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Groucho Marx

Groucho's new wing mast

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Building in my back shed Groucho's replacement mast; the original got wrecked in a savage storm early last year while moored in Cox's Bay. Also the mast smashed down onto the beam and float damaging badly those areas too - which I've slowly repaired. In fact I lost interest in the larger boat and focused sailing on my two smaller boats. So unloved Groucho has been swinging on its mooring. But I've finally engaged gear; this new mast is a little less in chord at 500mm. Also has a few reinforcing changes that should make it less susceptible to letting go? But when the winter onshore storms arrive, I need to lower the rig. Which is not a problem because of our local pohutukawa tree gantry.

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Similar dimensions to my mast (built 15 years ago) but mine is too heavy. What does yours weigh? I'll be following the new build...

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Groucho's old mast weighed around 70 kgs with all standing and running rigging. Can't give you an accurate figure but I could pick it up and carry it around, although it was a balancing effort and was an armful with its over half metre chord.

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Weighed the mast parts: base, backbone, frames, stringers and ply sheets = 47 kgs.

then to be added is the alloy luff track, glues, epoxy coating for skinning, paint, halyards and rigging - so just guessing will be around 65 - 70kgs, about the same as old mast, Here's a plan drawing of it. You can see I changed mind while pricking out frames.

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Hi Gary

 

Could you pleas share a little more details about the construction and dimensioning of the mast?

What kind of loads will this mast be able to take?

 

Regards Mada

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First I scarph and glue the near central longtudinal 3 or 4mm thick, 175mm wide ply thwart on floor, then glue mount the frames which have been cut at the widest part of the airfoil shape (also you have to cut out the middle of the frames, both leading and trailing sections for you halyards) - so you glue the trailing section first, then add, after glue cure, the longitudinal scarphed stringer that makes the base for your alloy mast track. I use 6mm curtain track and cut off the wide flanges with bench saw - but that is the last job, not necessary at this early stage.

After the trailing section of the wing is cured, turn it over and because the mast trailing leech is straight (vertical when erected), it can be propped flat on shed floor, then you glue on the leading edge mast sections, then the scarphed nose stringer. My mast leading section is straight to the hounds then tapers to the peak, Also I narrow the the mast atwartships from hounds area to peak as well. Cuts weight, looks more refined.

Now the 3 or 4mm ply used for the longitudinal thwart is too narrow a glue edge area for decent adhesion when you bend over the thin ply outer mast skin, so I cut thin stringers to glue one side of the main thwart. You can do both sides if you want but I've found that one is enough. I try to keep everything as minimal as possible because weight aloft is something you don't want if the finished boat starts pitching in a seaway. The very first mast I built for Supplejack many decades ago (we knew nothing in those days) was way too heavy, well over 200 lbs for only a 42 foot mast and the cat really pitched badly if you didn't keep the power on - until I built a new, lighter version ... learning the hard way.

You'll have to grind or saw a cutaway on the frames for this to fit. This stiffens the beam considerably. Actually it is better to glue the stiffening stringers to main thwart before you mount the frames but it can also be done at this construction stage too.

Okay hope you can decipher this gibberish. I'll finish this attempt at wing mast building description tomorrow..

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Well, I've covered the more important aspects of wing mast building but you have to remember this is what I've learned the hard way ... and there is no rigid and fast rule; my stuff it is low technology building, nothing like the exotic construction that goes into the latest multihull rig designs. But the comparison in expenses between backyard wood construction, for example, to high tech professionally built mast, is extreme too, meaning building in your shed and piecing it together outside under trees; we are talking of only a few hundred dollars - compared to some astronomical figure put together in Nomex and heat cured carbon. The only carbon I use is in uni-directionals laid up vertically on the thickest section of the mast after skinning; the area between the hounds and base needs beefing up for extra stiffness. On my masts I also have 3 point lower stays similar to the main stays. And I have runners going to the stern too.

Anyway, enough of this, where were we?

Skinning is straight forward enough; just fairly slow. I glue the scarphed ply to leading edge and let it harden overnight before coating inside and bending to the air foil shape and gluing/stapling to mast track stringer. You can't bend cured epoxy ply so you do it wet. Well, you can but it will be a distorted and cracked mess.

My hounds are simple triangular wooden shapes (beaks) protruding a couple of fingers or so from the leading edge of mast, same with the lowers and beefed up with a lot of carbon running at 45 degrees around the mast to thickest section. I drill out a large hole near beak end and fill it with epoxy for the hounds rigging shackles, then drill later to fit..

I've seen many wing masts built (also from professionals and at great expense) with the side stays at hounds position attached to the mast side. If you do this you won't be able to rotate the mast beyond 30 degrees - which is near useless and defeats the purpose of having a wing mast.in the first place.

There are other more elaborate ways of designing/building hounds (like horizontal tracks that have movable carriages around mast sides) but I've never had any problems with my simple method.

Here's my mast spanner setup.

Mada, if you can't handle my boring English descriptions, send me an email: coxcreek@slingshot.co.nz

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That's awesome Groucho - I have huge respect for the craftsmanship that involves....

 

Here is a cross section of mine, built by the original owner. It is built up out of strips of clear spruce with 3 layers 1.5mm aircraft ply on the sides. Covered in two layers of glass. The mast is 13 meters long.

 

i just dropped it after 6 years rigged, and upon inspection, it seems to be holding up well.

 

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That's awesome Groucho - I have huge respect for the craftsmanship that involves....

 

Here is a cross section of mine, built by the original owner. It is built up out of strips of clear spruce with 3 layers 1.5mm aircraft ply on the sides. Covered in two layers of glass. The mast is 13 meters long.

 

i just dropped it after 6 years rigged, and upon inspection, it seems to be holding up well.

 

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Dude?!

 

When I first read that I thought oh sh*t but then realized you mean pulled it not dropped it. I dropped mine once due to my own stupidity. Don't do that, LOL!

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Sometimes I think it would be so much easier to build a smaller chord mast like yours Paxfish ... but then change mind. Because I like the more streamlined shapes of the larger wing.

Your shape/reinforcing/materials/design looks very strong to my eye; how heavy is your complete rig?

Whereas I seem to be cutting away materials to the bare bone ... and still end up with a 65-70 kgs mast. It is a juggling act, weight/strength.

My problem is that my boat is on a drying out mooring and that is when, in the past, all damage has occurred to the rig because in high winds (we have many hard blows in Auckland) the trimaran foiler rocks from side to side after smashing the cradle. It is this violent rocking that breaks rigging connections and mast comes down.

So I watch wind direction and strength with religious attentiveness and if necessary shift boat to a more protected area in the bay. Repairing can be boring and annoying.

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Weight on mine was about 3 pounds a foot for the core - that's about 60kg for the 13 meter long core. Figure double that with glass plus rigging: twin spreaders and dyneema diamonds, 3 halyards, fittings.

 

Probably over 300 pounds all up and a bitch to handle. 20 foot (6 meter) beam helps tame all that weight up there.

 

Shrouds are overkill at 9mm dyneema, but they held up well with very little stretch. So I replaced with the same size, substituting Colligo deadeyes for the old turnbuckles..

 

Might step the mast this weekend if I can find enough HOs.

 

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Pax, that is too much weight aloft; your boat will pitch its arse off.

My first wing mast built 4 decades ago ended up around that weight and we broke it a couple of weeks later Ridiculously stupid hounds beak attachment (recommended by a certain M. Tennant; we knew nothing in those days) naturally ripped out; a great lump of metal sort of glued and bolted to the inside and outside of mast, just pulled out in a gybe in hard winds, bent solid stainless bolt into a U.

So then went over to uni-directionals and epoxy, no metal, spread loads over outside mast area. The only problems I've had since then (aside from whole boat being blown over) has been with a couple of my homemade blocks breaking. However once beefed up with more uni-carbon, no more troubles in that department.

Here's a shot of original Bamboo Bomber effort; you can see the crude reinforcing at mast base after mast tumble.

I need to add, in those days we made the main luff track, routed out wood and then glued two halves together. We couldn't reef otherwise the track sprung and main luff pulled out. So we either hung onto sail far too long - or dropped main and sailed under headsail and mast ... or if wind really howling, just under wing mast, which was surprisingly efficient. Once averaged 17 knots for 30 minutes running for shelter with just mast.

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Hey Gary,

Do you think your mast construction method could be used on a mast with smaller chord, say 30-40 cm x 13 m and still work? Or does it need the extra ply for the stiffness? What about a couple of more layers of uni carbon as a substitute? I am trying to save weight aloft as well over a heavy Gougeon wing used previously on my 30 foot tri.

Tim

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I built these two 6 metre wing masts for 5.5 metre Cox's Bay Skimmer; the chord is around what you're after, I think around 350mm. They work fine but then, they're only 6 m tall. I've not built a taller rig with the dimensions you're after but I think it is definitely possible. The Skimmer's masts have an alloy tube as a core with the frames and stringers attached together; see photograph.

I beef up the below hounds mast areas with carbon laminates at the thickest mast sections on my larger rigs.

But the Skimmer is simple bent ply with a couple of coats of epoxy, no reinforcement.

And these were initially freestanding - but the central tube was heavily laden with glass, then carbon in the low cantilevered areas -

but the forward mast bent its base in fresh winds so I chopped off the low tubes and made male bearing shapes at base and went over to simple three point fibre rigging. Which is lighter than the freestanding setup.

Freestanding would work but obviously I didn't have enough carbon layers there.

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Pax, that is too much weight aloft; your boat will pitch its arse off.

My first wing mast built 4 decades ago ended up around that weight and we broke it a couple of weeks later Ridiculously stupid hounds beak attachment (recommended by a certain M. Tennant; we knew nothing in those days) naturally ripped out; a great lump of metal sort of glued and bolted to the inside and outside of mast, just pulled out in a gybe in hard winds, bent solid stainless bolt into a U.

So then went over to uni-directionals and epoxy, no metal, spread loads over outside mast area. The only problems I've had since then (aside from whole boat being blown over) has been with a couple of my homemade blocks breaking. However once beefed up with more uni-carbon, no more troubles in that department.

Here's a shot of original Bamboo Bomber effort; you can see the crude reinforcing at mast base after mast tumble.

I need to add, in those days we made the main luff track, routed out wood and then glued two halves together. We couldn't reef otherwise the track sprung and main luff pulled out. So we either hung onto sail far too long - or dropped main and sailed under headsail and mast ... or if wind really howling, just under wing mast, which was surprisingly efficient. Once averaged 17 knots for 30 minutes running for shelter with just mast.

 

 

 

Very Nice work, Groucho! Next time I drop the mast, I will consider your advice on building a big uni hound point. Right now it has a thick SS plate pinned and laminated though the center of the mast, roughly 200mm by 300mm. It is set on the diagonal such that the lower corner comprises the Hound attachment.

 

From there I have a Jesus shackle and the Amsteel shrouds tied in directly to the shackle.

 

Pitching hasn't been an issue in our 3rd season, and the mast stood for a least 7 seasons on the previous shrouds. Also, part of my weight aloft is the fairly heavy Tides marine sail track.

 

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Very Nice work, Groucho! Next time I drop the mast, I will consider your advice on building a big uni hound point. Right now it has a thick SS plate pinned and laminated though the center of the mast, roughly 200mm by 300mm. It is set on the diagonal such that the lower corner comprises the Hound attachment.

 

 

 

 

Tow is easier to use (goes round corners, fewer voids) and cheaper than uni.

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Correct. But I have difficulty finding carbon tow.

In the old days when you couldn't (or I couldn't) find any carbon, we used glass tow, nothing wrong with that stuff either, except requiring more layers, also heavier of course.

But what I do with uni carbon is cut it into strips a finger width wide or so and run the layers in the directions required for carrying the loads. Works fine.

And carbon expense these days is not excessive, even for backyard wankers who use only small amounts like me

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Correct. But I have difficulty finding carbon tow.

In the old days when you couldn't (or I couldn't) find any carbon, we used glass tow, nothing wrong with that stuff either, except requiring more layers, also heavier of course.

But what I do with uni carbon is cut it into strips a finger width wide or so and run the layers in the directions required for carrying the loads. Works fine.

And carbon expense these days is not excessive, even for backyard wankers who use only small amounts like me

 

Smart move.

I have half a ton of tow I'm selling for a friend. ~5.5 kg rolls @ $Aus50 per kg. This is Zoltek 50k, which is thick, so you cut fewer pieces. There are also ends of spools available on Ebay sometimes. I also use it for making carbon rod, bent and straight and a bunch of other uses.

 

Gary, let me know an address and I will send you a part spool which will be enough to keep you going for a while.

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Rob, that is very British er Kiwi of you.

I bought a part roll of carbon a couple of months ago from High Modulus; they wouldn't sell anything less than that quantity. Obviously back yarders such as myself are just a nuisance - see photograph.

But the uni carbon tows would be very interesting to play with. As mentioned have used uni glass tows in the past and found it very useful. Arnie Duckworth from Adhesive Technologies introduced that idea way back in the 1970s.

But carbon is kind of magical compared to glass.

My address:

Gary Baigent, 9 Sackville Street, Grey Lynn, Auckland 1021.

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Haven't got a full rig shot of Groucho under sail - (I'm usually on board) but here is an early image taken by Jacques with older non square top main,. Mast is 15.6m, foot is 3.15 so total area around 50m2. Reacher is not large, maybe 26m2. Boat is light, 650kgs with 2 crew. Bruce Number to windward is 2.1.

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Nice work Rob, spiffing actually!

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Hey Gary,

Almost all the recent pics of your boats are shown sailing in ghosting conditions. Do you always sail in those conditions or do you venture out in stronger wind? What type of speeds? Any worries about your masts? Any more info would be appreciated.

Tim

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Having purchase a spool of carbon from Rob I can confirm it's brilliant stuff. When you have it lying around you just keep finding uses for it.

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Nueva, the boat is fairly brutal in fresh conditions and takes plenty of concentration and I mostly single hand - so haven't got time to dig out camera from below when fast sailing. But will make an effort to do so. Here's Flash Harry (prototype of Groucho) in some fresh stuff..

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Gary, I am also interested in getting some Gps speed records from your foilers (easy to obtain with a cheap Garmin); Two days ago I broked a foil at 15 kt during trials on my modified Strike 15 trimaran. I used curved daggerboard from a Bim zero A catB before breaking I observed a gain on mean velocity around 1.5 kt upwind and downwind.

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Sanding mast at Cox's.

Life is hell in this superb Auckland autumn weather.

Had to strip plank the leading edge outer skin to central I beam in 4mm ply - the only thickness I could locate; would have preferred 3mm or less and then could have bent it in a sweet curve.

More sanding tomorrow.

Maybe get some carbon on the worked over side.

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A few more days and mast will be finished.

Thanks Rob, your present of uni-carbon arrived this morning - IOU, maybe crate of Belgian beer when you come back to Kiwiland?

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