DN NA Class

Other than "use West System epoxy and never look back," does anyone have any advice on using other glues, at least for some specific applications when assembling a DN? It's my understanding that West System, Gorilla Glue (polyurethane), and Titebond III (PVA) are all waterproof and stronger than the wood once cured.

There's some data here:
http://www.woodworkingadvice.com/pva-glue/strength-of-glues.html
www.titebond.com/Download/pdf/HowStrongisYourGlue_FWW.pdf

From what I've seen, success depends more on my ability to properly clamp things (and there are some difficult-to-clamp angles when building a DN) than anything else. It also depends on having a good mechanical fit before gluing. I've also seen my glue survive (in this case it was West System) and the glue in the plywood fail between layers. Makes me want to use dowels in some strategic places.

I'd like to be able to occasionally use a glue like Titebond III for convenience (rather than trying to mix up a small batch of epoxy) and still be confident in the joint strength. Yes, I know you can't make a fillet with PVA like you can with thickened epoxy. I also realize that a small digital scale is a great help in mixing small batches of epoxy.

Advice; comments?

    A good friend of mine is a professional wooden boat builder. He informed me that Titebond III, as long as you can get proper clamping pressure, creates as strong a bond as West ( he uses gallons of West a year and is even a dealer for it). I've build over 20 DN hulls and I use it in places like mast step blocks, nose and tail blocks and other such parts. Glue is considerably lighter and cheaper then epoxy. Though it might work, I'd be reluctant to use in in parts that flex a lot like planks, although before epoxy, planks were made with glues.

I'll echo what Bob said and go a little further. I wouldn't use poly type glues at all. These are proving to be not nearly as robust or water resistant as their marketing suggests. Since the stuff is as expensive as no-name brands of epoxy I can't see any reason to take a chance on them.

I would use Titebond III in any situation where I was gluing long grain to long grain and had a good fit. I would always use epoxy when glue short grain to long grain, such as bulkheads to sideboards. I always coat the end grain with straight epoxy and let it soak in for a few minutes. This is very important! Then glue as usual with thickened epoxy. Eight boats and no joint failures later I’m very confident this approach works. I also use epoxy in any cross grain scenario but I don’t have any proof this is better than Titebond. I just think epoxy stays a little more flexible and will cope with expansion more easily.  Incidentally cab-o-sil type thickeners work fine with Titebond, I just wouldn’t make fillets with the mixture.

Weighing epoxy is a fine way of calibrating mixes but I’ve used mustard pumps for ten years and never had a single epoxy failure. Just be diligent in counting the strokes and you won’t go wrong. I found that by marking calibration lines on the pump plungers I can make tiny batches of epoxy.

Dusty,
     Would you be confident using titebond III for planks, springboards and other items that are going to need to flex?

Milo

I'm confident that TBIII would work for any laminating situation where the mating surfaces are milled flat. I've never built a plank with it but I have used it to build a set of curved akas for a trimaran. I don't know if the forces on an aka and a plank are comparable but I do know that the forces on the akas are considerable. I'm quite sure the wood on my akas will break before the glue fails and have been in sailing scenarios where I had to absolutely trust them not breaking.

If you use TBIII for plank construction make sure you have enough clamps and cauls to clamp every six inches at least and double that amount wouldn't hurt. You can make good cheap ones from 2x stock and threaded rod, washers and nuts. TBIII works best in a very thin layer and I doubt you can overclamp it. Not so with epoxy where you need a healthy layer or else the joint will be starved.

The only problem I can see using TBIII for plank construction is the shorter open time. If you are laying up strips you will have to move very fast. Slow speed epoxy allows an almost leisurely pace.

  On a semi related thought, several years ago in the West System magazine"Epoxy Works", they had a helpful hint on how to measure small quantities of epoxy without waste. Take any kind of syringe with divisions on it and cut off the end (obviously the needle end). You then, in the case of West, fill it with 4 or 5 divisions of resin and one division of hardener.The syringes I have when filled like this equal 1/3 pump of epoxy. I've halved this with no problem. I hope this is helpful.
   By the way never use Titebond for end grain gluing.
                                                                            Bob

Thanks, I'll try that on my next boat and see how it works.

When I built my last hull, I was concerned about the unsupported roundy end of the seat back.  I trimmed up a small 3/4 by 3/4 inch chunk of wood, painted it black, and put it in place with super glue (cryno-acro-cyanate?) Its still in place after three hard seasons.

A friend has just finished two hulls with 'knees' that are really laminated frames - they satisfy both the knee requirement and provide a cockpit floor 'rack'.  The radii at the floor/side joint is rather tight so he soaked his laminations in water, and then used Gorilla Glue the next day (his laminations looked to be between 1/16 and 1/8 of an inch).  It's a good use for a glue like polyurethane that requires moisture to cure.  Epoxy might not have (wouldn't have?) worked with such wet laminates.  I have no idea how these laminations will survive over time, but the application seems logical.  I will probably do the same for my next hull (whenever that is - my current one is 15 years old.  I have a box of fittings to shame myself into getting started ....)

Warren Nethercote, KC 3786

Measuring tips Go to baking isle in food store and pick up small set of measuring  spoons
tey go done to a tea spoon  just use same measure for  resin and hardener in appropriate ratio.
Also i us a lot  of small plastic cups, just draw a line on side use proper ratios.