Build a boat! Build a Tolman Skiff! All it takes is to start making sawdust.
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Well I did not quite catch what your purpose was in your post. About gluing the seams...
A hard chine boat form can be defined with only 3 lines in the 3D space: The keel, the chine and the cheer. The chine flat can be derived from the chine line. Traditional wooden boat builders have created the hull form with the help of molds/framing at stations. These forms/molds have then been incorporated into the hull as its stiffening structure or removed later as the hull is finished. Renn tried to get rid of these structures in the building process, and managed to do it for the most part. Renn did it with a simplified structure and detailed drawings and instruction on how to cut the ply. Basically the form of the hull is based on stitching the curves together.
==> The seams are extremely important for maintaining the proper hullform. There is nothing else to maintain the hullform in the middle of the build untill you have finished all the seams. Renn suggests some temporary pieces every now and then, but still... seams are crucial for the proper form. So I suggest a few things.
1. Be precise in cutting the pieces according to Renns instruction.
2. Make sure both sides of the bottom and side panels have the same mirrored form.
3. When using zip-ties or copper wires... or whatever, you maintain the same tightness and hole distance from the panel side. This helps maintaining symmetric form. Rounding the edge of the plywood with a block plane or router so that you only have 1 point of contact to the next plywood panel indpendent of the angle, might also help in getting the panels fit nicely. It also increases the surface area of the plywood in the joint.
Above should be self evident. Just remember that the zip-ties / seams / corresponding 3D lines define the form of the hull.
How to GLUE the seams? (In general)
1. Wetting the wood fibers with epoxy.
All gluing of wood with epoxy should have as the first stage, the saturating of the wood fibers with unthickened epoxy. Warm epoxy has lower viscosity than cold epoxy, so it penetrates wood better. You simply add as much as it takes. Especially end grain need to be filled properly. Different epoxy brands have some differences in viscosity, but in general, any laminating epoxy should have low enough viscosity. There is no need to by any special penetrating epoxy. Especially do not fall for the idea to use a thinned down epoxy version. Adding a thinner to lower the viscosity or using an epoxy brand that has in it some thinner that evaporates IS BAD. It makes the end result worse, as the evaporated thinner leaves the epoxy porous. The proper way to lower viscosity if its needed is to store the epoxy in a warm place before usage or put the can in a warm water bath for a while before use. Warming up the workplace also helps. What ever suits your situation.
2. Before the first layer has fully cured you start the gluing process with thicker stuff. The timing is important. The thickened epoxy adheres to the epoxy you have wetted the plywood with chemically, provided you are adding it while the curing has not gone too far. If you add the second layer within the open period it all cures as one piece. Chemical bond is the strongest. That is why you want to have a chemical bond whenever you can. So its important to find out the open time frame for the epoxy brand you are using. Ask the rep for this data. If you cannot get this data make a small test and time it in the conditions and temperature you have. For how long can you still make some dent in the epoxy surface with your fingernail. You do not have exact time, but you have a basis for planning your workflow. You always need to do the next layer within this timeframe. ==> Chemical bond, no sanding.
The thickness of the stuff used to fill the seam and form a nice rounded surface depends on what you are doing and what works best in the situation. For seams you probably want the stuff to be quite thick. People talk about peanut butter consistency. You cannot really form any round forms or fill anything properly if its too watery. There are many things you can use as filler. Most brands also sell some fillers for this purpose. Different fillers work best in different places. If you have some sawdust lying around, you could use that also. If you watched the videos I proposed you saw Dan use a metal ball on a stick to form a round seam. He also used a silicon kitchen spatula. You could use a piece of plastic that you cut to proper form. Keep it clean. Do not leave excess filler epoxy around. Its hard to remove once it has hardened. The aim is to make a smooth round seam in preparation for the actual strength that comes from the glass strips across the seam. In the ideal case you will be able to get a smooth properly rounded seam that is filled with peanut style epoxy, and your stiches will not stick out too much to mess up the nice seam.
3. The next phase is using glass strips. You need to stagger the layers. For example first layer 2 inch wide strip. Then 4 inch wide on top of that. Then 6 inch... The idea is that you get as much fibers across the seam as possible, while still keeping the edge low. Putting several edges of glass on top of each other will create problems with smoothness. First put a rich layer of epoxy on previous semi-hardened layer of epoxy putty, then add the cloth strip and the add unthickened epoxy again to fill the cloth. If needed to make a smooth curvature you can also also add thickened epoxy. Just fill the cloth first and avoid air pockets, and work within the open time period. Read the book for required total thickness of the glass in the seam. Pay attention to the direction of the glass fibers when you acquire the glass strips. Fibers should go across the seam, preferably +/- 45 degree.
4. On top of the last layer add peelply to smooth out the seam and squeeze excess epoxy out.
(Try to keep the rest of the plywood panel clean. You could use masking tape if needed. Its best to do the rest of the panel similarly in stages: Wetting the wood with epoxy, second layer of epoxy, cloth and filling with epoxy.... so that you always continue the next layer within the open period for chemical bond, so keep the surface clean until you start that process.)
5. You should be able to take the Zip-ties / copper wires out from the other side, once the epoxy has cured. This leaves a small hole that you can fill when you do the other side.
6. One additional step that sadly Renn does not tell anything about is raising the temperature for a few hours for additional development of strength. In industrial processes epoxy is usually put in a big oven for some 12 - 48 hours for proper curing. The epoxy products that are made for boatbuilders are specially designed to allow for curing in normal room temperature, but they usually also benefit from this oven treatment. So if its possible to raise the temperature for a day or two after the initial cure, you will have stronger epoxy. You can see also how Dan did this in the video series by covering the boat and having a heater.
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Think this through before starting
The placement of the zip ties is crucial for a smooth seam. If you manage to make a nice round seam with the peanut butter stuff with the zip ties in place, then everything after that is easy. You can easily get the glass strips cleanly in place after that, but... if the zip ties are too far in, you might have problems making a clean seam. If the zip-ties stick out from the seam its harder to make a clean seam. So you need to think through this in detail before you start the whole process!
How are you going to hinder peanut stuff leaking through to the other side if your have too much space between the panels. In this case you could for example use some masking tape on the other side. How are you going to remove the zip ties /copper wires? Are you going to remove them? Can you get a smooth seam while they are in place? If not, do you have to make this part in stages? The panels must be held in place until you have proper seam. At first stage you only glue enough to make it possible to remove the Zip-ties, and then make the final smoothed seam after removing the ties. You need to figure out what is realistically possible. Much depends on the placement of the zip-ties and the accuracy of your panel cuts and placement.
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Jallii, there are two kinds of countries on this planet... those that use the metric system, and one that put a man on the moon.Corrected quote: "There are two kinds of countries on this planet...those that use the metric system, and one that put a man on the moon (using the metric system)."
https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure
Ha! Too funny.
You mean the country was the first to put a man on the moon and had its space program blow up in one big bang and is depending on its enemies to continue bringing people to and from the international space station while China and India sending stuff to the dark side of the moon and russia is putting its permanent station on the moon.
Jallii, there are two kinds of countries on this planet... those that use the metric system, and one that put a man on the moon.Corrected quote: "There are two kinds of countries on this planet...those that use the metric system, and one that put a man on the moon (using the metric system)."
https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure
Ha! Too funny.
