skin on frame kayak, first time, many mistakes to learn from

Discussion in 'Boat Design' started by yoram, Aug 15, 2011.

  1. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    hi all
    i was asking a question here about a canoe and it has developed with the help of some good members of the forum and i have found myself building a skin on frame kayak. i have done many mistakes in the process of building it and i would like to share them with everyone so it could be a helpful info for other who want to build. i know there are people here who are dealing with much much bigger projects but for those who are interested in building kayaks for the first time, i hope this thread would be helpful. please DO criticize so others could learn from your insight and experience and knowledge.

    I found a bundle of Beech wood size 85X4.5x1 cm in the school where I work. They were used for the bottom of the beds as a structure on which the mattress was laid. It is hard wood and it was hard for me to see such a quality wood being tossed away so I thought about using it for building the frame for a sof kayak.

    I used Yostwork website and choose Seabee model.
    The length of the Seabee was barely fitting with the length of the workshop. First step was to put 5 pieces (85X4.5x1 cm) together in order to create the stringers. I wanted to use stuff that is already available here in the workshop so it could be almost no cost to build. So I used “carpenters’ glue” (the white stuff used for furniture) and had most of the longitudinal pieces needed with butt blocks.

    What I did wrong:
    Connecting 5 pieces to create a stringer is a bit too many.
    the butt blocks should have been longer
    the glue should be good quality, water resistant like epoxy
     

    Attached Files:

  2. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    phase 2

    When I was trying to bend and torque longitudinal pieces at the same time (so they could attach to the bow and stern properly), it seems impossible so I cut them longitudinally with a jigsaw into halves so now I had more then enough longitudinal pieces and the torque became possible.

    What I did wrong: I did not use a table saw to cut them (did not have one) so they were not evenly shaped. That made it difficult to estimate the size of the groves on the cross sections to fit them in.

    you can see in the photo that the stringer is not cut strait.
     

    Attached Files:

  3. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    phase 3

    I cut the 5 cross sections. Off course I measured 2 of them wrong and had to cut 2 new pieces. I could still find pieces the right size in the dumpsters of the near wood shop so I was content about keeping it low cost, so far, no cost. I did not mention it before but one of my main goals was to build the kayak with minimum expenses.

    Now it is time to assemble it all together. I tried to do it on my balcony but it was raining a lot so when the workshop became free I moved it all in there. I used a 5X10 cm wood logs as a strong back (I think it is called like that, strong back) and screwed shelves holders to hold the cross sections, the bow and the stern. Then I started to assemble it all.


    What I did wrong: I used metal shelves holders which have their screw holes (to hold the cross sections) in fixed places, not always where it fit with the cross sections. Some times the screw holes where below the cross section. Better to use a wooden shelve holders where it is easier to screw in any place through the wood.
     

    Attached Files:

  4. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    phase 4

    I cut grooves for the stringers in the cross sections and cut out the middle part. I have managed to assemble it all into a frame on a strongback. My suggestion here is that you do not fix the bow and stern yet to the strongback and wait to see where the “natural” ending of the stringers meets and place the bow and stern there. I did not do that and already cut the stringers where I placed the bow and stern. I had to add 8, 30 cm pieces with butt blocks to the stringers so they would follow their natural curve and meet with no pressure to bend them.

    What I did wrong: not placing the bow and stern at their natural place which made me add pieces to the stringers to lengthen them into the right length.
     

    Attached Files:

  5. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    phase 5

    I used screws and glue to fix the stringers to the cross sections and it seems pretty strong. I used this bit that makes a “crater” in the wood so the screws’ head would not stick out.

    I spend a lot of time to shape the part of the stringer that connects to the bow and stern with a saw and planner and knife and sanded it very carefully to make it smooth so it will not tear the skin. It is a tricky part since they do not come parallel to the face of the bow or stern but you still want to have enough wood on the stringer in the part where it connects to the bow or stern but you do not want it to stick out. I do not know if I make myself clear here…
    i remembered that i have some epoxy left from other canoe i built so i used it for the joints stringers-bow stringers stern

    you can see in the photo that i have already used epoxy putty

    What I did wrong: I did not use stainless steel screws.
    Since the stringers were from hard wood and were only 1 cm thick, it was more difficult to shape them.
     

    Attached Files:

  6. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    coam

    To build the coam, I had many pieces of plywood but not wide enough so I decided to build the coam from a few pieces that I will glue together. Then I have found a bigger piece of plywood and could cut it in one piece.

    What I did wrong: used poor glue and not epoxy, thinking anyway it will all be held to the frame with screws so I could save epoxy here.
    The other thing was that I didn’t do a good job in cutting the coam with a jigsaw. Just poor craftsman’s’ work.
     

    Attached Files:

  7. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    another coam photo

    this is the second part of the coam that is attached to the first part which is already part of the frame
     

    Attached Files:

  8. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    more kayak,

    I have sanded it all so there will be no stick out parts and then I have added screws to all the butt blocks joints, 2 on each side, since I could not fully trust the glue. i have added the sit which i just screwed 2 pieces of 2x10 on each side of the keel. i screwed it to the cross sections. I also used some kind of silicone that is used for the outer part of the joint wood-glass in windows to coat all the end grain which was a lot to apply and then painted over with oil paint. The silicone was here in the workshop but I bought the paint for about 100 Dkr , about 19$. I used the same paint for the skin.
     

    Attached Files:

  9. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    skinning

    After it dried, I have tried to use the wrong polyester skin. It was way too light and thin. So I have ordered the right polyester from George Dyson. I have ordered 12 meters because that was the maximum possible for a flat box and it costs $43.00 for shipping, plus $78 for the material = US$121.00 I had to pay also tax on it another 65 $, import tax. Very expensive. Now, if I had known that, I would have paid much more attention to build a better frame but I did not have the energy to start a new frame.

    What I did wrong: using the wrong polyester

    I also spend about 65 $ for stainless steel staples thinking that I might use them instead of stitching but then I thought I should stitch. It had a more “right” feeling to it. I had some practice in stitching on the thin Polyester that I got before and also as a veterinary surgeon in my past, stitching up many animals. But when I came to do the kayak, I thought I give this job to someone who really has done professional art hand work so I asked my girlfriend who is an art restoratore, to do the stitching work (which to be honest, is the only quality work on this kayak). From what I saw, the stitches should be even so you get almost no crests and follow the center-deck piece of wood as a guide so the stitches would go straight. Cut the left over skin in an un even length to fit the second stitches and we used cross stitches on the bow and stern.
     

    Attached Files:

  10. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    more photos

    my better half stitching.
    close up on the cross stitches
     

    Attached Files:

  11. thedutchtouch
    Joined: Feb 2010
    Posts: 91
    Likes: 2, Points: 0, Legacy Rep: 39
    Location: baltimore. MD

    thedutchtouch Junior Member

    what you did wrong: admitting to all of those "mistakes". the boat looks great. and i see why you thought it was "more right" to stitch- got the wife to do the work! good man!:D
     
  12. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Looking good Yoram. I am enjoying your thread and watching your progress. A few points:

    Using such short wood material will result in a lot of joints on the stringers but there's is no real problem provided the joints are good. The clamps you are using are not strong enough to provide enough pressure for carpernter's glue, which in any case is not waterproof. There are water-based glues that claim to be waterproof, I use them but only where I think they will not get soaked, just a bit damp occasionally, that's about all those glues are good for. If your finished boat has carpenter's glue in the stringer joints then you will have to take great care to seal the stringers against water. It will always get into the boat even if it is perfectly watertight from paddle splashes, rain or hosing down, and once water is inside a kayak it can be difficult to get all of it out again. This would have been easier before adding the fabric.

    The strngers must be cut straight or they will bend unevenly. They seem fine in the pictures.

    Most of us don't use shelf holders to attach sections to a strongback; a simple block of wood is fine provided it is square. Self holders sometimes are not square.

    it is usual practice to fasten the stems (bow and stern pieces) to the strongback at the same time as the sections. At this time the builder will check carefully for such things as symmetry, and will bend a test batten (=stringer) over the form to ensure nice bends without kinks or dents; this activity is called "fairing".

    We understand the business of fairing the stringers into the stems - we all have the same challenge sooner or later on a boat built. Using steel screws is OK to hold things together while glue sets; most of us remove them and replace them, depending on the appicaltio we can use brass screws, bronze screws (sea-going boats) or dowels to reinforce the glue which is normally adequate all on its own. For a boat that is dried out after each trip, zinc-plated screws are fine; I have several in a boat that I meant to replace, they have been there for two years and show no problems. It is hard to get a perfectly fitted joint here so I am relieved that you are using epoxy, which retains its strength across a gap. However, I am not sure what you mean by epoxy putty. A lot of "epoxy" products are not epoxy-based, and products called "putty" are inteneded for filling dents not gluing parts together. glue a couple of pieces of wood together using some, let it set thoroughly, and try to break it, that will tell you how well it is performing.

    Epoxy is a much better choice to seal end grain. I am not sure if paint will adhere over a silicone-containing product.

    The boat is looking great, and the stitching is an art form in itself. looking forward to seeing it in the water.
     
  13. messabout
    Joined: Jan 2006
    Posts: 3,032
    Likes: 226, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Yoram; you are a good man. It is not easy to admit to all the mistakes, to say nothing of sharing them so generously. Your GF is a pretty lady so it is clear that you have done some things quite well.

    Happy paddling
     
  14. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Yoram, think of building the same boat on the beach in far north Greenland, with maybe a nail and a bit of knife blade as your only steel tools, from driftwood scavenged among the dunes, then killing some seals or a walrus to skin it with.
    It would not be nearly so fine as the one you and your sewing master have built.
    You have done a very nice job, overcome obstacles and learned a great deal in the process. Don't forget where it all comes from.
     

    Attached Files:

    1 person likes this.

  15. yoram
    Joined: Nov 2010
    Posts: 120
    Likes: 2, Points: 0, Legacy Rep: 14
    Location: denmark

    yoram Senior Member

    thanks you guys for your comments.

    ancient kayaker, as always, very good tips. i am sure it would be great help also for others who want to build a kayak.

    thedutchtouch , thanks, it wasn't easy to expose all the mistakes but as you saw, i put my girl friend in the front to divert the attention from my poor work...
    messabout, thanks, i am just lucky.

    battan, i know you half joking but i recently met with this guy here in Denmark that have been building sof kayaks for the last 30 years almost like the people in Greenland. he chops the wood himself and use only natural materials, only linen canvas, very heavy one etc. he is building now a 15 meter sof boat, some kind of replica to a bronze age boat that was escavated here. i and some others are helping him when we have the time. i will ask his permission next time i see him to post the whole story here.
    his link:
    http://www.bronzealdercenter.dk/Bronze_blog/?p=180

    you would have to use google translate if you do not speak Danish
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.