Hybrid Construction

Sorry to hear health woes, Terry. I know the rotator cuff can be painful. I am eager to see you progress on your build. I'm getting ready to order some ply from Noah's and have it shipped down here for my own new build. Hope you get to feeling better.

 

Hope you're feeling really well again soon.

 

Thanks for the sympathy guys! The garage is full of lawn furniture waiting to be stained and sealed but apart from a new fence the rest of the yard jobs are done now. It's wall-to-wall rain for the next few days so the furniture will have to stay under cover for a few days after it is stained, then I'll have room, and hopefully inclination, to resume boatbuilding. That's after the fence. Oh yeah, I have to repaint the canoe and sailboat and replace the sailboat's rudder . . . *****, *****. And to think before retiring I held down a full-time job that involved World-wide travelling - however did I find the time?


A wise man once said, give a man a garden and make him happy for life. I think another wise man said the same thing about boatbuilding. All these wise guys actually do is sit around spout stuff like that. That's why we call them wise, I suppose . . .

 

Best of luck with it Terry, I know my back sure set me back for a while but things heal and I'm sure you'll be back to it soon.

TB-3 is a PVA ? I thought it was just like TB-2 an aliphatic type or basically an animal hoof type kinda like Elmers.

I'm making a panel of cedar ply in my shop now and used a vacuum bag to clamp with but at best that system will only deliver 16lb/in^ and not the 100 your suggesting. TB-2 I use regularly and if you apply to much clamp pressure you end up starving the joint. I'd think 100 lb/in would end up pressing all the TB-3 from the joint, no?

anyway T glad to hear your getting better

cheers
B

 

I don't use nearly as much as 100 psi for TB3, if the joint fits well that starves it unless a wide area is being glued. I get good results with about 10 psi on small joints around 3/4 sq. If the joint doesn't fit well it takes far longer to set and the joint is then much weaker and TB3 in a gap is brittle.

FYI Gorilla Glue will fill a gapped joint better, but if the gap's too much it just foams, and it must be clamped to immobilize because it expands. It makes clamping thin material demanding. GG relies on moisture in the wood to kickoff - opposite of TB3. If the wood is very dry and I am using GG I breath on the joint to ensure the GG kicks off.

I haven't used TBII.

TB3 sets up quickly; it can be slowed down either by lightly moistening one surface or by diluting with clean water about 5-10%; this extends the handling time maybe double without any noticeable weakening of the resultant joint.

I mostly apply TB3 close to the edge of a ply plank to glue on a batten such as a chine log or inwale. I work with canoes a lot - thin floppy planks - so that stiffens the plank for later handling. I pull a machine bolt along the joint behind the glue aqueeze bottle as a spreader; a fine thread 1/4" bolt spreads the glue just right and I can see if I am applying enough or to much and adjust squeezing pressure on the fly. A nice little "bow wave" of glue builds up in front of the bolt and acts as a reservoir so I get even distribution, and the amount left is just enough with very little squeezeout or waste, or cleanup.

I don't trust TB3 for continuous exposure to water; when soaked it softens; it will harden when it dries but that's no help if the joint let go in the meantime. My rule is, the plank joints exposed below the wateline are done with epoxy, TB3 everywhere else. That is for boats that are dry moored. I have never had a joint failure.

However, for a boat that will stay on the water for long periods, and might get rain water in places normally dry, I would use more epoxy.

 

I use a paint roller with a short nap and it works like a charm, cleans up easy and spreads the glue evenly.

I'm still debating using the titebond products, Most of my stuff is indoor but all of my outdoor products have held up well and I've yet to have a failure even in prolonged exposure to moisture.

I suppose I could get a gallon of epoxy and see how it goes but I was hoping to simply coat the exterior in the stuff and call it good. Kinda like Guzwell did once he developed a reaction to the epoxies.

 

When I'm using Gorilla Glue I keep a spray bottle of water handy and either spray one surface with the water and apply glue to the others, or just spray the general area and apply glue. I also use it as a filler / sealer to fix gaps.

GG will expand to 3-4 times it's original volume as it dries. In the early stages of the drying process you can collapse the bubbles in the foam, but beyond a certain point I think this damages the strength of the joint. I find the best option is to squeegee the foam off with a piece of scrap wood and then take a single edge razor blade to the remnants after it dries.

A couple of other quirks...

Because it's a polyurethane product, the solvent in polyurethane coatings will dissolve it. I haven't had this be a problem in terms of joint strength, but it does leave a little bit of white stuff in the can of varnish.

Also, nothing I've found will wash it off effectively. Isopropyl alcohol will a little bit, but soap and water is just useless. If you get it on you you're just going to have to wait for it to harden and peel it off. If it gets on your clothes it's never coming out.

Personally, I love the stuff and it's my go-to produce for most wood applications, but to each their own.

 

The cold hard reality I've been trying to avoid for quite some time is that epoxy is still hands down the best material for the job. Toxic evil stuff that it is, there is simply no replacing it, cleans up with water ( before it dries ) is stronger than the wood itself, relatively impervious to water and its repairable. TB or GG or any of the others all have there drawbacks but epoxy is unfortunately ( because of its environmental effects ) still the way to go.

I'm trying to make do with TB-3 but I'm somewhat paranoid that I'm playing with my life. The creep issue I can deal with by steaming everything into position but the idea that it loosens its grip under prolonged exposure just makes me cringe.

ok we now return you to your normally scheduled programing

cheers
B

 

Agreed, Boston. I can get away with using glue like TB3 because my boats don't stay soaking in the water as they can be dry-moored after relatively short trips.

The paint roller should be great for larger areas but the screw spreader works like a charm for long narrow areas along an edge, for gluing chine logs and inwales for example. A fine thread works best, and I run a nut down it first to set the width of the glue strip. I don't have a picture (it takes both hands) but this pic shows what I'm doing. For very light boats like canoes I glue the logs and inwales while the sheer plank is flat, it is easier to get a good joint and stiffens the plank for handling later.

 

For those who are still subscribed to this thread, I have taken a short break from the build to test a modified version of the cylindrical molding method with a scale model of a similar strip-built canoe. There is a thread that starts of with a discussion and the build starts here http://www.boatdesign.net/forums/boat-design/strip-building-cylinder-mold-38132-2.html#post500642

 

I wonder if you have found out that this isn't the case yet.

The strips will not lay like the ones in the initial drawings, the will want to ride over each other as they progress around the curve of the bilges.

 

I appreciate your concern but they did lay exactly like the drawings, with no tendency for the strips to ride over each other.

AFTERTHOUGHT: RW, I realised you may have been referring to the other (Cylinder Mold) thread I have going: the problems you describe are happening there but it's a different situation to the hybrid build where I was able to clamp the strips.

 

Yup - that was the one. So many threads, so little brain ....

 

Back to work!

Finally got back to this build a few days ago. No new pics yet, I measured the hull and it seemed a bit lower than I wanted; realized the strips were 5/8 instead of the planned 3/4 so I added a couple more. Ply sheer planks are cut to shape and dry fitted: I want to glue the outwales to the sheers first to stiffen the 4 mm ply as they are 12+' long and only 3.5" wide midships . . . I don't want them to break during handling.

The 'wales will cover the edge of the ply so they'll need to be rabbeted.

Rant du jour: I am modifying my router table to handle the long rabbets - why is it most power tools come with all sorts of lawyer-approved safety gear that's often a damn nuisance, but a router table can be sold without any provision for attaching finger boards which are essential for safe work? Some genius designed the tabletop with all sorts of ribs on the underside that make it impossible to clamp a featherboard properly, and of course it is aluminum to ensure the magnetic FBs can't be used. So tomorrow is drill-and-tap day . . .

 

The best router tables I've seen are home made by experienced router users.