Pygmy Osprey Triple Kit Conversion to Double

Discussion in 'Boat and Accessory Building' started by Allan, Aug 17, 2017.

  1. Allan

    Allan New Member

    Joined:
    Aug 17, 2017
    Messages:
    4
    Location:
    North Vancouver
    I would like to convert my triple kayak kit to a double.

    The only difference is the deck panels for the triple have been pre-cut for 3 cockpits where as the double has 2 cockpits spaced closer together.

    Pygmy will not swap the old triple panels for a double, instead they would charge $160 for a custom order for making the new panels.

    I am hoping to get opinions on buying a sheet of the 4 mm BS 1088 Okoume plywood and tracing the outlines of the panels that I have. I would trace the 2 cockpit openings shifted to the same positions that the double uses - anybody know what that is?

    How hard is it to cut the plywood to achieve the same clean edges that the Pygmy kit has? Will it match the other panels in the kit?
     
  2. Dan_Millsip

    Dan_Millsip Paddler & Admin

    Joined:
    Mar 8, 2005
    Messages:
    9,294
    Location:
    Beautiful BC
    Spend the $160 with Pygmy. You won't be saving very much on the wood and the panels will be cut precisely.
     
  3. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    Allan wrote:
    How hard is it to cut the plywood to achieve the same clean edges that the Pygmy kit has? Will it match the other panels in the kit?

    Very difficult. Theirs are cut with a CNC router to a precision exceeding +/- 1 mm. The gaps from patterning as you describe will be unsightly and will produce slight deck warps. The extra work to correct these flaws will really annoy you. 160 bucks is a bargain.
     
  4. mick_allen

    mick_allen Paddler & Moderator

    Joined:
    May 15, 2005
    Messages:
    2,799
    I would spend the $160 also as wood cost is a small part of the overall and it'll save so much time and possible screw-ups.

    However I strongly disagree with Dan and Dave: if you make good templates from the existing panels [ie the edge of the pencil pressed along the edge], cut outside the lines and handplane right to them, you'll end up with a result that is insignificantly different from the original.
     
  5. Dan_Millsip

    Dan_Millsip Paddler & Admin

    Joined:
    Mar 8, 2005
    Messages:
    9,294
    Location:
    Beautiful BC
    Perhaps. The result would very much depend upon the skills of the person doing the tracing, cutting, and planing and it would certainly take considerable time and skill to achieve results of a cnc machine.

    Having said this, it certainly can be done with results that would work well enough but it's going to take two sheets of okoume (which may or may not have matching grain) and considerable time.

    It's been a while since I've shopped it but marine grade 4mm okoume runs about $80-120 a sheet in my neighbourhood. Even in US dollars it would seem more convenient and better to buy the panels from Pygmy -- that will have matching grain.
     
  6. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    What Dan said. I have edge-mated okume panels to form a fair line, both before I had the skills to do a decent job, and after.

    "After" was a few years of serious boat building after the "before".

    There is no substitute for skill in a job like this.
     
  7. mick_allen

    mick_allen Paddler & Moderator

    Joined:
    May 15, 2005
    Messages:
    2,799
    Well, he's already built a complete boat, so is familiar with what the panels look, feel, and glue like. If he just removes those existing panels carefully at the shear and then heat blasts ['cause it doesn't matter any more] the remainder - he'll have full size edge templates that he could just run and laminate trimmer around to make new panels from, as well as the hatches maybe if he wants.
    And then just the ckpt openings which typically have huge gobs and thicknesses of ply to shape away to one's hearts content.
    And if he has other experience or is a careful guy, I think there's a good chance he could pull it off. He's already done it once.

    **

    actually re-reading, he's just go the kit and hasn't built one yet so doesn't necessarily have build skill . . . but he's got the bare panels right there for the tracing. So how hard is that: cut close, sand or plane to the line?
     
    Last edited: Aug 19, 2017
  8. Allan

    Allan New Member

    Joined:
    Aug 17, 2017
    Messages:
    4
    Location:
    North Vancouver
    Thank you everybody for your thoughts.

    I laid out all the panels over the weekend. The finished kayak will be 20 ft long but none of the panels are longer than 8 ft. 12 panels are used to make the deck but only 6 panels are in the center where the cockpit openings are. Of these 2 short panels at one end of the boat are not touched by the cockpit openings. So that leaves a total of 4 panels that I need to replace, 2 on the left and the mirror image 2 on the right. All 4 panels could be cut from a single sheet of plywood. The left and right sides meet in a straight line where I would like the grain to match. I think that the center line could be cut with a table saw and the other edges cut close and planed and sanded close to the line as p[. I recently made a Greenland paddle which got me familiar with using a plane again, although I don't claim to be an expert by any stretch.

    So I am tempted to practice on a lesser sheet of plywood first and then decide. If my practice attempt goes badly then I'll get the replacement panels from Pygmy. Otherwise Edensaw in Port Townsend list Okume BS-1088 4 mm plywood for $61.10.
     
  9. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    Sounds like you have a very sound plan. There is no reason it won't work.

    One precaution worth mentioning ... in the original build, there were some temporary frames used to maintain the hull and deck shape. Before you cut into the deck panels, you might hot glue in some bracing to maintain the hull cross section and alignment, to deck panels which will remain in place. Hot melt glue is easy to remove later, using a heat gun, and the clear version is almost invisible if small amounts remain.

    Another consideration is whether you want to retain the originl bulkhead positions. As a triple, the end cockpits are a bit closer to the ends than they are in the double , IIRC. This makes for less bulkheaded dry storage. In xonsrruction, when you have maximal access to the bow and stern areas, you might want to remove the existing bulkheads, and cut new bulkheads to fit into the bow and stern, closer to the center of the boat. You have to make sure you leave enough room ahead of the bow cockpit for the front paddler's feet, of course!

    When I set bulkheads for my double, I moved both bulkheads towards the center from the stock positions for this reason, and we gained quite a bit of dry storage. I patterned these off the stock bulkheads prior to assembly and cut them from okume scraps, installing them after the hull was fully assembled. Because the double has big cockpits, and is a wide boat, this was not difficult to do, especially with hatch openings already cut.

    I am pleased you are going to make this modification. The double is a great setup. I think you will like the extra storage, and having the paddlers a bit closer to the CG of the boat will improve its rough water performance. Plus, the forward paddler will not get a faceful of water so often, either!
     
  10. Allan

    Allan New Member

    Joined:
    Aug 17, 2017
    Messages:
    4
    Location:
    North Vancouver
    Thanks for your help; this boat is still in kit form so now is the easiest time to make this type of modification!

    One of my reasons for doing this conversion is to maximize the size of the buoyancy compartments front and back. I had not thought of moving the bulkhead positions until you mentioned it. Maximizing the size behind the bulkheads sounds like a great idea; I will do this. The limit I think should be to allow somebody up to say 6' 0" to sit in the front. I have not yet bought the bulkhead kit from Pygmy yet although I am planning to do so. I know that they supply the bulkheads with their kits. However as you say they will be too small for the wider spacing. Cutting the bulkheads to fit exactly must have been a challenge!
     
  11. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    Allan,

    Your job will be enormously easier if the boat is in kit form. Somehow I glided right over that in your first post.

    Yes, exclusive of the cockpit oval parts, the outlines of the panels should be the same. I suspect you can take rough measurements off the top view of the double on their web site to determine cockpit locations and use mated panels from your triple kit to trace out the "oval" for each cockpit opening. The temporary frames used to stabilise the deck/hull assembly should work for the double also.

    Once the hull is glued up and glassed, complete with coamings, you can cut openings for the hatches. That would be the best time to determine where you want the bulkheads to go. You can easily modify the kit bulkheads to fit the desired locations using a couple tricks to generate a pattern for each of the larger ones. When you get to that stage, post back for help. I am pretty sure I posted these tricks, some 10 years ago, but finding those posts would be impossible. Pygmy can help you with that process also.
     
  12. Roy222

    Roy222 Paddler

    Joined:
    Jun 2, 2009
    Messages:
    315
    Allan
    Bulkheads are super easy to design (make a pattern )
    Just tape, or staple, cardboard strips around the outside of the hull were you want the bulkhead.
    You only need to do 1 side. Lay the connected pieces flat on paper. Use a piece of hull plywood as a spacer to draw a line that represents the inside surface of the hull. Because your hull is made from flat plywood you should use a straight edge to clean up the pattern design. Cut the paper out to the line and fold over at centerline to create a symmetrical full pattern. Trace the pattern on your bulkhead plywood, saw out the the bulkhead and round off the corners.
    You could also use strips of 1/4" plywood and screws (clamp and glue) instead of cardboard and tape.

    Roy
     
  13. mick_allen

    mick_allen Paddler & Moderator

    Joined:
    May 15, 2005
    Messages:
    2,799
    There was another thread here by someone who wished to make a further modification to the deck of his double by dropping the cockpit rears. You may wish to follow through it to see if you might wish to do that also.

    http://www.westcoastpaddler.com/com...uble-recessed-rear-coaming-modification.5428/

    the photo links work for me if I click on them, but in any case here's a range of possibilities: He chose a version of the 3rd.
    OspreyRecesses.jpg
     
  14. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    Allan, Roy's method is a good way to go. If you skip the spacer, it will produce a bulkhead outline approximately 4 mm (ca. 1/8 inch) too large, around its perimeter for the location where you do this. Not a problem, just file or sand it a bit, which is needed anyway, as Roy mentions, to accommodate irregularities inside.

    No need to achieve a uniform fit, because filled epoxy (and glass tape, if you elect to use it, also) will compensate for small gaps.

    Go for it, Allan, and keep us posted on your progress. Easiest if you start a thread detailing your build, as others have done.
     
  15. Allan

    Allan New Member

    Joined:
    Aug 17, 2017
    Messages:
    4
    Location:
    North Vancouver
    Amazing to be able to benefit from the experience of others via this forum, it is an incredible resource! I think that I can safely say that I would not have thought of the method that Roy suggested for making the bulkheads but it makes perfect sense.

    Thank you for pointing out the other thread discussing the flat rear coaming. Looking at pictures of finished boats does show how high the deck peak is at this point. It is interesting how Pygmy have introduced many new designs for their singles but the double has to my knowledge remained unchanged. I will change the rear deck too as Mick suggested, following the approach used by Rick, using the triangular sloping flat sections.
     
  16. mick_allen

    mick_allen Paddler & Moderator

    Joined:
    May 15, 2005
    Messages:
    2,799
    As you'll be making the boat in two halves, there will be easy access to the interior, so you could rest a 1x2 across the boat at the b/h location you wish, mark the gunwale location on it, and then hang roy's method down with scraps to get the perfect inside shape. Repeat in same location for deck inside and then mark out on one template.
    Another method is to hang/glue a thin pointy bit of card down to each intersection - then lay out on a template pc and draw lines betw the points, then allow about a quarter 'titch' for the glass and shape errors and a little rounding for the fillets - or the converse, Roys, lay down partial flats on the flats and extend lines to the interesections when on the template. Barely noticeably hollow out the straight lines [as boats are 3d curved] and you'll be perfect.

    one of the things you can do to make the drops more aesthetic and balanced is to try and cut the top [upper] angles so that looking down they all make about 120 degrees to each other. That way they are individually balanced geometrically, in harmony with each other, and just help to support a comprehensive whole. You can see that the model is just a schematic and that I could have done a little better, but I think this gives the idea:
    topviewfacet.jpg

    A much more difficult approach that still just uses the ctr deck panels is to drop the ckpt rear just abt 1/2" or cm above the gunwale [for +ve drainage]. It would require a little mocking up with the hull restrained, but might be interesting also:
    OspreyDbleGWfacet.jpg
     
    Last edited: Aug 30, 2017
  17. Astoriadave

    Astoriadave Paddler

    Joined:
    May 31, 2005
    Messages:
    5,287
    Location:
    Astoria, Oregon, USA
    Roy's method is as good as the one I learned from someone years go, but Mick's variants also sound good. I have done this on three or four nonstock bulkheads:

    1. Cut a piece of stiff cardboard, or scrap okume if you like, just undersize, conforming more or less to the inner shape needed. Gaps up to half an inch wide are OK.
    2. Tape that template in place.
    3. Fix a ball point pen dead center into a small plastic bottle cap or other disk, approx 1 inch in diameter, with about 1/8th of an inch of the pen tip protruding.
    4. Run that arrangement around the perimeter of the template, to leave an outline on the template face. This outline will be the exact shape you need, but inside a distance equal to the radius of the disc.
    5. Tape the template onto whatever you plan to use for bulkhead material. Mark around it three places on each facet, out the radius of the disc. And connect the marks to make the final outline.

    This is fast, requires no tricky steps, and mimics the actual shape needed when the boat hull and deck are in their final configuration. I think somebody at Pygmy may have put me onto this. Too long ago to recall.