Do you feel lucky? If so the process of installing the keel trunk is the "make or break" step in the construction of the boat hull. Doing it wrong is a mistake that is hard to repair. This may sound strict, it is. Besides locating the point of where to install the keel, gluing in the keel trunk has the same equal importance. But don't fear with some good information, thought, and planning the job will be easier.
The goal is to have the keel hang below the hull at exactly 90 degree angle to the deck line, see example 1 above. Not doing so will cause the boat not to sail right and loose performance. To help avoid this problem of suspending the keel under the hull, this article will hopefully provide some help information.
The first question is how to create the 90 degree angle of keel to deck line without error? Getting this to happen with a boat hull provides a greater challenge, not so. This article will explain a simple way to do this. It is called gravity that's right, gravity. Why knock yourself out when using a simple act of nature to accomplish a complex task.
The first step is how to hold the hull to do this with? This is the easy part, the kitchen table. If you have a kitchen table that splits apart then you have the first problem solved. All you need to do is split the table to around four inches wide to where it cradles the hull well. Great, now how to obtain the 90 degree angle? It is easier than you think.
First get some white sewing thread and a lead fishing weight. Tie the thread to the lead weight, and tape the thread to the hull where the leading edge of the fin meets the hull. You have just created a functioning plumb line. By hanging the plumb's line right in front of the keel you now have a good way to gauge the perpendicularity of the keel to the deck line. Now all that is needed is to make the keel to line up with the plumb line.
To do this all that is needed is a simple pocket level that can be purchased from any hardware store for a few dollars. Just lay the pocket level on to a straight piece of wood right over or in front of the area where the keel box will be. Then to level the hull, just move the hull up or down until the level' s bubble is centered. Once done look below the hull, and see how the keel come inline to the plumb line.
Well there is the theory, now apply the fact. The first step is to find one end of the keel trunk box that allows the keel trunk to slide in and out with ease. If there is some resistance, correct it. The keel trunk must slide out with no effort. The reason for this will soon be known.
The second step is to make the keel trunk's end that goes into the hull flat and square, this can be done with a T square and some sand paper. Once the trunk box is square, insert the keel trunk into the hull from the outside bottom. Then place the keel box on to the trunk and make sure it slides off easily. To hold the keel in the box, barely screw in a long lock bolt with washer into the threaded hole on top of the trunk. Now the keel should stick out of the box about a half way from the bottom of the hull. Now hold the keel box and push the keel all the way in, and look at how the keel fits up to the outside bottom of the hull. It should be flush from the tip of the leading edge to well back on the fin. Next, the leading edge of the fin must be hanging at the correct angle from the hull, see Example 2 above. Some fins are straight and others are at an angle, make sure yours is hanging right, see Example 3 below. Along with that the keel box must be flush against the inside of the hull. If the keel is not right, correct it by sanding the trunk box until it is.
Next put the hull on to the split of the table with the keel half way in the box with the plumb hanging down ahead of the fin. Put the pocket level on a flat stick on top of the deck over the area where the keel box is at. Move the hull up or down until the bubble reads level, and check the plumb. The correct alignment is the keel fin must right in line with the plumb line, see Example 4 below. If not remove the fin and sand the box slightly, and test again. The keel fin must be on the line, and the pocket level's bubble must read level! Sand the keel box until it is. When done take a part and do again to check your work.
A long time ago I mention not to attach the lead bulb to the fin. The reason why is it gets in the way the plumb line, and the weight can cause problems when securing the trunk box. Now comes the most important part of the process, securing the keel trunk box inside the hull. No room for errors at this point.
With the hull level and keel true to the plumb line there are several ways to temporary attach the box to the hull before final gluing. One way is with CA glue, very dangerous. If the CA glue sticks to the keel while it is in the trunk box, disaster! The second way, and safer is to use Epoxy glue. All that is needed is two small drops at each end of the box in place so it won't move when the fin is taken out. The third way (the one that separates the men from the boys) is to glue a straight stick above the box, and lightly tape the box to it the stick.
I chose the third way (guts and glory). I very lightly attach the trunk box with tape while checking alignment of the pocket level and plumb line. Work carefully and check your work often. Now comes the magical time, getting the keel out without the box moving any. Remember I said barely screw in the lock bolt and no resistance of the keel sliding out? With a very gently turn of the lock bolt, the keel should drop out perfectly.
If your confidence is still with you, now comes the "gluing". With rapid setting CA glue, very carefully place a couple drops at both ends of the keel box where it meets the hull. Please, don't let the nozzle of the CA glue bottle touch the hull or keel box. Just allow the CA drops touch (if it would help practice first on something else). Once the CA glue is in place, let it dry then apply more, a lot more. If it takes a while for the CA glue to dry, let it, don't get "glue" happy.
For doing the final gluing of the trunk box to the hull, I use slow setting water proof two part Epoxy. I have used it on a fiberglass hull and a kevlar hull without any problems. So for this fiberglass hull I'll use it again. Since the Epoxy sets up in a half hour, I have some work time to do it right. I first cut up some small patches to fiberglass cloth that will reinforce the glue joint. I also cut two spruce support sticks that will be glued in too.
To start the process I mix up a medium amount of Epoxy, and apply it to the trunk box/hull joint with a small stick. Again, I don't touch the keel box (or the entire hull for that matter), I just let the Epoxy drip off onto the joint. I do this all the way around the joint on the first pass. At the end of the first pass the Epoxy starts to set up, I mix another amount, but before I apply it I place the fiberglass cloth on to the joint. I then start applying the Epoxy. Please, only use enough Epoxy to do the job. I lightly touch the cloth with the stick to make sure the Epoxy soaks through. I next place the two support stick into place, and drop on some glue. By this time the Epoxy has seeped into the cracks of the joint, soak through the cloth, and is now setting up. And that is it. During the "gluing" I make sure the glue joint is the same thickness all the way around and there is good coverage of Epoxy on the hull (a half inch).
When done I let the hull sit for eight hours and let the Epoxy cure before I touch it. At this point you have reach the "point of no return" so sit back a wait. After eight hours I clean off any Epoxy that leaked out to the outer hull with a sharp knife and finger nail file. I then take the keel and place it in to the keel trunk and bold it in. I then put the hull back on the split table, level the deck, and check the keel to the plumb line. Ah, a perfect success!
Now I must say this is my sixth hull so I have had some practice, but that does not mean mistakes can't happen, they do. To avoid mistakes, think, test, ask questions, and test again. Once this part is done the rest is easy!
