Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Sunday, March 31, 2013

Gluing Frame Assemblies - Second Attempt

I've worked out the kinks in my glue up process and have started making progress on getting the frames glued up. I'm still taking my time and doing each glue up in stages, and so far the results have been satisfactory.

The basic process is to edge glue two frames parts together first. Let that cure, and then clean up the glue line. Then edge glue the filler block for that joint and let that cure. Clean up the glue line for that and then glue on a gusset. So far I've glued up portions of frame 4, 5, and 6 with 6 being the furthest along. There are faster ways of accomplishing this, but I am not in a hurry and prefer to do it this way.

Here is frame 6 getting reglued. The cinder blocks are a cheap way of getting some weight to hold the parts flat (I bought 6 of them for less than 10 dollars). They are resting on a piece of particle board (MDF) which helps to hold the frame parts flat and protects them from the cinder block. There is wax paper between the frame and the layout board as well as MDF. This keeps the epoxy from gluing the frame to the layout board and MDF. In this first photo the left corner has not been glued up yet but the frame pieces have been nailed to the layout board to prevent movement.


Here is the result of that second glue up. As you can see, the glue joint is much better and the parts are aligned. Once the glue is cleaned up on this surface, a gusset can be glued to it.


These three frames are all assembled with two frame parts making the bottom section so I am able to glue them up separately, I will join them in the middle after finishing up the first side gussets. The two larger parts in the next photo are from frame 5 as these two parts are edge glued.


Then frame 4 parts are edge glued. The filler block for frame 6 has also been glued into position. 


Next step is to glue in the filler blocks for frames 4 and 5. Here is the filler block for frame 4 before gluing.



And here is the frame 5 parts after the filler blocks have been glued in.


The plan is to glue up the gussets for these three frames on one side only. Then I will flip the frames over and glue up the gussets for the other side as well as the floor timbers. The process will be a bit different for the second side because the gussets on the first side raise the overall assembly off the ground. So it will be necessary to support the frames with scrap plywood when I get to that stage.

The final picture shows the frame 5 parts after the gussets have been glued on. The glue has not been cleaned up yet. In addition to gluing the gussets, they are attached with bronze boat nails. Boat nails are nails that have ridges on the shank of the nail. The intention of the ridges is to hold the nails in place after they are hammered into the wood.



The process of gluing up the gussets is a bit more complicated than edge gluing. I read in the Glen L builder's forum that some people have had problems with glue joints being starved of glue after the curing process. The suggestion made in the forum is to do the glue up in two steps.

First apply the epoxy resin to the gluing surfaces before adding any filler material to thicken it up. A chip brush works fine for this. Then thicken up the resin and apply the thickened resin to the same gluing surfaces. The initial coating of unthickened resin will soak into the wood and keep it "wet" until the second thickened layer can cure.

Then, the boat nails need to be added to the assembly while the glue is still curing. It is best to pilot drill each hole with a drill bit a smaller than the nail shank diameter. This helps prevent the nail from splitting the wood as it is driven home. The gussets will want to move around as you are driving the first nails so I would drive a couple part of the way in, just enough to prevent movement. I would make sure that the gusset was in the correct position as I did this. Once those initial nails are partly in, I would pilot drill the remaining holes and add the remaining nails Afterwards, everything is cleaned up to get most of the excess epoxy off the parts. Finally the part is covered with wax paper and the cinder blocks are placed on top to hold the part flat until the resin cures. I usually let the parts cure a minimum of 8 hours before removing the cinder blocks.

For those unfamiliar with epoxy resin, I will give a brief explanation of the process I use for preparing the resin. This Marine grade epoxy resin was purchased from Glen L Marine and included a bag of white silica beads. These are very tiny beads that are used for thickening the resin. You don't want to breath these, so best to wear a respirator or dust mask.

The resin is mixed 5 parts of resin to 1 part of hardener. This can be done by volume or by weight. I prefer to do this by weight as it is more accurate. I bought a digital scale from Harbor Freight Tools just for this purpose.




The scale has a button to tare the scale. This means that you can put something on the scale and then zero it out. This way, it is easier to add the exact amount of weight of what you need. So I first place a plastic cup on the scale and reset it to zero. The I add the desired amount of resin. I have been typically working with 1 ounce at a time, (sometimes 2 ounces). The scale is then reset to zero again and one fifth (or 0.2 ounces in this example) of hardener is added. Then I use a wooden stir stick (popsicle sticks or tongue depressors) to stir the mixture for a minimum of a minute.



The last step is to add a small amount of silica to thicken the resin. This should be done after mixing. You need to add this in small amounts because it doesn't take much to thicken up the resin. Depending upon the application, I generally try to get it the consistency of warm peanut butter, (maybe even a bit less thick). This is mixed up and then it's ready to apply to the parts. The parts should be cleaned beforehand. I use denatured alcohol to do this.

One final note. Epoxy resin is nasty stuff and you don't want to get it on your skin. So wear protective gloves. I won't go into all the safety issues here, but suffice to say, it is best to read up on this before attempting this for the first time.

Until next time..............

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