The stringers on the Weekender were cut from 1X stock (3/4" thick) and even at these relatively narrow dimensions I managed to snap one while screwing it to the hull bottom. The Vacationer calls for 1-1/2" (2X) stock cut at a 27degree angle. A very hefty stringer. I'm using douglas fir for the stringers and am a bit concerned about how such thick stock will handle the curves. Has anyone tried using narrower and thinner stock for the Vacationer's stringers, and how much structural integrity do I give up if I choose to do this?
Dave
No Sir, But they handled the curves quite well, I did snap one but it was not to bad to fix and continue.
I built a stream box for my previous build that worked great for bending the taffrail etc. I could build a 10 footer to bend the stringers! Should be easy, and eliminate any cracking. I'll post some plans.
Dave
(04-19-2012, 10:31 AM)Dave Blake link Wrote: [ -> ]... I managed to snap one while screwing it to the hull bottom...
Greetings Dave,
If you do not want your stringers to snap, then you must use perfectly straight grain that is parallel to the edge of the board so that there is no grain run-out. The stringer will snap where the grain runs off the edge.
While picking through the wood piles at the lumber yard I found two 1x10s that were cut straight through the heartwood of the tree. These boards would be mostly useless for boat building except that the grain was perfectly straight out near the edges of the board. Both boards had a little run-out, but were otherwise dead-straight with the grain. So I took them home and re-cut the edge of the board to follow the grain, and then cut all my stringers from there. No snapping. Just for grins I tried bending one of the first thin wedge-shaped cut from the board to straighten the grain, and no surprise, it snapped right where one of the lighter grain lines met the edge of board.
I have read that canoe builders do not cut ribs, opting instead to split out thin strips along the grain to guarantee no run-out, and are then able to steam-bend the ribs of their canoes to ridiculously tight bilge curves.
Cheers,
Tom
This is a common problem with novice builders. The best way to purchase dimensional stock (2x4's, 1x6's, etc.) is to buy 2x12x16' framing stock from the local big box store. These big pieces have to come from older trees, so you can easily find 16' long pieces of straight grain, knot free wood. You do have to go through a stack of 2x12's, but about 25% of them will be really clear and straight.
Once you've got your 2x12's (2x10's too) you "re-saw" them on a table saw or even with an edge guide and a circular saw. If you need 1x2's, just set the fence or guide at 3/4" of an inch and rip the edge off one of the boards. If you need 1x4's you will likely need to make two passes on a table saw, but it's the best way to get dimensional, stock with preferable grain. The average 10" table saw will cut though 2.5" thick stock. The average 7.25" circular saw will do nearly this too.
If you're having a lot of breakage, don't try to bend in 2" (1.5") stock, just bend in two 1" (3/4") pieces, gluing them together as you do. This is actually stronger and lets you control the dimensional stability of the piece, by gluing the pieces with opposing grains. Opposing grains simply means if the end grain on the first board in this laminate has a "U" shape, make the second piece lie down with the "U" shape facing the other way. This way if one pieces tries to move or bend, the other glued to it, will resist this because the grain is running the opposite way.
I've never tried this, but couldn't you use a crappy 4X2 with a bad case of case hardening? You know the ones. You rip them into 2X2's and they turn into some serious bows. If they don't bend all the way at least you got some of the bend before you start horseing on them.Â
Al
I built a steambox, powered by two wallpaper steamers. Using a meat thermometer the temp inside the box was prestty steady at 205-210 degrees F. Two hours in the box and the big hefty 8' long stringers bent fairly easily.
Dave
Yeah, I've done my fair share of steam bending. Work fast and wear thick gloves.
Al
I'm thinking of using 1-1/4 X 1-1/4 stock for the stringers. With the cut at 27 degrees, the surface width at the bottom is 11/16" and at the top it's 1-1/2". I'll use a roundover bit to ease the right angle. I can't see how this could negatively affect the strength of the boat. The 1-1/2" X 1-1/2" stringers seem like overkill. Anyone disagree?
Dave
Is that a stringer or chine log (substantial difference)?
So, lets see if I have this right. You've cut your stringer stock with about a 25% reduction in sectional area and further reduced this to about 55% less on the bottom edge? If this is a stringer, probably not a concern as they act mostly in longitudinal flexual modulus, but if it's the chine log, you've lots a huge amount of "meat" on the bottom edge.