The last couple of days I have been lazing around not doing much (reading my Christmas present book and tv Sydney to Hobart/cricket, a boxing day tradition), but today I started the prep work for hanging the rudders and hanging the ladder.
To help me visualise how this will all need to look Jo transposed 2 photos for me. I know they are to scale by her matching the size of the ring on the rudder and the ring of the shaft. I will eventually close that gap at the forward edge of the rudder under the ring around the shaft, as well as add some height to the rudder to close the gap to the hull. In the mean time I have dry fit the rudder tube and glassed the bottom ring to the tubes and cut all of the ply for the webs and bases. The top one is at a height so that only the tiller protrudes over the bulkhead. On the front face of that bulkhead will be the ply shelf that will house the hydrualic ram.
The rudder tubes need to be mounted in the hulls. Very strongly. All of the loads generated by the force of water on the rudders will travel through the shafts and then into the bulkhead and because the rudder shaft is so strong, it wont bend or break so the force is going to want to rip the entire assembly out of the boat, especially if they hit something. So long as it cant, the steering will work.
With the rudders now working inside the tubes it is also critical that I mount the tubes into the boat plumb, square and level, so assuming the bulkhead it is mounted to is already plumb to the hull then the tube needs to show as level on either side and the exact distance from the bulkhead top and bottom. That will ensure that the rudder shaft is also plumb, square and level. The ply web is cut at 30mm wide top and bottom so that will ensure that the tube is glued to the bulkhead at that distance top and bottom.
Although I will glass the tube into the bulkhead all along its length, the bulk of the work needs to be at the hull skin (base) and the top of the tube. I initially intended to mount the tube hard up against the bulkhead but changed my mind after thinking it through a little more. Firstly, the boat was originally designed to have a kick up rudder. With a kick up, the rudder tube is mounted in a plywood canister that is hinged at the top and can kick up, if something causes force against the rudder the canister would break a timber dowel holding it down (at the aft end) and the entire assembly would swing up on that top hinge. I decided that the benefits of a kick up rudder were not so great and that having them was not necessary. They do allow for a slightly shallower draft, but in the up position they cannot steer the boat so I figured the number of times I would wish I had them would be minimal and I could do without the extra work needed to make and fit them, they have a tricky hinge assembly that also adds some cost and work. They are also another part that could break, I have heard stories of them breaking their dowel at the most inopportune time, I guess, any time underway is an inopportune time.
Anyway, I wont be having them, but the mechanism reminded me that with kick up rudders, the rudder tube moves aft of the last bulkhead by about 40mm to allow space for the canister and its hinge mechanism. The second reason I want to move the rudder slightly aft is that it allows me to mount a narrower shelf in the area in front of the rudder bulkhead, the space in there is already tight for fore and aft space for the outboard so keeping the hydraulic ram further aft helps there.
So everything suggests I should move the rudder tubes back 40mm. I will do this by running a 25mm x 30mm ply web between the rudder tube and the bulkhead and glass that all in full length (the bearings make up the other 10mm). I will then glass ply webs in from the side of the tube on about a 30 degree angle to the bulkhead each side. This will dissipate some of the lateral loads on the tube. At the top and bottom I will also glass ply pads onto the bulkhead with a hole in the middle for the rudder tube. And finally I will glass a beam probably made from 2 or 3 thickness’s of 25mm ply from the inside hull skin and they will be about 100mm high. The bottom of the tube is where the most of the load is going to be. These beams will end up under the lower rear steps.
I have already removed the balsa for 150mm around the tube in the hull, I will glass skin to skin to seal that area, then add ply to replace the balsa (because balsa compresses more under load than ply) then glass that all down with about 3 layers of glass staggered in size from about 400mm then 300mm then 200mm around the tube. A hole has already been cut to allow the tube to pass through to the outer skin. The tube will then get a lot of glass, probably about 6 or 8 layers of uni to attach it to the bulkhead along with all the aforementioned ply webbing and glass and beams.
Once the tubes are glassed into the boat, under the boat I will have to fair the gap around the tube to the hull. To this end, the first task I did was to glue and glass 2 glass rings to the tubes, these will form the base for the uhmwpe bearing to seat against on the bottom face and be the base for the faired fill to the hull on the top face of that disc. Once its all faired the bearing will be put in again and that will pretty much be the finish of the rudder tubes.
After all that is done, the next bit of work will be on the top of the rudders to fill the gap between the top of the rudder and the underside of the hull. This gap needs to be minimised to reduce the turbulence created if the gap is too big. That turbulence reduces the effectiveness of the steering and causes drag which slows the boat.
I have also sanded the highbuild on the davits ready for another coat. I have to fill some pin holes, but I plan to try adding some filler powder to the highbuild, and use a scraper to fill the holes first then spray the highbuild over wet on wet. Once sanded again that should pretty much do it. Or perhaps another coat might be needed. I can glass them in once I am satisfied.
You can see where I have sanded through the highbuild to the bog below, this is quite normal. These are the high spots, where the highbuild isnt yet coming off are the lows. When the highbuild is starting to sand all over and there is still highbuild on most of the area you are very close. Next coat should do it. Fill the various pinholes and knicks and dings and you are about done.
At the other end of the boat I have drilled the shaft holes in the forebeam plates and drilled the holes in the hinge plates ready to attach the ladder. I drilled from the left hand side first. The steel shaft then spans the area the ladder will hinge over. I tried to keep the shaft level with the beam from side to side so that the hinge plates (and ladder) would swing over it evenly. There is a little play in it so its not so critical. I got it pretty level to the beam by eye (and spirit level) but when I looked from the front looking back I noticed that the steel pin travelled up from port to starboard about 3mm. Its not terrible. Its annoying, but wont stop anything from working. Funny thing is, it actually looks right from behind, but not from in front, but in the end, I will spend all of my time looking at it from on the boat not in front of it, so it will always look right to anyone on the boat, and you have to look very hard to see it not look quite right from in front of the boat. So all good.
Before drilling the side plates I used the template again to make sure it all works. The mdf template is the exact shape of the glass plates so with the hole drilled and working, drilling the actual plates was easy. (Having said that, on one of the plates the drilled slipped on the shiny surface and scored the plate, I will have to repair that with filler). The plates shape will start to make sense from the photos below, clearing the front of the beam past 90 degrees vertical.
The hinge plates rotate on the shaft perfectly and hang in the correct position independently of each other, but they must work when connected to each other via the ladder. I wont know that for sure until I finally attach it all, temporarily via screws at first then if it all works by glassing it all together. The dry fit looks good though.
My concern now is the joint of the side plates to the ladder. This needs to be as strong as any of the other areas of the ladder/plank configuration so that its not the weak point that breaks. But for now I am happy with the design. The bow roller is sufficiently elevated so that a rope can reach the winch capstan without touching the edges of the hatch, so that if I deploy a rope rode emergency anchor, I can retrieve it using the winch rather than having to raise it by hand.
Once I have mounted the ladder I will have to configure the gang plank hinge to the same steel axle, however, this hinge will have no load on it, the gang plank will sit on the ladder and its hinge takes all the load. All the gangway hinge will do is stow and deploy the plank to the correct position and maintain it, I could deploy the plank without it being hinged and then stow it again, but a hinge means I dont have to do anything other than swing it over when needed, it will stow or deploy to the correct position automatically. So that ought to be easy enough to make and attach. I will have a thread tapped or a hole for a split pin drilled in each end of the steel rod, and clean up the various parts and paint them and I am done.
And speaking of done, 2013 is done. Last day and last post of a tough year. Glad its over. 2014 promises so much. I am very exited by it. Very. Stay safe. Stay positive. Comments function is working again so feel free to drop me a line. Have a good 2014 with me.