I’m interested in making some wood frames frames for nylon webb seats. I have the materials. Can anyone who actually has experience with this tell me how to join the parts of the frame together. Thanks
standard wood joinery
A mortice and tenon joint would be the most solid.
Wood dowels are, of course, quicker and easier and seems to be what is used on most economical replacement seat frames.
And don’t use nylon
Nylon stretches when wet, so your seat will sag.
Use polypropylene or polyester web.
I wonder if you could get away with
half lap joints, if the cross pieces lie on top. One would need to use G-flex for permanent adhesion.
personally
I prefer nylon. Yes, it does sag some when wet, but no more so than cane I find. If the nylon is put on with good stretch (which is easy to do if you wet it some first) I find the sag makes it more comfortable, although others don’t. The tubular nylon webbing is also somewhat softer than the flat polyester or especially polypropylene.
But if you don’t want any sag don’t use nylon.
Because my butt is too big for many
seat frames, I can feel the “bite” of 90 degree corners on the frame. I recommend rounding or chamfering the inside corners of the frame. And making a frame that is big enough.
Half-laps…
– Last Updated: Aug-18-11 11:47 AM EST –
...are really only good for things like picture frames. There is no structural strength and it relies entirely on the glue joint.
Go with mortice and tenon. A dowel joint is a passable second option if you don't have the tools and/or skill to do a true M&T. Square shouldered M&T is the strongest. Most important is to make sure the fit between mortice and tenon is snug and straight.
edit: BTW - if you are lacking in tools, you don't have to do a blind mortice. You can lay out your frame members clamped to a flat surface and drill holes for your dowels from the outside of the long frame member, through that and into the end of your short frame member. Not as pretty as a blind mortice and slightly less durable (make sure the visible end get sealed well) - but a lot easier to get everything lined up.
I think I’ll try half lap with a slip of
polyester cloth across the joint. I could do blind mortices, I have the chisels, but dowels? No way.
The way the half lap works in this situation, all the force pushes the joint together. It’s worth a try.
Dowels. I hate dowels.
Yep - worth a try.
We’re talking about minimal expense in materials and the half-lap doesn’t take much time or prep. So, yeah - why not?
But I think - even though round tenons are usually inferior to rectangular tenons - that the dowel joint will last longer if properly done. Stresses on the joint won’t be perfectly perpendicular to the frame much the time, and nothing really holds the lap joint together but glue and gravity.
Furniture makers (the ones that care) don’t generally use lap joints where strength counts. Dowel joints are common enough to know how well they hold given proper fitting and gluing. Rectangular blind mortices are best, but require some tools and skill to get them right.
I’ve done work with round tenons (sometimes out of necessity and sometimes out of expediency) that has held up real well. Seen round tenon work from others that held up and some that did not. It depends a lot on the application, the glue, and the quality of the fit. Fit is more critical with round tenons than with rectangular, IME, and commercially-supplied dowel stock is often not quite the dimension that it is labeled. Selecting the right drill bit is crucial.
The half lap failures I’ve had were due
to the glue being too brittle (“yellow” glue). That’s where I expect G-flex to succeed.
Dowels
Let’s see, Old Town built over 250,000 wood canvas canoes. Just for fun, figure each had two seats, with four joints and two dowels at each joint.
That would be 4,000,000 dowels. Seemed to work for them.
Then there was Chestnut Canoe Co. with even more produced than that.
Dowels are a very good option. Mortise and tenon are fun to do too.
I have no data whatsoever on the
failure rate of those joints. They are certainly easy to do again and again in a production setting. They aren’t convenient at all for home construction.
mortise and tenon joints …
– Last Updated: Aug-19-11 2:32 PM EST –
...... a fine strong joint if cut and fitted well , crap if otherwise .
But for such small work as the frame of a canoe seat , that would be a real pain to cut in the mortise by hand .
Just great if you already have a mortising jig , square chisels and hollow mortising bits , and a drill press to use it all in ... 1-2-3 done , but the set up is a relatively expensive one .
Probably the most critical part of cutting in the mortise with that set up is making certain you have the work piece clamped down securely . Otherwise it tends to rise up off the press bench when retracting the square chisel back out due to friction .
Making the tenon is easily accomplished on a table saw ... 1-2-3 done , though other ways aren't so bad either as long as you maintain the precision required for a proper fit , if not , again it's just crap .
Double dowels are just as good , just as strong a joint as a mortise and tenion . As a mater of fact the dowel is a type of mortise and tenon joint . And for someone who hasn't the expensive tools and experience for mortise and tenon ... doweling is almost a no mess up proceedure that practically anyone can do with an inexpensive jig and hand drill .
We put a lot of faith in epoxy and rightly so because it sticks and stays stuck like no man's bussiness . So unless you have the equipment , experience and skills to fab mortise and tenon joints ... just use double 3/8" dowels and epoxy to join the seat frame and be happy . The biggest favor you can do yourself there is to use a brand new sharp bit , the end grain on hardwoods practically demands it .
Personally I love Forstner bits for precision wood boring , but they won't work in a dowel jig because the Forstner shanks aren't the same dia. as the cutting head ... they do work fantastic for doweling in a drill press though .
Why?
Dowel joints are not at all hard to construct, I find. You can purchase fluted, hardwood dowels at any store that caters to woodworking, and most hardware stores as well.
You just cut the frame elements to size as if you were going to butt joint them together and drill holes for dowels. The holes should be a little deeper than the depth that the dowels will extend to.
The only trick is to make sure the holes you drill are lined up properly and go in plumb to the frame elements. A drill press is convenient but an inexpensive drill guide will also work, and for short dowels (as would apply for this application) I have done it by hand and eye and come out OK.
If you like doing that, go ahead.
I’ve had more dowel joints fail than mortise and tenon. Dowel joints are inherently cheesy.
I admire your faith. It isn’t worth the
wood to do a series of actual tests comparing double dowels and mortise and tenon. So I’ll just imagine the results.
My original speculation was that lap joints with superior (G-flex) glue might work well for canoe seats. It’s an empirical question and I don’t yet have results.
sure half laps would work fine too …
– Last Updated: Aug-20-11 12:44 AM EST –
...... plenty strong enough with epoxy or marine glue for canoe seat frame . probably never be flippin the seat over anyway since one main is gonna be longer than the other .
The only thing I'd add to that is a few stainlees or brass screws from the bottom up . And I'm not so sure the end grain really matters anyway because you still gonna have end grain at the cross mains .
Besides , the half lap to join the members of a canoe seat together is really more a half lap and dado joint . and if you really wanted to you could just as well make a stopped dado in the mains so the end grain needn't be exposed , but the stopped dado still requires a closed squared off end which means a bit of hand fussing with a chisel unless you have the mortising equipment set up , otherwise just run the dado clean through .
If ya really want to get kinky with the dowels , go to 1/4' dowels and pilot a stainless screw through the center . That's best acomplished with a 1/2" Forstner bit for the round plug hole followed by a pilot hole . The plug would cover the screw and get sanded flush , neat look too , cause the sanded wood plug (end grain) comes out darker , looks like a big dot .
Cheese heads.
Nothing to a through-dowel joint. You clamp the short member to be butt-jointed to a flat surface - a 2x4 will do. Now clamp the cross member against the end of the short member - all preferably near the end of the 2x4. Now drill through the cross member and into the end of the short member. Press in glued over-length dowel and let glue cure. Trim excess and finish. You can get a nicely finished joint if you use a plain round dowel matched to the appropriate drill bit - then make your own glue grooves stopping short of the exposed end by dragging lengthwise across hand-saw teeth to score.
M&T does not have to have square shoulders to be superior to dowels. Make a round-shouldered M&T joint with common woodworking tools - a router (preferably table-mounted, but you can make a jigged base plate too) for the mortise and table saw for the tenon. Using a plain spiral bit 1/3 diameter of the thickness of the wood, take multiple passes with the board on edge against a fence. Use stops or marks at each end of the mortise cut for accuracy. Cut the tenons on the table saw and round the tenon shoulders with whatever hand cutting tool you have available (chisel, draw-knife,…I have even used a half-round scraper.
Heck - Norm taught us this stuff - where were you? 
yes
My experience has been the same. Double doweled joints hold up as well as mortice and tenon joints. Just a little less elegant perhaps.
It is important to use either a rectangular or squared tenon, or double (as opposed to single) dowel joints for the frame of a canoe seat because either resists twisting much better than a joint done using a single round dowel does. The webbing attaching to the short frame members causes them to want to twist about their long axis when someone sits on the seat surface.