Building a Sling Shot

Discussion in 'Boat and Accessory Building' started by Kudzu, Oct 19, 2010.

  1. RoyN

    RoyN Paddler

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    Not sure about the round hatches, but the larger oval hatches are air tight. On a hot day you can see the oval hatch covers swell like a balloon. If it's hot out and you put the boat into the water, you can see the effects of the vacuum.
     
  2. Kudzu

    Kudzu Paddler

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    Thanks, that's good to know. I remember complaints about their old style and so never bought any. I was ordering and decided to get a couple and see. They sure look good so I am not surprised to hear that. Make me feel better about my idea.
     
  3. Kudzu

    Kudzu Paddler

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    DAY 8

    Skeg is back on. I decided to go ahead and do this even if I don't need it I can prove or disprove the idea and the methods. Here is the skeg box almost completed. The purple cord will be a bungee. What I had in the shop is to large so I have pick up some smaller cord. The tubing that the cord runs through is just standard vinyl tubing. I was going to epoxy it in place but I am thing that I will just rough it up and put it in with Lexel. That way I could remove it if I needed to.

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    Did the stretch test and shaped the recess a little more to clean it up so there are no lumps.

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    Then I took the frame off the strongback. Hoping to get the skeg mounted today and then I can oil the frame. Once the glue gets here I can start to build the float bags and attach the hatches. Once that is done it will be time to skin.


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  4. Kudzu

    Kudzu Paddler

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    NO SKEG FOR SLINGSHOT

    Something kept bugging me about the skeg but I kept working on it. I had the box finished and clamped in place for the final check before attaching it to the frame.

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    Here is on the boat finished. The two screws you see are just temporary BTW. I had figured out how to seal the skin to the box, had everything like I wanted and was just making a final check and marking where I wanted it attached the frame. I sighted down the keel to make sure it was all square and then I saw it.

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    Do you see the problem?

    If you run over a stick or a rock it will push the skin upward into the boat. With the skeg box there is a good chance of the skin being lifted and then hit the box. Given the right conditions and it can rip a big hole in the skin.

    I had my floorboards mounted too low in one of my prototypes boats. We were paddling in some swift water, I hit a rock and it caught on the floor board and ripped the skin. Granted it's probably not going to happen on flat water at slower speeds but I am not going to take that chance. Even if it didn't rip it would probably get hit repeatedly and over time wear a hole in the skin.

    So I decided to scrap the idea for this boat. I have some ideas on how to make this work but that will have to wait for the next boat. I don't see this as a failure, just the first attempt and now I know how to improve the next one.

    Late this afternoon I started skinning. It took me a little over 3 hours to have the skin in place and that included shooting some video while I worked for a tutorial on skinning with the loose weave polyester.

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    Tomorrow morning I plan to install the coaming and then I will move on to the hatches.
     
  5. Kudzu

    Kudzu Paddler

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    I finished skinning it this morning. Shrunk the skin and it ready for finishing now.

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    The recessed hatch on the front came out very well. Must say thanks to 'wysedav' over at Blue Heron for the idea.

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    I start applying color in the morning. I wait and just post photos of it once it done rather than tell you what I have in mind.
     
  6. Kudzu

    Kudzu Paddler

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    While waiting on the Turkey this Thanksgiving morning I got in the shop early and applied one last coat of paint. Now it's time to show you the color scheme. Probably not what you were thinking but I like it.

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    Even added red floorboards to add a little 'spice' to it.

    It's painted with off the shelf Rustoleum oil based paint. 3 coats of each color.

    Tomorrow I will start rigging it out, installing the hatches. I am waiting on the cordage I ordered to come in for the life lines. But I can get some bungees installed mean time. Probably take it for a spin Saturday, if the weather is good that is. That is really questionable though.

    I built some float bags that I need to finish and install too. Basically should be done this weekend and finished by the end of next week.
     
  7. Alana

    Alana Wave Seeker

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    Wow it looks terrific! :D
     
  8. Kudzu

    Kudzu Paddler

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    WHOOPS!

    Launching Day! I didn't have long but since I live 5 minutes from the water I could not longer resist and had to take the boat to the water. I spent the morning rigging out the deck lines and taking care for a few minor details. I was still waiting on a shipment of cordage so life lines and painters were not finished.

    Not a great photo but it shows the lines of the boat really well. As you can see the rear deck is really low at the stern so it might not be be a good boat in really big waves. But it wasn't really designed for that either.

    [​IMG]

    Carried it down the waters edge and snapped a few photos. I have to say I am extremely happy with the recessed front hatch. I will write up some instructions on how I did that and put it on the web site latter on. Not really crazy about the rear hatch. Looks like it was just stuck on there but as low as the rear deck is on this boat there really wasn't any reason or space to recess it. So it's a form follow function thing and I can live with it.

    And so far I am very impressed with the quality of these hatches and may start stocking them in my store.

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    I was unloading the boat off the car I realized something. I had not installed the backband! How I overlooked that I will never know, but I decided to paddle it anyway. I wasn't going to be out long.

    I carried it out in the water being careful since I know the paint is not fully hardened not to scrub the rocky bottom. I got situated and first impression was good. It appeared to track very well but I expected that with the V shaped bottom. It seemed to accelerate really fast. For some reason hard chine boats always 'feel' like they accelerate faster to me. I tried a couple of lean turns and while it didn't turn as fast I expected it responded well.

    The breeze was picking up so I pointed it across the wind and seemed to want to weather cock. I turned about 90 degrees and it seemed fine. Back and forth a couple of times and the results were the same. OK, whats going on? The more I paddled it I started to realize that the boat was turning to the right, not weather cocking. So that meant there was something wrong with the hull.

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    I pulled it out of the water and flipped it over in the grass and there it was. The stern of the boat was bent to one side and acting like a rudder on a sailboat. No wonder it was turning! Needless to say I was sick about this.

    To keep this short I went back to the shop and studied the problem. I knew the frame was straight when I took it off the jig. So it had to happen when I shrank the skin and I just didn't notice it. Apparently I shrank one side more than the other and that pulled it to one side.

    So, with nothing to loose I did something I don't recommend, actually I did several things I don't recommend. But a little bit... OK a lot of brute force and I was able to 'persuade' the stern back into alignment. Making it slide underneath the skin was not easy but it worked and I didn't have to reskin it. So now the keel line is once again straight and I should be able to take it down to the water today for a longer paddle.

    I also need to go back to the plans and make some changes to reinforce the stern so that anyone building this boat doesn't run into the same thing.
     
  9. Tootsall

    Tootsall Paddler

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    Super Job. :big_thumb It must have been very satisfying to finally get it on the water and even moreso to discover that you were able to "tweak" it back into alignment. I know I'm not the only person to say that it seemed like a shame to cover that georgous woodwork with the skin but the final result is spectacular.
     
  10. paddlesores

    paddlesores Paddler

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    Location:
    Maple Ridge, BC
    Jeff,
    The boat looks great, I really like the low rear deck.
    You said earlier you have switched from nylon to polyester. Curious as to the reasons why. Also, how do you go about shrinking the polyester? Is it true that the polyester material is less affected by moisture than the nylon(in terms of expansion/contraction)?
    Thanks, Doug
     
  11. Kudzu

    Kudzu Paddler

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    Thanks Tootsall. It's always fun to paddle a new boat. What is more fun is to paddle along side it. There is just something about seeing "Your" creation on the water. Just not the same as paddling it.

    I still use nylon on boats that might see some abuse or rough use. Nylon is tougher, it will stretch a lot before it breaks and that is a great thing. Polyester will not but for most people it is strong enough. Still takes a lot to damage it.

    There are two reason I changed, the biggest being I couldn't build a boat for a client and then it wrinkle up and look like a raisin when he/she took it to the water. That drives me crazy!

    And yes it is true, polyester does not get slack when wet. The reason is nylon absorbs water and Dacron doesn't. I have found that after a boat is skinned sometimes the polyester will loosen up just a bit and I an not sure why. It will no longer be drum tight and might develop a few small wavy spots but that is it. Once it relaxes it stays that way from then on. It can be shrunk a little more if your brave. Just have to be careful applying heat to the finish on the skin. I typically just leave mine they way they are.

    Second reason I changed is that you can finish it with most anything. Oil based, water based, varnish, house paint, etc. I like the ability to use paint and all the colors that can be used. Nylon requires using acid dyes and I have had mixed results with them. I dyed one Turquoise and within weeks it faded to a dirty white. No signs or the orginal color. I have a purpleish blue one that looks as good 3 years latter as it did when I finished it. Go figure!

    I like paint because it's cheap. Easy to touch up if you mark it up. And I could probably be a little creative with it. Something I could never do with acid dyes.

    And by the way, I do not use aircraft dacron, it is WAY to light!
     
  12. Kudzu

    Kudzu Paddler

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    I got to spend a couple of hours in SlingShot and wanted to cap this story off with a few good in-the-water photos but it didn't happen. What are the odds of two guys showing up with two cameras and both having dead batteries? Both us went to take photos and found out we had dead batteries. So, no on the water photos yet.

    After spending a couple of hours in the boat I am pleased. This is good paddling boat. I am not sure why but it feels like it accelerates like a rocket. I have another skinny hard chinned boat that everyone comments on how fast it accelerates. I think it is something about the hard chines and the way they make it feel. I really don't think it is any quicker than Long Shot but it sure felt it.

    Speaking of speed, as I have said I am not a racer and do not have a good smooth stroke in a sprint. But I did manage 6.6 mph but I am sure I looked like a scared chicken flapping his wings. Someone with a good smooth stroke could beat that and it really doesn't mean much either. But it was easy to paddle it at 5 mph and maintain that speed for a while. It's a very easy to paddle boat.

    The one little surprise the was the lean turn. With Long shot and Firefly to turn the boat you literally just lean a little and the boat responds very quickly. I knew with the V hull it would track well so I put a good bit of rocker in it. So when I leaned it a little I was disappointed that didn't respond quickly. After a paddling it a while I discovered that if I leaned and just gave it a little nudge so speak with the paddle that made it start to turn and then it turned really well. I tired it repeatedly and it it was almost like you needed just a little nudge to start turning. After getting used to it became second nature and was easy to make small course corrections.

    It's hard to see what the back of the boat looks like but Dan was saying it was very low slung and said it was making virtually no wake either. I was concerned since the back band is lower than any of my other boats but it found it very comfortable. A little lower volume than my other designs but it was comfortable for me.

    Bottom line, I think it is a good boat. I didn't see any bad manners but of course I want to paddle it more in different conditions. Anxious to spend some more time in it. I am still going to try to get some photo latter on.
     
  13. VanIslePaddler

    VanIslePaddler Paddler

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    Very nice... Very nice write-up!
     
  14. Kudzu

    Kudzu Paddler

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    Thanks you.
    I forgot to mention that I finally have some new scales. Put it on the scales last night and rigged out ready to go the water it weighted 34 lbs.

    No doubt that the extra wood for the hatches and the hardware added 3 to 4 lbs of that. So without the hatches 30-32 lbs would be very likely.
     
  15. scottlong

    scottlong New Member

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    Dec 25, 2010
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    Looks good! What size and type of wood are you using for the keel, gunwales, etc? I'm about to start a pair for my kids. I think I asked you about this before but cant find the message.
    Thanks
     
  16. Kudzu

    Kudzu Paddler

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    It's a matter of what you have available but I use a lot of Western Red Cedar and cut it 3/4" thick.