S10N - Seeking gunwale Advice

[Tumalo]

Hi All,

Me again.  Boat is coming along but I've run into a bit of a mental hangup.  Hoping to get some advice as there isn't much direction in my plans or "instructions".  I'm trying to figure out the gunwales for my Spindrift.  My plans and supply list would seem to imply I construct a gunwale using a single piece of 1x2 stock.  However, I noticed on the boards lots of references to "laminating" stock to form a 1x2 which has me confused.

So can I take a single piece of stock and create my gunwale or do I need to form laminate strips using stock I'm interested in using.  While on the subject of stock what would be some suggestions for forming a very basic gunwale if I can indeed us single stock.  Would 1x2 strips of Alder work?

Thanks in advance,

Chuck

[brucee]

I laminated the gunwales for my S10N using 1/4 x 1" strips.  There was a fair amount of force required to get the laminated to bend along the sheerline curve and the bow to stern curvehull curve.  I am getting near doing the big cut into two halves but other projects and cold weather have put things on hold.  Two of my buddies used 1/2 x 1" successfully.

Good luck!

Bruce

[Hirilonde]

I used a single piece of Douglas Fir.  The bend is not so drastic as to require strips.

[Howard]

Don't know if the plans have changed, but my S10n plans called for laminated strips of 1/4" x 1". What wood you use may depend on what you intend to do with them. Are you going to nail on a piece of split fire hose to serve as a bumper and paint or finish bright, or??? The original suggestion was to find a long enough piece of flat sawn CCA "treated" yellow pine lumber. Flat sawn means once you rip the strips from that board, the grain is more or less quarter sawn as you would want it to be. Not sure if the new treated lumber is compatible enough with epoxy to use it. But CCA presumed you would be nailing a bumper to it, so the treated lumber was to prevent rot in the nail holes. If you don't intend to nail bumpers to it, options open up. Painted or bright? I found a piece of old swamp cypress and finished mine bright. Doug fir would work too, as would a variety of cedars.

At the bow, there is a fair amount of twist in a very short span of 2 to 3 feet from the bow. Laminated strips help you make that bend. This same twist that has to be forced in also has the potential to distort the hull shape, racking it out of a symmetrical shape. The solution to that is to do both sides at the same time. Clamp one side a few inches, then the other. I worked from aft to towards the bow.

Next problem is that once the "buttered up" strips come together, the epoxy makes them slip and slide all over the place. To solve that, I suggest you dry fit them in place and while in place, fit a series of small blocks to the side of the hull along the bottom of the strips. Maybe 2 to 3 foot intervals aft and as close as a foot or so at the bow. These will permit you to clamp sideways to the hull and the blocks will provide a shelf for the strips to rest upon to even them up. That way, they will come right to the edge of the hull where you want them and a clamp or two down to the blocks, especially in the bow area, will keep them in place. Remember, its side to side, back to front. Can be a real fire drill for one person. You will have to thread the strips through the block clamps, which itself is a helping hand to get control of them.

Lastly, the clamping force to get the strips to take the twist can be substantial at the bow. So much so, it's easy to squeeze out all the epoxy, leaving a starved and weak joint that will come apart on you. I suggest you mix in some "spacers" in your epoxy mix. I use a couple items. One is the plastic granules System 3 sells as non skid. They resemble table sugar. The other is 30/100 size ground walnut shell. The purpose of these is to act as a spacer to allow you to exert considerable clamping pressure, but still have adequate epoxy in the joint to hold. The "gritty" texture of these serves a duel purpose of locking the strips on place so they don't slide around as much.

The plastic granules or walnut shell are both machinable, meaning they could be cut, planed, sanded, etc. without harming tools as sand would do.

Using the blocks and grit in the epoxy mix makes all the difference in the world on how these will turn out for you.

[Tumalo]

Thanks guys . . .very helpful info.  Love the "gritty" trick!  An additional follow on question I have is whether or not to put the gunwales on before fillets or after?  My plans/instructions suggest the gunwales be put on prior to fillets/taping to assist with squaring/shaping the boat but I've noticed several pictures of builds on the board where folks appear to fillet before gunwales are added. 

Thoughts?  Fillets before or after gunwales?

Thanks again ...I'll post some pictures soon.

Best,

Chuck

[Howard]

Stick with the plans.

There are two times you get to "shape" the boat. The first is when you stitch the panels together. As long as you cut the panels out the same and didn't do anything crazy, that should take care of itself. I might make sure my stitches are snug, but would not tape it up just yet.

The second is when you install the gunwales. Once those are in place, your shape is pretty much set. Again, do them side to side so you don't rack the sides out of shape. I'd even take the laminations clear to the front, and hold off on the final snugging down of clamps until I had convinced myself it was till in good symmetry. Depending on your stock of clamps, you can use those simple PVC clamps aft of amidships. Those are mostly straight runs with little stress. Save the real clamps for the bow section.

BTW, forgot to mention the need for something like duct tape over your position blocks so you laminations don't stick. I assume you knew that, but a reminder may not hurt.

BTW, once the gunwales are on and the seams taped, you have a boat that would float. Not finished by a long shot, but a boat just the same. There are people who have made it from Cuba to Florida on less!  :shock:

[Hirilonde]

The original suggestion was to find a long enough piece of flat sawn CCA "treated" yellow pine lumber.

CCA treated lumber is no longer available, at leastnot to the general public.  The new treating chemical is supposedly safer.  Hopefully it stands up over time as well.

[Howard]

My concern about the new treated lumber and old CCA is not what it's treated with, but that epoxy would stick to the old CCA and based on my tests, does not stick to the new stuff.

I glued up some test planks (sold as 5/4 treated deck lumber) and stressed the epoxy glue joints and they gave way like the wood had been waxed. Most woods will splinter, leaving the glue line intact. This stuff did not. And it didn't take much force to get them to part company.

[Hirilonde]

Treated lumber takes 6 months to dry after treatment.  Most of the time the lumber available is barely a month out of the tanks.  This may have a lot to do with the problem of gluing.

Why do you want to use treated lumber any way?  You can buy untreated SYP.

[Howard]

As I recall, using treated lumber for the gunwales was recommended in the plans IF you intended to use a piece of split fire hose for a bumber/rub guard. Fire hose is nailed on and the nail holes draw water which may get rot started unless the wood is treated or some really rot resistant wood is used.

Having said that, I didn't use treated and I have not seen many pictures of Spindrifts with fire hose bumpers.

[Hirilonde]

Here is a picture of my Spindrift 9N with fendering all the way around.  It is screwed every 4 inches.  I did not use treated.  So far no sign of rot, but using treated is a thought worth considering.  But I would have to know that it could successfully be glued first or it would cause more problems than it remedied.   

[Palolo Hawaii]

Sharp dinghy.

I'm liking the inset dark wood detailing on the thwart and the boom tapered to both ends. So many small craft end up with untapered spars, seeing them even on the small boats is refreshing.

The little stuff adds so much.

Those sawhorse hydrofoils look like they need some angle-of-attack tuning to generate lift, though. 

cheers,

pat.

[Hirilonde]

Thanks Pat.  The insets for the center seat is structural actually.  The Port Orford Cedar I had was a bit checked and the mahogany is to reinforce it.  The tapered boom is right out of the plans, so credit for that goes to Graham.