Sunday, August 26, 2007

Float foam fairing continues

Having the floats side by side in the garage is working out OK. I get full access to one side of each float. When I want to work on the other side I pull them out from the garage and turn them around.

I've cut out the templates at the 3 positions the plans provided but I'm finding that working the keel to a shape that matches the hulls adjacent curve gets you very close.

Along the keel I am only using the long board. I'm sure I would be putting hills and valleys into the keel line if I used a power tool.

I still have to fill all the screw holes and fair down the foam a bit more. For whatever reason I can see that where the foam strips were glued it resulted in a slight high point. I have to admit though that whatever I did, I was very consistent on all the float halves. To bring these down just a bit I have used the power orbital sander down all the glue seams.

Wednesday, August 22, 2007

Strategy for outer hull laminations

The other day Andrew asked a very good question by email. He asked for my thinking in choosing Aeropoxy light filler when the same company produces a filler with reduced moisture absorption(MVS products) specifically for marine applications. This product is heavier, 7 lbs/gallon vs 4 lbs/gallon for Aeropoxy light.

His question gave me pause to think and I had to respond as follows

I chose Canada Composites as my supplier for my materials on the advice of friends who have been working with advanced composites for years. I originally inquired about the 12 and 18 oz knitted bi-directional cloth that Ian Farrier states as the basic spec. The staff at Canada Composites (particularly one who is a sailboat dinghy designer and builder) talked me into using more advanced materials. We discussed the MVS epoxy resin line but I ended up going for the highest quality product that they supply. Aeropoxy resin states the best high temperature (float interiors can get very hot) and tensile properties. I also liked the fact that the hardeners do not have the harmful stuff and is fairly safe (and not smelly) to use. I thank Aaron at Canada Composites for giving me this alternative.

At that point I accepted the fact that I would be approaching the build a little different than most, ie making the F22 more like an aircraft (light and strong) than a traditional marine approach(heavy and durable).

So, the Aeropoxy light filler is light, and that is why I am using it. As far as moisture absorption is concerned I do not think that the filler will absorb any more moisture than the foam itself. I have a link somewhere from a boat surveyor who is very concerned about moisture absorption.

I do not think I would use Aeropoxy light after the floats hull exteriors are laminated. The MVS product does indeed look like a good product for the final fairing. I obviously want to minimize this work and get the foams as good as I can. I think that my use of the glue rather than the epoxy putty makes preparing the foam even easier.

I also had the thought that the boat will be a trailer tri and will not be sitting in the water for whole sailing season.

I have to admit that as a test and for my own peace of mind, I have also sprayed some water on the filler and the exposed foam. To my mind the filler dried quicker.

I'm also thinking that I have spent so much time thinking about hull interiors and structural issues that I had not thought through how to best proceed on the outer hull and below waterline parts.

So here is my revised strategy for resin and fairing compounds.
  • For inside laminations (9 oz s-glass) and structural components I will to continue to use Aeropoxy resin.
  • Filling foam in preparation for lamination I will continue to use Aeropoxy light.
  • Outer hull laminations and fairing I will use MVS resin and fairing compounds.
  • I will continue to plan to vacuum bag the outer hull laminations to ensure good adhesion properties.
Thanks again for the timely question Andrew.

Monday, August 20, 2007

Float keel and outer hull fairing

So here we are, my two float hulls side by side and my flexible long board. I'm just getting started on the keel shaping and the foam smoothing. There is lots of work ahead but the potential of these two shapely structures is quite encouraging. I can comment already on the following

  • I am very impressed with my first application of the Aeropoxy light filler. When fully cured it really does not seem to be that much heavier than the foam itself. The manufacturer states it is only 4 lbs/gallon of filler. It is also very sandable. I will not hesitate to use it on all the areas where filling is required. By the way I have lots of these 'areas'. It looks like I did a crappy job on the vertical foam strips at the keel join. Much of the my keel centre join line is slightly depressed which I can now relate to my attempt to make the foam strips fit perfectly. I thought that I could sand down this centre depression but I have changed my mind and am in the process of a small centre buildup. I also have the low spots that other builders have noted close to the forward bow bulkhead.
  • I have already commented that my foam turned green from the Divinycell blue when stored outside under the tarp. I suspect it is a thermal effect (there were some high temperatures at times out there) but I'm also wondering if it could be algae. Get out the microscope. Anyway, on the three halves that were stored outside I do not have to spray any colourant ink on the foam to help identify the low spots. ie a low spot will remain greenish brown, high spots will sand down to the blue. You can see some of this in the picture above.

Saturday, August 18, 2007

Beam Bulkhead Flanges

Well, this work is finally completed on the two floats.

Here is a look at one of the forward beam bulkheads.

And, a view at one of the the rear bulkheads.

Here are a few of my observations

  • I started out by wetting out three layers cloth tape at a time (remember I had to apply 6 layers at 4 inch width and 6 at 6 inch width using my 9oz aircraft cloth) making the job tolerable in duration. By the end I was wetting out and applying all 6 layers at the same time.
  • At a few of the locations I simply hot glued the mold plate to the bulkhead. On the forward bulkheads this was working fine. There was room to get in there and pry it out, breaking the hot glue seal. However on the rear bulkhead the lack of space and the width of the mold plate I chose to use, made removing the mold plate extremely difficult. I ended up using the clamping approach shown in my last entry on the rear bulkhead locations.
Over all I think it turned out OK. If I were doing this again I would use thinner mold plates.

There is still some clean up to be done under here, but it will wait until I turn the floats over and I am moving on to shaping the float keels. I want to see how little filler I can get away with on the keel area. I know that I made some poor foam strip joins to the keel strip in a number of places.

Monday, August 06, 2007

Setting up the beam bulkhead deck flanges

I had always wondered when I got to this point in the build how I would set up the mold plate, 20 degrees from normal, upside down and have it properly supported. The above little critters indicate my first shot at it. I made eight of these so that all 4 beam bulkheads could be set up at once.

Here is a shot of a rear bulkhead looking forward. Keel is above. (This makes it the starboard side float, inner side on the right.) Shown is the plywood jig that confirms the angle and the correct distance from the locating dowel at the centre.

I have to say that getting my upper torso into the floats to work on these areas has been very challenging. It has been hot in Toronto, and I have sweated buckets. However, with that said the restricted access to these areas has made this work pretty much the most challenging to date. Having said that, I cannot imagine the efforts builders have made on the other Farrier designs where the deck is incorporated in the hull forms. At least on the F22 I can see what I am doing.

Similar set up for the forward beam bulkhead.

On the forward beam bulkheads (inner side) some extra foam bracing is specified between the deck and the hull. I'm all set now to cut the cloth strips for laminating the flanges. The call is for 6 layers of the outer hull cloth weight. This means that I will be building up 12 layers of the 9 oz e-glass aerospace cloth that I am using.

I have made use of my small dremel tool grinder to smooth out rough spots before the next layers are applied.

Here is another view of the set up on the rear side of the rear bulkhead. I had to sand down the mold plate thickness in the corners and edges on the rear bulkheads to get them to fit. The plans show the use of a much thinner mold plate.

This is where the beams bolt on to the floats so I am trying to make sure I do the best job that I can.