Query: Joinery technique for redwood sign blank glue-up

[knedert]

Folks -

Okay, Rose and I have got a prospect that wants a sign carved out of redwood. The sign will be 4" thick, 36" tall, and 9 1/2' long, V groove lettering on both sides, and the design is a gentle arch, not rectangular. The sign will sit on a base and be fully supported along the bottom edge.

I have found a source for full dimension 4" x 6" and 4" x 8" beams. My question is what would be the best, most durable method of joining them all together for a large sign panel? Given the width, part of me wants to just go with a glue joint. But, this is an exterior sign in a seaside environment, and I *don't* want ANY issues with glue joints failing or the ends opening up.

So, I was thinking about cutting 1" or so stopped dadoes on the centerlines of each beam and using a marine plywood spline between each pair of beams. Ideally, I would use Titebond II (or 3) but don't know if that's tough enough. I hate Gorilla Glue, so that's out... Would TB be strong and durable enough? Is splining a reasonable method, or is there a better way out there? I come at design from a furniture building background, so my first thought, naturally, was tapered, sliding dovetails going the full 9 1/2 feet. Kidding!

We will probably have other issues to address, primarily registration of the sign blank on our bot, for carving both sides, and moving the blank so we can edge the entire perimeter...

I'd sure appreciate all y'all's input on the best glue up strategy and adhesive.

Thanks in advance!

John Moorhead
Rose Davidson
Sleeper Woods Design

[billp]

John/Rose,
Get your hands on some epoxy. I like the MAS brand (masepoxies.com) because of it's ease of use, and vinegar based cleanup, and since you have SO many marine outfits in Lakeport you should be able to find a source nearby. Redwood accepts glue very well and the epoxy glue line would be pretty close to invisible.
This will eliminate the stopped dados, etc.
If your V carving will not be too deep you could simply add biscuits instead of a full length spline, and this would certainly hold up in an exterior environment. Add the fact that the sign will have full support from below, and this should make the entire process much faster, and just as strong as your initial suggestions...

[gerald_d]

The mechanic in me says to put vertical tie-bars right through it.

[paul_z]

Don't forget the wind load on a 3' x 9.5' panel. That will be a lot of torque on the bottom mounting. I'd give Gerald's approach serious consideration.

[gerald_d]

...those tie-bars go into the concrete.

[beacon14]

In my experience you are best off not using any splines if you don't need them for alignment. The glue joint is stronger than the wood and if you introduce a second material or even the same material with the grain running perpendicular, plus voids here and there where the spline is shorter than the groove, that is where the rot/movement/splitting/joint failure will occur eventually.

If you can get nicely jointed surfaces, essentially good wood-to-wood contact throughout, you can use Tightbond III. It's supposed to be as good as polyurethane (Gorilla) glue but easier to use. I've used it a little with good results, although it doesn't have a 30 year track record it's worth considering.

If you use epoxy, the surfaces can be less exacting as epoxy will fill the gaps.

Get (or make) a bunch of good clamps, or use Gerald's tie-rod and nuts to clamp the boards up.

[tuck]

Well it's too bad you don't like Gorilla Glue. I've used it to glue-up hundreds of cedar and redwood sign blanks and never had a problem. Most folks use too much of the stuff. The thing about polyurathane glues is that a little goes a long way. When it foams up and out between the joints, I let it dry thouroughly and scrape off the excess with a sharp paint scraper, then sand it smooth with a palm/belt sander.

Do you know how to "crown" lumber? This is very important, no matter what adhesive you decide on.

[joe]

Epoxy:

It's a tried and proven product used in the boat building trade. David B. know what he's talking about when it comes to splines and biscuits. They are mainly used for alignment and do not add much for stregnth. The stregnth has more to do with surface contact area.

I've tried all-threads with little success. These have two potential problems. First, they expand and contract and will ultimately loosen when used outdoors. Second is the concern with salt water. I used some galvenized all-threads on an ocean side resort sign a few years back. What a mess.

I would strongly suggest, good old tried and proven, Epoxy.

J

[cedarknight]

I have to say I have a lot of craved signs with biscuts and gorilla glue, out there. So far no problems. And I am a full-time sign Fabricator. Have used epoxy too. With gorilla glue, you just have to keep wiping off the excess and put down some paper on your table, if your planning on walk away. I have seen some sign blank almost get glued down to a table and the cement floor before. Have to keep your eyes on the new guys in the shop.

[beacon14]

Mark is right about not using too much. I just used it to glue the platens to my new table, 32 square feet total, which allowed me to compare my spread rate with what is recommended on the bottle - I used about 1/3 of the 16 oz that would be required at the recommended 1/2 oz./sq.ft.

For an outdoor sign I'd err on the side of using more than necessary, but even then anything that squeezes out or drips on the floor is wasted - and the stuff is not cheap. The more you use it the more you know how much to use.

Another reason many people don't like polyurethane glue is that it tends to stain your skin black for a few days. I find that by using liberal amounts of good-quality hand lotion just before working with the glue (enough so that I wipe the excess off on my forearms - common glue targets), then washing with soap immediately after, the staining is reduced or eliminated.