This is the one area where I have tried several different ways to secure a radio board to the inside of the model yacht without satisfying results. Most radio board mounts I have seen are attached to the hull itself. I guess for the most part this is ok but I have never enjoyed the effort of gluing the mounts to the inside of the hull. Just trying to keep the mounts level and parallel was more than what I wanted. Not only that, I just didn't like the idea of gluing stress points to the hull. It may be me, but I only like to glue needed items to the hull (keel trunk and rudder tube).
Well, my problem was resolved a few years ago when I obtained an Orco Skinny Marblehead that was built by Swede Johnson. Swede had a great idea. He attached his radio board mount to the keel trunk! No more trying to setup and glue to the inside of the hull. No more trying to measure the crossbeams and making them level. No more anything, the keel trunk did all the work!
With Swede's idea, I have put the radio board mount on the keel trunk of five boats. I have changed a couple things from the way Swede did his in the Orco Skinny. The mount in the Orco Skinny was made of aluminum and ran the full length of the keel box. Instead of aluminum I use ¼ inch oak and instead of a full length, I make mine only go half the length of the keel box. Now you maybe asking a few questions like "Is it strong enough?" or "Is it too heavy?" or maybe "Can it slip off?", The answers are yes, no, and no.
First, is it strong enough? I use ¼ inch thick oak wood to make my radio board mounts. The reason I use oak is because of its strength. Oak is strong, even with the shape of this radio board mount design. You'll need to tap a hole so you can screw bolts into oak.
Second, is it too heavy? No. Once construction is done, the weight of an oak radio board mount is no more than one made out of spruce, and far less than aluminum. If you add up the wood needed to attach a standard horizontal mount to the inside of the hull, it will be almost the same weight as the oak radio board mount. For the added strength, a slight more weight is well worth it.
Third, can it slip off the keel trunk box? No, once it is glued on it is not going anywhere. But you may ask what about with a full stress load of the sheet lines and rudder connection? Not a problem. With a little "extra" support from non-wax dental floss that's right, non-wax dental floss it will never slip off. Once the primary gluing (with Epoxy) has been done and allowed to set up, non-wax dental floss will then be used to make sure everything stays in place.
As you can see in Example 1 the radio board mount is rather simple in design and construction. Using ¼ inch thick oak gives the best results for what is needed for a 36/600 or 1 Meter, (or similar size boat). For Marbleheads you may want a slightly thicker piece of wood, say 5/16 of an inch. As for the length and width, it is really up to the builder on the size. For 36/600s, the size displayed in Example 1 has been successful and has held up to the stress of sailing without failing.
As previously mentioned, to make sure the radio board mount does not slip off the keel trunk, I have drilled two small holes, one at each end of the forks to loop the non-wax dental floss through, see Example 2. Don't use waxed dental floss because it will repel the Epoxy. Dental floss is very strong and light (try to break one strand with your hands, you can't). To attach the floss to the mount, I only loop ten times through the two holes around the keel trunk box. Once done, I tie off and glue the floss to the keel trunk.
It should be understood the keel trunk will take a lot of the stress, so it is important to make sure it has been connected securely to the hull and deck beams, and is of good construction. That is why I put a little more bracing to the keel trunk box. For the past three 36/600s radio board mounts I have built this way, there have not been any problems.
When installing the radio board mount, the goal is to get the radio board down as low as possible inside the hull. This is because you want the weight of the sail winch, rudder servo, and receiver as low as possible for better stability. You don't want the sail winch or the rudder's servo cases touching the inside hull and causing wear spots. Nor do you want the sail winch case or rudder servo case touching water that might get inside of the hull. I keep my sail winch case (since it is the longest) about a ¼ inch up from the inside of the hull.
To place the radio board mount correctly on the keel trunk, you can hold the radio board (with gear) in the hull and adjust up or down until you find the right spot. Or you can hold just the sail winch in the hull and "eye ball" it, and mark the spot on the keel trunk box. The best way is with a complete radio board.
Once you have sawed out the radio board mount, sanded the forks enough so it fits snug on the keel trunk, remove it and drill the holes. Drilling the two small holes on the forks is simple, but the two other holes need more work. Oak is great to drill and tap, so select the size of bolt you want, get the correct drill and tap, and do the job. Once I have drilled and tapped, I like to place a drop of CA glue into all four holes to harden them up. The CA glue makes the holes even harder and stronger. Before you glue the mount on, check and test your work. Failure to double-check now could result in problems later.
With that all done, it is time to glue. Just put some on the inside of the forks and slide it on and level it at the marked spot. Check to make sure everything is right and let the glue set. Once the glue has set, loop the non-wax dental floss through the two fork holes, tie off, and glue. When the Epoxy glue has set and dried, you now have a nice radio board mount. This design allows quick and easy access when you need to work on the radio board.
Next time we will go over making radio boards that work well for this type of mounts. Until then, have fun building!