Boatbuilding Blog

January 16, 2007

Questions for Sam (and Answers)

Filed under: Building - Before Flipping — tomlarkin @ 7:01 am

I wrote Sam Devlin with some questions about how the hull is assembled. He replied right away, with nice clear answers.

 

Your book says to assemble the hull right-side up by stitching the panels together, install the bulkheads, and then flip it over to finish the hull exterior. However, the Godzilla is assembled upside down because of the forms needed for the round stern. The panels are laid over the bulkheads at the stations and stitched together. The stern is laminated on. Then the outside of the hull is finished normally and the hull is flipped right-side up to install the interior.

Questions:

  1. Q) Do you attach any or all of the bulkheads before flipping the hull?    A)We set up the bulkheads on the shop floor or on a simple strongback jig and then drape the panels over the bulkheads.. see pics.I recommend using the real stuff for the bulkheads and do at least tab everything together before rolling rightside up.. Building upside down helps to eliminate one of the rollovers and saves a bit of time… We glass the verticals from under the hull and tab the overheads (the overheads can be final glassed after the hull is rightside up, avoids epoxy in hair…
  2. Q)In the drawings all the bulkheads run to the gunnels in height. However, on my model, all of the bulkheads (except number 5) are cut down to deck height, about 18″ lower than the gunnels. (I’m not making a raised foredeck.) That’s a lot of extra work and wasted marine ply. Do you see a problem with me making my bulkheads shorter and letting the side panels run wild the last 18 inches? See drawing:
  3. A)I would proceed as you are thinking but put some stand legs along the edges of the bulkheads to give support at the sheer….. You will need to add some structure for that support anyway….

  4. Q) I’m planning on pre-coating the insides of my hull panels with epoxy (3 coats, wet on wet). This would happen before assembly, while they are laying flat. Before stitching together I would wash any amine blush off and sand the surface with a dual-action sander. I think this will save me a fair amount of time and labor later. On the outsides of the panels I plan only on sanding and filling the scarph joints before assembly. Do you have any reservations about this approach?   A) I am okay with that approach, it adds some stiffness to the hull panels but that doesn’t hurt anything in this design…

He enclosed some images of the bulkheads on the strongback. They are for a different boat, but the idea is the same.

January 15, 2007

First Epoxy!

Filed under: Building - Before Flipping — tomlarkin @ 2:37 am

After all the preparation I finally glued together the two side panels for the boat. This is the first actual boat assembly I’ve done yet so it seems like a big step. It’s been way below freezing all week, with about four inches of snow on the ground. The tent gets warm enough with my two electric heaters and the big propane heater, but I can’t leave the tent with the propane one running. To get the epoxy warm enough to cure I put one heater below the panels and draped tarps over the top to hold in the heat. I hope it works!  I’m tired of weather. I just want the normal drizzle and 50 degrees we’re supposed to have all winter.

The epoxy is late in coming from the MAS factory so Joel Mill bought me three quarts through Fisheries Supply so I wouldn’t lose a weekend of work. That was very nice of him – Devlin  has been great to work with so far.  

January 7, 2007

2-stroke vs. 4-stroke engines

Filed under: Building - Considerations — tomlarkin @ 8:14 am

I’d always heard that 4-stroke engines were always more environmentally friendly, quieter, and more robust than 2-stroke engines, but I was just reading a thread on the WoodenBoat Forum and they mentioned a new 2-stroke called ‘E-tec’ by Evenrude.  It turns out that the new generation of 2-strokes can compete with 4-strokes and surpass them in many ways.

Here’s a Yachting Magazine article comparing them: http://www.yachtingmagazine.com/yachting/gear/article/0,24579,1169547,00.html

All things being equal, a DI motor costs less and accelerates noticeably quicker than a comparable four-stroke. As for sound quality, and contrary to perception, DI motors register a few decibels quieter.

Here’s Evenrude’s E-tec home page: http://www.evinrude.com/en-US/E-Tec/E-TEC.Advantage/

E-tec won an environmental award from the EPA:

http://www.epa.gov/air/caaac/2004awar.html

2004 Clean Air Excellence Awards Recipients

Evinrude® E-TEC™ Clean Air Technology
Bombardier Recreational Products Inc.

In 2003, Bombardier Recreational Products Inc. (BRP) introduced Evinrude E-TEC, an outboard engine for marine recreational products, which is based on a two-stroke engine technology. Compared to a similar 2004 four-stroke engine, carbon monoxide emissions with Evinrude E-TEC are typically 30 to 50 percent lower; and at idle are lower by a factor of 50 to 100 times. In addition, Evinrude E-TEC emits 30 to 40 percent less total particulate matter on a weight basis than a similar “ultra-low emissions” four-stroke outboard. Furthermore, oxides of nitrogen and hydrocarbon emissions for Evinrude E-TEC are similar, if not lower, than a four-stroke outboard. There are no oil changes with this engine, as well as no belts, and no valve or throttle linkage adjustments. This makes Evinrude E-TEC engines easier to own than comparable four-stroke engines. In addition, numerous advancements combine to create the Evinrude E-TEC quiet signature sound including an exclusive idle air bypass circuit.

January 1, 2007

New Years Day

I ordered 15 gallons of MAS epoxy from Joel Mill at Devlin. With the 10% discount I got from ordering the plans from them earlier, the cost was about a third lower than System Three.  I got a nice mix of fast and normal harderers and normal and thin resins, and a bunch of thickeners and cups and stuff. I don’t have any experience with MAS resins – I’m just going on the recommendations from Devlin.

This plywood is odd – it has a twist and won’t lie flat without being clamped down. I’ve never had to deal with that before.

I started scarphing the hull panels yesterday and expect to finish the process today. I power-plane them pretty close and clean them up with a belt sander. My Fein vacuum cleaner is set up to turn on automatically when the tools start up – it works great. I don’t need to wear dust protection. I’ve filled a whole large trash bag already with the shavings.

   

Next steps:

  • Laying out the panels and gluing them together
  • Cutting out the four panels (2 sides and 2 bottom)
  • Cutting out the bulkheads
  • Setting up the bulkheads on the strongback
  • Building the hull!