How to build a wingmast??

[StriderTurbo]

Hello! I was thinkin of building the mast by the strip plank method.
With the WINGMAST profile. Build it in two halfs and with fiberglass on inside and the outside. I am wondering about the dimensions of wood, the profile itself ex: 30x13 cm?
Mast 11m, boom 3m , fully battend 21 sqm mainsail on the
Strider Turbo 7.3x5.1m
How can I do this??????
Or just buy a mastpofile and mount it myself???
Any good ideas???
Thanks!
Kenny
Stavanger

[Raggi_Thor]

Did you read the answers to your last question?
Build a mast?

[Chris Krumm]

Kenny -

Gougeon Brothers (WEST System Epoxy) had a set of strip planked mast plans designed for a trimaran with about 20,000 lbs * ft righting moment and about 325-350 sq. ft. sail area in a high aspect sloop rig. 1/4" spruce w/ 1" carbon fiber tapes as exterior "spar caps" with a laminate schedule tuned to the displacement of the particular boat. Wrapped in 6 oz glass cloth for torsional and shear strength. Single spreader with diamond stays, designed to rotate. About a 2:1 section aspect ratio. About 32 feet overall length. Came with plans for a roller furling boom, which you might drop for a standard boom and slab reefing.

Sounds about right for the Strider Turbo, eh? I bought the plans years ago for informational purposes. Check and see if they'd still sell you a set with a laminate schedule tuned to your boat. If not, I could give you some more info (very busy right now - better next week).

Chris Krumm

[Dutch Peter]

Strider,

Build a mast?

[Phil Thompson]

Hello

I am just new here but got to try and compare mast building methods when I had to build a strip plank mast for a 38ft tri and a mast for my 38ft cat. After building them i was very happy I did not go the wingmast road for my own cat. The wingmast will take a lot of time to build and probably be heavier than an aluminium section. After cruising with a rotating mast on a 31 ft tri for two years I was gald to get rid of the the complication of the rotating mast and go for a standard stick. If you cruise and want to go downwind fast get a nice reacher and kite.

I put the aluminum mast together in about 2 days. I have no spreaders and use a wishbone on the main. I love this rig. It took us longer than this to plank up one half of the mast.

I feel the speed advantages of the wing mast may be overstated for some sailors. If the mast is loosely rigged to allow it to rotate easily it will wobble in a seaway. This is enough to set anyones nerves jumping and you want to slow down. At least I did.

cheers

Phil

[Tim B]

I don't agree, Phil. If any rotating mast 'wobbles' I wouldn't even pootle around the harbour! it should be properly mouted, preferably on thrust-races / Ball races. rotating masts do need a lot of maintainance though for just that reason.

As for srip planking... build yourself a mould (carve/mill/plank, however) for each side, then see if you can find some long rubber tubes or something similar. Layup a carbon/glass composite (with epoxy) in one side of the mould,fold the layup over the tubes (ready to meet the other side of the mould), part-inflate the tubes, and put in place the other side of the mould, now fully inflate the tubes.

The only problem with this method is that it induces rather large stresses in the moulds, so you may want to back-fill them to make them more solid. You can try this method on a test-piece. make yourself a small mould and do a small GRP layup using a few of those long thin party balloons for pressurization.

Alternatively you could cut you're profile in some foam using a hot wire (so you have a continuous 'mandrel' but a two part mould), though you'd have to do it in sections, then use the middle piece of foam (the 'mandrel') to do your layup around and then close the mould around it. I strongly suggest that you line the mould with baking paper if you do that though. The finish won't be great, but it has the advantage that you can put in internal structure as you do it (if you needed a sail-slot).

Hope there's something of some use in this ramble, e-mail me for more info,

Tim B.

[Eric Sponberg]

Ken,

I am a great advocate of wingmasts, and you can see some examples on my website, www.sponbergyachtdesign.com, go to the freestanding masts section. It describes two masts that my clients built, one for a boat called Copernicus, the other for a charter ship called Nai'a. Nai'a's was all wood. I would advocate using carbon fiber instead of glass over a wood framework--carbon is much stiffer and stronger, and lighter to boot, than glass. You don't need a mold. Build the primary shape with wood as described in my website, then laminate carbon over that.

Eric

[casavecchia]

Kenny.
about ten years ago I built a stressed plywood rotating wingmast reinforced with glass and carbon.
I bought the plans from Gougeon Brothers and I think they still sell the plans .
Construction went quite fast
The mast is still in use, no problems.

Marco.

[Tim B]

why not mould it? I've given a few examples of easy methods (especially the foam one). and you get a lighter mast. you can even use a thin piece of foam inside the laminate to produce a totally monocoque mast. Now isn't that smart? I'll do a couple of short bits for my own interest sometime, and work out how light + stiff they are relative to normal.

Tim B.

[CT 249]

Re Tim B's comment "I don't agree, Phil. If any rotating mast 'wobbles' I wouldn't even pootle around the harbour! it should be properly mouted, preferably on thrust-races / Ball races."

Tim, I believe that the "wobbling" referred to is the mast actually rotating back and forth as it should do (but at inconvenient times), not slopping about in its base. The same problem is experienced in small wing-masted catamarans. Unless it's windy, downwind the mast rotates back and forth over a considerable angle as the boat moves through the chop. You can use rotation lines to control the wobbling, but they are a pain; yet another thing to work on in a rig that is already quite labour-intensive due to the (generally) stiff wing-mast's inability to automatically react to gusts in the way that a flexier smaller section can. Rotation lines also normally rely on a rotation lever, which is yet one more thing to go wrong and can also result in the occasional nasty blow.

Not all experienced designers have used ball races, by the way; Lock Crowther (and I think Dick Newick) commonly used a simple ss ball that is retained by a cup.

[Chris Krumm]

The strip plank Gougeon wing I referred to earlier used a SS ball in a molded/cast FG and epoxy socket. When I spoke to JR Watson at the time I purchased the plans, he mentioned the mast had worked quite well on a small Marples tri- a 23' loa Cyclone, I believe. They went with strip plank and the 2:1 chord length:thickness ratio for the smaller masts to get adequate lateral rigidity without having too much wing area in unsteady conditions or while moored.

The stressform masts were designed for larger multis and have closer to a 3:1 chord:thickness ratio.

[Phil Thompson]

Hello

Thanks for the feedback. I did leave a few things out on my reasons why I don't like rotating masts for me. I cruise with my kids and don't race so performance is not my guiding light. I also find that most of the time I am slowing my boat down. We often sail along the coast in Australia with just a kite up keeping things slow enough to use the autopilot. This is usually at the most at an average of 8.5 knots.

For me and maybe someone like me I think a wingmast is not a good idea. As I stated before you will finish building a spreaderless cat mast before you have even cut out the molds for a wing mast - or at least I did, let alone make a really nice flat strongback.

As for wobbles what I meant was that a wingmast can't have the rig tension pulled on as tight as a normal mast or the front gets heavily loaded and reverse bend becomes a problem. So the rig is usually looser. When you start jumping off waves and look up it can be quite a scare.

BTW I am not a fuddy duddy sailor. I love to sail fast in skiffs, sailboards and even our cat when conditions are right. But for me the solidity of a widely stayed rig with intermediates is very encouraging. Our easily built rig is a bit old fashioned but has served us well and has done sterling service on the designers cat when it went to Antarctica and raced more than once across the Tasman.

cheers

Phil Thompson

[StriderTurbo]

Hello! what do you mean with "a 3:1 chord:thickness ratio."
thickness of the mast?
Thanks!
Kenny!

[StriderTurbo]

To Tim B!
Do you have work drawings of the wingmast?
Thanks for your help!
Kenny

[casavecchia]

Kenny,
the beauty of the Stresform wing mast lies in the fact that you dont need a mould and neither a strongback, only a bench on sawhorses. With a 3mm wall thickness should be light enough for a catamaran like yours.
And besides it's a beautiful piece of engineering too.
Marco.