2014-03-18

Post XIV - Stem and Stern Installation

I have been thinking about quite how to post this part of the build. It wasn't exactly straightforward, but I'll do my best to describe it. Sorry about the wordiness, but it's complex to put in words

I did my lamination late Friday night, in hopes that my epoxy would still be in somewhat of a green cure stage in the morning. Having the epoxy a bit soft still would keep my plane and spokeshave blades from dulling too quickly (so my thinking went). I have no idea if that is the proper thing to do, but that's how I did it and had no issues. I was about 4 whiskey drinks in the bag at that point, so I'm actually amazed it worked at all!

On to the woodworking

At Harry Bryan's hand tool course last fall, he and Wyatt taught us some techniques for cutting complex shapes out of wood. Their application was a small canoe paddle, but the principle is the same here

The stem plan is complicated. It calls for a rolling bevel reaching from inside to outside face, all along its curved length. There is also a narrowing of both inside and outside faces in the middle of the curve. At the bow it starts out as a wide, 60deg bevel with a broad inside and outside face, then tapers to a much steeper bevel with narrow inside and outside face at the sharpest part of the bend, then flares out again to a 45deg bevel with a broad inside face and narrow outside face.

Luckily, the sheet containing the stem plan was very detailed, so I was able to establish a centreline and mark out the nominal widths on both inside and outside faces before beginning my cuts It's tough to see in the picture above, but there is a centreline and a spline to either side of it.

Figure 38: Aft end of stem showing bevel, centrelines and splines on top



The planing operation seems daunting at this point, but the trick is to do only one "projection" at a time. I started by establishing the bevel between the edge of the inside face and the splines drawn to either side of centre on the outside face. I carried this all the way around the stem (even though I know the width of the inside face should be changing, but that comes later). The projection I'm completing here is a trapezoid shape with a gently rolling bevel and a projection axis parallel to the curving longitudinal axis of the stem piece.

Once I had that all done (with 0.5 mm or so to spare outside the lines) I flipped it on its side and worked with my blade perpendicular to the inside face, adding the hourglass-like projection on an axis perpendicular to the inside face at any point along it.

At this point, I had 2 projections done, and the stem cut down to my drawn lines on both inside and outside faces. Not done yet though - there is still some material to be removed. Because the projection axes were perpendicular, the offending wood stands out like a sore thumb. It appears as a ridge with tapering ends through the narrow section on the tightest part of the curve. At this point it's safe to forget about projections and plane away the ridge to create a flat bevel from inside to outside face all the way along.

Figure 39: The completed stem. It's hard to take a good picture that shows the rolling bevel and tapering.


Harry and Wyatt both use a pencil to get good results with this type of complex shape. Simply score a crosshatch over the area you want to work. As you pare away unwanted wood, the pencil marks get pared away too, and you can always see where you *didn't* plane. This is unbelievably helpful at keeping your plane or spokeshave on the correct angle and in making sure you don't pare away too much from one side or the other.

Last check after the you get "close as possible" to the desired shape is to run over the whole thing with a straight edge held against the bevel. This will reveal any remaining bumps or rounds that you might want to get rid of. Again, mark the raised areas with pencil and shave away carefully.


Stern

Last thing I did while a buddy was helping with a section of the stem was to cut out my transom piece. Nothing too special to report here. Edge glued (with epoxy and adhesive filler) 1" ash boards and transferred the transom pattern from the printed plans using carbon paper. Cut it out on my wobbly bandsaw. I was looking forward to making this part and it definitely doesn't disappoint! Gonna look cool when it's all planked in.

Figure 40: Transom piece roughed-in



2014-03-12

Post XIII - Fixups and More Steamboxes

Fixup

Well I am glad I took a few seconds to ask on the woodenboat forum about my alignment issue. Peerie Maa, a member there suggested I pound nails into the tops of my molds and use those as alignment guides. I did this and in the process shifted my strongback around a bit to position it better in the workshop. I realized all of a sudden my centreline had hardly any of the wonk it had before...and the only thing that changed between now and the day I stretched the string is that I shifted the strongback to a new spot on the floor. 

Curious now, I busted out the level and checked at several points along the strongback. Sure enough, the beam had a twist! I didn't think of it as a possibility since the strongback is very rigid, but such a beam would be poor at supporting a torsional load. Considering the eccentric weight of the molds (and the considerable weight of the beam itself) I should have foreseen issues with twist. 

My sawhorses are too high, and I can't be arsed to make legs just now. A temporary solution was to slip 2x4 scraps under the strongback all the way along and level them using shims. This took the twist out of the strongback and I was able to reposition the 3 molds that were still obviously out of alignment. 

Figure 34: 2x4 scraps and cedar shims to level the strongback.


I believe I will make legs before I start planking...'cause fuck doing all that work on my knees. If things get twisty during installation of the legs, I'll just have to re-level the strongback and I can be confident that the keel alignment will remain pretty close. 

Steamboxes Again!

This process is really cool. I loaded in all my white ash stem laminates at once (on advice from Ted Benson in Canoecraft) and fired up the lobster boiler. Once it hit a rolling boil, I whipped off the aluminum lid and stuck the steam box in its place. 10 seconds later and steam was pouring out of everywhere - some at the seams but mostly out of the end with the holes. This is good from what I read. You want the steam to fill the box completely from source to outlet, and judging by the amount of steam coming out the end, I definitely ticked that box. 

Steaming time was 15 minutes for 1/4 inch laminates, based on the general rule of 1hr of steaming per inch thickness of wood. 

======================================================
***TO FOLKS LINKING HERE FROM HOMEMADETOOLS.NET***

No clue who keeps linking here from homemadetools, but whatever. More 
pictures and details on construction of the steambox on Post XII if you're 
interested.


In all honesty, I scabbed this idea for using the lobster boiler from some other guy 
on the internet. Credit to him for the idea. Will post the original source if I can 
find it again. 
=======================================================


Figure 35: Steamy


Figure 36: More Steamy



Then came the bending, which was really scary. I tried dry-bending a piece just part-way around the curve of the stem and it broke like twig, so I was surprised that I met with such steamy success on the first go-round.

The critical time is the first 45 seconds after you pull the sticks out of the oven. They must be bent within that window, or the lignin in the wood will harden up and you're shit outta luck. My wife and I coordinated it so she was ready to install the 2 topmost clamps the second I got them on the mold. As the second clamp was being screwed home, I started bending around the tight radius and with surprisingly little effort, the things flexed right around! A couple more clamps finished the job and we were done in probably 45 seconds to a minute.

Figure 37: Completed bend. Ready for lamination once it cools and dries. 


I then treated myself to a beer to dilute the adrenaline and quell the anxiety. 2 more days to wait until I can glue it up - that's what the books say anyway. Glue will not displace water, so it's important to allow enough time for the moisture to come back out. Hopefully I'll get a few minutes to do my glue-up over the weekend.

2014-03-10

Post XII - Screwups and Steamboxes

Screwups:

In a previous post I mentioned that there was a noticeable sway in the inner keel line. I was reading about this and other common pitfalls in my books over the weekend and they suggested tying a line from bow to stern molds in order to check alignment of the intervening stations. I figured it was worth a try if only to get the 1 or 2 stations in good alignment and holy shit am I ever glad I took the time. 

The entire thing is out of alignment for fuck's sake - but there's a pattern. The offset is all to one side and it lessens at the bow and stern. Amidships, deviation from centre for each mold is around 3/4 inch! If I don't correct this now, I'll have a boat that perpetually turns to starboard - which is the opposite of awesome. Figure 30 shows the problem. 

Figure 30: Portside arc of station placement relative to true centre. 
 

I'm confident in the straightness of my stern and bow molds, I took a lot of care in making sure each mold's centreline is perpendicular to the strongback surface. There should not be any problem with the strongback itself (since it is a 5/8" plywood box-beam, which by rights should be dimensionally stable in all directions). I'm guessing my problem has to do with the way I established the centreline. I did it with a chalk line and must have snapped the string a bit sideways...it's the only thing I can think of that would put that type of swoop in the centreline placements. I'll triple-check the strongback to be sure, but the chalkline seems like the likely culprit right now.

So assuming I'm correct, I should just be able to correct the swoop by sliding the offending molds to starboard, using the string as a guide. A setback, yes, but not as bad as it might have been if I'd been hasty. I'll be triple-checking everything else on the mold from now on - that's for sure.

Steambox:

Those pieces of ash I milled up are not going to bend around the stem radius without some steam, so I took a few hours this weekend and set about making a steam box. There is a lot of advice on how to do this, but it basically amounts to:

  1. find a good steam source
  2. build a box to appropriate dimensions
  3. steam your wood at 1hr per inch thickness of stock. 
I found a DIY steamer on the web that a fellow made out of scrap plywood and a lobster boiler, so I decided to copy that. I have the lobster boiler for homebrewing beer anyway, and it definitely boils the shit out of water, so there's step 1 taken care of. 

For step 2, I ripped the plywood into 6" x 7.5' planks and screwed them into a box shape with drywall screws (these tend not to split plywood when screwed into the end-grain). Added a permanent end-cap on one end, some wire racks to support the stock, and a plywood lid to fit the lobster boiler. The finishing touch was a hinged end-cap (not shown) on the business end with holes to allow some steam to escape. 

Figure 31: Wire racks in the steam box



Figure 32: Steam box and lobster boiler steam source


Figure 33: Steam port. 



If I feed the stock in edgewise, this box should give me capacity to do all 8 laminates for the inner & outer stem at once. There was no time this weekend to actually do the steaming unfortunately, so that is priority one for this weeks' shop night.

2014-03-06

Post XI - Keels and stems

 Tonight I worked on the inner keel. I realized when trying to fit it to the mold that I ripped my stock about 1/16 too wide. Not to worry though - perfect opportunity to do some more planing! I have an old Stanley No.28 transition jointer plane that I only recently got back in good working order, so I was itching to try that out. I met with mixed success...the horned part of the handle on it is busted, so it's very difficult to use comfortably, and its hugeness makes it difficult to control on a narrow edge. I ended up going back to the No.3 plane. It's more finnicky to get long even cuts with it, but it's really the better tool for work like this I think. Also, thanks again to Harry and Wyatt at Bryan boatbuilders for the instruction on proper plane use (unsolicited plug).

harrybryan.com

Once I got it all planed down to the right size and the inside corners beveled, I fit it to the molds. Looks pretty cool on there.

Figure 26: Inside stem laid up on the mold.


I don't know if it's visible in this picture but if you look toward the transom, there is a noticeable wobble in the keel line, somewhere around station 10-11. I think maybe I should have stretched a string between stem and transom before putting up all the molds. I might be in for a bit of repositioning now. Not too big a deal, just a bit annoyed that I didn't take the time to do it right earlier.  

Figure 27: Tiny wobble in the stem line toward the aft end of the boat.


...but instead of doing that right now, I wanted to get my ash stem laminates all milled up. Inside and outside stem are each 1 inch, and I decided to build each up out of 1/4" stock. I really wanted to saw these to get the vertical grain facing out, but with the stock I had left, there was no way to do it. Keeping true to my economical build, I decided to use the stock I had, and milled them up flat grain style. It might make them harder to bend, but the stem curve is fairly generous and I don't anticipate problems. I have some spare stock to mill up another strip in case I break one anyway. 

Figure 28: Stem laminates all ready to go.


No time for doing the stem glue-ups at this point, so I finished off the evening with some nice relaxing bit & brace work. Not to go too philosophical on you, but man, they knew how to make tools back in the day. this 1" auger beats the everloving shit out of the hole saw I was swearing at for the first 2 holes. I bored a dozen perfect holes with this bastard in the time it took the useless wood-scorching hole saw to do just one! 

Figure 29: Bit & Brace. One of the most satisfying tools in the box.



Post X - Gluing

Just a mini post today. I took 1/2 an hour and glued up the scarphs I cut last week. I checked with folks on the woodenboat forum because I wasn't quite sure how to do this. Two reasons:
  • My scarphs weren't perfect and there was about a 0.5mm gap
  • I was worried because of cautions I'd read RE wood sucking all the epoxy out of a scarph joint into the end grain and ruining the joint's strength. 
Solutions to these were quick and simple from a member called keyhavenpotterer. First off, don't worry about small gaps. Epoxy and fillers are designed to fill them and as long as the gap isn't very big. Second, to avoid the problem of glue-starved joints, simply paint the scarph surfaces with unthickened epoxy just after you mix up the pot. Add fillers into the epoxy while you wait a couple of minutes for the wood to suck up some of the unthickened stuff. Then, before anything cures, do the final glue-up.

For gluing I use WEST system with the slow-curing hardener and WEST adhesive filler fibres. The slow hardener is great because it leaves lots of time for messing around if you don't entirely know what you're doing...like me! Slow hardener apparently gives marginally better strength than the fast hardeners too, but It probably doesn't make a heck of a lot of difference here - I'm more concerned with a long pot life.

Figure 24: Scarph mounted in a gluing jig built on a piece of scrap MDF.


I also did the top 2 boards of the transom. I hadn't planned on doing this right away, but I had a bunch of epoxy left over and the stuff is too damn expensive to waste!

Figure 25: Glued up transom pieces