AeroE

The closer the skeg is to the longitudinal center of rotation, the more it affects side drift in a wind. If directional stability is needed, then the size has to increased. Nearer the stern, the area can be reduced to provide sufficient directional stability, plus a smaller degree of lateral drift. (I'll have to read up on the naval architect's vocabulary for the air vehicle analogs.) Jeff, What you "need" is an experimental mule with four or five skeg receptacles ranging from the boat's design CG to the stern. The construction part wouldn't be to much more difficult if the manual retraction/extension is eliminated. After about 15 seconds of thought and no sketches, I would start with a long trunk from just behind the cockpit all the way to the stem, either with a series of slots where a skeg could be slipped in and secured with a wedge, or build skegs into the trunk from the start to be deployed one at a time. Some minimal ballast might be needed forward of the cockpit to trim the boat.

I have a spreadsheet set up that allows quick calculation of the effect of changing the shape of the waterline on sinkage. I integrate a fourth order polynomial equation to get the waterline area, then calculate the volume required for a particular displacement. I'll post a typical example if I can figure out what I need to do to host the picture(s). I'll put the example I intended to post into words. Waterline length: 15 feet, beam: 20 inches, location of maximum beam: 0.55(15) feet from the bow, entry angle: 7 degrees, required displacement: 50 pounds, water density: 62.4 pcf. The slope of the water line plane is zero at the maximum beam. The resulting equation for the waterline shape (half shape along the centerline) is buttline, y = 0.000 000 029 71x^4 + 0.000 014x^3 + 0.000 884x^2 + 0.1222X. Multiply the integral by 2 to get the waterplane area. The waterplane area is 15.81 square feet, so the sinkage to support 50 pounds is 0.61 inches. Not much. But, the perimeter length is 30.23 feet, so the added wetted area is approximately 1.5 square feet (using a constant area cross section). This squares with a bunch of layout work I made last summer; these little boats have wetted areas that are very sensitive to minor changes. (I was working on minimum wetted area shapes for the E340 race which requires solar power and battery storage with no other motivation for propulsion, so the power required to move the boat has to be extremely small in order to complete the long race. Or even get to the end of the first day of the race!) Fooling with length in addition to the beam can screw up the stability simply due to the loss of volume along the length of the boat even though that volume might be relatively close to the centerline of the boat, it's still contributing small righting moment. This is the reason long boats with beams and reasonably similar cross section shapes equal to a shorter boat can yield more rolling stability. It's also the reason very short kayaks get fat, the volume and stability has to come from some place and there ain't much place to get it from lengthwise.

I have made some sketches of a SOF surf ski, but after paddling a V8 (owned by the dealer in Olathe!), I'm way less enamored by the idea unless the seat includes drainage. If I want to sit in a puddle of water, I'll get a wash tub. The bailers work pretty much well enough to keep the cockpit from completely filling, but the boats are light years from "dry" inside. That's probably okay for skiing in surf for short periods, but not for cruising, floating in the Ozarks, or racing. In my humble opinion. Seats with drainage and floor boards go a long way to cure that problem.

'Tain't big enough!

Avoid any sealer containing silicone at places where a permanent patch follows. It won't be permanent.

I caught the error when I lofted the boat in a graphics program, but it's so obvious that there's no doubt.

Tie the noodles in before skinning. Access for replacement is a good reason for two piece skins. Noodles alongside the cockpit exclude water at the widest part of the boat to aid stability if the boat is full of water, besides excluding as much water as feasible. Those are easier to remove and replace.

Build a finished boat and a bare frame to raffle or auction to help fund the project. The bare frame would be either for the buyer to finish or as a display as art. Several paddles, too. I think I would build one boat to start and use that one as the training aid and for development of patterns and fixtures, then pile into the 20 boat project. Man loading on a single boat will be a little bit of a problem as every kid needs to get hands on and not just observe, but the lashing should go quick! Maybe two training boats, slightly staggered in the schedule. Standardize the boats and limit the customization to finish and decoration.

Make a little "dollar" patch to cover the tear. Borrow your wife's pinking shears to cut out a circular patch to cover the hole. Bond it on with heat bond tape from the fabric store; the wife might have some of that, too. You'll need to remove the paint at the bond joint. Iron the edges down tight, then repaint. The repair will be hard to find from more than a few feet away. If anyone is bending over to inspect your boat, give 'em a boot in the butt.

I'll bet the bonded fabric will release with heat if it's ever necessary to reskin your boat. I guess there will be an aftermarket for good clothes irons now. An iron sold for aircraft fabric might be required for progress in boat building.

Boiled linseed oil is just about the worst choice possible for any wood project and particularly a boat. It offers no moisture protection, and requires days and days to reach anything like a cured condition. It looks great for a while, but there are better choices, such as one of the polymerized versions. Linspeed and Birchwood Casey's Tru Oil are two, although not in the quantity required for a boat frame.

A sail is about useless in the head wind that seems to favor this race. The MR 340 is an endurance race. Not a Saturday night dosey doe with a pretty gal. Whether the Missouri River is too dangerous is a matter of opinion from an assessment of one's personal risk tolerance and is not a universal opinion. Or particularly defensible. The first two legs check in times designed to push the paddlers in order to eliminate racers that will be too slow to complete the race. This year a new record time was set; 35 hours, 58 minutes. Pretty cool, that team earned the record. I have no idea about how the sponsors arrived at the 88 hour limit, but it's a practical limit on the demands from the race volunteers, and it's obvious that there's no point in a longer period, 88 hours is sufficient for every paddler that wants to complete the course but isn't interested in being the first boat to finish. Finishing the race is a considerable accomplishment.

When I was active in Scouting, we learned a suite of lashes for different purposes. Old scout manuals included tables and chairs, albeit more rustic than necessary. That idea does make wheels start turning ...

Thanks. I'm not necessarily looking for "free" per se; I've made a 3D model in which I modified the 12 foot boat's off sets to ~14 feet overall length in order to understand how a boat based on the 12 footer's parts might look. I think I kept one part unchanged in the second or third pass.

A linked .pdf file can be found with a search, but the file is corrupted. If there is a direct link from the Kudzu Craft web site, it's more than well hidden. I've looked through every page of this forum for information with no luck. Please advise if they have been pulled for use.

I'd try a sharp cabinet scraper first.

Have you tried a lint roller or a piece of duct tape on a small area of bare fabric? I have to think that a coat of finish would support enough of the fibers well enough that they could be removed with clean, sharp aluminum oxide paper.

How do the surfaces feel? Are the fibers causing the fuzz noticeable after three coats of paint? I would like to see a photo of the skin under a glancing light, in the shade or exposure to the Northern sky. I also wonder about how the fibers would respond to sanding.

Plywood in Peachtree City, Georgia: http://www.aircraftspruce.com/categories/building_materials/bm/menus/wp/plywood.html Lumber in the St. Louis region: http://www.beyerslumber.com/ http://www.wicksaircraft.com/index.html http://www.stcharleshardwoods.com/marine-plywood.html The Rockler's in Bridgeton, Missouri had half inch Baltic Birch for less than $30 for the 5 foot "half" sheets.

This afternoon I figured out that "where" the flotation is added is at least as important as "how much" due to the effect on the stability of a filling boat. (Besides preserving basic flotation and reducing the volume of water that has to be removed. I already understood the need for flotation above the CG, that's more or less instinct, but hadn't considered the benefit of flotation along the sides. I like the idea of air bags, I don't like the idea of leaky air bags, and even with a "pre flight" to check whether the bags are holding air, they're most likely looking for an excuse to leak.

The primary question I have is - How much flotation is recommended in a kayak? In other words, "What is the design weight or load?" Is it 100% of the gross weight (vessel plus crew plus equipment) or design displacment, 50%, or some other value? Does the Coast Guard provide guidance? Kayak and canoe flotation goes into the ends (first), because that is the volume that is available and the need to displace water from the ends to ease rescue. But that is also the most inefficient place to displace large volumes of water. Foam flotation adds weight. A light weight boat of 300 pounds displacement with 100% flotation requires 4.8 cubic feet of foam that weighs something like 2 to 3 pounds per cubic foot, so about 10 to 14 pounds of weight is added; that is significant in a boat that weighs 30 or 35 pounds before adding foam. Foam that is allowed to get wet will absord water, too, unless a conscious effort goes to drying the boat out and storing it in a dry place. Flotation bags are light weight, but it's hard for me to warm up to welded seam pvc or bonded neoprene assembly. The question is not whether the bags will leak, but when. Foam is dead reliable, cheap, and heavy. I intend to build a skin on frame kayak and I have no relevant experience in kayaks. I will use the boat on Missouri rivers. I'm concerned about the safety of these boats due to the low sheer, plus I'm interested in understanding the underlying design and engineering.

Right now I'm not trying to "improve" anything, just to understand. I hold a firm belief that we need to know what came before, first. I also know, for a fact, that the only way to know whether or how an idea or process works it to try it out first hand; there's no other way. But I'm also willing to listen to the experience of others, and I'm not against stealing good ideas.

Jeff, adhesives and bond lines always exhibit the poorest strength under peeling loads, so we have to design to avoid that condition. The best adhesive I've personally used and tested was a polyurethane made by PPG. Although that was not the primary purpose of that material, it developed 50 pounds per inch in a climbing peel test. The failure mode was mostly adhesion, but there was some adherend failure in the composite part. I failed to complete my thoughts about stitching as I got in a rush. Part of my objection is that the stitch line along the top of the boat looks a little too expedient. Which I have no problems with when warranted, but that standing seam just doesn't sit right. The seam along the stems clashes with my sensibilities of flow around an object in the water or the air. Maybe I just need to get over it, or figure out how to sew a French seam. Or give both a try. I'll have a harder time reconciling use of a skin that won't shrink and stay that way, but I may have to try that, too.

I've been reading everything I can find about skin on frame boats for the last week or 10 days. I've been contemplating a new canoe to replace the 18.5 foot Alumicraft I own; my goal was something shorter and lighter and easier to transport, preferably in the bed of my pick up. Photos of a new Cod Rib 12 set me off to research skin on frame boats. I have been familiar with Platt Monfort's boats since the first one he built, but hadn't looked at the current "state of the art"(!) of SOF building going on, and so I'm interested in these kayaks. The relatively simple assembly process meshes with my needs and my personality. My question; has anyone skinned one of these kayaks with the 8 ounce or heavier fabric using the adhesives for the Stits or Randolph process? I have experience recovering airplanes, I like the ability to shrink the fabric, and I'm confident in the seaworthiness of process. I'm not wild about the heat activated adhesive film used by Monfort and others, but I have no first hand experience with that process so I might change my mind after a trial part. I can't say I'm all that crazy about stitching the covering on either, although I suppose a relatively large whip or blanket stitch makes that go pretty fast. I'm wondering whether the skin squirms around the frame since it appears to be restrained only at the coaming and the stitching around the stems. I have a few more questions that I haven't seen addressed, but I'll hang onto those, this post is getting long. Lee