40' Yankee Star, wood species for frames & hull?

Discussion in 'Wooden Boat Building and Restoration' started by Prudhomme, Aug 10, 2013.

  1. Prudhomme
    Joined: Aug 2013
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    Location: Arkansas

    Prudhomme New Member

    So my wife and I have been planning a large build for some time now. We've decided on the Glen-L Yankee Star, a big boat by our measure and a scary undertaking. As it is we have one ace up our sleeve and that is we have lots of trees and the means to saw them (We also have access to family land to build right next to the Arkansas river, for which I'm very thankful). The design calls for plywood cold molding over bulkhead frames with a little glass epoxied over all that. Cold molding with veneers is specified as an option, but not elaborated on in the plans.

    The frame can be built of any of the species at our disposal. To save even more money I'd like to cold mold the boat rather than use expensive plywood. It seems like a win-win to me since veneers are generally considered superior and since time is the one thing not in short supply. I have my doubts about our species though. We have plenty of black locust, white oak, and ash on our Arkansas land. Are any of these suitable for cold molding?

    The plan is to use white oak for the framing (the original plans do not specify a particular species, but a range of suitable ones). I was going to veneer the hull to the same thickness as called for if done in ply. Then I was going to 6 oz. glass the outer hull in one layer and a second layer at the bow and below the wl. I assume a cold molded hull built to the same thickness as plywood molded will be a little heavier depending upon species. I'm sure my frame will be on the heavy side since it will use white oak.

    I'm considering reducing the frame scantlings a little if I use veneers at the same thickness as the ply hull. It seems ok to me to save 10% weight in the frames. I think I could save a lot more than that, but I'd hate to drown my family so an overbuilt boat is ok so long as I can have supplies aboard without running her too low in the water. Am I wrong in my plan?

    I'm asking these same questions in several forums and over at Glen-L to try to get some info to help me decide my course. The timber will be felled this Winter so I need to get my plans finalized.

    Oh, and hello everybody. I've been reading this forum for years, but this is my first post. Thank you all in advance for your input.
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    I fail to see the logic in changing scantlings without understanding the impact this might impart on loading and integrity.

    Cutting your own stock is wonderful, but it will need to season. Rough sawn stock, with live edges, 1" thick, will need a full year to season. Are you prepared for the wait? You can expedite this with a solar kiln, but you're still looking at 6 months minimum with a well controlled solar kiln, 9 months minimum if stickered and well ventilated in a sealed storage box, placed in the sun.

    Without a really good understanding of the load paths and some engineering background, you'd be best advised to stick with the scantlings provided, especially on a 40' sailing yacht.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A plan that gives you a different option but does not elaborate on it is rather poor. The designer should give all the information for all the options. When you say "a little glass epoxied over it", does it mean the laminate is not structural?
     
  4. michael pierzga
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    Location: spain

    michael pierzga Senior Member

    Dont know your boat, but always the best, fastest and most economical way to build a boat is to follow the designers instructions to the letter...no changes of material or technique.
     
  5. Prudhomme
    Joined: Aug 2013
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    Location: Arkansas

    Prudhomme New Member

    Ok, so using slightly thinner frames may not be a good idea. I doubt I could save more than a hundred or so pounds like that anyway. My reasoning was that a stiffer hull combined with one of the strongest species specified for the framing would allow me to shave 5-8mm or so from the width and thickness of every frame member, excluding the floor.

    My plan was to air dry the lumber about 4 months and then put it in a kiln. I figured some plastic and a dehumidifier would work ok so long as I tried to monitor board weight and keep the drying out process from happening too quickly. I want to start the build by late Summer next year. That'll give me 6 or 7 months. If I cut my own stock for veneers I can rough saw it at .4 inch and fully air dry it to the ambient moisture level (about 13% here in Arkansas) before bringing down to 10% in a kiln. That ought to make for some good wood.

    I wonder if veneers should be flat sawn or quarter sawn?

    Right now my biggest concern is whether or not I can cold mold using the species at hand. As best as I can gather I shouldn't use black locust, white oak, or ash. So that would leave me using plywood if that ends up being the case.
     
  6. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you mill green lumber to 1/4" and dry it, the veneers will be all twisted and warped as they dry. One of the main purposes of slow drying is to allow the wood to settle into a stable shape. Then it can be milled and have a reasonable expectation that it will not cup or twist too much.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The recommend veneer choices will be spec'd in the plans. Veneers aren't something you can mill easily or economically, unless you have the ability to peel or slice the logs. Quarter or rift sawn planking stock would be more desirable, though not as important on a molded build as a solid plank over frame build, as the layers are glued together.

    Adding a little bit here and there is a classic novice engineering mistake, which most often makes for a weaker over all structure, rather than a stronger one. This is because structural elements are sized with each other, so if some elements are bigger or stiffer, the surrounding elements now will have to bear higher point and localized loading. This introduces stress risers, these pieces weren't intended to tolerate and things break unexpectedly as a result. So, unless you're willing to explore the load paths and structural dynamics of the frame work and related attachments, sticking with the plans is the best idea. This isn't to say you couldn't use a thicker veneer schedule and decreased frame dimension/centers allotment, but some research would be wise, before attempting to make these types of changes.

    I've you're going to mill your own stock, knock it down to 6/4's and let it season. You can then mill this down further, once it's ready. Forget about the kiln, unless it's a solar thing to speed up the natural seasoning.
     
  8. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    The middle paragraph is excellent advice. This has needed stating for a long time. Don't mess with scantlings if you don't know what you are doing engineering wise.

    Eric
     
  9. nzboy
    Joined: Apr 2011
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    nzboy Senior Member

    Here in NZ many John Wright design yachts including my fathers were built in a similar fashion Bulkhead framing with stringers. Normally 2 layers of 6mm by 70mm were glued diagonally on then dynel plus epoxy .Not for the faint hearted, clamped on every stringer .One boat building firm was building them over a mould with no stringers or frames!Back then there was excellent planking timber 30 years ago Today some plans call for 4 layers of 6mm ply yet Ive seen a local builder planking 4 layers of 12mm ply for same boat, some plans are minimum standards Some boat builders are obviously not happy with minimum standards Normally planking timber for diagonal planking should be knot free(clears) So Im guessing this boat will use 3 layers 6mm ply as a minimum So Im thinking it would be cheaper and easier to buy ply than to mill, dry, machine and throw 50 % away for defects even if you have the trees A local mill says if they see any clear stock an exceptional run, they stack it away to season for years for boat builders and of course there is a premium
     
  10. Petros
    Joined: Oct 2007
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    Petros Senior Member

    looks like a nice design. most modern cold molding I have seen is done in ceder, a very lightweight wood. Using ash or white oak would make the hull very heavy, I would not do that.

    I am not sure ash is used much in boat building because if its durability, white oak on the other hand is an excellent boat building wood, but not for cold molding.

    It appears this boat has been built before and Glen-L has a good reputation, making changes from the plans would risk not just the strength of the hull, but also the resale value since you went off plan. I do not think there would be any savings to "use what you have" by the time you are done. Without professional guidance, it is always best to stay with the plans, or the options that the designer approves.

    Good luck with the build, it looks like a long term project.
     
  11. MoePorter
    Joined: Nov 2012
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    MoePorter Junior Member

    Being a wood guy I appreciate the romance & theoretical cost savings of cutting your own wood. Personally I go that way whenever I can...I don't think I save much money when all the effort is honestly evaluated BUT the feeling at the end of the project more than makes up for it.

    As has been pointed out your Glen-L plans don't lend themselves to making the hull out of any of your available woods - by all means use them for the framing! But none of the mentioned species are great cold molding woods and the process from tree to veneers is very wasteful & tedious in any sort of home mill situation. Ash is the exception - not rot resistant but if well sheathed in glass & epoxy it would work well, but again check it's weight against the specified material in the plan. That's a lot of ash & the waste turning it into veneer would astonish you...

    Consider working with a designer to adapt the designs scantlings to your available material - certainly sheathed strip construction would work with with ash & the strips would be relatively easy to mill. That's what I'd do...you've got some great material to work with...Moe
     
  12. ericclark

    ericclark Guest

    Yah, all know that there are several sources that manufacture boards, building a DIY wooden boat can be both satisfying and economical. If you can afford the cost and the materials are not your problems. You should follow a suitable plan.
    On <unlinked> woodworkexperts.com we have some useful information and some good recommended plans with step-by-step blueprints for your great boat building project.
    Go luck.
     
    Last edited by a moderator: Sep 8, 2013
  13. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Eric, welcome to the forum, but do you really think this is the best way to advertise, your web site or do you think, it will be simply just viewed as spam and have your board membership tossed in the trash?

    Simply put, you've made two posts, both with seemingly innocuous statements, about what could be found on your web site. I haven't reviewed your site, nor do I care to with this marketing approach, but if you expect to be taken seriously, you'll have to show your expertise in some fashion, then maybe someone might be interested in your site.

    Personally, I just think your a spammer with a lousy (read stupid) business model. Lastly, you might want to run a spell and grammar checker before posting, so folks will see you in an appropriate, reasonably educated light. There's not much worse than a poorly worded/written lead, ad or even bit of advise. Most tend to kiss these off a 'drunkin ramblings.
     
  14. dskira

    dskira Previous Member

    Yes he is a spammer
     

  15. dskira

    dskira Previous Member

    This is quite a boat to built yourself.
    I wish you a great journey.
    Follow the advises given by Par and Eric, don't start making your own changes, you will end-up disappointed with an unfinish boat in the backyard and start a family feud.
    Glen-L has a very good reputation, follow to the letter the plans.
    A lot of time and money is involve, and I mean a lot, twice what you are thinking.
    So play safe.

    [​IMG]
     
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