Spar to wall adhesive technique

[Graniterich]

I am using solid 3/4 plywood, any advice on how you applied adhesive to the end of spar and slid in between walls with out wiping it off?
Maybe pull walls apart a touch?

[noseoil]

Make sure you paint the ends well, and make sure you have enough glue on the wall surface as well. The last thing you want is a "starved joint" on a structural connection like that. An acid brush from the hardware store works very well for covering the ends with enough glue. If you need to pry things apart slightly, that's a good way to go, just be careful.

Are you using screws from the outside of the wall into the strut ends? If so, make sure you use a pilot hole in the plywood strut and use some longer screws with big threads to bite well into the wood. Do a "dry run" on the spars with some smaller screws to hold things temporarily, while you check the holes, lengths, etc. Don't use a power driver with too much torque, just enough to set the screws firmly is about right. If you strip them, go to a longer screw. If you split the wood, it's only half as strong and you lose structural strength.

[aggie79]

End grain (spar) to face grain is not a very strong glue joint no matter how tight the tolerances are. But that is a reality for typical teardrop construction, so as the previous poster said the joint strength relies on fasteners- screws - for the most part. Pre-drill for screws and dry-fit all spars (with screws) in place. Disassemble, apply adhesive - I recommend PL Premium - and then reassemble from the end working toward the center. Leave the temporary connection on one sidewall and glue and fasten the spars on the other sidewall. Then repeat for the other side.

[bobhenry]

http://tnttt.com/viewtopic.php?f=40&t=23312&p=331047&hilit=spars#p331047

All 5 of my small trailers have set in spars. I cut an 1 1/2" wide pocket in the wall and 3/4" deep and cut the spars as shown above. Wood glue and one 3" screw thru the side upward across grain in the spar. The wall trim will hide the head.

No it was not my idea it was utilized before I was even born...............

[coyote]

i glued/drilled/screwed as everyone suggested, the pocket idea sounds great. All I can add, is I put spars every 8 inches from front to the galley hinge. Probably overkill, but 40 years of Caterpillar mechanican causes that! ( why use a 5/16 bolt, if a 1/2 inch will fit ). Of course you never see a Cat. being towed behind the family car. coyote

[jonw]

I used my Kreg jig for pocket screws on mine, plus Titebond III glue. Worked great!

[absolutsnwbrdr]

I used my Kreg jig for pocket screws on mine, plus Titebond III glue. Worked great!

Yup!

I am using solid 3/4 plywood, any advice on how you applied adhesive to the end of spar and slid in between walls with out wiping it off?
Maybe pull walls apart a touch?

Yes, you can spread the walls a bit as you insert the spars, but you'll still have excess glue to wipe off. A damp rag works well for that.

[HornD]

If you wanted really strong and had the time a dovetail from the top would not be that hard.
You could cut the spars with the tail on one end on table saw (60" up in air is tough) or cut with jig saw carefully then use that for layout on Side Frame.
Now that is a tough joint with plenty of surface area for the Polyurethane glue to bite to

[Lambertdarr]

If you wanted really strong and had the time a dovetail from the top would not be that hard.
You could cut the spars with the tail on one end on table saw (60" up in air is tough) or cut with jig saw carefully then use that for layout on Side Frame.
Now that is a tough joint with plenty of surface area for the Polyurethane glue to bite to

Tough joint yes, just don't ruin it with polyurethane glue. Especially if you are making dove tails with a jigsaw. Your joint will most likely be loose. Titebond III is your best bet for strength.

[tony.latham]

Are you going to install blocking between your spars? (Do we need a blocking/no-blocking poll?) If you are, the blocking will lock your spars in place, and then the ceiling and roof plys will really strengthen the whole thing up. We need to look at teardrop strength from a totality of the build, not one particular joining system.

Me? I'm a sandwiched-wall guy that builds with a shelf and blocking. I have no questions about the strength. If I was going to go with just plywood walls, I'd stick to Bob's suggestion, but still add the blocking and nothing is going to move.

T

[rowerwet]

I put a row of shallow saw cuts into the end of the wood grain, then packed them with adhesive using a bondo spreader, never had a failure that way.

[mezmo]

Besides the full-through sidewall notch, you could also router
out a 1/4 to 3/8 inch deep pocket [blind notch] in the 3/4 plywood,
corresponding to the spar end size, and glue the spar to the wall that
way. Of course, you haven't cut your spars yet, I hope, as they'd be
longer by whatever sum of depths the two blind notches would give.
Otherwise I don't see a way to do it other than pulling the side back
enough to insert the spar. It will be aggravating, no matter what you do.
Could you make a little jig, that you could clamp to the wall, to help
locate the spar(s) if you still just do the spar insertion between the
wall surfaces?

Cheers,
Norm/mezmo

[Graniterich]

I Appreciate all the input, ended up using pocket screws and. and titlebond three. It is very solid

[Graniterich]

Pictures

[Diemjoe]

I am going with a Grumman 2 profile. To profile is mostly curve but spars have at least 1" flat surface to connect to. I am hoping to not have visible nails. Is there anything special I would need to do (shaping the spar) in order to get full contact or is adhesive thick enough to cover the gap? I am planning a wood roof so am wondering if square to curve may cause some ripples in the look?

Thanks