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Bending Mahogany

Discussion in 'Wood and Canvas' started by Fitz, Oct 25, 2007.

  1. Fitz

    Fitz Wooden Canoes are in the Blood

    I'm just about finishing up a nice old (1929) AA grade OTCA. The major outstanding issue standing in the way of relaunching is that I'm pretty much convincing myself that the old outwales are junk. So this will require me to mill and bend new outwales - new territory for me. Nothing like trial by fire (and steam)! Any tips from the good folks here would be greatly appreciated.

    What species of "mahogany" these days might help me out the most, bend, and come close to matching old mahogany?

    Any bending suggestions? I've managed ribs fine, but the bow of an OTCA is daunting. I'm assuming I have to make a form that matches the sheer with a little more for springback.

    What else am I forgetting?

    Thanks in advance. I'll let you know how I make out:eek:

    Fitz
     
  2. Andy Hutyera

    Andy Hutyera The Red Canoe Guy

    I'm not familiar with the characteristics of mahogany in terms of bending but I did just bend some ash inwales. I'd recommend puting the taper in the ends before you bend. Considering the likely severity of the bend on an Old Town, I'd likely try to use a metal compression strap over the wood. I just went to the hardware store and bought steel cross bracing strap which they sell for cheap by the foot. You'll probably have to come up with a clamping arrangement to secure the strap to the long end of the stock. The strap really helps if your are puting a severe bend in the wood. I use it on stems and have a very low failure rate.

    Beyond that the following is a really helpful source of information on bending. It indicates the suitablility of various species:

    http://www.leevalley.com/wood/page.aspx?c=2&p=31161&cat=1,45866,45867&ap=1

    Happy bending!
     
  3. smallboatshop

    smallboatshop Restorers

    Hi Fitz,

    I haven't had any luck finding air dried mahogany so I've gone to Old Town for these Otca rails - prebent. The last time I ordered it took a while and when I called to check up they said that they had snapped the first ones and had to do another set. I thought 'there but for the grace of God' or as we say in Maine - better you than me...

    At any rate the OT rails were okay. They are rough and I had to let one straighten a little to fit but they looked good finished. I've steam bent straight mahogany OT rails and mahogany for coamings without problem so I don't think you need to worry much as long as your stock is air dried.

    As for species - OT, as you probably know, used various mahogany's and stained the wood to present a uniform finish. Hope this helps.

    Dan
     
  4. Paul Miller

    Paul Miller Canoe Nut

    Gunnel bending

    Hi Fitz,

    You may want to search through the Chapter Happenings for the Great Rivers Chapter spring workshop the dates are 4/27/07.

    We discussed gunnels, soaking, bending, jigs and strapes and have pictures too.

    Hope it helps,

    Paul
     
  5. Blue Viking

    Blue Viking Wooden Canoe Maniac

    Outwale material!

    I had an occasion to pick up a 20' piece of 5/4 decking material that is mahogany and got 5 strips out of that one piece and the price was right! Now, not being at all familiar with the kind and quality of "mahogany" I am satisfied with those strips...Will use them in the future on two "re-builds" and if they bleach out I will just add some mahogany stain to make them the color I desire.....;) Just throwing in an "apprentices" thoughts!:p
     
  6. Scot T

    Scot T LOVES Wooden Canoes

    Hellos Fitz. I've bent a lot of Honduran mahogany (the one I'd choose) in my years of guitar building and find it quite easy to work with. I'd stay away from any of the Philippine variations if you have much of a tight radius to bend. It tends to be more porus than any of the the other mahoganys and there is usually a lot of run out. African Mahogany does not bend well as it is harder and will buckle severely on the inside of the curve. I can tell you it is a real PITA.

    I know guitar sides are different than canoe gunnels being 2mm+/_ thick but the process is much the same. I'd soak the wood a while before (especially if using kiln dried, which is mostly what you will find) and use the 1 hour to 1 inch rule. In my experience, don't over-cook mahogany as it doen't have a lot in the way of natural oils so tends to get brittle very quickly. And take your time, bend smoothly and with even pressure. Remember the fibers in the wood have to release from each other and slide past each other a bit to make a nice bend, Much like the cells/fibers in your muscles do when you stretch. If you stretch too far or too fast they snap....Not good!

    Hope something here helps. As I said I've not bent any mahogany much over 3mm thick so others might have better info for thicker pieces.
     
  7. Dan Lindberg

    Dan Lindberg Ex Wood Hoarder

    Fritz,

    In addition to the other comments.

    Try a few test bends before you start on the real thing.

    And, if you end up using Phill "mahogany" watch for compression cracks on the inside of the bends.

    Dan
     
  8. Dave Wermuth

    Dave Wermuth Who hid my paddle?

    All steamed up.

    Fitz, here is a photo of my gunnel steamer. I soak gunnels in the pond for several days to a week first. I know nothing of mahog. But this is my steamer. The blue is sewer hose from my camper. Holds up! the elements:
    propane burner,
    steel gas can (water can)
    metal exhaust flex pipe
    Radiator hose.
    Sewer hose.
    I stuff a rag in the end to hold the steam in a bit.
    One hour per inch. I fasten the middle and work toward the end. The blue hose can be pulled back accordian style as you go. I learned this from Brian Baker. He has a similar set up. the wood kinda tells me if it wants to bend or not. \
    Gives new meaning to the term 'staining' the gunnels don't it?
    Regards, Dave.
     

    Attached Files:

  9. Scot T

    Scot T LOVES Wooden Canoes

    Slick steamer contraption Dave. I've always bent my gunnels before putting them on. Might have to give that idea a try.
     
  10. OP
    OP
    Fitz

    Fitz Wooden Canoes are in the Blood

    Steaming in place

    Dave:

    Thanks for the photos on your In-Situ gunwale steamer! I've been meaning to try in place steaming. There is a fella up in NH who uses tubes of polyethylene. It is material that folks use to make individual baggies to contain items. It comes in different diameters, on a roll, and you can cut it any length. Anyway, he puts the poly tube over the frames of boats he builds and steams them in place. He simply cuts the poly off went done.

    I was going to try it on this canoe, but I'm already done with the paint job and I don't want to risk screwing that up with the heat.

    As an update, I'm going to try some meranti ("philipine mahog) that the local lumber yard had in long lengths (5/4 up to 20 ft). (I know, I know, I may regret trying to bend this stuff). It is dark red material and is straight grained. I've finished the milling and that went really well, so if it takes a bend I'll be happy.

    I plan to soak it for awhile and give it a shot.

    Thank you all for all the helpful advice.

    Fitz
     
  11. Ed Moses

    Ed Moses LOVES Wooden Canoes

    Fitz,

    I attempted to bend meranti inwales for a 1917 OT Otca, quite a steep bend on those old Otca's..
    I found the meranti to be very dense , ridgid wood with very little flexability. After soaking for 7, yes , read that 7 days, and steaming for an hour on pre tapered inwales, they both split. I was not using a piece of metal to minimize fiber lifting and would highly recommend that you do. I gave up on the meranti after the second unsuccessful bending attempt and went with some western spruce inwales. Found 20' spruce at Bolter plywood in Somerville.

    Good luck with the meranti . Sure hope you have better results than I did.

    Ed (in NH)
     
    Last edited: Nov 3, 2007
  12. OP
    OP
    Fitz

    Fitz Wooden Canoes are in the Blood

    Oh boy.

    Thanks for the fair warning Ed. I'll give it a shot. If I can get my act together, I'll try a practice piece this weekend, and let the rails destined for the project canoe soak as long as possible - a week or more. I'll report back.
     
  13. Douglas Ingram

    Douglas Ingram Red River Canoe & Paddle

    I bent some gunnels for a Tremblay that I'm working on. Nice long stuff, but not Honduaran, one of those other Mahoganies.

    Regardless of how you go about it, I'd recommend that you start clamping at the MIDDLE if the curve, and work out from there. The middle is where you're most likely to split/snap/break the wood. From there, you effectively have only half as much curve to bend the wood to.

    There will be considerable springback, so leave the gunnels on the form as long as possible.

    Also, if the gunnels are higher than wide, arrange so that they don't twist or fall over in any way during the bend. During the bend is NOT when you want to have to deal with this.

    Oh, and keep track of which side is "up". Don't ask why I ensure to mention that seemingly obvious detail...
     
  14. Dan Lindberg

    Dan Lindberg Ex Wood Hoarder

    From over on the Wooden Boat BB,
    http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=71595
    It maynot help you directly, but it gives you a comparizion of different species.
    Dan




    Bob Smalser:
    Re: Another logging question

    Stevens and Turner's Wood Bending Handbook done at the UK Forest Products Laboratory lists walnut as capable of bending to a 1" radius when supported by a steel strap and to an 11" radius unsupported. Their tests were on European Walnut but Black Walnut should demonstrate similar results.

    For comparison with some of the best bending woods, the radii for White Oak are .5 and 13, Red Oak 1.0 and 11.5, Beech 1.6 and 13, Ash 4.5 and 13, Hickory 1.8 and 15 and Rock Elm 1.5 and 14".

    Some boat woods that don't bend especially well are Doug Fir at 18 and 33, Khaya at 20 and 24, H. Mahog at 12 and 28, Port Orford Cedar at 18 and 34 and Western Red Cedar at 35 and 37". They qualify their published results for the cedars and H. Mahog with the note they had limited stock for testing resulting in a poor sample size.

    The tests were done using airdried and steamed, 4/4 stock.

    Go to Home Depot and buy some Henry's #107 Roofing Compound, a water-soluble tar, and paint the log ends immediately after bucking to length. Your winters are sufficiently dry to cause the splitting at the board ends resulting from drying too fast. The tar only costs around 6 bucks a gallon, which should do all your logs.
     
  15. OP
    OP
    Fitz

    Fitz Wooden Canoes are in the Blood

    Steaming Meranti

    So I will post my trials and tribulations here so others may learn...:rolleyes:

    I did a test run today with the kiln dried meranti and the steambox to see what I might learn. Part of the fun outside of paddling is learning something new - no? :rolleyes:

    1. So I soaked a scrap piece of the meranti only for a few hours this morning. I figured I could decide whether is was going to bend or not even after a brief soaking.

    2. Fired up the steam box.

    3. Left meranti in there for various lengths of time. 45 minutes, 55 minutes, 1 hour, 1 hour and 18 minutes.

    45 minutes -FORGEDDABOUTIT! It ain't gonna bend

    55 minutes - better, but FORGEDDABOUTIT! It ain't gonna bend.

    1 hour, It bent but not easily (this is the one I put on the form)

    1 hour 18 minutes (I forgot this piece in the steamer) softest wood yet.

    So Lesson No. 3 is a good long steam is a good thing (I do know you can overcook it).

    4. Lesson No. 4 is don't make your form out of cheap pine you have laying around. It can't take take the bending pressures necessary for this stuff anyway.

    So, after considerable thought, I think I can get this stuff to bend. I'm waiting to see what the springback looks like too. I will build a decent form and use a metal strap. Soak the real gunwales for a week or so, and try again.

    I suspect my chances of getting 4 bends to go well with this stuff are not good.

    I've attached a few pictures of the stock, the milled gunwale, the steam box rigged up, and the attempted bend. Note split in attempted bend.

    Cheers,

    Fitz...
     

    Attached Files:

    Last edited: Nov 4, 2007
  16. Scot T

    Scot T LOVES Wooden Canoes

    Fitz, your pine form would/should be fine except for one thing. The holes for the clamps look like they might be too close to the edge. The general rule I use for bending forms is that the edge of the "clamp hole" (for lack of the better word right now) is at least three times the distance from the form edge as the thickness of the stock being bent. For example 1" stock = hole 3" from edge. Some might think it over-kill or silly but it works for me and the size of my clamps.

    I'm not fond of metal straps. They can leave a stain on the wood and especially with wet wood. I have had the stain penetrate deeper into the wood than I would like and that resulted in a lot of sanding to get it out. You can do a couple things, line the metal with heavy paper (which can sometimes stick to the wood a little too much and be a PITA to get off, but very much better than metal stain). Some advocate using wax or varnish on the metal but being an instrument builder first I don't let wax, oil or anything else slippery near what might be joined to another piece of wood. I know canoe parts are different but I thought I'd make it clear I have not tried that method so am not qualified to comment on it. Except to say that with the heat from the steamer the wax or varnish could melt and get into your wood and you might not want that.

    My preference is to use a wooden strap. I use a scrap piece trimed from the same wood I'm bending. It doesn't have to be more than 1/4 - 1/3 the thickness of the wood being bent. It just has be flush with the wood all along the section you intend to bend in order to supply support to the outside of the curve. It also gives a good pad for the clamps so you avoid clamp marks in your stock. I throw it in the steamer at the same time as I steam the important piece.

    Just a couple thoughts from my experience. Hope it might be of some help.

    Remember, free advice is worth exactly what you pay for it....nothing ;)
     
  17. martin ferwerda

    martin ferwerda LOVES Wooden Canoes

    For what it is worth, I have use meranti on my last two canoes, the sheer line of a Thompson canoe is a lot less drastic than an Old Town OTCA. I steam about an hour or so, and the stuff bends OK. I use a jig that uses wedges instead of clamps, and I use a wood backing strip. One thing to watch out for if you do get them bent, is meranti still has a tendency to split when drilling holes to install the gunnel, so if you do get them bent, have a sharp drill bit and drill slowly.
     

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  18. Andy Hutyera

    Andy Hutyera The Red Canoe Guy

    Likewise for what it's worth, I use floor joist straping material which i believe is galvanized (It's also wonderfully cheap!). Never had a problem with staining, but then I haven't tried it on mahogany, just ash and cherry. Bending those long outwales is going to be nerve racking and getting four to go well is going to be a crap shoot. How good are you at scarf joints?
     
  19. Denis M. Kallery

    Denis M. Kallery Passed Away July 3, 2012 In Memoriam

    An old furniture makers trick is to use aluminum foil between the metal strap and the wood. It doesn't stain. Denis
     
  20. fred capenos

    fred capenos Canoe Pilot

    For what it's worth, I've had success bending Mahogany.
    My first attempt went like this:
    Soak in water for 24 hrs. steam for 1 hr. under tension for 7 days. the radius' on the forms were 43 1/4 in. The spring back was 50%.

    Second attempt went like this: Reduce the radius to 39 ", back into the steam box for 1 hr, (no soaking), under tention for 20 days and "viola" perfect bends. I clamped the buggers on top of the old inwales so they won't remember how they grew up, till I get the ends tapered.

    BTW I wanted a 43 3/4 in" radius.
     

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