Thanks in advance for the answers. I've ordered the sliding seat kit, and am currently sourcing wood for the riggers. I know it says pine is okay, but is this stiff enough? I've got access to some nice hardwoods including oak and mahogany. What would be the ideal wood to use for the riggers?
I have just finished mine. I used rimu (a New Zealand hardwood) - but I recommend any hardwood over pine. I also went with 23mm thickness (a little over 7/8 inches) rather than the specified 3/4 inches. I have a friend who has just laminated an aluminum plate between two pieces of timber. Stiffness is vital.
Overall, your choice of wood and lamination streategy depends on a few variabilities including weight constraints, beam of boat, budget and whether a clear beatiful look is desired. If budget or weight are your primary concerns, I would go for pine. If less work is desired or you want a rich clear finish, I would go for something like mahogany.
The narrower the beam of the boat, the greater the unsupported span of the rigger, so greater reinforcing is of benefit. So our Cambridge Racer (a narrow scull) for example would benefit with extra reinforcing in the rigger (two layers of 6 oz glass over pine,). Our RowCruiser (beamier), on the other hand, has a relatively short unsupported span off both sides, so flex is less of an issue.
For greatest strength to weight, I would recommend pine or spruce. Both these woods have excellent mechanical properties and good strength for weight (better strenght for weight than most hardwoods). The wood alone isn't enough to provide sufficient stiffness, but it acts as a strong coring for outer reinforcing. To add significantly more strength and stiffness the wood needs to be sheathed in fiberglass and epoxy (or other composites). S glass will provide even better stiffness than e-glass, so is highly recommended. Multiple layers of glass can be used if maximum stiffness is desired. Carbon fiber can also be used (this is the sfiffest material), however it is a bit more difficult to work with than glass.
A strong hardwood may be less work, as you may not need any composite lamination (for an application such as the RowCruiser), however, it will be heavier.
Overall, my personal preference - best bang for your efforts and budget is pine with a composite coating. I've only used regular glass, but undoubtedly S-glass would be a step up. And for the pinnacle in strength, stiffness, and weight, I'd recomend carbon fiber. Having rowed over 30,000 km I've become a big fan of reducing weight wherever possible, and this is the way to create the lightest strongest riggers without getting into advanced vaccuum bagging composite techniques.
I blew it with my rigger! It was the first thing I did in 2019 to get used to doing the fiberglass and glue-up. Since then it has been absorbing hot Texas sunlight and even though I had coated it with Spar UV-protected varnish it has now come delaminated. So I will build another out of some nice pine that Home Depot sells from New Zealand at $35 in Texas. When I made the first one I had difficulty with the loose strands of fiberglass getting in the way. Then the top layer eventually separated from the bottom layer. How do I avoid this the next time around? Would fiberglass tape work better for the rigger?
Hey Ricky,
Fiberglass tape won't work so well because the fibers are constrained at the edges meaning they won't shift as required to conform to more irregular shapes. The best way to keep stray fibers from the edges getting in the way is to have more cloth overhang so you're not needing to work near the edges. Four to six inches overhang would keep you well away from the edges. Be sure the cloth can hang straight down without making contact with supports. And also, be sure (before starting the epoxying) that the glass is able to fully conform to the shape. There are a few areas where you will need to cut some slits in the overhang to allow the glass to take on the correct shape. When epoxying you will need to be a little more careful around the slits to keep from picking up stray glass strands. Wait until the epoxy cures (or is almost cured) before trimming the glass with a sharp knife. To reduce chances of delamination, make sure there is a chemical bond between layers - making sure that the epoxy is not fully cured prior to applying the next layer. Did it delaminate off the wood or between two glass layers? It's pretty rare for epoxy and fiberglass to delaminate off the wood.
Also, I'd definitely recommend two layers of 6 oz glass off the top and bottom if using NZ pine. NZ pine isn't very dense, so much of the strength will need to be provided by the glass.
