Sunday, January 12, 2014

Building two CLC Kayaks

the beauty of boatbuilding

After a lifetime of small sailboats, Julie and I are building two kayaks from Chesapeake Light Craft.  I'm still a sailor at heart, but Julie is probably more suited to kayaking. We can envision all sorts of fun combinations of sail + kayak.

I will build the Shearwater 16 and Julie will build a Chesapeake LT 16.  We bought the kits while at the Mid Atlantic Small Craft Festival and picked up kits a few weeks later from CLC's shop in Annapolis, MD.

The first  step was to augment my already extensive set of boatbuilding tools.  This included lots of different clamps from Harbor Freight Tools.  I also added to my workbench a few bench dogs manufactured by Record.  I inherited these beautiful cast iron devices from my grandfather.  They probably date from the fifties or sixties.
Record Bench Dog
 I also made a few light weight saw horses for assembling the panels.
light weight saw horse

Here's a view of panels being joined together.

Panel assembly

The temperature in my basement shop is in the low 50 degrees F so we are using work lamps with 70 Watt incandesent bulbs to get the surface temperature high enough to cure the epoxy.

heating lamps
The book case in the background has every issue of Small Boat Journal and most issues of Messing About in Boats.
the beauty of machine cut plywood kits

Sunday, January 5, 2014

Tulip Poplar for Oars?

Our new Core Sound 20, Summer Breeze, needs a set of oars.   After researching various oar designs on the web and comparing the mechanical and subjective qualities of various woods, I've decided to make them out of Tulip Poplar which is cheap and plentiful here in south eastern Pennsylvania.  People are surprised when I tell them of my choice so I'm posting my analysis here.

Table 1 shows a few select woods that I wanted to compare.  Most of the mechanical properties are taken directly from the Wood Database, a fantastic resource for investigating boat building woods.

Table 1. Properties of woods for making oars

The table provides Density (how heavy the oars will be), Modulus of Rupture which denotes strength against bending force, Modulus of Elasticity which denotes bendyness, and price per board-foot.  FAS is code for furniture grade wood.

I want a wood that is light, strong and bendy.  It should look good but not cost too much.  Typical woods for oars and other spars include Sitka Spruce, Ash, Pine and Fir.  I am lucky to be 30 minutes drive from one of the best hardwood suppliers in the country, Hearne Hardwoods. The large yard is piled high with flitch cut logs air drying or waiting to be milled.

Flitch log at Hearne Hardwoods
They have great prices on Ash, Cherry, Pine, Tulip Poplar and lots of other exotics.  Most of the prices in Table 1 come from Hearne.  I've ranked my selection based on weight (density), elasticity, strength (modulus of rupture), quality (FAS, common, select, clear) and price:
  • Sitka Spruce is very expensive ($15/BF Chesapeake Light Craft).  It has a good strength to weight ratio and is very elastic.  Too expensive around here.
  • Eastern White Pine is the lightest in my list but also the weakest and most brittle (least elastic).  Hearne has some very clear white pine, but it is expensive.  
  • Spanish Cedar is great to work with and beautiful to look at but it is brittle, a bit heavy and on the expensive side.
  • White Ash is the strongest (modulus of rupture) and most elastic but also the heaviest.  Many great paddles and oars are made from White Ash and it is inexpensive but too heavy for my taste.
  • I included Black Cherry just out of curiosity.  I think it might make fine oars.  It is more rot resistant than Ash but also less strong and elastic and costs more.  It is prettier, easier to work but not as tough.  There is a lot of locally grown cherry in PA so it is relatively cheap here.
  • Western Hemlock (Hem-Fir) 2x stock from Lowes is cheap and has great mechanical properties.  Because it is only available around here as construction lumber (common grade), even the best planks will have some small knots.  
  • Tulip Poplar has great mechanical properties, is fun to work with and looks good.  Hearne has great pricing on FAS grade (furniture grade) stock in many dimensions.
Grahame Byrnes of B&B Yacht Designs told me that Hem-fir is a great alternative to sitka spruce.  The wood database confirms this (Table 2).  Tulip Poplar appears to be another great alternative.  Robb White, a well known boat builder and writer used Tulip Poplar for many of his beautiful custom boats. Compared to hem-fir it is much prettier, easier to work with, just as light, about as strong and elastic and not much more expensive.

Table 2.  Hem-Fir and Tulip Poplar vs Sitka Spruce

Tulip Poplar is the wood for me.