PK78--First time builder progress report and recommendations

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Stainless
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PK78--First time builder progress report and recommendations

Post by Stainless »

This is my first stitch and glue project. I'm a reasonably competent woodworker (I've built houses and furniture). HOWEVER, I'm probably much more particular about the quality of my work than many people--certainly much more than is needed to build a seaworthy boat. Please bear this in mind when reading the rest of my ramblings.

I am building from fir marine plywood with 3/8" frames and transoms. I have completed all of the "stitching." This puts me, by my estimation, about 30% through the building process. I would say I'm about 20hrs into the project. As I said, I'm particular and a bit fastidious.

1. Read the directions. All of them. Read them again! Stop at every phase and read them again. This is especially true if you're building the sailing version because the prose isn't that clear (the sailing version directions are not well integrated into the main directions).

2. Plan on splinters from the wood and scratches from the wires. All other shop safety rules (eye protection, ear protection, dust masks, etc.) fully apply. Be Safe!

3. You're going to loft. The good news is, this isn't hard, and you'll get a much better set of lines on the plywood than through any pattern transfer method that I'm aware of. If there's interest, I can write up instructions on how to do this.

4. I bought the Skil 5.5" circular saw (trim) saw. Home Depot carries it at a great price. Blades are a little tricky to come by, but Orchard Supply Hardware carries a plywood blade that fits it. This combination yields a saw that is light and maneuverable and gives very clean smooth cuts. I highly recommend it.

5. Forget nailing or screwing the frames to the sides. I tried that and it caused me nothing but trouble. 3/8" plywood won't hold much of anything in the plys (endgrain). Stitch the frames to the sides. That means a hole about 1/4" on either side of the frame and one through the frame. Run the wire through all of the holes and twist it up. Two stitches per frame is plenty.

6. For drilling the stitching holes, build a jig. It astounds me that this is not part of the standard process and tutorial. I wish I had a way to attach a picture or two, but let me try to describe it. The jig is a piece of junk wood about 5" to 6" long and 3" to 6" wide. Along the long edge, glue a 1/4" to 1/2" straight strip of something. Then at about 3/8" in from the inside edge of that strip drill two holes 4" apart. The holes need to be the size of the holes you will be drilling in the plywood. To use the jig, you measure the location of the first hole and drill it. Then you put the jig on the plywood so that the strip hangs over the edge. Take a nail (put some tape or something on the head to make it easy to grab), and put it through one of the holes in the jig and through the hole in the plywood. Hold the jig against the plywood, and drill through the other hole in jig--this will be 4" from your first hole. Pull the nail out of the hole, slide the jig to the new hole, but the nail through the jig and the new hole and drill again. You just work your way along the edge until you are done. It is very easy and almost foolproof. I had my 11year old son do most of the drilling for the sides and bottom panels.

7. As a further time saver, clamp the side panels together and drill the holes through both at the same time. Same for the bottom panels.

8. The centerboard trunk cutout is 1" plus 2x the thickness of the material being used. The dimensions for the cutout are not given in the plans (but lines are shown). You may want to build the trunk first and take the dimension directly from what you have built. You don't have to be too fancy with tabs. Just cut from the bottom of the center frame up about 6". It's easiest to do these measurements while you're laying out the frame, and do the cuts as part of cutting out the frame (don't ask).

9. Vice grips make twisting the wires easier. Cross the wires and then pinch the cross with the vice grips. Twist the vice grips. Less strain on your hands and you can focus on getting an even twist.

10. Stitch the seams up loosely and then go back and tighten to the final seam. When tightening, work from the center to the ends. After tightening a half dozen or so stitches on one side of the boat, go and do the same to the other side of the boat. This will keep things from becoming twisted (when I measured the diagonals for the first time, my boat was less only 1/8" out of square).


I have mentally broken the project into 3 more major phases: Epoxying,
Fitting and Finishing, and Rigging, All try to update this thread as I get through each of those phases.

I hope this was interesting or even helpful.


Cheers.



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Post by Rick »

These are clear, helpful suggestions. Thanks for taking the time to write them up.

I have a couple of comments on your hole-drilling jig. First, 3/8" from the edge of the plywood to the edge of the stitch hole is a l-o-n-g way. I would recommend more like 1/8" or 3/16". You will appreciate this when you start your fillets. The closer your holes to the edge, the smaller the fillets you can make. Small fillets are better.

Second, stitch holes every 4" are way too close together. I used 18" on the NC16s I built and supervised building, and my PK78 holes at 6-8" are too close together. For the PK78 I would start at every 9-10" and be prepared to drill a few more at high stress spots when you start stitching the boat together. You really cannot screw this process up, and everything you are doing at the stitches is covered later.

I use a bunch of jigs in furniture work, but you just don't need that much precision at this stage of the game. I would save the nice woodworking for seat tops, rub strips, breasthooks, transom knees, and your spars and blades. No one will ever see tidy stitch holes.

Have fun, and I really hope you aren't offended by this. It's taken me 10 stitch and glue boats before I really relaxed about this stuff. I've built about 20 bookcases (I'm an amatuer woodworker, not a pro), and I'm finally about as relaxed about building small boats as I am about bookcases.

I've started to wonder about making a dresser for my 14-year-old son out of stitch-and-glue plywood...

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Post by Stainless »

Not offended in the least.

Don't know about the spacing off of the edge for the holes... This is fir plywood. It's pretty stiff. I'd be worried about tearing them out at 1/8". Maybe a 1/4" would work.

Stitch holes at 4" are what the plans call for. When in doubt, follow the instructions. :wink: Also and again, the fir plywood that I have just doesn't like to bend. I suppose that amidships I could have gotten away with 6-8" spacing, but at some of the ends, I had to go to 2" spacing to get nice fair seams.

Yes, it's going to suck come seaming time... I have planned on using the "spot weld" procedure. I have to remove the wires because they are galvanized steel (and water will get to them even if they are encased in epoxy). Because of all of the stress on the wires, I'm worried about the spot welds holding. I'm thinking that I might have to epoxy over them and heat the wires to remove them instead.

The jig that I describe is not perfectly precise, but it's fast and pretty much idiot proof (as long as you are careful with where you set your origin). Building a longer jig with various hole spacings wouldn't be that hard either. We started out trying to measure along the edges, but we found that measuring along the curved surfaces was a pain. Sliding the jig along worked great. I can't imagine a better way, but if you have another way that works better for you, then use it.

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Post by Johnmon »

Stainless wrote:Not offended in the least.

Don't know about the spacing off of the edge for the holes... This is fir plywood. It's pretty stiff. I'd be worried about tearing them out at 1/8". Maybe a 1/4" would work.

Stitch holes at 4" are what the plans call for. When in doubt, follow the instructions.
Everyone will do theirs how they feel is best and it seems like it will really depend on the boat a lot. For smaller boats or places on larger boats where there is a lot of curve, you will probably put your stitches closer together. On long, relatively straight stretches, you will not need so many.

I personally really like the plastic zip ties except that I tend to over torque and break them sometimes.

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Post by Stainless »

Johnmon, what size of ties do you use and what diameter of holes do you drill? I started with zip ties and the ones that fit through the size of holes that I wanted to drill weren't strong enough. The ones that were strong enough required displeasingly large holes. That's why I went with wire.

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Post by st »

A note here that cable ties are not all created equal. You can't buy a bag from the dollar shop and expect high strength. Make sure you buy proper cable ties, electrical suppliers are a good place to shop. Bags I have show product details such as length, width, tensile strength and whether they are UV stabilized.

Scott.

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Post by Johnmon »

Stainless wrote:Johnmon, what size of ties do you use and what diameter of holes do you drill? I started with zip ties and the ones that fit through the size of holes that I wanted to drill weren't strong enough. The ones that were strong enough required displeasingly large holes. That's why I went with wire.
I used the smaller ones for most of my stitches and then went with the bigger ones as needed. It seems like I used a 3/16 drill bit which was a little small for the larger ties, but I forced them. There can be a strength issue, but as Scott said, you can look at the tensile rating and get ones that take more force. I wasn't too worried about hole size since the holes get filled with putty anyway.

I was a little aprehensive about using wire just because of the possibility of corosion. Depending on what you use(or if you can get the wires out) it might not matter. I saw on a video(put out by GlenL) that you can heat the putty up with a heat gun and pull the wires out if you use something like steel.

John

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Wire ties...a bit of history

Post by JustRight »

I've never had a problem pulling metal wire ties. Of course, I don't fillet over the ties, just tack between.

I built my first stitch and glue boat in the early 70's, perhaps so long ago that the plastic wire ties hadn't been invented yet. At that time, the idea was to use copper wire so it could be clipped off and left in the epoxy joint. The copper was tough to work with since it tended to stretch and break. I switched to soft annealed iron wire, commonly called stove pipe wire. It is strong, cheap and easy to pull out. I find that I can really torque down on a wire when I need too. Also, the wire tie is formable so I can align the panels rather than having to rely on a wood to wood joint to give the desired shape.

Another discovery on my second taped seam dinghy, was to build what Jacques now calls a basket mold. With the simple female mold, very few ties are needed. It is a tradeoff in time to construct the basket mold over having to work with perhaps three times as many ties and then have to true up the wired hull before filleting. With a larger hull like the Vagabond, particularly with the long 1/4 inch ply panels, truing up the chine joints without a basket mold would seem difficult to me.

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Post by Stainless »

It's been a while. Here is my update on the "Epoxy Phase" of building my PK78. This also includes some further construction notes as the building process doesn't neatly break separate into woodwork and epoxy work. Same caveats as last time with the additional note that I have not worked extensively with expoxy or fiberglass previous to this effort.

As I said, this was my first serious experience with this process, so I learned a lot. Weather during this work was mid-70's to mid-60's. Moderate humidity. (Coastal south-central California Aug/Sept/Oct.) I started with an "Epoxy Kit" order from Jacques. I ran out of a number of supplies. I have been buying additional supplies .
Let me say here that my hat is off to ANYONE who can complete one of these boats in the time budget given in the plans with an attractive finish. I have put in at least 20 hrs since my last write up, and I can see that I probably have that much still to go. If I was sloppy or didn't care about filling in the fiberglass weave, I guess I could finish much sooner. I would guess I'll have close to 80hrs into the boat by the time it is totally complete.

Here's what I have done thus far. I will follow with my list of observations/suggestions.

- "Painted" epoxy into all of the joints to coat the wood.
- Put in a small fillet--about a 3/8" radius--interrupted by the wire stitches.
- Removed the wires by cutting them on the inside and pulling them out from the outside. Because the holes were so far from the seam, the wires weren't in the small fillet.
- Put in the full size fillet (1" radius) on the longitudinal hull seams a the bow and stern bulkhead seams.
- Applied the fiberglass tape to all seams with full size fillets.
- Turned the boat over and ground radius on all the exterior seams.
- Applied fiberglass tape to all exterior seams.
- Turned the boat over and put full size fillets on remaining bulkheads.
- Applied fiberglass tape to all seams.
- Cut out seat tops.
- Fit seat tops to seats.
- Built daggerboard trunk.
- Put the cleats on the bulkheads.
- Filled stern seat space with flotation foam.
- Cut mid bulkhead and placed trunk.
- Filleted in trunk (3/8" radius).
- Applied tape to trunk fillets.
- Cut out daggerboard hole in hull.
- Filled bow seat space with foam.
- Faired daggerboard hole.
- Have just begun fairing the fiberglass tape weave.


0. Small batches of expoxy are good. You can't get too much wrong, and also the whole exothermic heat problem is more manageable. I most usually mix 3 oz batches, occasionally 6 oz batches, and I gave up on the 9 oz batches.

1. I made some fillet shapers out of 2" plastic putty knives. I cut the end of them round. One at about a 3/8" to 1/2" radius and the other to a 1" radius. These worked very well. I "discovered" the filletting method described by the Gougeon Bros. in their book on boat building (which I just acquired and read last week). It is succintly described in figure 18 of chapter 9. I recommend it.

2. I tried the "plastic bag as a pastry bag" approach to putting the putty in the seams. It worked well for the small fillets. It didn't work very well for the larger fillets. I found that for the larger fillets that it worked best to use the spreader/shaper to just scoop out the putty and wipe it into the seam for further shaping.

3. In an earlier discussion about wire stitching, a correspondent opined that I would be unhappy with how far from the seam that I put the holes for the wires. This was not the case. Because the holes were so far away, the wires were not in the smaller fillet, and thus they were very easy to remove. For people that are planning to remove the wires, I very much recommend putting them 3/8" or more from the seams.

4. Making up the wood flour putty to the right consistency is an interesting challenge. When mixed on the thinner side, it self-levels to a very nice smooth surface. The downside is that it also sags out of any vertical joint. When mixed thick, it doesn't sag, but you end up with a rough surface after shaping. For the first quart of wood flour, I just guestimated. Then I ran out... Which brings us to my next observation:

5. The epoxy kit may not have enough material in it. I'm pretty careful, and not wasteful by nature. As best I can figure, the 1" radius fillets just consume a fair bit of material. Maybe I'm getting a lot of loss due to the small batches. I don't know. I do recommend that a builder early on figure out where they will source additional material if needed. I didn't do this, and it caused extra delay.

6. When I ordered more wood flour, I also order some other fillers/modifiers. I have been using a wood flour/cab-o-sil mixture for the remaining seams that I'm pretty happy with. It is 1/2 epoxy volume of cab-o-sil and 1 epoxy volume of wood flour. It doesn't sag, it has a fairly smooth finish and it is nicely workable. For the best tape joints, it still seems to need a little bit of sanding though.

7. I used the dry method of applying the fiberglass tape. I put epoxy on the seam, then the dry tape, and then worked epoxy into the tape. I like the method.

8. I found that it worked well to apply the first coat of epoxy about 1-1.5 hrs before putting the tape on the joint. The epoxy was very tacky at that point, but still workable. This made placing the tape easier.

9. I spread the epoxy over the tape with a 1" foam brush. This worked well, but I had to be careful not to work small air bubbles into the epoxy.

10. Rollers are nice, but not as useful as fingers (in gloves) and a 4" spreader. I found that I could work bubbles and smooth things best by holding the center with my finger and very gently spreading to the edge with the spreader.

11. Exterior corners are so very much easier than interior ones.

12. The interior seams around the daggerboard trunk were the most difficult. Deeply inside the boat they were difficult to get to. Also, many of them were purely vertical.

13. The selvedge of the tape is obnoxious. I tried cutting it off for some seams, but this causes the tape to come apart while spreading epoxy into the tape. I tried cutting it off while the epoxy was still soft, but that was still a bit rough. I gave all of that up and have been grinding it off.

14. Rotary rasps in my pneumatic die grinder work very well for shaping any part of the boat thus encountered. One of the best things about them is that most of the dust the produce is fairly large particle. Grinding the selvedge off with the rasps was much less itchy than using the sander to grind it off. I didn't try my angle grinder, but I can't imagine it being better.

15. The seat patterns provided in the plans didn't fit very well at all. I am skeptical that they would fit properly for anyone. To begin with, they don't properly allow for the 3" tabs of the bulkheads up the sides. They weren't a bad starting place, but I'm going to have to think about a better way to shape seats in the future.

16. The floatation foam is nasty stuff. I was a little paranoid about having it burst the seat boxes, so I poured without the tops being on the seats. It is impossible to get a nice level top that way, so I had to cut/shape the top. I got what I needed, but I don't like working with the dust generated-it is gritty and sharp.

17. I used my rotary rasps to grind out the hole for the daggerboard. I didn't think that I could get the trunk perfectly aligned, so I put the trunk on and cut the hole to the trunk. It worked OK, but grinding to nice straight lines is a challenge. I think that next time I'll cut the hole first with a saw and then use a jig to align the trunk.

18. I suck at cutting all of the swoopy curves that are in the plans for the seat tops--especially for the bow seat. Maybe it's just lack of practice, but what I got the first time out was atrocious. I'm redesigning the bow seat to something that I can cut and like the looks of.

19. I still don't like working with fiberglass. My first tape joints were ugly. My last ones were beautiful. I expected this, and so my first joints were in the places where I knew I would be pouring the flotation foam. No one will ever see them.

20. Working with epoxy is like performance art. Know your lines and hit your marks. You have to get started and just keep going. Once you start, you have to keep going and not waste time. It can be a little stressful. Medium speed hardner was a little fast for the warmer temperatures that I encountered--especially when I just starting out and learning as I went.

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Post by MNagy »

Stainless, thanks for posting your experiences and reccommendations. They are helping me a lot as I get going on my first boat.

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