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Thread: How I build Mahogany Runabouts (in pictures I hope)

  1. #36
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I have dealt with some of the same problems you discuss. I use rosin paper to make patterns. It is fairly stiff and comes in 3' by 100' rolls; very dimensionally stable. I cut it slightly oversize because the consequences of being too small are grave, but it is surprising how accurate these patterns can be. I use push pins to hold the paper in place while tracing. Sixteen feet of panel (in my case 19') is way too much to handle alone when you are bonding with epoxy. Thus, I predetermined exactly where all scarf joints would be and pre-scarfed two pieces into an 11' panel, then fastened a backing board on the framework where the 11' and 8' sections would join. The backing board made it fairly simple to assemble the other panel scarf in place, in separate steps, on the frame with temporary fasteners. I made a shallow water basin using scrap 2x4 covered with plastic. I soaked the plywood panels, weighted with bricks, for several hours before attempting to initially bend and clamp them into place. After drying in place for a day or two, I trimmed them to exact fit and then repositioned them on the frame with the final fasteners and epoxy bonding. Fortunately, I do not have to deal with compound curvatures which I am sure may require further steps.

  2. #37
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Rosin paper- that's a great. A pattern needs to be a little stiff. Its Home Depot for me today.. The wet terry towels seem to have done it overnight.

  3. #38
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Drafting Mylar is even nicer.... It's clear(ish) so you can trace directly onto it from a print, and position it directly onto a piece of lumber, and read the wood grain right through the Mylar pattern..... But rosin paper is probably much less expensive.

  4. #39
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I've been fooling with the plywood for a week now and I have learned a few things. The water treatment works pretty well, but there will always be puckers and bulges- either concave or convex. Here's what the plywood looks like after its wetted and screwed into place. No glue yet-just fasteners.

    Last edited by Dale R. Hamilton; 09-30-2012 at 05:08 PM. Reason: additional material

  5. #40
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    That looks like it has potential!..... Have you considered attaching a temporary batten along the bottom edge of the forms/bulkheads so you can clamp/screw the top edge of the ply to that while it dries?
    (Top edge in the picture)

    (You have too many toys, Dale....... A fork lift?!)

  6. #41
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    Default Re: How I build Mahogany Runabouts

    as you can see, a lot of bulges. But here's the fix:



    Take a skill saw and make cuts through the ply every inch or so through the bulged part. The bigger the bulge, the closer the cuts.



    Then take a stiff batt and screw it across the bulge- either inside or outside depending on the bulge. The screws will pull each cut tab back into place. When all looks smooth, take thickened epoxy and squeegee it into the cut lines filling them. Finally, apply a fiberglass cloth tape across the filled cut lines




    Here's what it looks like when dry and you pull the batt off. It should be pretty straight- but stitching the bottom in will further straighten the shape of the hull. Now the plywood can be removed. Make any additional beveling of the frames, apply epoxy to the frames and the sheer and screw the skin back on with fasteners every couple of inches. I like square drive lubricated 8x 1 1/4" screws from McFeeleys.

    I know this looks pretty rough- and it is. But keep in mind the plywood is only the inner core of the composite skin.. Then at least 1 layer of chopped strand mat must be applied, the joints must be taped with 6" wide glass tape, and then the whole hull is wrapped in 12 ounce glass cloth. Then comes fairing- but alas I get ahead of myself.
    Last edited by Dale R. Hamilton; 09-30-2012 at 05:32 PM. Reason: pictures too small

  7. #42
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    OK one of you whiz kids is going to have to tell me why some of my pictures are so damn small and some are large. I don't think I'm doing anything different.

  8. #43
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Good thread Dale!

    Are you unticking the 'reference locally' box when you post your images?

  9. #44
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Dale, In our business[Boat building] we have been using 2 inch wide strips of 1/8 th inch luan ply, hot glued, for patterns, for years. We x brace them for a little stability. After you are done, you can usually recycle most of the strips for another pattern. It is so easy and fast, we use tin snips to cut the stuff to length. Hope this helps. Rich

  10. #45
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    So Rich: expand on that idea. You strip plank the hull with luan, X brace for stability and then use that for a pattern of heavier ply? What then? Do you cut this out of 1/4 or 1/2 and this will take the compound curves?

  11. #46
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    well the sides are planked after a great deal of frustration. I really think I am approaching the limits of plywood. The previous hull wrapped much easier than this one. B ut the changes made to accommodate the larger engine made it much more difficult to wrap the skin. I think maybe cold molding is in order for the next boat. Of course I will have to add a chine. Now comes the double bottom..

  12. #47
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    How is the bottom coming along?
    Tom

  13. #48
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Hey Dale, Looks good. I am building an 18+ ft inboard service runabout with tumble home. Planked with 3/8" marine fir plywood, I kerfed 1/8" deep on 1/2" centers, wet with rags, and clamped in position with a ratchet strap. Came out well.

  14. #49
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I've not posted in a couple weeks because I've been dealing with this plywood problem. Its just not going to lay right over these frames. So, I'm starting over. I tore off all of the skin today and refreshed the edges of the frames. Tomorrow I'll add a chine to both sides and a couple of ribands between chine and sheer. Then I'll rip plywood into 6" wide strips and lay them diagonally over the longitudinal members. This boat was originally drawn stitch and glue without a chine- but the ply simply won't do right after raising the decks.

    One lesson I've learned building boats, is that the willingness to do things over again and again until they are right, is absolutely crucial to success. If your counting costs in wasting materials, you are never going to be a boat builder. The "Trial & Error, Hang the Expense" School of Boat Building will produce results- if you can afford it. More soon after I've completed the additional framing.

  15. #50
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Dale, I have been cold molding, with plywood and epoxy for thirty plus years. If I can help with some pointers, let me know. I posted a picture of my latest build on this site under "Pretty in plywood" pg 11, check it out. Or go to tributeboats.com. Rich

  16. #51
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I planked my runabout using a diagonal ply planking for the first layer and it did work very well. If i could just get the nest step done.... lol

    Always something of higher priority coming up. I really gotta get on it...
    Tom

  17. #52
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I give you top marks Dale for the attempt, but after seeing that warped ply in place, i didnt see how that was going to turn out fair. I think what you have decided to do is right, as there is only so much you can do with ply.The thinner pieces you will know be working with will be far easier to deal with. Look forward to your progress.

  18. #53
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)



    Ok, this is how I should have done it. I added a 1x 1.5" chine and 2 1x1/2" battens to each side. The Fein multimaster tool is just excellent for notching into frames. The new framing is beveled and epoxy coated. Ready for skin.

  19. #54
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)



    In this picture I have cut 6" sections of Baltic Birch 1/4" plywood and am fastening them at a 45 degree angle to the longitudinal frames. I'm using thickened epoxy to hold the planks which have been set in place with 3/4" pneumatic nails. This technique is very fast. The Baltic Birch has 5 plys and since I cant get Ocomee, its the best substitute I've found.

  20. #55
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    [IMG][/IMG]

    and here's how it turned out- way better than the full sheet method. There is some fairing to be done and for this I'll use Bondo. Remember this is core for the epoxy laminate- its only function is to support the glass/epoxy/ chopped strand mat which is next to come. It will never see water. Keep that in mind before you condemn the use of Bondo.

  21. #56
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Today I scraped thickened epoxy into the seams of the diagonal planks. Tomorrow I'll Bondo fair the outside planks.

  22. #57
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    QUOTE=Dale R. Hamilton;3575359]Today I scraped thickened epoxy into the seams of the diagonal planks. Tomorrow I'll Bondo fair the outside planks.[/QUOTE]

  23. #58
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)



    This shows that I've faired the planks with Bondo and sanded them smooth. I've learned that you can't wait until the final sages to fair- indeed, it must be done at each stage. This picture also shows the first layer of bottom in place. This first layer is scarfed to 16', laid in wet epoxy and then shot with 3/4" pneumatic nails. The second and final layer of Birch will be but jointed and fastened with 1" screws through both layers.


  24. #59
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Will the topsides be mahogany planked? If so, how thick will that planking be?
    Tom

  25. #60
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    OK, Dale....... Time to get back to work, man....... Christmas is coming, and I expect to see this baby under my tree with a big red bow on it......

  26. #61
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    ok sorry for the long pause. I was on a cruise around Spain and the canary Islands, then a trans Atlantic passage. But back in the shop and here's what I've done


    http://im1.shutterfly.com/media/47a2...D550/ry%3D400/

    The double bottom is on. The sides have been faired with bondo, and now am fiber glasing the whole structure with 6 oz Eglass. The seams and the chines have a double layer of 6' tape. After the glass cloth has cured to the green stage, I'll go back and fill the weave with epoxy and then squeegee Peel ply into the wet epoxy. This gives a smooth mat surface. I will fair once more then prime and paint.

  27. #62
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    The first layer of 6 oz glass cloth is on, the weave has been filled with epoxy and its been faired. Now comes the second layer of glass. Its 53" wide and I cut it long enough to go from just past the keel centerline, over the chine to the edge of the sheer. Optimally this is a 2 man job, but of course, I do everything alone. Here's the method I came up with. Tape edge of the cut material to a 2" PVC pipe the same width as the cloth. Swab the hull with epoxy and then lay the rolled material into the wet epoxy just past the centerline. Now, just unroll the cloth keeping some tension between the roll and the laid cloth'



    When the cloth is rolled to the edge of the chine, go back and fill the weave with a foam roller and epoxy. Don't worry about the small bubbles (now).



    Next take a plastic spreader (like used with bondo) and squeegee out all the bubbles working them to the closest edge



    Now you can run the rest of the cloth roll over the chine and overlap the sheer. Repeat the steps listed above. When the entire hull is fully wrapped and dried, you will roll on 1 or 2 more epoxy coats to completely fill the weave. Then guess what?- time to fair again. As I've said, I've found this to be necessary at every step. Hope to prime next week- I'll send you a picture.

  28. #63
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Forgot one last step. When you roll the last coat of epoxy over your hull, I've found it helpful to lay peel ply into the wet epoxy as before. This reduces the tendency to develop raised bubbles and it produced an even mat finish.

  29. #64
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    I'd like to see a picture of the peel-ply step, if you've got one. I've heard about this a number of times, but I'm not sure I understand what "peel-ply" is or how you folks use it.

  30. #65
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Good Morning Dale,

    Welcome back from your trip, sounds like a great time. Thanks for taking the time to keep this thread going.

    Regards, John

  31. #66
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Peel Ply is a layer of 2.7 oz. Dacron fabric strips or tape laminated into a layup as if it were an extra ply of glass. The peel coat wets out with epoxy like glass cloth and cures along with the rest of the layup. However, the Dacron does not adhere structurally to the glass and when peeled away it leaves a surface ready for glass-to-glass bonding without sanding. Poly/Dacron blend is excellent as peel ply for composite lay-ups. I'll send you a picture although its exactly like the cloth.

  32. #67
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Another trick to pass on. When you are laminating glass cloth you will invariably get bubbles, epoxy-starved areas, and raw selvage edges. Here's a dandy example:

    The way I fix these is to use a die grinder with a course Roloc disc as shown. Grind off the bubble or rough edge of the cloth like this:



    The Roloc disc is fast and it tapers the side of the crater which a knife cut would not do. Then mix your epoxy/cabosil putty and apply with a squeegee. I use a mixing pad on a palette which is a stack of chemical-proof paper. You mix one batch, use it, and tear off the top sheet to expose a new sheet. (See www.mixingpadsusa@aol.com). These are available at most auto paint stores. Lots of good things we can find at these places.


    Finally, it should look like this:

  33. #68
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    The last step after the glass cloth has been completely filled is the application on one more coat of epoxy with Peel Ply laid into the wet epoxy just exactly like you laid the glass cloth- except you don't need to cover it with wet epoxy-EXCEPT and unless you see dry areas under the ply. If this is the case, roll more epoxy over the dry area until you see it wet. The epoxy will roll right through. Here's what it should look like;



    Notice no dry spots. Give it 24 hrs to dry and then pull the peel ply off. It has done its job and should leave a uniform mat surface, Like this:



    The laminate is now complete. Two layers of 1/4" birch ply epoxied together, two coats epoxy, two coats 6oz glass cloth, weave of both filled twice, and a final coat of epoxy set in peel ply. That makes a bottom that's pretty much bullet proof. Now comes final sanding and filling any little dings that surface. I'll report back after I've laid down several coats of high build primer.

  34. #69
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Nice. A trick I have learned from glassing over 20 wooden kayaks and canoes is to heat your shop to over 80 degrees, apply your fiberglass and epoxy, and then cool the shop down to 65 degrees as quick as you can. The air in the wood will contract and suck in the epoxy. If you epoxy in the morning and the temperature rises over the day, the air in the wood will expand and outgas through the fiberglass. It gets worse when you have covered one side with fiberglass and then glass the other side, the air has no where to go but out the fresh side. I also roll on a thin precoat about 8 hours before with 1/8 nap foam roller made for epoxy use. This helps the outgassing by sealing the wood.

  35. #70
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    Default Re: How I build Mahogany Runabouts (in pictures I hope)

    Thats an interesting point. I would have thought that was only an issue on "real" timber and not on plywood? Im assuming you are talking about cedar? I believe some people use a heat gun for the very same purpose which may be fine to lay on an initial sealer coat before glassing. For those of us who work in "well ventilated" conditions, a poly tent is the only way to raise heat, but a good way to cool down fast.

    Looking good Dale. Do you use any special kind of cloth for your sheathing of the bottom? E/S glass Bi/Tri laminate? Cheers

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