laminated beams

[P.L.Lenihan]

A comment about the technique shown so well in post 35.
Although I think a hollow in the joint is good, I think 1/8" over the 3/4" width is excessive, as much epoxy is used in the hollow as is saved from lack of squeeze-out. 1/32" or so seems better.
Also, I rely on the squeeze-out to assure there is enough 'googe' to fill the joint. Waste is mitigated by scraping and re-using( to the extent possible) the squeeze-out, and experience in knowing how much to apply.
My 2cents anyway.

I whole heartedly agree jackster! 1/8" is way too deep for 3/4" but that was because I was understanding the dimensions of the beams incorrectly. Experience certainly keeps waste to a minimum too. I often use the squeeze out from thickened epoxy to help form a nice wee fillet just to soften up the joint jnction.

Your thoughts are worth a whole lot more than .2cents, in my opinion!



Cheers!


Peter

[P.L.Lenihan]

From my point of view, this is terrible. Now the standard practice is doing poor joinery because of a adhesive that is not made for wood...
Take a wood adhesive, and you can take your wood right of the planer and clamp them together for a nice looking join without all that fuzz. Weldwood plastic is a good one, Resorcinol also (My favorite).

Hi Stephané,

What I was showing has nothing to do with a "standard practice". Instead, it was to illustrate how,when using thickened epoxy, a glue starved joint may be avoided. Epoxy is much more viscous than Weldwood or resorcinol and kicks quicker too.Thus it may not have the time to penetrate very deeply into the grain.Also,due to its' relatively shorter working time, it is entirely possible for an amateur builder to over-tighten the pieces being assembled,creating a perfect situation for a glue starved joint or in the case of heavily cambered laminations, the pressure from the bending alone will force out the thicker epoxy before it has time to penetrate much.

The trick is to discover exactly what the difference is between "snug", "firm" and "tight" when assembling bits together with epoxy.The product will perform much better in the joint than outside of it

I've never worked with resorcinol due to my terrible wood working skills but would certainly avoid creating " hollow " faying surfaces if I were to ever use this type of glue, as it is not gap filling.....


J'espère que la tempête de neige récente ne t'a pas ralenti! Lache pas!!



Salut mon ami!!

Peter

[Matti]

For having less epoxy waist, mill about 4" wide planks and glue, after that rip it four individual beams( with thin blade table saw ), much less spilling glue.

[Sayla]

Good drawing.
I'd change the captions, to 'reassurance there's sufficient epoxy in the joint' and 'uncertain'.
The 'expensive' squeeze-out costs about $.02 per ml. and can easily be removed.

I'll second that

I should think that "squeeze out" = mated sufaces......as a younger person, in a cabinet shop, everything we made had to have some level of squeeze out

If I didn't get squeeze out, I'd do it again

Besides, filling a void with epoxy sounds like yet a more expensive option again

sayla

[JimConlin]

For having less epoxy waist, mill about 4" wide planks and glue, after that rip it four individual beams( with thin blade table saw ), much less spilling glue.

A very good idea for several reasons:
Saves stock
saves epoxy
Saves time in slicing stock
Saves time in glueing up.
Maybe the finished parts will be more consistent in shape.

[jalmberg]

John, I do understand the use of Epoxy for certain things and do appreciate that it bring more wood boat on the water.

But on laminating rectangle strip for beams straight from the planer with Weldwood (Which is gap filling to 1/32), which turn out less expensive, good joinery and faster... It make no sense in my head to make hollow on freshly planed wood to use a more expensive adhesive which ask more work.

We agree 100%.

[JimConlin]

Originally Posted by JoshuaIII

John, I do understand the use of Epoxy for certain things and do appreciate that it bring more wood boat on the water.

But on laminating rectangle strip for beams straight from the planer with Weldwood (Which is gap filling to 1/32), which turn out less expensive, good joinery and faster... It make no sense in my head to make hollow on freshly planed wood to use a more expensive adhesive which ask more work.



We agree 100%.

-- John

It's news to me that Weldwood is gap filling to 1/32". The tech data at the Jamestown site recommends .003-.006" glue line.
The six-month shelf life and "interior use only" bits there don't don't give me much confidence either.

True, this glue has been commonly used for many years, particularly for spars, but I've lost count of the number of threads here about such spars that have come unglued.
When I consider how much of a pain it would be to deal with a failure here, the small cost difference for epoxy is irrelevant.

[JoshuaIII]

It's news to me that Weldwood is gap filling to 1/32". The tech data at the Jamestown site recommends .003-.006" glue line.
The six-month shelf life and "interior use only" bits there don't don't give me much confidence either.

True, this glue has been commonly used for many years, particularly for spars, but I've lost count of the number of threads here about such spars that have come unglued.
When I consider how much of a pain it would be to deal with a failure here, the small cost difference for epoxy is irrelevant.

The 1/32 is writed right on the can, which I do use often. This is for a deck beam which is protected from sun light, water & is in the interior.

Anyway everybody is how way

[SScoville]

I marked out the camber for the forward cabin beams on a scrap of ply and cut the line. I now have this:

Is there any reason I cannot use the two pieces as a male and female laminating jig?

Harry Bryan wrote an article in Wooden Boat about bending wood in which he states: "A note of caution: If you use a deckbeam mold to draw the curve of the form, the beams will be too flat because the mold represents the top of the beam whereas the laminating form should represent the bottom of the beam. To get the correct curve for the form, sweep a curve below the beam mold with pencil dividers set to the depth of the beam."

Does this apply to my situation? I can't see how using pencil dividers on either one of these pieces is going to give me anything but a parallel line, which is what the other piece should in theory already be.

[Peerie Maa]

No, if you use the dividers to step off the moulding of the beam perpendicular to the line you will get a curve that has a radius to the underside of the beam that is smaller than the radius of the crown of the beam by the amount of the moulding. Use the dividers to scribe arcs, and lay your batten round to tange those scribed arcs.

[SScoville]

Thanks, but I'm a bit confused. You first say "no." Is that no, I cannot simply put my laminates between these pieces and clamp them down, or no, Harry's warning does not apply to me?

[Mrleft8]

In order to get a good male/female clamping form, you need to cut the plywood you have there twice, once to the inside arc, and once to the outside arc. So if your inside radius is 15', and your laminated beam is 2" thick, your upper piece of ply will need an arc with a radius of 15'2"..... Your piece of cut off waste will look something like a fingernail clipping.

[Gib Etheridge]

I expect that the plans show the radius to the top of the beams. You probably tacked the ply to the floor and used a stick tacked to the floor at it's far end and a pencil at it's marking end to describe the arc. The lower side of the arc is going to have a shorter radius, by 2" if I remember correctly, so you need to set it back up with a 2" shorter stick, assuming that you didn't do that already.

That looks like about 10" of crown to me, didn't you say 5" in a previous post? Looking at the plywood I would expect about 1/4" at each end of springback with 10" of crown for a 3/4" X 2" lamination using 1/8" lams. I don't know anything about the springback equation, that's just what I would expect.

If you do get that, and if you think it matters you can always add more lams and shape to a pattern, although that may look like a mistake was made if you finish them bright. You'll know what to expect after the first try.

If you're concerned about creep and sag after all of the discussion you could run a few screws dow from the top, not quite through. It won't creep then, but it might actually be weakened, although I doubt it.

Make sure to dry fit before doing the actual lay up, that can save you some headaches.

Laminating is fun. Have a good one!

[Peerie Maa]

Thanks, but I'm a bit confused. You first say "no." Is that no, I cannot simply put my laminates between these pieces and clamp them down, or no, Harry's warning does not apply to me?

I meant no, do not use the dividers to create a parallel line. By swinging arcs you will remove the 2" moulding and create the correct curve. If you carefully hold the dividers "straight" all of the time, you will create the parallel curve which is not what you want.

[Jim Ledger]

Deck camber should be a section of a circle. Your plywood template looks like it flattens out as it nears the ends. There is a way to lay out a proper arc using a couple of sticks and three nails, if you know the beam and the rise of the deck in the center.