Mast support blocks cut and fit

With my mast rounded and epoxy coated I decided to complete the parts needed to actually hold it in the boat.  SCAMP is similar to other small sailboats in that the mast is secured in two spots, at the base and somewhat further up.  This design has a mast trunk, a box that the mast fits in  (see this post: <mast-trunk-installed>), so two blocks need to be made that fit the mast and the trunk, and hold the mast tipped aft at a 2 1/2 degree angle.

I used a scrap of pine cut from a lumberyard 2x6 to make the upper block. Rather than attempting to tilt the drill press head to exactly 2.5 degrees, I instead left it vertical and made a ramp to hold the wood at the correct angle.

This was a good chance to drag out the old high-school trigonometry to calculate some dimensions. I could figure the length of the ramp needed assuming I would put a 3/4" shim under the end of it.

As it happened, I took my 3/4" shim and first jointed one face of it at 2.5 degrees, so the height ended up about 5/8" rather than 3/4".  Not a problem, I just recalcuated the position based on the lower height and glued the shim in place.

I then added a fence, clamped the ramp to the drill press, and clamped my stock to the fence.  I didn't want the 3" hole saw to grab and fling things around.  I drilled until the pilot bit cleared the other side, clearing the sawdust frequently, and then flipped the stock over and completed the cut from the other side.

I did a test fit on the mast and things were pretty close.  However, it would be very difficult and messy to epoxy the block on if it had to slide over the end of the mast, so I cut it in two pieces, and enlarged the opening as needed to make up for the saw kerf until I had a nice fit.  I then trimmed the block to width and length and epoxied it on, using a level to make sure it was aligned with the square block on the base of the mast.

Note that when cutting the block to length another session of trig came in handy to figure out how far off center the hole needed to end up.  Turns out they need to be between 1-1/4" and 1-3/8" offset.

Next I made the block that holds the base of the mast.  Since I glued in a square block at the base of my mast, I needed to make a block with a square hole, angled at 2 1/2 degrees.  I have about another half page of sketches figuring out the correct dimensions to make this up from four pieces of wood as shown below.

OK, five pieces.  I was not thinking clearly at one point and cut off my blank in the wrong place, so the hole wasn't where it belonged.  Rather than starting over, I decided to trim the far end and add a piece on the near end to move the hole over.

The center portion of this lower block is made of 2x material, which ends up not thick enough to hold the mast plug off the bottom once the taper is cut.  That's why the side runners are deeper.  This has the side benefit of providing space underneath for water drainage and ventilation.

I epoxied the pieces together and then cut the top at a 2 1/2 degree angle and rounded all the edges.  2 1/2 degrees doesn't sound like much, but as you can see it's quite noticable.  Over the 16 foot length of the mast it tips the top back over 8 inches.

Here's the lower mast step ready for a coat of epoxy.  This piece will remain in the boat when the mast is removed, while the upper block is epoxied to the mast and is removed with the mast.  I coated the inside of the step and the square block with graphite thickened epoxy to make them slide together easily. 

I won't be able to see how easily the mast inserts until I have the boat out where there's no ceiling overhead, but I think this will work well.

Mast trunk installed

I have now installed the mast trunk, which I assembled outside the boat some time ago. This part had a bit of twist to it and I was a little worried about being able to get it installed straight, but having the surrounding pieces firmly fixed helped a lot, and I was able to get this nicely aligned using only a couple handscrew clamps.  The lower portion was fixed in place over the keel and in slots in the bottom hull, and applying the clamps twisted the top portion straight against bulkhead 3.

After installing with silica-thickened epoxy I followed up with fillet mixture.  I was glad to be done with the fillets back in the narrow hard-to-get areas. 

Here's a view down from the top.  I'll have to reach in through the front of the box to try to get a fillet on those corners (to the right in this photo).

This was a good job done.  Nice to get the 'engine room' in place.

Mast box fiberglass

I finished up the mast box construction by applying fiberglass reinforcement to the forward face (9 oz tape) and corners (6 oz tape).

And I applied a couple scraps of 6 oz cloth to reinforce the ramp and the portion of the trunk that will eventually poke out above the deck.

And while I was at it, I reinforced the bottom sides of the box, though this was not called for in the plans.

First fillets

Today I made the first fillets of many to come.  I used a mixture of epoxy, wood flour, and I added a bit of colloidal silica in hopes that it would make a little smoother mixture.  Not sure if that helped.  On past boats I've just used epoxy and wood flour.

Turned out pretty nice, I think.  After this has hardened I'll install the fiberglass on the outside corners and this part can be set aside for later installation.

Sanding, epoxy, and fiberglass work

Since last update I've spent quite a bit of time with the sander, sanding all the parts that had their second coat of epoxy (bulkheads), and some bid ones with their first coat (seat longitudinals and centerboard case side).  

I still need to scuff up the edges by hand, but after that the parts with two coats applied are ready for installation in the hull.  After they are in place paint is the final coating.

Digging through the scraps of 6 oz. fiberglass I had from a previous kayak project, I found a piece just large enough for the inside pieces of the centerboard case, so decided to install that next.  I'll have to place an order for some more so it's on hand when I need it for the bottom of the hull.

It's always fun to see the fiberglass go clear and show the wood grain underneath as the epoxy saturates the cloth.

I also put the second coat of epoxy on the inside of the bow transom and the inside of the mast trunk pieces.  I used a section of foam roller to tip out the air bubbles left by the roller, and it leaves a pretty nice finish.

And today I sanded the second coat of epoxy on the inside of the mast trunk pieces. Assembling this will be one of the next jobs coming up, and it will be fun to be at the point of starting to put some parts together! 

Sanding, more epoxy, first fiberglass on mast trunk

Since last update I've been spending a lot of time sanding all the parts that I've previously epoxy coated.  The power sander made a good job of the flats, but all the edges including access holes and  scuppers were done by hand.  Took some time.

Today I put the second coat of epoxy on the original parts, and the first coat on some new pieces.  It works good to hang them up on a 2x2, otherwise it would take a lot of room to lay them all out somewhere.

A couple days ago I gathered together the parts of the mast trunk to see how that fits together.

I'm going to preassemble this part, as it's easier to work on it on the bench.  I started by putting two layers of six ounce cloth on the inside where the mast will impact as it's inserted.  After that was cured I trimmed the glass.  The remaining parts of the mast trunk got the first epoxy coat today.

I had a bit of epoxy left over the other day, and mixed in some microballoons (tiny glass spheres that make sanding easier) and faired some of the rough and uneven portions of the centerboard and rudder.  I haven't tried sanding this down yet, so will have to report results later.