Steam bending

I've always wanted to try steam bending, and the upcoming work of installing the carlins (under deck supports) and gunwales is going to provide a good opportunity to try it out.  The plans call for several narrower piece of wood to be bent and laminated in place without steam, but I was not looking forward to handling and securing long skinny, slippery, epoxy covered pieces, so I thought I would gear up for steam bending.

Traditional steam bending involves placing the wood to be bent in a box and applying steam until the wood gets flexible.  Then you remove the wood from the box and quickly put it in place before it cools off and stiffens up again.

Recently I saw a video on the net showing a variation of this, where the wood is steamed in place on the boat. Using this method there's no frantic dash to beat the cooling wood, as you can keep the steam on until everything is in place.  The key is to do away with the traditional steam box, and substitute a plastic tube.

So, excited about trying something new, I placed an order for an Earlex steam generator and soon it showed up at the door.  A quick visit to eBay and 200 feet of 6-inch wide 4 mil lay-flat tubing was also on the way. 

The steam generator comes with the tank, a hose, and a electrical cord.  The hose is nice and long, about 10 feet, and has a flare fitting on one end and a threaded fitting on the other - very nice.  The steam generator is pretty simple, and consists of a heating coil in a plastic box, but it has a pressure relief valve and over-temperature shut off (if you run it dry).  It's a nice setup.

For my test bend I planed some pine to 20mm x 30mm.  Nothing special about this stick, it has knots and all - kind of a worst case scenario.  I cut off a section of plastic the same length as the wood.

And installed the hose in the middle.  The threaded end and jam nut is inside the tubing in this photo.

Then I put the wood inside the tube, filled the steam generator with water and plugged it in.

After about 15 or 20 minutes steam began to flow.  Some flows through the tube and out both ends, and some condenses in the tube and eventually runs out the ends.  I put a bucket under each end to catch the drips.

After about 45 minutes I put on gloves and easily pulled the wood into place.  This bend is in two dimensions - curving both upward and inward as it approaches the ends of the boat. 

Pulling the plug on the steam generator, I let the wood cool.

And then slipped it out of the plastic.  There was very little spring-back - this experiment was a success! 

The wood took on a nice smooth curve for the most part.  If you look in the background you can see there is a straight section there as the piece ended and there was nothing pushing it into a curve.  With a full-length piece this shouldn't be a problem.  Or if I wanted this shorter length to curve in that area I could have pushed it out a little with a brace - the bending was easy and did not require much force.

Since the final, full-length, part will have one or more scarf joints joining shorter sections of wood, I plan to do another experiment like this, but with a scarf joint in the test piece to make sure the steam heat does not cause the joint to fail.  If it does I'll have to come up with a plan to work around that.

First panel filleted and taped - home made pastry bag

Today I got the first hull panel filleted and taped.  I decided to push the wire ties down into the crease and run my fillets over the top.  After the epoxy has cured I will snip them flush on the outside and the remainder of the wire remains in the joint.  This speeds the process because I don't have to install 'tack' fillets and then take a second pass to pull the wires, complete the fillets and apply the fiberglass tape.

I decided to use the 2-inch wide tape that that spanned the joint just fine.  There are a couple different ways to handle the application of the tape - what I did was to cut it to length before starting any epoxy and set it aside.  After the filled was run I laid the tape on top dry and smoothed it out with my fingers.  It sticks to the fillet, so you need to get it in the right place the first time.  I then wet it out with unthickened epoxy using one of the little metal handled acid brushes pictured in a previous post.  That was a little slow but allowed for good control

And the end result is clean and neat -

Even in the hard to access forward-most joint -

To get the epoxy right down in the joint where it needs to be I use a home-made pastry type bag made from a gallon zip-loc.  I fold it as shown, and tape it across the middle and along the edge.

Then turn it partway inside out and put it in a container that holds it up for filling.

I mix up my fillet mixture (here 6 pumps of epoxy, 2 plastic spoons of silica thickener, and about 4 spoons of wood flour)

And put it in the bag.

Use some type of roller to smoosh it to the corner, zip the top closed, and snip off the corner with a scissors.  Don't cut too much of the tip off!

I can refill this several times before it's too messy and I switch to a new bag.  To refill, I open the top a bit, blow it up like a balloon to separate the sides, fold over the tip and hold it with a clothespin, and then put it in the container ready to refill.

First hull panel wired!

I think this is exciting - tonight I got the first hull panel wired on and ready to epoxy!

I used a few copper wire ties, one clamp, and some bracing on the forward end to hold in in place, and it fit very nicely.  

The front end of the panel took quite a bit of force to get into position.  In this photo you can see I've got two braces running up and left against the wall to keep the bow from being pushed off to the side.  The larger C-clamp and its partially hidden twin are holding a piece of 3/4" pine against the keel plywood to keep that from flexing.  

Barely visible running off to the lower right is the brace bearing against the hull panel.  Its lower end is kept from sliding out by being against a pipe clamp that runs back to the building jig base. 

A nice fair curve is what we're looking for here...

.

Here's a close up of one of the wire ties, secured through 1/16" holes and twisted with an aviation pliers, which is made for doing just this kind of thing.

I ran out of time before I could epoxy, so that's next.  I have two different widths of fiberglass tape on hand, 2" and 3", and I need to figure out which to use.  I believe the narrower is what is recommended, but it seems very narrow compared to my previous builds, which all used the 3" tape.  I just need to double check on that before going ahead, as this is applied over the fresh fillet and wet out, all in one session.

Almost hull panel time

I've now completed the second coat of paint on the interior spaces, and it looks great.  Two coats of Rustoleum Gloss White covers nicely.  Here you can see the shine.  That should go a long way towards brightening the storage areas, and it will be easy to see whether they are clean or not.

So I thought I was finally at the long-anticipated point of starting to put on the hull panels.  I grabbed the garboard panel on the port side and put it in place to check for fit and consider my strategy for keeping it on the boat.  

As of now, I plan to stitch the panel in place along the bottom seam with copper wire, and probably at each bulkhead, then fillet in place.  I haven't yet decided whether to push down the stitches and fillet over them, as I did on my kayaks, or to fillet between them, and remove the stitches before filleting those areas.

At any rate, I discovered I was a little premature with the hull panel, as I had neglected to epoxy seal the edges of the bottom of the hull.

Nothing for it but to take care of that now, so I went around the edge of the hull bottom and applied unthickened epoxy with a disposable brush.  I got a box of about 100 of these for not much money, and they are really handy for jobs like this.  I also did raw edges of the transom which needed coating since I had beveled them to accept the hull panels.

Centerboard pin completed

The centerboard pivot pin in SCAMP is removable so the centerboard can come out if that is ever necessary.  There are bushings in the side of the centerboard case, a permanent plate over the inboard end of the pin, and a removable plate on the outboard end of the pin.

The removable plate needs to be sealed in some manner so that water from the centerboard area doesn't follow the pin and leak into the underseat compartment.  One way to seal that plate would be to apply silicone sealant before screwing it down.  Another way may be to fit a gasket of some sort.  I think a simple o-ring will do the job.

I drilled a recess big enough for the o-ring, and to maybe 2/3rds of its thickness.  I wanted the o-ring to be compressed slightly when the cover plate is screwed down.

I coated the new recess with unthickened epoxy to waterproof the wood.  The o-ring will bear against this bushing, and should provide a nice seal.  

I was concerned about excess epoxy fouling the inboard bearing when I installed that cover, so I took a little packing tape and trimmed it to a circle,  

and installed it over the inboard bushing. 

I then applied thickened epoxy to the inboard cover, and put it in place, holding it with a couple flexed battens until the epoxy cured.

Finally, I epoxied the pin into the outboard cover.  So, there's another item done off the checklist!  

Little jobs

This morning I found that my paint was still tacky, so rather than putting the second coat on I tackled a number of other little jobs.

I applied fillets to the transom, and epoxy coated the bevel I had planed on the bottom of the transom doubler.  I test fit the cockpit sole and found it was a touch long, so I planed off about 1/8" on the back edge.  I believe the bevel on the doubler is doing it's job of making the installation easier.

I then trimmed the centerboard pivot pin to length and made the solid cover that will be glued on the water ballast tank end of the pivot hole.  I also made the cover that holds the head of the bolt and screws on from the underseat area.  Here the rough first coat of epoxy over the bare wood is shown.  I'll smooth that down and recoat before installation.  I also drilled out to 1/4" and epoxy filled the anchor holes for the screws.

Then I clamped the hull to the building jig and removed the screws that were holding it in place.  I put the final coat of epoxy in those areas, and will sand and paint, and then reinstall the hold down screws.  Then I can remove the clamps so they are not in the way of hull panel installation.

A couple days ago I received in the mail an Earlex steam generator, and an eBay purchase of some 6" layflat tubing 4 mils thick,and so I experimented with some steam bending.  

This is a piece of lumberyard pine 10mm x 30mm.  I steamed it for 1/2 hour and was able to easily put a twist in it.  I'm going to try 20mm x 30mm next and if that bends easily I will do that and not have to laminate the under-deck carlins.  I will need to join shorter lengths with epoxy and scarf joints in either case, and I will be running another test with a test joint to ensure the epoxy doesn't soften and let go at that temperature.  I know I can soften epoxy with my heat gun, but that's quite a bit warmer, I think.

By steaming inside the plastic tubing (which is similar in weight to a zip-loc bag), I should be able to do this right on the boat, and not have to hurry from the steam box to the boat before things cool off.  I'll be providing more information on this later.

I also spent some time thinking about where I wanted my seat hatches and how large they should be.  This is the port side with one of the B3 hatches, which is 12 x 18".  I think that looks about right.

But on the starboard side, I have to set it further outboard because the centerboard trunk is under that seat.  this puts it too far out, in my opinion.  I plan to cut a new template so that I can cut the hatch, hatch stiffener, and underseat backing plate about 1 3/4" narrower.

Interior painting started

Another thing I wanted to do before starting on the hull panels was to paint some of the areas that would become more inaccessible as construction proceeds.

I decided to use Rustoleum Gloss White for the interior spaces, and with the prep work done I was able to get to painting.  I used a brush for the corner areas, and the same type of foam roller I use for epoxy for the larger spaces.

I tried to stay well away from the edges where I would be installing fillets later on.  I was glad to notice that the paint rolls on easier than the epoxy did.

I expect I'll have to do probably one more coat to get even coverage, but it's a good start and will save time and effort later.

Transom installed

I'm itching to start getting hull panels installed, and not having the transom installed on the boat was one of the things standing in the way.

Earlier I had epoxied the transom doubler on to the transom while the two parts were off the boat and easy to handle and work with.  But one potential problem I could forsee was possible difficulty in getting the cockpit sole (the floor) installed later on, since that piece fits up against the transom and fits under the doubler.  And is a tight fit up forward.

I had read of another builder who ended up trimming the aft edge of the sole off to get it installed.  I'd prefer to not do that, so I decided to plane off the corner of the doubler at the bottom to give me some clearance to install the sole later on.

I got out my trusty #5 plane with the Hock blade and started making shavings.

It didn't take long and the job was done.  I really like using the plane - such a sense of getting something done!

Looks pretty good as I dry fit the transom.

So I mixed up some thickened epoxy and installed it.

Interior paint preparation

I decided that before I got hull panels installed, I wanted to do as much inside finish work as I could while access was still easy.  So I started out by rolling on the final coat of epoxy on the bulkheads and other interior areas.

Everything looks so shiny and nice!  

I thought I was good to go and could proceed immediately to painting the interior spaces white.
  

I had purchased some porch and floor white enamel for this job, but it was a latex paint, and I just felt more comfortable putting on something oil based, so I returned what I had and purchased Rustoleum Gloss White for the job.

To make sure I was getting good adhesion, I painted a small test patch, let it dry, and then was disappointed to find I could scrape it off with my fingernail.  <sigh>

I sanded up another area with my random orbit sander and painted a test patch there, and found I had much better adhesion.  But I couldn't get into all the spaces with my power sander, so I did a third test patch, just removing the gloss with a 120 grit sanding sponge.  That also worked well, so I proceeded to sand all the gloss off my latest coat of epoxy by hand with the sanding sponge.

With everything dulled up, I can start on my painting after cleaning up the dust.

A Hole in the Boat!

It was time to install the fill hole/drain in the water ballast tank, so I took drill in hand, took a deep breath and drilled a hole in the bottom of the boat!

I had cut out the backing plate from 6mm ply, and then put it in the lathe to turn a recess to inset the fitting so it will end up just shy of the outside of the hull.

I drilled pilot holes for the screws, smeared everything up with thickened epoxy and put it all in place.  I installed the three screws through the epoxy blobs and snugged them down.  Then wiped up the excess and and left it to cure overnight.

Here is the result after scraping things smooth with a utility knife blade.

Next I coated the water ballast tank with graphite.  I'm hoping this will provide a slick, durable surface so that the tank is easy to clean out when needed.

I modified the drain plug by drilling a hole through it and inserting a short length of brass rod.  I then flattened the ends of the rod so that it can't slip out.

And here is the final result ready to go.  The rod on the plug makes it easy to install and remove.