Building a Sling Shot
Posted 19 October 2010 - 06:34 PM
Slingshot is a new design and this is the prototype build. Sling Shot is a skin on frame 18' 6" long, 23" wide. Hull has a fair amount of rocker and V in it. Stability is on the lower side but not really low. I want to use this as a test bed for a couple of ideas I have had for a while now. I want to add a retractable skeg and I want to ad some nice looking hatches too. I have ideas on how to do these but I will just have to work out the details as I go. Once the frame is together I will probably change it some.
Here is a quick run down of what I got accomplished today.
First step is cut out all the full sized patterns and glue them on the plywood. I always save any larger scrap pieces since I build so many and can often get several parts out of scrap.
Then I like to rough cut the pieces out and then I do the final cuts on the bandsaw. There is no reason not to do them with a jigsaw, I am just more comfortable with the bandsaw so that is what I prefer.
It takes a few hours but here are all the frames cut out. Actually I see a mistake in the pile but I am not going to point it out. ;-)
Before I quit for the night I ripped my stringers to width and since I use cedar siding I plane the rough face. I end up with a 5/8" thickness. This is my old Powermatic planer at work.
I recently found some really good cedar which is very rare around here. It was 12' lengths so I cut and scarf them together to about 18' long. I normally have to cut out a lot of knots but these were small enough I didn't see any I couldn't just leave.
Posted 20 October 2010 - 05:26 PM
Posted 20 October 2010 - 05:38 PM
Full day in the shop and I didn't take a lot of photos. I sanded all the frames to smooth up my cuts. Then I rounded over the insides because it makes lashing easier. I also round over the edges on the exposed frames in the cockpit just because it looks better. And it feels better on your legs if you hit them.
Next I ran the stringer that I glued up last night through the shaper to round over othe edges.
Last I set up the strong back and started to assemble the frame. By the time I quit it was ready to start lashing.
Here is link to a time lapse video I shot while I assembled the frame. I think the dog is as interesting to watch as I am.
A couple of photos of the frame. It is ready to be lashed together now.
Here is one of the Sea-Lect, formerly Sea Dog, hatches I am going to install. Have an idea on how to do this and make it look good.
Posted 20 October 2010 - 07:45 PM
Jeff, hurry up and work out all of the frame kinks. I'll b ready for a set of plans shortly.
As you can see I got a lot done today. It's going to be a couple of days before I can work on it again I suspect. But everything looked pretty good. No nasty surprises. I was too tired to get down on my knees and sight down the hull really well and make sure everything was fair. But that is next. We will know by next week if I missed anything.
Posted 22 October 2010 - 06:25 PM
I basically spread one day out over two days but I have the hull lashed together. I want to leave it on the jig since it is nice and stable and work on the the hatches before I install the deck beams.
'wysedav' over at Blue Heron came up with a great looking way to build in a recessed hatch on a skin boat he built and I have been wanting to try that ever since I saw it. So that what I will work on next. I don't think I can recess the rear hatch since the deck is virtually flat now. If I lower it any it's going to have water puddle around it and that's not good.
Here are few photos.
I sketched out the skeg box and skeg. I decided to draw up something to scale figuring I could work it out on the computer a little quicker than my usual way of just designing on the fly. The skeg is 'spring' loaded with a bungee cord, the orange line. I will add a line that is not not shown to pull the skeg up in the box and it will end up on deck with a jam cleat or clam cleat to tie it off. I used this setup on another boat it worked flawlessly.
Still got to figure out what method I want to use to attach the skin and seal it to the skeg box.
Posted 24 October 2010 - 04:59 PM
I worked on the hatches today. I started with the bow and how to recess it. I started by gluing some rails to the inside of the gunwales. Then cut a piece of 3/8" plywood to fit between the gunwales and rest on the rails. I took some 2" stock and cut it in a circular shape larger than the hatch. I marked the angle, cut and started rasping and sanding a radius on the inside edge where the skin will wrap over.
I cut the hole for the hatch and glued the plywood to the stringers. Here it is with the hatch resting in place.
At the stern I did basically the same thing except I didn't have to build the trim block since the deck is almost flat on this one. It will be slightly recessed, but I just rounded over the ends of the stringer so that it would make a nice smooth transition. The ring on the hatch will pull the skin down just fine. I used the larger piece of plywood because of the effort it takes to 'peel' these hatches off. Just attaching them to the skin wouldn't work well. The plywood was the simplest way to provide a good firm base for the hatch base.
With the hatches finished I needed to trim up the joints to make sure you don't end up with a lumpy boat. For exampleAt the rear I needed to work on the where the stern and stringers meet. A rasp makes quick work of this. I just need to go over it with the sander to smooth it up before I skin it.
Last step was to lash the last of the deck beams in place. One more quick look and any touch ups it should be ready for to pull off the jig and start working on the skeg box.
Posted 28 October 2010 - 04:07 PM
I almost talked myself out of drop down skeg but it is something that I wanted to try and I knew if I didn't I would might never. The problem is the boat is basically ready to skin and like everyone I am anxious to get it on the water. I have spent a lot of time sketching this trying to figure out how to do make it work and still not totally satisfied with what I came up with. But to learn what works and doesn't you have to start somewhere and then you improve on that.
Once I got my design drawn I pulled out some scrap and mocked it up. Clamped it to the frame to see how it would fit.
The more I played with it and looked at it on the boat I decided to make some changes in the design. While it all looked good on paper it just didn't look 'right' on the boat. So after a few changes I made my skeg and started to glue together my skeg box.
While waiting on glue to dry I started ripping some strips up for a coaming.
I discovered really quickly that Cherry is not as easy to work with as soft maple! I had to go back and cut the strips a little thinner, even heating them they still wanted to break on me.
Posted 09 November 2010 - 02:34 PM
After a lot and I mean A LOT of arguing with myself I have decided not to put the drop down skeg on this boat. It is not because I think it will not work because I am sure it will. It's just I am 95% certain this boat will not need or benefit from one because of it's V shaped hull. So I am going to put what I have built aside and will save it for another project.
I cut some aluminum angle I have in shop into 4 short pieces and drill a few holes to mount the footrests to the stringers. I have always thought that footrest would be more comfortable (for me at least) if they were lower. With this boat if I put them on the upper stringer they would have been way to high. So I mounted them on the lower stringer and that really put them down low. I had to make sure the levers (red ends) would not hit the skin. I think with all the V in the hull they will not be as low as they look to me. But they look really low.
I finished up a few other minor odds and ends and the frame is ready to come off the jig. Once it is off I will lash the joints at the brackets where I clamp it to the strong back. Then it will get slathered in oil and it should be ready to start skinning.
Not the best photos but it is hard to get good photos with all the shop clutter in the background.
But before I skin it I want to make some float bags and install them. I have had an idea for a long time now. Why not attach and seal the float bag to the hatch? If you have a good seal and these seem to seal tight, you then have dry storage inside the float bag. There may be a reason that this will not work but I don't know what it is yet.
I figured I would start with some heavy clear PVC from WalMart and see how it works. I suspect if you use these a lot you might tear/wear a hole in the bags. If that is the case I know where to get some reinforced vinyl that I will replace these with down the road. It's just rather expensive so I figured start with the cheap stuff and learn.
Posted 12 November 2010 - 07:55 AM
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.
Did the stretch test and shaped the recess a little more to clean it up so there are no lumps.
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.
Posted 18 November 2010 - 10:21 AM
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.
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.
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.
Tomorrow morning I plan to install the coaming and then I will move on to the hatches.
Posted 19 November 2010 - 08:11 AM
Posted 19 November 2010 - 11:13 AM
Not sure I follow exactly what you're suggesting but any time you have a hard edge you risk catching it on something. So anything I mount to the side of the stringer could be a problem. Partially glassing the bottom would leave you with a hard edge and I am not a fan of glassing them anyway. It takes away the flexibility of the skin.
What I need is wider keel with a skeg box attached to that. Of course that present some interesting issues too.
Posted 19 November 2010 - 01:00 PM
Posted 19 November 2010 - 04:55 PM
Posted 19 November 2010 - 06:42 PM
Posted 20 November 2010 - 08:48 PM
The recessed hatch on the front came out very well. Must say thanks to 'wysedav' over at Blue Heron for the idea.
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.
Posted 25 November 2010 - 01:51 PM
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.
Posted 25 November 2010 - 06:51 PM
Posted 25 November 2010 - 08:15 PM
The seat is from Joe over at Redfish. You can by precarved blanks, he does the tractor seat and then you can trim it to fit to hull. But for $10 more if you send him a template he will cut it to fit and it's well worth the $10 too. I did two and now I let them do them for me. They are not cheap but they are the most comfortable seat I have used and I gladly pay his price. He will ever make you a complete seat. It has the hip pads and back rest all built in one unit. If I ever settle on one boat I might get him to make me one, but I keep swapping boats.
As for the seat boards, if you don't get them up some you can tear a skin. I have only torn one and it was because I had the seat boards too low. A rock lifted up the skin and hit the seat boards. It ripped it right open. Now I design all mine with more clearance to prevent that. All my frames are cut out for the same reason.
Posted 25 November 2010 - 09:19 PM
Well done. Beautiful.
Let us know what it weighs...
...and how it paddles.