Gougeon Wing Mast Plans

Discussion in 'Multihulls' started by HydroNick, Apr 4, 2010.

  1. Eric Sponberg
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    Eric Sponberg Senior Member

    Stressform was a marketing name by the Gougeon Brothers for their stayed, wood-epoxy wingmast designs. After some years of selling plans, they gave the business over to Georg Thomas, who had some mast building experience, because the Gougeons were afraid of the potential liability. I think they found that the mast designs were being used for boats that they weren't intended for, or that people weren't following the plans properly. At any rate, the liability exposure was enormous, and they just could not accept that any more. I don't know what has happened to Georg Thomas and the Stressform designs--maybe he came to the same conclusion. If the mast breaks and kills somebody, the designer really is on the hook, no matter what the plans say.

    The liability, indeed, is enormous--this is why I do not design stock plans for masts, and it is mostly likely why you are not finding many, if any, stock mast designs. The mast designs that I create, and the laminate schedules that go along with them, are designed strictly for the boat at hand. They are highly dependent on the skill of the builder/owner and on the availability of the materials at hand--the carbon fiber and the epoxy resin. The length, section shape, taper, wall thickness, strength and bending characteristics are all tailored to the boat's sail plan and righting moment. What works for one 40' sloop likely will not work for another 40' sloop.

    To create a mast design and it's laminate schedule, I need to know which carbon fiber fabrics the builder/owner is going to use. I can specify what I think will work, but if the builder/owner can't get those fabrics (and the carbon fiber market is still very volatile in that regard) then my design is useless. Same for the resin--it has to be readily available and be appropriate to the task at hand. Finally, the laminate really must be laid up under vacuum bag to a minimum 50% fiber content by weight, and the mast has to be post-cured in an oven (a make-shift temporary oven will do), and the temperature of the laminate should be monitored during post cure to guarantee the post-cure temperature of the mast. All this takes a lot of skill and preparation, and it is why mast design and construction is a pretty complicated process. A fault in any link in this process can lead to mast failure and a resulting dangerous situation out at sea. Going through the process with the builder/owner as his design is being developed gives each of us the assurance that the mast will be built properly. You don't have that assurance with the sale of stock plans that just anybody, who may not have the necesary building skills, can buy.

    Eric
     
  2. rob denney
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    rob denney Senior Member

    You will have a long wait for me to finalise any build method! There is always a new idea to try. The wing from flat panels uses infused panels but has no cutting or shutting to get the shape, so is not much like KSS. All my panels are infused, but that is because i have an infuser with a big table next door. Could just as easily hand laminate and vacuum them which would use less material, but not have the luxury of time to get everything set up. I get the wing shape by varying the laminate. Have just built a pair of rudders using the same technique.

    I assume the wing mast will bend very little along the long axis. Sail shape is altered by rotating the mast, not bending it, except for the depowering that happens when it bends sideways. Making it bend fore and aft is an engineering problem, but to me it defeats the purpose of the wing.

    For a tube mast, core does nothing except add weight. At some chord dimension, it becomes a panel stiffness problem and core is required. On my 600 mm chord mast it is 3mm, on the mast for a 7 tonne 20m proa it is 6mm, so not much weight. At some chord thickness a sheer web is also required, which adds to the complexity of the build, but not the difficulty.

    We have no problem sourcing the carbon for my masts. I use tow, but you could replace it with uni if you don't want to build a wet out machine. I am still trying to figure out the best way to use tow in infusion, so for this, uni would be better. I scored some cheap carbon cloth so will be using that for my mast, but our cruising masts use glass for the off axis loads which reduces the cost significantly, at the expense of a little weight. I am using vinylester for the infusion, but would use epoxy for hand lay up for the longer out time and no horrible smell.

    One of the big advantages of an unstayed mast is there is only one thing (the mast) to break. Therefore, it can be bench tested to quite high loads (the limit is usually supporting the mast at the bearings) and the deflections compared with the engineers numbers. If they are the same, you won't have to worry about the mast breaking in normal use. There are so many reasons for a mast breaking, that I find it difficult to believe there is a liability problem for a designer although I can understand a negative publicity problem. I don't know of any mast designer who has ever been sued, successfully or not. Have there been any?

    Building your wing masts is easy enough if you have a long table, a vac pump and know how to follow a string line. I am still waiting for the infusers to finish their 15m table, but my mast is the first job when they do and there will be photos of it's build on my web page. Should be some rudder ones next week as well. You will not match autoclave results unless you pressure compact your mast. This is easy enough with a round mast and a (cheap(ish) steel mould, but not with vacuum. The weight difference will be insignificant compared to vac bagging. Much less than the weight of a bolted on alloy sail track compared to an integral carbon one.

    The hardest part of building a mast is getting started. If you buy a sheet of glass say 1m sq and a vac pump (your mate next door should have both), I will send you the approx layup and measurements for a section of mast which you can infuse and build. The only difference between doing this and doing it full size is the need to follow the string line.

    Nick,
    they were very expensive, hard to build, over engineered and relied on partial vacuum to make the panels thick enough not to buckle, which scared the crap out of me.

    rob
     
  3. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

  4. idkfa
    Joined: Sep 2005
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    Location: Windward islands, Caribbean

    idkfa Senior Member

    Another good article:



    ...............When a bending overload occurs the El equivalence between our carbon mast and the aluminium mast goes out the window since a stress concentration occurs at the partners. This means that our primary loads are no longer shared throughout the cross section of the mast but rather are being concentrated in parts of the section at the partners. If these loads exceed the capability of that small area then that area will fail locally. Local failure usually leads to global and down comes the mast.

    Why has failure at the partners not been an issue in aluminium masts? Go back to our El equivalence and you have your answer. Since the aluminium mast has a lower E the I needs to be higher which translates to a thicker wall by around two times. The local stresses generated by the partners are thus distributed over a greater area reducing the opportunity for failure. However, when you produce the carbon equivalent the El requirement generated by the proven aluminium design leads to a reduction in wall thickness of two to three times. Suddenly the loads from the partners are being applied into a much thinner wall as well as being in the weaker load axis of the carbon laminate ........
     

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  5. Eric Sponberg
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    Eric Sponberg Senior Member

    The AES website has a lot of practical advice. However, the "fiber layup schedule" is a rough approximation and guideline at best--it is no substitute for a properly engineered design. Also, all of the discussion relates to stayed rigs, and there is not any discussion on free-standing rigs.

    Many of the lay-up principles do apply to free-standing rigs, such as the use of all three fiber orientations--60 to 80% UDR, with some 0/90 and +/-45 fabrics. Whereas they recommend a 30/10 split between the +/-45 and the 0/90, I tend to make these an even split--20/20. If the percentage of UDR goes up, and I agree that 80% is an upper limit, the off-axis fibers reduce in amount in proportion, and I keep their amounts approximately equal. The other best advice on there is that the laminate should definitely stack in a mirror image through the thickness. I tend to keep my innermost and outermost fabrics the +/-45 instead of the 0/90 cloth.

    Eric
     
  6. HydroNick
    Joined: Apr 2010
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    HydroNick Nick S

    French homebuilt mast plans

    In the end...based on my wife saying "why don't you just buy a boat"...I bought a Farrier F-25c, so mast construction is presently not on the cards, boat construction even less so; however, I did recently find this:

    http://www.nauticaltrek.com/12524-c...-pour-le-trimaran-drifter17-de-mark-gumprecht

    which seems to be quite detailed instruction in french on how to build a mast. My schoolboy french only allows me to comprehend a little of it. If you scroll down there are some other links in the responses to the above. This one

    http://www.pinoyboats.org/forum/viewtopic.php?t=2132&postdays=0&postorder=asc&start=45

    is fairly interesting and there is other information on amateur mast building, though some of it circles back to this group and Messrs, Sponberg and Baigent.
     
  7. Ilan Voyager
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    Ilan Voyager Senior Member

    Nice links, but I know by experience that wing masts are not the best for cruising boats (specially at the mooring, it's incredible that can circle a catamaran with a wing mast in a strong wind, and the mast flaps very nicely if not solidly attached) and it's really very long to make, even with "simplified" methods. The price of a home made carbon mast is simply hair raising, compared to the equivalent in alu.
    Except for racers it's not worth the expense and time (even free).

    Hydronick; your wife is a wise one. Cherish and take care of her...
     
  8. HydroNick
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    HydroNick Nick S

    I shall! Thanks
     
  9. SpiritWolf15x
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    SpiritWolf15x Senior Member

    I'm not sure if it is a Gougeon.... But I have a 60foot wing mast mold... Maybe you can make use of it...
     
  10. redreuben
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    redreuben redreuben

  11. Eric Sponberg
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    Eric Sponberg Senior Member

    Yes, that is the same information/opinion we were talking about, further up the thread. This is an old thread going back three years.

    Eric
     
  12. HydroNick
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    HydroNick Nick S

    Well I guess this still intrigues me. Eric Sponberg has this article from Professional Boat Builder on his site, can't remember seeing it before. As Eric is a frequent contributor/ helper it is probably on here somewhere...but memory is a strange thing.

    https://www.ericwsponberg.com/wp-content/uploads/wing-masts.pdf
     
  13. Eric Sponberg
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    Eric Sponberg Senior Member

    Hi HydroNick--Thanks for posting that article, written by Ted Hugger in Professional Builder magazine, Issue #14, Dec/Jan 1992. There are other articles on my website regarding the design and engineering of free-standing masts and wingmasts. Link: Articles http://www.ericwsponberg.com/articles/

    As you may know, I am retired now, and I haven't been on BoatDesign.net in quite awhile--I see the graphics have been updated! I have referred a lot of my boat and mast design requests to other designers and engineers, including Rob Denney who posted above. I am not longer practicing naval architecture, having discovered that retirement is one of the world's best kept open secrets ever--I'm loving it! I am currently in Puerto Rico on board my boat Corroboree, my very first commissioned design that I bought back from the original owners about two and a half years ago. My wife and I refurbished the boat over a 15 month period on 2015/16. We sold off all our belongings in St. Augustine and left Florida on 4 January 2017. We are staying in Puerto Rico long enough to have our engine rebuilt because it was burning a lot of oil--thanks to worn out pistons and corroded cylinders. In a couple of weeks the engine will be back in the boat good as new, literally, with lots of new parts, and we'll be heading further east to explore some of the Caribbean islands we missed 40 years ago on our transatlantic/Caribbean cruise coming the other way back then on our 27' boat. By the end of this year, we hope to be heading toward Panama to go through the Canal and across the Pacific. Corroboree was built in New Zealand, so we'd like to take it back there, and then continue around the world.

    It is interesting to see the mix of boats on our way. There are four kinds of boats, generally, that we see making long passages, either coming south and east from the States, or going west and north to the States: There are 1) power cats and 2) sailing cats, and there are 3) older American/Canadian monohulls, and 4) relatively newer or brand new French monohulls (Jeanneaus and Beneteaus). Of the older American and Canadian boats, they range from about 20 to 40 years old, with a few exceptions to newer and older boats. Many of these boats are in the mid-30' length wise, with the ocassional 40'+er. Most of the French monohulls are 40'+. Of the catamarans, most are in the mid-40' range, with some at 50' or so. I mention all this because it's an interesting mix of boats that reflect what is available for cruising boats in the States and Europe. That is, there are no new American or Canadian boats to be seen--all are older, much older, boats, like ours which is 30 years old.

    As for free-standing rigs--we have come 1500+ miles from Florida, and we are the only one I have seen on a cruising boat. There have been one or two in marinas--there is a Freedom 25 here in Puerto Del Rey Marina, but it is resident here, it is not rigged for cruising. And there was a Nonsuch 30 or 36 in Dinner Key Marina in Miami back in February, again, not a cruising boat. Again, I mention this only by way of observation.

    Thanks again for posting the wingmast article.

    Cheers,

    Eric
     
  14. HydroNick
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    HydroNick Nick S

    Thanks Eric: I hope that I am able to follow your lead shortly, both in terms of retirement and cruising around. Thanks for all the great responses and information that you posted on this site, thanks also for the advice you gave me about the fittings on my mast and what I should do (In the end they were rebuilt and re-anodized by a guy that rebuilds aircraft parts). Your observation of boat types is interesting, I am surprised there are no trimarans.

    If you ever get to the west coast of Canada and the Georgia Strait (Salish Sea) up around Campbell River, let me know, we may be able to find you a berth.

    Fair winds

    Nick
     

  15. Eric Sponberg
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    Eric Sponberg Senior Member

    Hi Nick,
    I think we have seen maybe one trimaran, in the Georgetown area of Great Exhuma Island in the Bahamas. There may be others as we move east toward St. Martin and Antiqua, which as I recall from my professional travels down to that area, is more of a haven for multihulls.

    Thanks for the offer for a berth in your neck of the woods. I doubt we'll get up there with our boat--too cold! We took an Alaskan cruise there about 5 years ago, so we know a bit of what it is like. However, some friends of ours are in the middle of buying an old wood trawler up in Vancouver which they are going to move onto so as to cruise the Canadian and Alaskan coast. We have an open invitation to join them whenever we want. Who knows, we may take them up on that spend a short time up there.

    Cheers,

    Eric
     
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