Drawing out the next major Zip part

At first glance, the Zip has some rather odd frame designations.... Specifically, frame number "5-1/2".

It seems odd until you understand that the designations are logically based on boat design drawings. If you look at a cross-section drawing of the boat, there are several vertical lines that divide the hull into sub-sections. Each one of these vertical lines is called a "station." The numbering starts at zero (the transom), and ends at "F.P." (which stands for "Forward Perpendicular") at the foremost tip of the boat. In the case of the Zip, there are 8 stations including "F.P.", dividing the hull into 7 sub-sections of about 24-1/2" each. Frame # "5-1/2" is the frame placed between stations 5 and 6. It is located near the base of the stem.

Frame number 5-1/2 is a very important part. As the instructions indicate, the horizontal line formed by the floor member of frame # 5-1/2 is the plane from which the rest of the boat is set up. The instructions specifically state to take extra care to ensure that this part is accurately measured and constructed.

I just finished drawing this part, and I thought it would make a good blog post to illustrate how the Glen-L plans are copied to the wood.

First of all, you fold the carbon paper in half, so that the lines you trace through it are transferred to both the wood AND the back of the actual plans. Then you place the plans on the wood, and flatten them down securely. Push pins help for this.

Secondly, trace the plans for the part you want to build. As I mentioned in an earlier post, the centerline is THE crucial reference point for the boat. ALWAYS carefully draw the centerline. Make sure you extend your traced centerline beyond the needed dimensions of the part, for this reason:

Third, draw "sight holes" that are centered on the extended part of the traced centerline. I like to trace a small coin for this purpose. Use an exacto knife to cut your sight holes through the paper. Youll need these holes to align the plans after you flip them over.

Here Ive traced out the floor timber, and have cut sight holes on the centerline.

Next, remove your push pins, plans, and carbon paper from the wood. The half-width of your part should be clearly visible.

Half-width of the floor timber drawn onto 3/4" Douglas Fir marine plywood.

Now, un-fold the carbon paper, and place it normally onto the wood where the second half of your part is to be drawn. Flip the plans over, and youll see the carbon-copy you made on the back of the plans. Carefully and accurately align the sight holes on the extended centerline that is traced onto the wood. Again flatten the paper down securely. Now youre ready to trace the second half.

Plans flipped & aligned. Ready to draw the second half of the floor timber.

Trace the carbon-copied lines onto the wood, just like you did the first side. When youre done, the full part will be drawn onto the wood.

The full floor timber drawn onto the wood, waiting to be cut out.

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The seat support turned out great

I was very pleased with how the center support for the seat went together. I wanted it to be 1/2" plywood, which I did not have on-hand. So, I cut two pieces from 1/4" marine-grade Douglas Fir plywood, with the intention of laminating them together.

Plywood parts, cut from the poster board template.

Plywood parts, cut from the poster board template.

Once I had all the parts cut, (two 1/4" plywood supports, and 4 pieces of 1" x 1" mahogany blocking), I glued them all together with thickened epoxy. The Raptor stapler I bought last year once again proved perfect for holding the plywood parts together while the epoxy cured.

The plastic Raptor staples were perfect for holding the plywood pieces together.

Seat support, prior to being sanded & planed.

After the epoxy cured overnight, I sanded the edges smooth, and snipped and sanded the Raptor staples. These staples sand away very easily, and virtually disappear. No need to pull them, and fill the holes... just leave them there.

Then I ran the top & bottom surfaces over a planer/jointer, and it was ready for the next step.

The sanded & planed seat support, sitting in its position on the keel.

The sanded & planed seat support, sitting in position n the keel.

From that point, it was time to cut the seat. According to measurements, the front edge of the seat needed to be 49" wide, and the back edge 47.5". The side edges needed to be cut at a 15° bevel to match the sides of the hull.

So, I drew and cut it from a piece of A-C exterior grade plywood I had on-hand. With a little minor fitting, it set into place just as well as Id hoped.

Seat cut from A-C exterior grade plywood.

Seat cut from A-C exterior grade plywood.

Without intending to, I cut the A-C plywood "ugly side up" (the C side). However, that wont really matter. My plan is to laminate a piece of the BS1088 Meranti plywood on top, so that the seats will match the transom and deck.

The next step, however, is still to fit the blocking on each side of the hull to support the seat at the ends.

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Out in the daylight

It was such a glorious fall day, that I really needed to see the boat out in the open.  Additionally, it is so much easier working when you can stand up without bumping your head!  The building frame rolls out on four 2" PVC rollers.  It is so easy to move, that I needed to watch the speed we were going at!  When the boat is in the garage, I can now easily slide the whole thing against the wall, or move to the center.  This is now a much more usable space and more comfortable to work in.  Oh, the seat frames are finished.  Now its on to the centerboard.  

out in the daylight.  

Nice lines.  But, someone get the shop vac out before the photo is snapped.  

I also trimmed the bulkheads that were standing a little high, and then trimmed the seat sides so that it is all level in preparation for installing the centerboard trunk.  

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Minor epoxy miscalculation turned out fine

One of the wisest investments Ive made in this whole boatbuilding project was the $30 I spent on a kitchen scale at K-Mart. My "close calls" with epoxy miscalculation basically evaporated.

That is, until yesterday afternoon.

Something I didnt mention in yesterdays post, was that when I ran out of epoxy, Id upturned the resin & measured out 144 g. Silvertip epoxy, measured by weight is mixed in a ratio of 1 part resin to 0.44 parts hardener.

Heres a photo of the kitchen scale Id purchased at K-Mart.

Taking the 144 g of resin, and multiplying it by 1.44 meant that I needed to add hardener until the overall weight equalled 207 – 208 g. (144 x 1.44 = 207.36).

So, I upturned what was left of the hardener into the mixing cup. Unfortunately, the combined weight had only reached 194 g when the hardener ran out completely. I was 13.36 g short.

Marine epoxy is expensive. "Besides," I thought, "Ive had closer calls than this with estimated measurements." I decided to mix it for 3x longer than I usually do (6 minutes, since I usually mix for 2 minutes), and then just use it.

It worked just fine.

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