Forward deck and gearbox mount

The chronology is getting a little fuzzy, but since the last boat post, I have spread on two fill coats of epoxy to the outside main hull.  It looks like I managed to avoid making a big mess of anything on the outside.  I can definitely see improvement with each of my last boats.  The next general step is to complete the remainder of the forward deck.  This includes the footwell panels, the gearbox mount and the seat bottom.  I can then work my way from the gearbox along the driveshaft and complete remaining panels as I go.  

I tried to minimize the number of panels, but this does mean that there are some aggressive curves to form transitions.  

It has taken a significant amount of time to glass each of the individual remaining panels separately.  It also creates a lot of waste as there will be cloth trimmings and left over epoxy.  If I try this again, I will hopefully negotiate to pre-laminate a full sheet of plywood and have the CNC shop cut the small panels all out of this sheet.  

 

I am making a slight change from previous designs and mounting the gearbox inside the boat.  I will need to allow for leg length adjustment, so these panels have slots for the crank arm axle.  I will extend it all of the way to the front edge once the rest is put together.  However, having big slot in the boat means it will take on a lot of water if it is to capsize, so I have added a partitions to seal this area (except for the gap around the shaft and bushing) and to add some strength.

I used the same stitch and glue steps for the footwell panels.  I started in the middle where there is no curve and waited for it to cure.  I need to create a lot of leverage to bend the strips into place, so I wanted a portion of the length to be secure.  I used some clamps to provide the leverage in one area.  Once the clamps created the bend, I tightened the stitches to hold the gap closed.  For the transition to the seat bottom, I cut some scrap wood into bending forms and prebent the panels before attempting to stitch.

I added 2" tape to the inside seams.  On the outside internal corners (such as between the footwell and gearbox housing) I used the System Three gel epoxy to make a small fillet.  I thought I would avoid visible filler there, and the gel is supposed to waterproof and structural for this type of application.

Total time up to this point (not including gearbox): 56 hours

Custom bevel gear box

I took an unexpected break from fabrication this past week.  We live in Minneapolis, Minnesota, in the northern US, a state that borders Canada (thanks to all of the international readers I've had so far).  Summers are usually warm, but not too hot.  The past week was a record heat wave of the decade.  We had the same temperatures as Texas for most of the week.  I wasn't motivated to work on the boat dripping with sweat in the garage.  Fortunately, the weather is now back to normal.

I have been doing more prep work on some of the remaining panels.  However, the biggest update is that the gear box parts were complete, and I now have them assembled.  The gearbox is similar to the recent custom boxes Rick has made.  He uses pillow blocks for bearing mounts, and this allows for easy manual machining in his garage shop.  I don't even have a drill press, so I knew I would be sending out these parts to a local job shop with CNC capability, and I designed a similar box with flange bearings.  It requires some precision holes for the bearings, but most shops should be able to manage.  The motivation is to get a box that should be able to hold up during a sprint, and that is fairly light weight, and has an efficient gear ratio without need for a chain to reduce further.  The gear ratio is 4:1, higher than any stock gearbox available.  It weighs in at 5.4 lbs including crank arms.

The housing is 4 x 6 x 1/4" aluminum extrusion.  I had a small spacer block welded in to provide a gap between the two output shaft bearings.  Everything is held in place with stainless dowel pins and aluminum shaft collars.  The crank shaft is 17 mm (this is the largest flange bearing size I could find) with taper square ends for standard bike cranks.  The output shaft is 3/8" stainless.  I left it long because this end will telescope inside the drive shaft tube to allow for leg length adjustments.

We had some machining hiccups and I also needed to fine tune the fit a little between a few pieces using sand paper, but overall the result looks really good.  I think it should hold up really well.

Total time up to this point (just for the gearbox assembly): 5 hours.

Glassing the hull outside

I used a palm sander for a quick pass over the panels and soft and hard sanding blocks to round the seams.  I needed to be able to reach all sides of the hull and deck, so I set the boat upside down on saw horses on top of the bench.  I could just barely see over the top to work there.  I had a length of 50" wide cloth for this step.  I draped the cloth over the hull and, except for the deck, trimmed off the excess to save for smaller panels.

For the outside I used a thin foam roller available at marine stores.  I think I waste a lot less compared to pouring and spreading when it is a large surface.

The end result turned out well.  My plan to wrap the deck was successful, although I wouldn't recommend it for a first boat.  It was more difficult, but it saved a step and cut down on areas where glass is doubled up.  I saved the deck for last and had the rest of the hull finished.  I rolled on epoxy to the deck and held the cloth in place while I trimmed it with a sharp razor blade.  On one side I trimmed along the center up to the deck top panel and followed one side of the top.  On the other side I did the same but wrapped over the top and trimmed to the same edge as before.  This would leave one edge without reinforcing cloth on the outside, but I added tape to the inside, and I would be very surprised if there is any structure deficiency.

The next day I added a layer of 4" tape and also a layer of 2" tape to bow for extra abrasion resistance.  I also added the tape to the underside of the deck top and finished a few fillets inside as well.

 At the same time I added a layer of tape to the inside of the splash guard.  Finally, I layered cloth over the outside of the seat back.  This wrapped over the sides and overlapped the previous layer about an 1 inch.  I use the same technique in the book I mentioned, and it gives a very clean transition.  I put masking tape along the line where I would like to stop the new cloth.  I wet out the cloth just past the tape and finish smoothing everything.  At the end, I take a sharp razor and trim at the tape line.  If you can avoid messing with it, you will end up with an edge free of lots of unraveling threads.

Total time to this point: 40 hours

Next up: fill coats for the outside and since the gear box parts are almost done, I can take a break from wood for a bit.

Panel prep and stitching the forward deck

After glassing inside the main hull, I needed to do some basic prep work before I could do any other construction steps.  I glassed both sides of the bulkheads and also glassed the inside of the deck panels.  I also did some general prep work (sanding) on some panels I will get to later.  The next step was to glue in the bulkheads.  There is one forward and one aft.  These will seal off portions of the hull that are hard to reach for storage and create independent chambers for bouyancy in case of emergency.  I used 5 minute epoxy to set the bulkheads, then ran fillets on both sides.  I admit I didn't tape here, I guess no one's perfect.  After curing, I put 2 inch glass tape on one side over the fillet.

Next I had to deal with my first misstep.  Fortunately, it was only cosmetic, but I am very particular about the aesthetics, so it was still disappointing.  I had decided to use up some of the water based wood dye I had left from my last boat.  I covered several of the deck panels with dye and sealed with an epoxy coat.  It looked great.  Then I needed to glass the underside, and since they were individual panels they could sit flat on my work bench.  I put them over my plastic covered bench and carefully spread epoxy over the glass.  But I was not careful enough, so in several places epoxy ran off the edge and pooled under the panel (which is the good side).  It is impossible to sand off this stuff without sanding into the dye and leaving a light spot.  It isn't possible to reapply dye because the grain is sealed with the sealing coat.  So rather than have a few spots on each panel I chose to sand the entire panels to lighten the color somewhat uniformly.  I definitely know now to put panels on spacer blocks (1/2" or more) next time.  It's rare on a regular kayak to glass panels individually, so it hasn't been an issue before.  Hard to say how it will look finished up, but its time to move on.

Stitching on the deck panels generally went without any hangups.  I also stitched on the splash guards, which are one addition to Rick's previous design.  I also made the transition from the footwell to the forward deck curved so I could use a single strip for a splash guard.  The software did a great job unfolding this panel.  Once it was stitched on, the only way it could be bent to align with the mating edge was to sit at a 45 degree angle.  I am also taking advantage of early feedback from Rick and Michael who have both taken their similar boats out a few times.  I had originally designed the forward deck to be pretty tall.  I think partly it is hard to judge proportions of a 20 foot boat scaled to fit on the computer screen.  I want room for storage, but it will perform better in a cross wind with a shorter deck so I manually cut these panels down and cut a new top piece out of scrap wood.

Now the next steps are the same as before, taping the seams, gluing, removing the stitches, filling holes.  The photos show one area where the panels would not line up as needed.  Sometimes, the wire cannot create enough tension.  In these cases, I use push pins to prevent one edge from sticking out too far.  It is better to spend the time here making the adjustments rather than spending time later fixing the fiberglass when it doesn't lay smoothly over the sharp edge and leaves a bubble.  Nice to see it look more like a boat.

Now its ready for a final outer sanding and glassing the outside of the main hull.  As I mentioned it will be a first for me to wrap around and glass the deck in the same steps, so I hope it works.

Total time up to this point: 32 hours.  

Glassing the hull inside

Elapsed time to this point: 15 hours.  Now the hull is ready for a final sanding, primarily the seams and inner fillets.  Typically with a stitch and glue boat (kayak), you have a deck that is a single piece and it is built almost the same way as the hull and glued down at the end.  With this boat, the deck has the seat and foot wells and drive train housing so it is not feasible to build in one piece.  For this reason, I am changing the typical steps.  I will glass the inside of the hull first.  Then I will assemble the forward deck to the hull (I will glass the inside of these individual deck panels beforehand) and then attempt to glass the outside of the hull and forward deck at the same time.  Then I will assemble remaining deck pieces.  I ordered extra wide cloth for the outside and I hope it will work out.

To glass the inside, I vacuum out the inside and spread out the cloth, centered as best I can.   I pour the epoxy onto the cloth and spread with a squeegee to saturate it.  I work from the center so the cloth can’t shift as easily.  Then I use a squeegee and remove as much excess as I can.  Then I lightly smooth with a dry brush to remove squeegee marks.  There are always some air bubbles to work out, especially on the inside because the squeegee will pull the cloth away from the corners.  I’ve found that if I wait until the epoxy is tacky and squeeze the bubble out it generally comes back as soon as I leave the garage because there is tension in the cloth.  It’s better to remove the bubbles right away as I create them, and if they ever come back, I take the time to adjust the cloth so it has more slack.  To do this I push the cloth from the edges toward the seams with a stiff brush.

After the glass is wet and nearly smoothed out, I rough trim the cloth to about an inch above the deckline.  If the cloth is too big and folds over the panel, it tends to pull away from the wood at the top.

In this case, since I had already put glass on the tips of the panels, I could stop the full sheet at that point, and it worked well.

After this is cured, I trim the cloth at the deck line and sand off the sharp edges.  I will add a top coat just over the area where I will likely stow gear near the hatch in the deck, but I think I will wait until bulkheads are installed so I can coat over the taped seams in the same step.

Gluing the hull seams

Elapsed time up to this point: 7 hours.  After the main hull was fully stitched together, the next step is to glue the seams.  I generally position the panels so the inside edges are close to touching (rather than one panel overlapping the other).  This way you don’t need to worry as much about making adjustments for material thickness, and you can create a smooth radius with the filler material in the gap without sanding through the plywood veneer.  I also tried the SilverTip system seam filler mix rather than using epoxy and dry powder.  It works well but is harder to measure the ratio when using paste.

I would say I subscribe to the general methods outlined in the book I first read on the technique: Kayaks You Can Build, by Ted Moores and Greg Rossel.  This is to say carefully tape off all unwanted areas before adding glue to the wood.  This seems like a lot of work, but I tend to agree that for every minute you spend taping, you save a minute of sanding and the final product looks a lot cleaner.  Generally speaking, since it is darker, the filler will show up in the wood grain even if you sand off the excess.

I first taped off the two seams, putting tape down on top of the stitches.  Then I simply filled in the gap with epoxy paste on my gloved finger.  Sometimes it’s easier to remove the tape before the epoxy sets, so this is an option.  After the epoxy is cured and tape removed, I snip all of the stitches and pull them free.  I sand lightly to remove high spots.  Then tape the same seams again in order to fill in the spots left by the wire stitches.

No need to sand again now, because it is time to fill in the wire holes.  This is considered optional in the kit instructions I have read.  Again, it seems tedious, but I still do it to prevent problems down the road.  If the holes are not filled, you will get liquid epoxy drips on the other side of the panel when you first laminate the fiberglass cloth.  The epoxy drips are much harder to remove than the extruded paste as you can see here below.  It also helps prevent trapped air in the hole.  Filling the holes does mean more taping.  

I drill a hole in a roll of masking tape every two inches or so, not going all the way through the roll since I don’t need that many pieces.  The smaller the drill the better.  Then I tear off pieces of tape and line up the tape hole with the wire hole.  I fill the holes using a plastic stir stick as a small spatula to avoid missing the tape.

Remove tape and once epoxy is cured, use a small scraper on the other side to remove the extruded stuff.  Now its time to create fillets on the inside seams.  This will allow the fiberglass cloth on the inside to conform the surface without worrying about sharp inside corners (the cloth would pull away and leave air bubbles).   This means more taping.

I tape about 3/8” from the edge on both sides and try to trim the tape at the very ends to match the tapered panels.  I plan on using hatches in the hull to allow for storage, so I will see the inside and would like it to be reasonably clean.  But even if you never see the inside, a second reason for the tape is it helps you form a small and consistent fillet to reduce unnecessary weight.  I apply the filler with a small syringe and smooth with my finger.

Remove tape and the hull is ready for final pre-fiberglass sanding (and not very much of it if the tape did its job)!

Hello and stitching a hull

Dear blogosphere,

This will be my modest attempt to share my latest fun project, building a high performance pedal powered boat.  It will be my second "hpb" and third stitch and glue craft altogether (including my kit canoe you will see hanging in the garage).  You will see where the name "stitch and glue" comes from in the photos.   I apologize in advance for not consistently using proper maritime terminology, I'm still a cyclist who wants to bike on water rather than a boater who wants efficient human power.

If imitation is flattery, I should point out that I am borrowing heavily from a boat and drivetrain design by Rick Willoughby and getting inspiration for a blog from Michael Lampi.  You can see very similar creations by both enthusiasts.  Mine will be slightly different in ways easiest to explain when we get to that point.

The boat is made from 4mm okoume marine plywood and was cut to exact shape by CNC router according to CAD files created by DelftShip design software.  The hull length is 20 feet, limited by my garage, and the first step is to glue multiple pieces cut from 8 ft plywood end to end to make long enough panels.

The butt joints are glued and reinforced with 2 inch fiberglass tape on top of 4 inch tape.  It was done in one step and covered in semi-rigid plastic (scrapbook cover sheets) and wood and weights to ensure a smooth surface.  I am leaving the exterior side without tape reinforcement as this will be laminated in a full sheet, and the glass will already be 4 layers thick at the joints.  You can see faint lines from the tape even in my best fiberglass attempts.

The hull is formed from 3 panels, two sides and one bottom.  The sides I designed included integrated seat back forms to avoid additional seams.  Altogether the panels went together pretty well with just one joint that had a few air bubbles.

 I tried something new on this build, which was to glass the inside ends of each panel before stitching and avoid cramped quarters trying to laminate the inside after assembly.  The hull is so narrow, it will be hard to work close to the ends.

Once the panels are complete, I drill 1/16" holes every 12 inches along the edges joining the three pieces.  This is wider spacing than usual but the panels have very little bend, so it seemed appropriate and worked fine.  These holes are used to stitch panels together with wire.  The stainless wire I ordered turned out to be too rigid, so I picked up some .8mm copper wire at the hardware store and, while more expensive, it is far easier to work with than any other type I have used.  It is also much less likely to break when tightening.

Most of the stitches have the "twist" on the inside.  This makes it easier to glue the seams on the outside without getting scratched constantly.  On the end, the twist in on the outside due to space constraints.  Loosely stitch everything first, then tighten by pulling slack out and then twisting until there is enough friction between panels that they do not easily move against each other.

I used one forward bulkhead, and one rear.  I also decided to stitch the seat back on at this point to help provide some rigidity.  Lastly, I taped the rear deck on temporarily to create the proper taper of the hull sides.  I also noticed a slight amount of twist at the stern, I'm not sure why.  I think I corrected this with some tape anchored to the workbench.

Next up, gluing the seams - as in stitch and glue.