Thread: GIS beginners build in Concord, NH

Originally Posted by callsign222

YO

So I started gluing tonight, and I'm having problems keeping my frames from wandering after I clamp them down. What the heck?!? There's obvious some sort of physics going on here, or an alien being hiding in my workshop manipulating my cedar with his cosmic rays. Anyway, no real method to the madness, the top and bottom frames creep into the ply while the side arms tend to creep outwards. My starboard side arm on BH1 crept out enough to leave a generous gap between the top of it and the top frame. How can I prevent this? Should I be screwing these things down?

Epoxy makes a really efficient grease and magnifies any misdirectional pressures from the clamps. Mate, I suffer your frustration everytime I try to stick two things together - feel free to swear and snarl at the work The worst offenders are spring clamps which, if they go on slightly crooked, push the bits to one side *&^%$#%^&*(()

There are three techniques.
The first is to allow for the movement when you put on the clamp either by offsetting the parts to start with or angling the clamp as you put it on. Yes, this is hit and miss and something that after awhile you'd think you'd be able to do subconsciously It does work though.

The second is to use higher clamping pressures. Yes, I know all the talk about not clamping too tight and squeezing out all the glue - you've got to really try hard to do that despite the claims. I prefer to use F clamps rather than spring clamps because they allow you to lock a part into place - the trick is to stop screwing them tight just after glue starts oozing from the joint and at the point where you've got enough pressure to do the job.

The third option is to just whack in a screw. Yes, it leaves a hole to fill but it holds things nicely in whatever place it was when the screw went in ... and which you hope was the right place I don't do a lot of bright work so screw holes aren't an issue for me but even if you do, never hesitate to use a screw if you need to.

You're fighting one of the traditional battles of modern boat building. Experience will ease the problem or at least make you more adept at fighting it. In the meantime, do your best and prepare a useful collection of general purpose swear words

Richard

Originally Posted by callsign222

YO

So I started gluing tonight, and I'm having problems keeping my frames from wandering after I clamp them down. What the heck?!? There's obvious some sort of physics going on here, or an alien being hiding in my workshop manipulating my cedar with his cosmic rays. Anyway, no real method to the madness, the top and bottom frames creep into the ply while the side arms tend to creep outwards. My starboard side arm on BH1 crept out enough to leave a generous gap between the top of it and the top frame. How can I prevent this? Should I be screwing these things down?

Same happens with me and probably with many other builders. Screwing is one option, but they make bigger holes.
I do a cold fit first ( without the glue ) and drill a few 2mm holes through both surfaces if the fit is right. Then I apply glue, put both surfaces together and put a few nails ( 2mm or slightly smaller ) through these holes, leaving the heads above surface.
If you use f.e. 1.8mm nails you could slide them in place by hand. These nails are only to prevent any side movement, they are not used for pressure. You can use "whatever" clamps to get pressure. After the glue has cured you can easy remove these nails and they only leave these small 2 mm holes to be filled. This "cold fit - center holes - glu in place" trick is great to avoid lots of stress with slippery surfaces and does not add real costs. You could do similar with 1.5 drill holes, but these drills brake very easy. For me 2 mm drills are a good compromize.
I hope this helps
Succes in building!

I read on your blog that you had trouble getting stuff mixed and on the boat fast enough.

The trick I use down here on the 7th level (60+ days of 100F+):

Before I start, I have a tin can with the bag draped into it and the opening draped around the top of the can, open and ready.

Then I divide up the fillers and mix them in to the resin and the hardener separately. No rush, the clock is not ticking yet.

When they are fully mixed in, I combine the resin and hardener in a paper bowl and stir them together quickly and then scrape them into the plastic bag.

This is especially useful with mixing in stuff like the fumed silica that takes forever to get wet into the mix.

Great advice guys, thanks. I went ahead and drilled two holes per piece of frame and dropped in some 4d nails to hold the pieces laterally. Great idea that works great, I'll just go back and fill the holes with epoxy later.

I neglected to fill the small gaps that occur in between the side frames and the top and bottom frames, so I need to do that too.

How long do you keep the clamps on the project? 6hrs? 12hrs? 24hrs?

I'm itching to pull them off and clean up the squeezed out epoxy, but I don't want to do it too soon. The glue has set, nothing's going to move, but I don't know what it'll do to internal pressure blah blah blah.

ALSO, I looked all over the Duckworks site and Storer's site, but I couldn't find a good tutorial on basic wood gluing when boatbuilding. I'm finding things are a little different when I was slopping epoxy all over my Laser (#194!!!) after yet another collision at speed with submerged object/dock/ground after falling off car while driving/etc. etc. etc. Anyone know of any? Too late now for me, but it would be nice to put it on my blog at least.

If I am gluing with epoxy, I normally do not put that much pressure. The gap needs to be filled, do not squeeze all epoxy out. If epoxy is not sticky anymore I remove clamps, but I am still carefull not to put too much force on it. At that stage it's easy to remove (cut away) epoxy that has been squeezed out. Before you put full force on it, is has to be fully cured, depending on temperature that can take 24 hours or more.

NB this is not a "proffesional" advice, it's just what I do and it seems to work.

Good Luck

Originally Posted by callsign222

YO

So I started gluing tonight, and I'm having problems keeping my frames from wandering after I clamp them down. What the heck?!? There's obvious some sort of physics going on here, or an alien being hiding in my workshop manipulating my cedar with his cosmic rays. Anyway, no real method to the madness, the top and bottom frames creep into the ply while the side arms tend to creep outwards. My starboard side arm on BH1 crept out enough to leave a generous gap between the top of it and the top frame. How can I prevent this? Should I be screwing these things down?

G'day!

Sorry I'm weighing in a bit late, but a simple trick is to drive a very small panel pin into one of the faces to be glued. Don't drive right through, just 1/4 inch or so! Then simply snip off the pin, leaving only 1mm or so protruding. When you mate the surfaces the pins stop them sliding. It's also invisible and you have no nail or screw hole to fill.

This works pretty well when you are laminating and you have a number of pieces all wanting to move at once, as with the foils etc. I used it for repairs to cricket bats when I had odd shapes to clamp. Also, if the timber has to be machined, the small pins won't damage blades etc.

For boat building you can use brass or copper pins or wire if you don't want to run the risk of a stain down the track. (Unlikely anyway because the pin is embedded in the timber and doesn't break the surface).

Hope this helps...

Funny thing about small holes like nail holes, they can be a lot harder to fill than a bigger hole such as a screw hole - just scraping some goop over the top usually isn't enough ... and man will I be filling holes in the Little Black Dog - fortunately, many will be under glass tape

Richard

I don't know how many of these fine folks are also following your blog (I am), but may I say... PLEASE USE A RESPIRATOR when handling the silica and other epoxy fillers... you don't really want to risk COPD or other respitory problems from your hobby... millions of folks found out the hard way with their jobs.

jtz

Regarding your question about cure time for epoxy--the manufacturers usually provide a chart of cure times for their products, at a range of temperatures. There is a lot of variation between the time-to-cure at, say, 60 degrees and 85 degrees. Use that chart as a guide for when to pull the clamps.

If you've used any assembly screws back them out just a little when you're around 80 percent of full cure time. Do it one screw at a time and drive each one back in before moving to the next one. This will break the bond to the screw shank. Once you've done that the screws can stay in forever and still come out easily.

I'm working with MAS resin and their medium hardener. The temp in my "shop" is whatever it happens to be in the house, usually around 74 or 75. After gluing and clamping and screwing some part I will make a mental note of the time and, 6 to 8 hours later I'll go do the screw business--back out 1/8 inch then drive them back home. If the part isn't under a lot of stress and I want to move on to the next stage I am comfortable with removing the clamps after about 20 hours. If the part is highly stressed I will wait 2 days.

When you're having trouble mixing and applying epoxy without it going off you're usually mixing too much at a time. A half-cup batch will go off in the cup about twice as fast as quarter-cup batch. If you must mix large batches get the proper slow hardener for your resin and set the mixed epoxy cup in a tray of ice water. With my MAS resin and medium hardener I will not mix more than 2 strokes of the pump at a time if it is going to be thickened. You can mix larger batches of pure epoxy (for sealing, etc.) if you pour the stuff out and spread it with a squeegee. One more factor that affects how fast the stuff goes off is the size of the mixing cup. It will go off quicker in a tall and narrow cup than it will in a wide and flatter cup. In other words, even a smallish batch that is 1 1/2 inches deep will go off much quicker than that same size batch in a wider cup so it's only 1/2 or 3/4 inch deep.

Great advice here guys, thanks a lot. I've been using 1 to 2 pumps now of resin and the reaction has slowed way down, I also try to spread it around quick too.

I definitely pulled my clamps off well before 20 hrs. oops.

confusedSea, thanks for a head's up, that was probably the most valuable advice I have received. I'm going downtown right now to go get one. A little research on silica-based pulmonary problems was enough to convince me. My Uncle was a stone-cutter/glass-cutter/concrete-cutter/etc.etc. and he died a horrible death related to this stuff. (Of course over a lifetime of work) I'm surprised I didn't make the connection sooner.

Again though, does anyone know a location for a rudimentary primer/tutorial on wood gluing and boat building?

20 hours is not always necessary but is a good guideline. I always use my fingernail and try to drive it into the glue ooze. If you feel any elasticity at all (ie it is not rocklike) then it might not be safe to remove clamps if the piece is under stress. However if the stress is low (inwale blocks preglued to the inwale) some elasticity might be OK.
MIK

Oops. I hope Bulkhead #3 isn't too stressed!

I may be confused but it sounds like you're gluing frames to the bulkheads, not assembling the frames and side panels. If so, you're probably OK. That is all flat work so there is very little stress involved.

When it's time to attach the sides and frames here is what I would recommend: Dry assemble the sides to the stem being very careful to get them right. A tiny misalignment at the stem translates to a pretty big error at the after end. Once you know the stem is vertical and the sides run true take one side off and apply the thickened pox, then screw it back in place. Do the same for the other side then re-check to make sure it's still true. Even though you're using the same screw holes the wood can shift a little (the epoxy is slippery).

Let the cure at the stem continue for at least two days. That piece will be very highly stressed when you start pulling the sides in around the bulkheads. If you've broken the screw-epoxy bonds you can leave the screws in place indefinitely to supplement the epoxy bond. Then start installing the bulkheads one at a time, working front to back. You don't need to wait for the epoxy to cure at this point. Work as fast or slowly as you want

I struggled with a variety of bar clamps when I was doing this assembly but the strap clamps some have shown on here would make the job much easier--I wish I had thought of it. When you get to the transom leave the straps or other clamps in place for a couple days. Like the stem, there's a lot of stress at the transom.

This is another of those threads loaded with many ideas, tips and techniques!

To those who have been down the road ahead of the rest of us, Thank you for the help!

Bob