Preparing to stitch the hull
Feb - March 2007
Well, it's finally time to actually start what we'd describe as proper hull building. The first step is to join the front and rear parts of the hull together. This made us muse on why a mirror has hull panels that require joining in the first place - surely a single piece of ply the full length would make more sense? We could only come to the possibilities that (a) back in 1963 marine ply wasn't available in lengths over 8', or (b) the Royal Mail had size restrictions. Probably a mystery that will never be solved.
(1) Anyway, on to the joining. The first issue was trying to figure out what the heck a 'butt strap' is (OK, we snickered too...) as we needed it to join the panels. Anyway, we finally figured out it's just a couple of short, flat, plywood pieces that hold the front and rear sections together. So we followed the instructions, marked out where we we going to stick it, used Saran Wrap to stop it sticking to the tables we put out and added some West 403 microfibers to the epoxy to thicken it to a light paste. Spread within the marked area and on the butt straps, and glue the parts together. On went the weights (yes, they are lead, and no we didn't steal them from a church roof) after checking all was snug. It's worth cleaning up the edges for a good fit, and don't forget to rough sand the spots where you want the parts to join for a good epoxy joint.
An neatness alert is necessary at this point. We slopped too much epoxy with microfibers (to make a glue) on the upper part of the butt straps. The bottom doesn't matter as it's hidden but the top 5" is visible. Right now, even with a bit of sanding, ours look like a couple of amateurs did the work (wait a minute, we are amateurs, but that's besides the point...). A quick wipe of the excess would have done the trick in seconds - instead we're going to have to put some elbow grease into making this look decent. Bummer.
At this point, pre-403, we resealed the notches we'd cut out on the inner gunwales since the epoxy was out anyway. Medium-sized oops to report here - make sure you put the butt straps on the correct side (ie. the inside of the boat). We didn't on one of the topsides leading to an emergency prying of things apart, fortunately before the epoxy had really cured. A few hours more and we'd have been in big trouble... Phew, dodged that bullet. Note the weighted blocks over the butt straps.
(2) Well, after about 36 hours, off came the butt strap weights, and out came the joined pieces. Despite having some reservations that such a small strap and a bit of glue could possibly hold things together, it does - very well in fact. Epoxy is pretty darn strong stuff! We did discover that epoxy does actually stick to Saran Wrap too - it's just easier to remove than a Safeway bag. Did a bit of light sanding to remove any excess bits and tidy up a bit, not that anyone will ever see most of this joint (see above for the exception). Came out very well, and as mentioned, super strong.
(3) Next step is to mark the places for the wood blocks, which involves marking up the panels previously joined. The official instructions do say 'not to scale' but would it kill anyone to make this diagram a bit clearer? Since this is somewhat important we did a lot of musing, and penciling before we got it right. The instruction diagram is very cryptic, and features some odd measuring conventions. Baffling to say the least, so to make your life better, here's Mark's version with a few instructions. Follow this and it'll take you less that 10 mins a side.
Here's how to to do it easily:
(a) Using a carpenters square, mark line A roughly in the middle of the panel at 90 degrees to the aft. This gives you a reference point to start to draw everything else from. The instructions don't tell you this magic trick.
(b) Measure 451mm along line A, then using your carpenters square, mark line B at 90 degrees to line A.
(c) Measure 384mm up line B from the center edge of the hull panel which gives the correct position for line C.
(d) Use your square, from the 384mm mark, draw a line back to the aft (giving you the back part of line C) now you know where it should be positioned relative to the aft of the boat.
(d) Now draw the long 2134mm line starting out on the line you just drew. This requires a long straight edge - we used the outer gunwales. Make this as close to 90 degrees from the aft as you can but it's going to drift a little. Don't worry about that. Mark the 2134mm position, then draw line D at 90 degrees from line C using your square.
(e) At this point fine adjustment is needed. We were 5mm out (not too bad) when measuring line D which should be 400mm from the center edge. Adjust line C and redraw so that it's 400mm along line D and 384mm along B.
(f) Everything should now be relative to these lines but re-measure everything. Once you're sure you've got the lines drawn right, the rest is easy as all you have to do is measure along the lines as shown.
(g) The diagram is vague about the position of the blocks forward of the butt strap. This is actually pretty easy so mark a line that's 38mm forward of the joint and draw the line. The rest is just positioning along it.
Here's the secret carpenters square trick. Easy, huh. Oh, and the glimpse of the outer gunwale shows a bit of masking tape on it. This is because, after taking the weights off, it springs back flat so you can't tell where the front is. That's what the tape is for. Just a thought. It's yours to use for free.
(4) Don't glue on the blocks yet - this would make drilling the holes for the stitching accurately difficult. Put one bottom hull panel on top of the other, butt straps inwards, and use loads of hand clamps to hold them together. Measure a line 1/4" from the edge all the way around. Not having a scribe, we did this using a simple compass, setting the pencil higher up than the pivot arm and setting the distance at 1/4" between the pencil point and the arm. Voila - a simple improvised scribe. Use this to draw the line you need around the panel. Mark drilling points as instructed (the important thing is the holes align so make sure the two sides are clamped well). Drill the holes making sure you hold the drill at 90 degrees to the panels. Piece of cake. So simple Shawn can do it.
Check out the 'table' shown above - it's actually the top of the packing case the Mirror arrived in slung between the two sawhorses. Very useful so don't toss out the case just yet. We don't care if we drill holes in it either.
(4) Final stage of the day after drilling is to epoxy on the blocks. Seat them well, and position accurately. This is very easy once you've got it all marked up. Make sure all the slanted edges point towards the center - double check this, and wipe off excess epoxy to ensure a snug fit for the bulkheads later. Note the action shot...
One very confusing thing is the center bulkhead blocks, which even allowing for the 'not to scale' disclaimer, look closer to the butt strap than they really are in the official instructions; they're really about 6" further towards the aft. Needless to say, given the permanence of epoxy, this created some doubt in our simple minds. Anyway, by checking out Richard Larson's website, and by test fitting the forward deck panel, this was enough reassurance that all was correct as marked. A somewhat 'to scale' diagram would be helpful here. Once everything is glued, call it a day as watching epoxy dry actually isn't fun.
(5) Next step is a bit of work on the topsides. Draw a line 1/4" from the edge (using the compass technique) on both ends, but then only for 3 feet along the curved edge from the front. Why do this for only 3' we asked ourselves? The answer lies in the boat curving and the need for the copper wire to line up exactly. After anything more than about 3' it's impossible to drill holes in the right places without the parts being in place. Mark the exact same places for holes to be drilled that correspond to the hull bottom but only in this 3 foot section. Later, we'll attach the front of the topsides and mark and drill to fit as we bend things into place.
(6) The final tasks are dead easy. Drill holes at the required distances at the front and back (where the transoms will go) on the 1/4" line, then draw a line 5" from the top of the topside (the straight edge). This is where the stringers will sit. Everything above this line is exposed, so we had to do a bit of sanding of excess epoxy we'd slopped on around the butt strap. So today's lesson learned is to glue visible things prettily.
(7) And finally a task we didn't do. At this point the instructions suggest fitting the floor battens, but MSD suggest it's better to do this later so the hull is easier to bend. We agreed and ignored this step for now - we'll fix them when things are more together.