Intro and new boat build
- Thread starter Kudzu
- Start date
LOL. They are tough but they are not indestructible. 12 oz nylon is probably the toughest fabric, it take a lot to damage it. But of course it has drawbacks but that is what I use if I have a boat that is going to see rough use.
Jack, in your case I would probably use the 12 oz. nylon from what you said. It takes a lot to puncture the skin but if you did, assuming it is something sharp it will cut it with ease. The good thing about nylon is it has a lot of stretch so it takes more to puncture it. If you do, pull it to the bank, pull out your emergency kit, dry it off and apply duct tape and off you go.
I have only damage one boat, I was running moving water, I hit something hard! It appear it pushed the skin up so far that it caught on one of the frames and the boat came to dead stop. I really thought it had broke a frame it stopped so hard. But instead it had pinched the skin and ripped it. My buddy was in a brand new plastic boat and he had some MAJOR gouges in his boat. We never did find what was in the water but it damaged both boats. Of course we shouldn't have been doing what we did but it was fun. :mrgreen:
Jack, in your case I would probably use the 12 oz. nylon from what you said. It takes a lot to puncture the skin but if you did, assuming it is something sharp it will cut it with ease. The good thing about nylon is it has a lot of stretch so it takes more to puncture it. If you do, pull it to the bank, pull out your emergency kit, dry it off and apply duct tape and off you go.
I have only damage one boat, I was running moving water, I hit something hard! It appear it pushed the skin up so far that it caught on one of the frames and the boat came to dead stop. I really thought it had broke a frame it stopped so hard. But instead it had pinched the skin and ripped it. My buddy was in a brand new plastic boat and he had some MAJOR gouges in his boat. We never did find what was in the water but it damaged both boats. Of course we shouldn't have been doing what we did but it was fun. :mrgreen:
I've gouged my plywood boats here on canoe landings that had been improved by our Department of Natural Resources. Their idea of improvement includes adding broken concrete - with rebar sticking out if possible to locate some - near a nice, sloping sand beach. They then stick up a sign reading "Canoe Landing". The Nazi's could have taken lessons from them for preparation of Omaha Beach.
I can imagine! I've seen fabric airplanes come unscathed from hailstorms that beat the dickens out of metal and composite planes!Kudzu said:
One Cub had the windscreen broken, the rudder-top beacon lens trashed, the metal engine cowling looked like it'd been through a hammer-mill, but all the fabric was still looking good.
That may fit the parable of the willow and the oak? The oak did not bend in a strong wind, and broke. The willow bent in the wind and survived.WDfrmTN said:
The fabric, like other good things, stretches just a bit to accommodate a foreign object. It'll stretch a mile before it'll tear an inch.
Not surprised... well a little bit. Airplane fabric is a lot lighter than even the lightest fabric I use. It really does take a lot to put a hole in one, I have never even scrapped out up except for that one. After that I went back and changed my designs to allow for more clearance too.
Help me here? Where did you add clearance? How? For what effect? I'm trying to learn here.Kudzu said:
Don't have a diagram handy but look past the feet at the frame in front of them.
See how the skin arches inward and how the frame is cut out? That is the clearance between the skin and the frame. The skin will arch inward some from water pressure. When you hit something it lifts the skin upwards and you don't want it catch on the frame. In the boat I damaged I had the seat boards to low and did not allow enough clearance. It would be fine 99.5% of the time.
But running moving water, a sharp something and the momentum of being in the current lead to a very hard impact. It knocked my spare paddle off the boat it hit so hard. My nose almost hit the front deck too. So this was not a normal bump into a rock. It was more like slamming into a rock.
See how the skin arches inward and how the frame is cut out? That is the clearance between the skin and the frame. The skin will arch inward some from water pressure. When you hit something it lifts the skin upwards and you don't want it catch on the frame. In the boat I damaged I had the seat boards to low and did not allow enough clearance. It would be fine 99.5% of the time.
But running moving water, a sharp something and the momentum of being in the current lead to a very hard impact. It knocked my spare paddle off the boat it hit so hard. My nose almost hit the front deck too. So this was not a normal bump into a rock. It was more like slamming into a rock.
OK, I think I understand now, thanks. Cutting an arch into the underside of a rib, (and, maybe adding a similar arch to its upper surface to maintain full cross section?) so the skin can flex. Has that put any strain on a smaller area of skin that has caused any problems?
I used to paddle with a fellow whose boat ribs were willow branches from his front yard. He claimed they had a lot of flex in them. The main beam supporting the entire boat was the gunnels.
I used to paddle with a fellow whose boat ribs were willow branches from his front yard. He claimed they had a lot of flex in them. The main beam supporting the entire boat was the gunnels.
I have a 21st century kayak SOF kit I am working on. Here's how it works on theirs.
The boat shape is defined by two things. Stuff that runs fore/aft like the keel, the gunwales, the chine stringers and the deck stringers. Those are held in place and given their shape by various ovaloid shaped pieces of plywood at certain places along the length of the boat (you might call these stations or bulkheads).
The skin is in complete contact with almost all of the outermost surface of the stuff that runs fore/aft. Now pick a point along the keel where say a bulkhead is. Place a straightedge there to say the chine stringer. The fabric will follow that straight line. If you look at the bulkhead, it will be arched inwards for the reasons Kudzu gave. There will be a gap between the straightedge and the outer edge of the bulkhead. I suspect its also one less place for sand/debris to get trapped as well as allowing the boat to be cleaned out easier.
I guess you could also arch the stuff running fore/aft, but it would make things much much more complicated .
The boat shape is defined by two things. Stuff that runs fore/aft like the keel, the gunwales, the chine stringers and the deck stringers. Those are held in place and given their shape by various ovaloid shaped pieces of plywood at certain places along the length of the boat (you might call these stations or bulkheads).
The skin is in complete contact with almost all of the outermost surface of the stuff that runs fore/aft. Now pick a point along the keel where say a bulkhead is. Place a straightedge there to say the chine stringer. The fabric will follow that straight line. If you look at the bulkhead, it will be arched inwards for the reasons Kudzu gave. There will be a gap between the straightedge and the outer edge of the bulkhead. I suspect its also one less place for sand/debris to get trapped as well as allowing the boat to be cleaned out easier.
I guess you could also arch the stuff running fore/aft, but it would make things much much more complicated .
If I follow your description correctly, the only wood touching the skin is longitudinal framing members. Transverse framing, (bulkheads, ribs, etc.) has longerons and stringers attached longitudinally along their outside edges. Edges of crosswise framing do not extend out to or beyond the longitudinal framing.
That clicks with my memory of pictures of some kayak frames. I never thought about why that was so, but impact would certainly be minimized that way. As the hull strikes an underwater object, it would tend to slide along it rather than impinge onto it.
That clicks with my memory of pictures of some kayak frames. I never thought about why that was so, but impact would certainly be minimized that way. As the hull strikes an underwater object, it would tend to slide along it rather than impinge onto it.
In my amateur opinion that frame is pretty heavy duty. Probably more than it needs to be. My 21st Century kayak kit is pretty similiar in shape and size to that boat and it appears to my eye to be significantly less heavy duty. Thats not to say my kit isnt heavy duty enough. If anything, I say my kit is also probably still a little overbuilt. When you are playing with the various "sticks", things seem pretty wimpy. But once you get that frame all glued up it really gains some strength so to speak.
I'd get rid of the stringer thats between the chine stringer and the gunwale stringer ( I think its totally unneeded). I'd also cut out a good fraction of that stern piece of plywood with "lightning" holes (both the deck piece and the vertical piece). Even the chine stringers and gunwale stringers could probably be a decent fraction smaller.
Just my hopefully useful opinion. I myself am a trying to reform diehard lifetime member of the brick outhouse school of thought
Did you weight this boat at various stages or get an all up and finished weight?
take care
Blll
I'd get rid of the stringer thats between the chine stringer and the gunwale stringer ( I think its totally unneeded). I'd also cut out a good fraction of that stern piece of plywood with "lightning" holes (both the deck piece and the vertical piece). Even the chine stringers and gunwale stringers could probably be a decent fraction smaller.
Just my hopefully useful opinion. I myself am a trying to reform diehard lifetime member of the brick outhouse school of thought
Did you weight this boat at various stages or get an all up and finished weight?
take care
Blll
I appreciate the input and I agree that a lightening hole on tail could be added but it's only going to save a few ounces. I usually cut one but this is the third frame design for this boat and I just didn't think of it. Add a lightening hole on the top piece would telegraph through the skin and look really bad so that will not happen.
I never have used a stringer down the side before but the previous prototypes of the frame had to much flex in the vertical plane due to the large open cockpit. I lost a lot of the rigidity that is normal there because of the deck tying the sides together. Adding that strip was a new idea and it worked perfectn no flex in the frame and no wasted energy paddling. Plus I have some ideas for a new design based on this one.
Finished weight was 37 pounds, a couple more than I expected but that includes the rod holders and considering the larger size of the boat compared to the Sea Kayaks I usually build, it is in line. At least an extra pound went into building the hard surfaces for rod mounts and the storage crate too.
Is 21st Century kayak still in business? They let their web site go looks like.
I never have used a stringer down the side before but the previous prototypes of the frame had to much flex in the vertical plane due to the large open cockpit. I lost a lot of the rigidity that is normal there because of the deck tying the sides together. Adding that strip was a new idea and it worked perfectn no flex in the frame and no wasted energy paddling. Plus I have some ideas for a new design based on this one.
Finished weight was 37 pounds, a couple more than I expected but that includes the rod holders and considering the larger size of the boat compared to the Sea Kayaks I usually build, it is in line. At least an extra pound went into building the hard surfaces for rod mounts and the storage crate too.
Is 21st Century kayak still in business? They let their web site go looks like.
I like the overall design of the frame. It seems that lighter materials throughout could suffice?
Your observation of an assembled frame gaining strength from integration of all other supporting members is absolutely correct. Both ships and aircraft bear that out.
Your observation of an assembled frame gaining strength from integration of all other supporting members is absolutely correct. Both ships and aircraft bear that out.
I have avoided asking this for risk of sounding like a smart alec,, so if this comes across that way it's not meant that way.
What make everyone think it is over built and so heavy?
I agree on the lightening hole on vertical pieces, that was just an over site but this is a prototype and the plans show one.
Stingers are only 5/8" thick.
The center stringer was to try to add a little stiffness because the first prototype flexed to much. This solved it and added just a few ounces.
Does the photo make it look big or is there something else? I have been confused and hesitant to say anything. I have built a lot of this style boat so this is not my first one. Here are few of my designs.
What make everyone think it is over built and so heavy?
I agree on the lightening hole on vertical pieces, that was just an over site but this is a prototype and the plans show one.
Stingers are only 5/8" thick.
The center stringer was to try to add a little stiffness because the first prototype flexed to much. This solved it and added just a few ounces.
Does the photo make it look big or is there something else? I have been confused and hesitant to say anything. I have built a lot of this style boat so this is not my first one. Here are few of my designs.
The photo of the finished frame just looks darn heavy to me. The lumber dimensions look over-sized. It could just be the camera angle. Or, maybe the camera just makes the wood look "fat".
Very nice looking canoe in that last set of photos. I like!
Mike
Very nice looking canoe in that last set of photos. I like!
Mike