Saturday, April 21, 2007

Bow cap shaping and float fairing

A short post to bring things up to date. I lost most of last weekend due to family events so progress mostly been made in short stints after work, plus today. The main focus has been on shaping the bow caps and on fairing the floats.

I am reasonably pleased with my choice of bow cap construction technique. As seen in my last post, I started with a huge hunk of foam on the end of each float. I started initially just trying to sand this into shape, but that would have taken forever. So I borrowed a neighbor's reciprocating saw and did some rough cutting of the excess foam:

After that, I mainly used the sander to get it close, with intermittent sessions with the longboard to true things up (I was a bit afraid of going too far with the sander). Obviously I turned a lot of expensive 3/4" Corecell foam into useless scraps and dust. However, because I used such thick foam, there were very few fairing lines to contend with and they were not a big deal to handle. Here's a couple pictures of one of the final formed bow edges:


It looks better in person that it does in this picture, IMO. The leading edge is a bit under 1/4" thick, and I rounded it over with hand-sanding. I'm hoping that's enough - -- any thinner and I think it would be difficult to get the laminate to bend around it. I emailed Ian a question today to double-check that though.

Another thing I've been doing is puttying all of the screw holes, cracks between the foam planks, and other blemishes on the floats:

Another view:

Puttying holes was tedious work -- I feel like I've been way too personal with every darn screw hole on these floats. But it's 99% done now (every so often I'll notice a hole that I missed), and both floats have been "good enough" faired on all surfaces, except for the decks. I don't want to try to fair the foam to perfection for a couple of reasons. First, the plans don't call for it, and second, I'd be worried about fairing the foam to death and ending up with 1/8" foam instead of the 3/8" I started with. I'm exaggerating but you know what I mean.

The decks though are one area that have me a bit worried. I'd like them to be as flat as possible, but I unfortunately ended up with many highs and lows. Not easy to see with a casual glance, but I can definitely tell. I don't think I should do the deck-edge rounding until I'm satisfied with the deck fairing. So tomorrow I'll be back out there, sanding away. Don't want to go too far, but it needs to be better than it is (sorry, I don't have a good picture here).

However, I did buy some 3" PVC pipe to use as a sanding tool for the float deck edges. Here I'm getting ready to glue some sandpaper into the cut pipe pieces:

I used super-glue for this which worked well. After doing some testing, I ended up cutting the 1/2-circle pieces you see above into much narrower chunks, like about 1/4-circle sections. Otherwise the edges of the pipe will dig into the foam too much -- during testing, I accidentally cut some grooves that I'll need to fill in. Based on my quick test though, rounding the deck edges won't be difficult once I'm finally satisfied with the deck fairing.

All in all, decent progress has been made. I feel I'm getting close enough to start thinking about the lamination.

Ian sent out a builder's email update earlier this week with tons of updates and new plan sheets. Lots of new information to look at, and he also announced that the beam mounts are now available for ordering. I should be ordering mine within a month or so. Then they can sit in my office and silently motivate me to get the rest of this thing done so I can install them.

[Edit: here is Ian's response to my question regarding the bow cap thickness:

> How thick should the leading edge of the bow caps be?

It is personal preference - knife edge is too easy to damage while a large radius has more drag. I would not go less than 1/4" - production boats have around 1" as less than that can't be molded very well.


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