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Princess 26


Howard

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Have moved on to marking out the transom and bulkheads. Plans suggest fitting as may of the cleats in place as possible before installing, as they are easier to get to now and will stiffen up the bulkheads and keep them flat and true going in.

 

At least three of these bulkheads will need cabin or deck beams installed. These have to conform to the curvature of the coachroof or decks and I'm using laminated beams. Plans call for these to be 3/4" x 1 1/2", but with 3/8" plywood tops on both decks and coachroof. Original plans do not call for insulated decks or coachroof, but I intend to install foam insulation in both, at least in the cabin areas. Foam deadens the sound, but also helps avoid condensation.  Even with foam, I'm sticking with 3/8" on the decks, but on the cabin, I was going to use a sandwich of 3/16" plywood, foam and 3/16" plywood.

 

For those who have experience in this, what thickness of foam is needed and do the beams still need to be 1 1/2" thick?  Also, what foam, exactly? Is this the same pink or blue stuff (Owens Corning or Dow) sold at home improvement stores or something else? If the pink stuff works, I can get thickenss of 3/4", 1", 1 1/2". The 3/4" is 25 psi density.......the others 15 psi. If left to my own designs (which is a WAG.......not good), I'm thinking 3/16" inner ply, mounted between the cabin beams, 1" pink stuff and an outer skin of 3/16" over the top of this. The inner surfaces painted white, with a thin strip of varnished hardwood on the seams. No exposed cabin beams to conk your head on, but not plain Jane interior either.

 

Any suggestions?

 

BTW, did a test run lamination for the beam to fit BH#1 (a complicated piece of work). Since each beam is unique, rather than cutting out a jig, I marked out the laminations and laminated directly to finish nails along the points.......rather to finish nails offset the width of the lamination, and laminated outside those. That didn't work, as the geometry was off and left the lamination too flat.  Will try it again, with lamination to the inside where it should finish up where it belongs. I have about 10 of these to do, so want to get it right.

 

 

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BTW, related to Brent's question about getting the tabernacles installed plumb, I intend to have my tabernacles built and dry fitted true and square to their bulkheads before the bulkheads are installed, up to and including pre-drilling the holes. If all goes well, when it comes time to install them,  and it may be as simple as dropping them in and screwing them into place.

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  • 2 weeks later...

On the foam core decks, got a chance to build a mockup using the schedule outlined above. Basically, 3/4" x 1 1/2" laminated deck beams, an inner plywood layer; foam core, layer of light biaxial glass, then the plywood deck.  The inner plywood layer, the one exposed inside the cabin, is covered with Formica plastic laminate (mockup used some old scrap Formica I had laying around), and the only exposed deck beams would be thin hardwood strips (the last or bottom laminate layer of the deck beam), just wide enough to create a shelf upon which the inner plywood rests. I had never tried gluing Formica to plywood, but it seems to work well and really stiffens it up. This type of thin panel will take a gentle curve, but just barely. By splitting the plywood up and using 3/16" on top and bottom, about the only weight that is added is for the foam core. The mockup is incredibly strong. At 200 pounds, I was able to stand on it in the middle and it didn't even budge.

 

This compares to the designed structure of the same deck beams, capped by 3/8" plywood.........deck beams exposed and no insulation. I don't think the pink stuff has much strength, beyond compression strength, but does add the insulation to deaden sound and to avoid condensation. And with only minimal exposure to the hardwood strips, less to conk your head on. My guess is the strength comes from the I-beam affect of the two plywood layers, fixed in place with a substantial curve, which this deck design has.

 

A little more labor intensive to build, but that would probably be cancelled out by having the Formica headliner instead of a paint job and would be pretty much bomb proof for the life of the boat.

 

Again, this all may seem premature, but I wanted to figure out the laminate schedule I was going to use so I can go ahead and get them attached to the bulkheads as they are being cutout.

 

If this proves to be a dumb idea, I shouldn't be harmed, as the lamination schedule will be the same either way.

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  • 5 months later...

An update:

 

For a guy who talks a lot, I don't seem to be making much visible progress. Have had a change of plans on where the build is to take place. Was originally going to take place in a shed at my folks house, where I had full access to a cabinet shop set of tools and an adjacent machine shed that wasn't being fully utilized. But that was 90 miles away and driving almost 2 hours each way quickly proved to be a bad idea. A new plan emerged when my daughter bought a house near us that had an unused 50' x 32' horse barn, of which 20' x 50' was open area on one side. So we worked out a deal and I'm using it instead.  In the past few months, I've poured a concrete floor so shop tools could be moved into it. During all this, have been stymied by cold weather and have found at least five major roof leaks that I'm in the process of chasing down. Anyway, plan is to get the stiff back built next week and assembly of all the parts I've been accumulating to start soon after that. Progress seems to be one step forward and two steps back. Frustrating.

 

Possible break has emerged on pouring the lead keel. Found a guy near here who has crucibles large enough to do the pour, plus foundry experience. By coincidence, he also sails and has his own boat, so he is interested in helping out. In Missouri, finding a guy like that is worse odds than winning the lottery.

 

One of the things we discussed, and where foundry experience pays off is in building the molds. For the CB tip, I did an open pour. But after it cooled, there was cavity left on top after it cooled. Not much, but something that is going to have to be faired in before it gets glued to the CB. Have been worried about that with the keel. Turns out that to avoid that, these should not be open pours, but need to have a casting box of some type placed on top of the mold cavity, with one or more risers placed above the pour. These are reservoirs of molten lead that continue to feed the casting as it cools. When cooled, it should have a dead flat top on it, and the only cleanup is to snip the connection between the lead left in the riser and the keel. With a cap, you no longer have to worry about having the casting dead level. Experience helps.

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Cabin top?  Have decided to use 3/4" balsa core instead of the pink foam stuff. It is structural and will adhere well. Otherwise, will pretty much stick with the graphic above and use 3/16" plywood top and bottom and glass sheathing on top. May only be 6oz or 8oz cloth vs heavier biaxial. Will probably do something similar for the side decks and fore deck, except those may get a heavier glass or xynole polyester, since it will be walked on all the time.  Need to visit with Graham about that as far as plywood size is concerned if it is cored. Cored decks are incredibly strong and stiff in addition to helping with the condensation and noise.

 

A person might not think a cabin top needs to be that strong, except I weigh 200 pounds and I know I'll be standing on it. Also, in the unlikely event the boat ever found itself inverted or rolled, the cabin top would briefly have to serve as the boats bottom, supporting the whole thing and keeping all the water out. Would hate to see it cave in cause it was too flimsy.

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  • 3 weeks later...

Thanks Wayne. Despite the apparent lack of progress, I remain inspired. Now that I've got a place to work, hoping the rate of progress starts to improve. To recap, I don't have room for a boat building shed where I live and was going to use my Dad's wood shop, but it was too far away to be practical. So when my daughter bought a place with an unused horse barn, it seemed like a good option, and about 10 minutes from home. It only took a concrete floor, wiring and patching roof leaks. (Free can be expensive)!

 

But all that is done and now I can concentrate on the task at hand.

 

BTW, while all the barn work may seem extreme, there is an ulterior motive. My son in law has an interest in wood working projects, but not much to work with. If he ends up with a few tools and a place to work once the boat is gone, worse things could happen.

 

 

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Marked and cut out BH#2, which requires two panels, joined in the middle. To get them symmetrical, I marked out the dimensions on one panel, then stacked a second and cut them out together, using a number of finish nails through the middle part to anchor them. Nails were put in the door area, which will eventually be cut out as waste. The door gets a 3" radius at the corners, so I went ahead and used a 6" hole saw to cut those and will cut the door out later on after the BH is installed and tabbed into place. To aid in the eventual alignment prior to gluing, I nicked the edge with the jigsaw.

 

Also, plans don't mention much about the cradle you need to build the boat, except you need one. This bulkhead (#2) has to drop through the cradle as the sides and bottom are being attached. This cradle is 24' long, the cross boards in the middle 62" and the legs 24" off the floor. Looks like it should be about right.

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Congratulations!
i bought the P26er Plans last winter. Unfortunately i did not find a suitable shed for building. So i have to build a temporary carport this summer before i start building.
Please keep us informed and updated with your progress. I like this cradle for the bulkheads it is a very good idea.
Will you install chine stringers? or do you build without them like in the building plans?
I wonder, if the boat will have better symmetrical shape if using chine stringers....
Or are this unnecessary doubts?
Best regards
Sönke

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Sonke:

 

I am building the stock plywood version, so my methods may be a bit different than Brents. I will be using stringers on the sheer (called inwales on the plans or as some call them, sheer clamps), but not along the chine. Instead of chine stringers (what some refer to as chine logs), I will use large radius epoxy fillets, most likely with 3 layers of 12" wide 12 ounce or 17 ounce biaxial tape, each layer offset or staggered about an inch or so to feather and fair them out. Initially, the bottom plywood sheets and topsides are simply joined together with a layer of thickened epoxy, which hopefully will hold well enough until she can be rolled the first time. Once upright, she gets trued up and faired, then "locked" into place, with all chines, bulkheads, etc. getting fillets and taped joints and the inwales permanently installed.

 

To set and hold the shape of the topsides during construction, plans suggest screwing the sheer clamp to the outside of the boat, just below the chine. That will spring it out and give the still somewhat floppy sides the right shape at the chine. What I will likely do is build a second set of sheer clamps.......the real sheer clamp clamped (not glued or screwed in place yet) where it will eventually go......to spring out the sheer, plus the second set along the chine. The second set will be made of scrap that will only be used while the topsides and bottom are being attached.

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Howard,thank you for your answer,
unfortunately my english is not the best, i have to ask another question to be sure that i understand right.
To achieve a good shape, stiffness  and symmetry you screw temporary chines just beneath the chine?
The shear clamp is clamped to its later position but not glued yet. 
so you just glue the edges of the sides to  the bottom without having done the fillets?
The bottom panels where cut oversize and just edge glued to the keel plank, stem and the sides.?
The bulkheads are just screwed not glued to the sides yet.
Then after turning the hull carefully everything has to be trued up, leveled and fixed with epoxy fillets, right?

For deadwood construction it would be easier to turn the hull upside-down again or will you mount it form the underside when the hull is right side up?
Thank you
Sönke

 

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Sonke:

 

You have provided a good summary of the process that is to be used, as I understand it.

 

However, the bulkheads are only 3/8" ply and I doubt my ability to hit the edge of them with a screw from the outside, or their ability to hold much if I did. So once the topsides and bottom panels are installed, if all looks right, I may use a few small "tack welds" of epoxy to hold the sides in place for the first rollover. Either that or wire them in place as is normally done with stitch and glue bulkheads and topsides. "Tack welds" are just small pieces of fillets along the bulkhead edges. If these prove to be in a bad spot or the bulkheads need to be adjusted for some reason, these can be cut with an angle head grinder. LIke screws, they would mostly be used to hold the hull intact and in place to survive the first rollover.

 

I assume the deadwood you refer to is for the keel stubs? I will install them AFTER the hull has been turned the first time. After the hull is all trued up and all bulkheads tabbed into place. I will install the CB trunk then as well. Then the hull is again turned upside down so the keel stub deadwood can be installed; the CB slot glassed and the entire hull glassed and primed for paint, with waterline marked off. I may paint the waterline then as it will be easier to get to it while still upside down vs. later on. I may not paint the topsides until the entire boat is ready to paint, both for convenience and to avoid having the topsides paint dinged up by ladders and dragging materials on and off during the interior build out.

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  • 1 month later...

Another progress report:

 

Projects like this tend to be several small tasks, each contributing something, but now and then you pass milestone. For those who have built one of Graham's designs using his butterfly joint method, you probably have vivid recollection of that moment when you unfolded that thing and it looked like a boat.

 

My most recent milestone isn't nearly as dramatic as that, but I now have my plywood panels scarfed together and marked out.

 

Putting together 3 1/2 full sheets of 4 x 8 plywood and making them look like something is a bigger job than it looks like on paper. First the joints. I chose to scarf my panels, as I was hoping to avoid the visual bump of the taped butt joint, not to mention the work involved in fairing the thing out. While I have scarfed smaller sections of plywood, I had never taken on anything as large as this. (more on this later).

 

To get started I made an attempt at matching the grain pattern on the plywood by laying out each of the side panels in the position I thought they should end up, noting an blemishes with the hope of placing them in a place that would end up as scrap. Probably moot as I don't intend that any of this will be left bright, all topsides will likely be painted inside and out.

 

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That done, it was time to start stacking and cutting. So for 1/2" plywood, and 8:1 scarfs, the scarf bevel to cut on each panel needs to be 4 inches. Unless you have a few special tools, no real easy way to do these but stack them, and go at it. One thing to keep in mind, if the bevels are not cut square, the scarfs likely won't be either and even if cut square, the edges have to be aligned right, or they won't come out square. Again, it sounds easier than it is. To help with the alignment, I premarked the 4 inches of offset I needed on all the panels. These marks were used to align the stacks prior to cutting the bevels, and later on to help align the panels to glue them up.

 

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My tools of choice for cutting the scarf bevels were a power plane and belt sander. Both are weapons of mass destruction. There are few power tools around you can do more damage with faster than a power plane....... one of the few I can think of would be a belt sander. Both of them will remove a lot of wood in a hurry and once removed, it's tough to put back. Best to use them initially for coarse cuts and fine tune things in the end with either a hand plane or if you stick with the belt sander, a fine grit belt.

 

But if you are careful and stick with it, you can get decent results. One thing I had to remind myself of was scarfed joints really need to be brought out to a feather edge on the down side and to the cut line on the top side. If not enough material is removed, you may end up with a bump that has to later be faired out. If too much is removed, or the bevel angle is not consistent, you are left with a gap. Dips and swales in the middle are OK.........epoxy will fill those. Humps and bumps keep the panels from pressing together, so they can't be. When in the thick of it, it is easy to get lost and not really know where you are as far as how much material you have removed and how much is left to go. I found marking the joints with colored chalk to be a help. When you get to the end, you can see the color disappear and the feather edge will start to show. And beneath the chalk, at the joint is a heavy pencil mark. This will also help you find your way when cutting the bevels, and later on, aligning the panels as you are gluing them up.

 

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A decent start:

 

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BTW, once you get the hang of this, and get the panels aligned, this is about a 10 minute job. Maybe less.

 

Finally, two 27' x 4' sheets of plywood!

 

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With panels glued up, it was time to start marking them out. First test was to make sure the panels were glued up true and square:

 

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So placed side to side and square on the aft end, measured the diagonals:

 

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Hey, that looked pretty good! Turns out looks are deceiving. Those panels were not square. Despite my best efforts, including putting a full plywood sheet below the scarf glue job so as to clamp the two panels square to the bottom one, they wound up with a "bow" or curve in them of about 1/8", enough that the edge could not be reliably used as "square" to mark out the side panel dimensions. So a straight line was added just inside the "curved" edge and was marked off that. So with that squared and trued up. I proceeded to measure and mark the station points that outline the shape of the side panel.

 

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Again, I have developed the habit of when I mark points I have to connect with a straight line, I usually set a small finish nail in the center of the point, then register my straight edge to the small nails. The ruler doesn't slip and slide and it is always a straight mark to the center.

 

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In previous posts I have also mentioned using trammel points on a yardstick to mark my offsets. This seems to work well with Graham's drawing dimensions as often times those either diagonals or simply a point where two lines intersect. The yardstick with trammel points (BTW, Stanley #2 Trammel points......look for them on Ebay) is essentially a beam compass, and when the coarse measurement is fine tuned on a calibrated scale, and accurate one. When I have two sides to mark out, I set this and mark them both at the same time.......the center point being the hole the small finish nail made. I have found this method to be as precise and accurate as any I have found.

 

I have been fretting about what I would be using as a batten to mark these 27' long panels out. All of a sudden it occurred to me that I might be able to use the 1" x  2" inwhales I had already scarfed together. They were made with straight grain wood and seem to carry a fair bend through the scarf joint that held them together. With only 3' (10 stations) between each point, what could go wrong? So I clamped them in and it looked good to me. I checked it with both inwhales and except for a small area on one of them, I got the same overlays,  and it looked fair to me.

 

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BTW, marking out the side panels is actually two separate jobs. The first is to mark out the stations that form the outline of the entire pane. Once that is accomplished, the second job is to go back and mark out the location of the bulkhead positions on the same panel. I marked out all these on both panels, but in reality, a builder could save himself a lot of trouble and angst by only marking these out on one panel (top one used for the cut lines), stacking them and cutting them both at the same time. I will be doing that anyway. What goes wrong with that plan is you still need the bulkhead positions marked out on both sides. If a guy could drill a hole 90 degrees square to the panels (no lean in any direction), he could probably stack both panels together ready to cut, then sink 1/8" pilot holes through both panels for the bulkhead points, then connect those points later on the bottom panel after the panels have been cut. I'm going to do that anyway, if for no other reason than to confirm that I marked out my panels the same. Just saying.

 

All marked out and once cut, another milestone will have been reached. Also, a second or third building page (out of about 23 or so) will have been retired.

 

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