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Posts Tagged ‘RC boat’

Lurking below the OPUS rig which has been getting all of the attention lately is my new hull design, the Dragon. Construction is a hybrid form of my usual system, EPS foam core, balsa wood sides, stem and transom with a high density foam bottom. The bottom is 5mm thick and this allows the chine to be easily sanded to give a nicely radiused ‘soft’ chine. The deck will be 1/32″ laser cut birch ply and internal structure to our usual pattern, which means simple and as little as possible.

dragon_25 

The Dragon shape is changing a little from the prototype seen above, the stem or bow will be 1/4″ deeper and the transom 1/8″ shallower. This gives a little more reserve bouyancy at the bow and increases the deck rake a little, the transom angle is being increased too. The trailing bulb is an important feature of Dragon which allows the weight to move aft without compromising the distance between the fin and rudder, and therefore rudder efficiency. As the kit version is being built I will be adding a dinghy style spray rail and a lift off wooden hatch as has proved so effective on the recent Pond Sprites.

dragon_24
Production version of the Dragon foam core. 

The Dragon is a long hulled (fits diagonally in the measurement box) ‘new rules’ boat. She is designed to use a 3x AAA cell battery box for race performance but is definitely capable of carrying a 4x AA battery pack in a standard square battery holder. Being designed for and alongside the new OPUS una rig that is how the kit will be set up.

I am really excited about this project and will be moving ahead with it at full pace. As a result I am going to move forward with this boat ahead of the Pond Sprite project. I also intend to trial the Pond Sprite with the OPUS rig because I know that some people prefer a wider, 12″ long plywood boat and if the combination works then Pond Sprite will be a nice beamy alternative to Dragon. More news as it happens.

Graham

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Over the weekend I was asked for my thoughts on windy weather footy sailing by a group in Florida. I thought more people might be interested in a few ideas of how to handle strong wind conditions and  I can perhaps expand here on how I answered them.

The first thing to say is that the wind can get too strong for any size rig, even the tiny ‘B-rig’ as specified by the footy rules will simply be too big for extreme conditions. So these thoughts will assume that although the wind is strong it is not enough to change down in sail size. So we will look at how to tune the sails to manage the conditions better. Also this discussion assumes you are using a sloop rig with a main sail and a jib sail. 

Your main tool to combat strong wind conditions is sail twist. Allowing the sails to twist away from the wind towards the top of the sail will dump more air from the upper parts of the sails but maintain a good drive from the sails. The mainsail twist is controlled by the kicking strap or vang fitted from the main boom to the mast. The jib sail twist is controled by the ‘topping lift’ which is the line running from the rear of the jib boom up to a point on the mast or mast head where the forestay is attached.

By loosening the kicking strap the main boom will be allowed to rise and in doing so will control the amount of twist in the main sail. Likewise tightenning the topping lift will raise the rear end of the jib boom (you may have to ease the forestay tension a little) imparting twist in the jib. Set the jib twist to echo the shape you see in the mainsail, look from the rear with the wind filling the sails to see this.

Pond Sprite showing sail twist in main and jib

Pond Sprite showing sail twist in main and jib

The balance of the boat in high winds will tend to gain more weather helm, in landlubber talk that means that the boat will turn up harder into the wind when you are close hauled sailing close to the wind. Using more twist in the main than the jib and flattenning the foot of the main more than the jib are ways to control this ‘luffing’ into wind. Also you can move the jib pivot further forward on the bowsprit if you have one to combat weather helm in strong winds.

Sail foot curve is generally reduced too in strong winds. Set the outhauls (rear bottom corner sail attachment on booms) to allow about a 1/2″ curve from the sail edge to the boom at the mid point.

For a strong wind racing day I like to have a rig (about the size of the original Kittiwake I rig) which is set up with the ability to add a lot of twist in the main and the jib. The rig can then be detuned to be almost like a B rig and tightenned up considerably if the wind does ease a little. Then if the wind does get even stronger you can still change down to a rules size B rig.

Victor V12 with nicely set twist in a blow

Victor V12 with nicely set twist in a blow

Those windy days can be enjoyed, not avoided with the right set up and tuning, give it a try… footys on a B rig can handle just about anything, just make sure they are watertight! And unsinkable is a plus!

Graham

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I am really enjoying the way the new Kittiwake II kit is coming together, it’s always exciting to see ideas in the head actually appear in 3D and work out well. An example is the new rudder standoff which I admit could be a bit tricky to align. The new unit pictured below uses a triangular piece which slides on to the rudder standoff ‘eggbox’ fashion. This sets the standoff at 90 degrees to the transom automatically, the standoff slots into the transom with two tabs as before. The triangular part also centres the new plastic rudder tube on the standoff rear edge so just a spring clamp at the bottom of the tube while epoxying will do the job. The plastic rudder tube will glue better than the brass one with epoxy or thick cyano.

The bowsprit is looking nice and ‘salty’ too, it slots into a support strip of 1/16″ ply which is glued onto the deck as shown below. This will handle the new larger jib sail with ease. The extra hole you see in the deck is the location to use if you wish to use a swing rig. I will be experimenting with a special swing rig I have built for light winds. I will give the location of this hole in the kit instructions for those who wish to use one of those una swing rigs.
 

I can’t wait to get this boat in the water now. Last night I gave the parts of the hull to be painted a coat of thinned laminating epoxy. After many experiments with different sealers etc. I am coming to the conclusion that thinned epoxy on ply or balsa is the best base because I like to have something to soak into the wood. Over this I will spray primer and paint, probably Rustoleum in this case. Varnished areas I just use Minwax Helmsman onto the bare ply, transom, keel and deck in this case. More later… have fun sailing.

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