forward of the mast’s leading edge and the mast mounted on a ball (captive or not) does have the ability to rotate. Then the question is if it needs positive rotation inducement, or rotation limiter to prevent over rotation. This being a subject/topic all by itself.[/i]

Most AMYA classes specifically rule out rotating masts - so how/who gets to determine how much rotation is normal or acceptable. I go back to my pinned base theory with backstay, that any mast that may rotate (or swivel) in that configuration is usually incidental. However, actually allowing a mast to rotate so it’s leading edge is 30-45 degrees or more off centerline with the hull (or hulls) and that would constitute (to me) a rotating mast.

The 10 Rater uses them and has a pretty well developed experience thanks to Mark Gee and the memebrs of tht class. Our F-48 and MultiONE classes (multihulls) allow them, but many are still using round carbon tubes to reduce weight aloft and reduce mast bend as much as possible. There may be other classes - but even in most “development” classes the idea of a rotating mast is disallowed.

Still, when discussing the slot effect between mast and mainsail luff, ignoring the rotating wing mast in the discussion is like ignoring a great hockey team when discussing hockey (my bad example)

So please , let discussion continue, and let’s not take anything personal here.?

Loops of Spectra (10lb Spiderwire) through sail at seams around mast. 1/8" space btwn mast/sail. Low-tech and the sail/rigging move effortlessly in the most miniscule puff of wind.


i tend to agree with dick here.
i use a back stay. as well as shrouds. and with just that in place, you are basicly pinning the mast in place. the backstay crane. is going to act as a arm. to also hold the mast in place. now I do sail a IOM with a 6 foot pole. so i am excepting a little bit of a twist midway down the mast. i dont have it pinned to the deck. it sits in a tube. the way i do attach the sail is with a jack line. aluminum pipe glues to the trailing edge of the mast. and that same pipe taped to the sail. then ran wire though it. like a hinge. works realy well for me.
'i never realy like the groovy tube idea. but that is my own personal opinion

Pinning the mast at the step, is the only way to keep atleast the bottom half of the mast from rotating. THAT will have an effect. I have never seen a boat, that I could not grab hold of the mast crane and twist it 25-30 in either direction without permanently being the mast. If you want to see a reverse of this, watch what happens when someone really honks down on the boomvang, the compression will actually cause the gooseneck to knuckle under and bind up the gooseneck. The gooseneck in these cases is screwed into the mast, it didn’t move, the mast did.

Dick, have you seen this?

Yes Jon -

just trying to see if there is any concensus of what works - or doesn’t. Also what most use.

As Lester noted, and I agree, it seems unless one gets a complete stall, it would be hard to tell the difference. - Might even be the big chunk of weed hanging from the keel that makes the boat seem slower. :smiley:

I tie my sails on on both Victoria and IOM. I have never been fond of a bolt rope after seeing the “RAF” sails designed for sailboards before the wide luff sleeves came into being. The RAF or “rotating air foil” is similar to what you get with the luff ties. The sail can rotate into the turbulent air behind the mast and hopefully give a smoother flow over the backside of the sail. Back side flow being more important than the windward side, IMO.

But as Larry says, go with what you like because one missed shift will make more difference at the finish!

Hi Dick

I also tied on my mainsails with my IOM, RM and R6M. The Marblehead is an ex-worlds from Martin Roberts with swing rigs and the R6M rig was built by the master himself - Graham Bantock.

Just like many others have mentioned, the rotation of the mainsail to the leeward side (“RAF” or “rotational sail” in old windsurfing terms) seems to get better sail setting and better performance, especially to windward. Having tried a groovey mast set-up and “tied on” set-up on my Widget IOM, the tied on sail set better, especially in light air.

Also, I have heard some theories about allowing some air to flow from the windward side, between the mast and the sail, to the leeward side makes for less drag and more attached flow…??