Tabbing The Hull and Peel Ply

February 11th, 2016

About half the hull has been tabbed. To tab the hull the area between the stiches is wetted with neat epoxy and allowed to soak in. The fillet material is mixed with epoxy to a very thick consistency so the fillet won’t run. A quart zip lock bag is filled with about 6 to 8 oz of the epoxy-fillet material, squeezed into a corner and the corner of the bag is snipped off. Similar to a cake decorator frosting bag, the epoxy-fillet material can be quickly applied to the seams without making a mess. The fillet material is then smoothed with a tongue depressor which make a nice 3/4 inch fillet tool. If you are wondering why I don’t have any photos of the epoxy process, it is because when I am using epoxy I have a Tyvek suit, gloves and a respirator on. Also epoxy is very sticky and I don’t want to get it on my camera.

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Tab With Peel Ply Still Attached

The next step is to apply 2 inch square pieces of fiberglass cloth over the fillet. More neat epoxy is used to wet out the fiberglass until it is transparent. Finally a 3 inch square piece of peel ply is put over the fiberglass cloth, smoothed out with a dry chipping brush and blotted with a paper towel to soak up any excess epoxy. A chipping brush is cheapest paint brush available. They are known to lose their bristles with regular frequency. To prevent the bristles from coming out I put a bead of superglue at the ferrule.

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Tab With Peel Ply Removed

I had left one of the tabs without peel ply to see if the peel ply actually worked. The peel ply leaves a smooth finish to the epoxy that will save me hours of sanding. Also I won’t have to remove the fiberglass tab when I tape the seams when I turn the board over to do the insides. I will now be using peel ply on all my seams.

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Tab Without Using Peel Ply

Good Stitch Bad Stitch and Tabbing

February 10th, 2016

Now that the stitching is finished and as I tab the hull, I am inspecting my work more closely.  The first photo shows the bow where there are several bad stitches that were not pulled tight against the plywood. Good_Stitch_Bad_Stitch (Medium) The two stitches closest to the bow are two good stitches which are pulled tight against the plywood.  There is a slight gap cause by not cutting the panels perfectly; fortunately the filleting material will easily fill it.  I found through practice that when I bend the wire into a large staple I need to make sure the width matches the holes drilled in the plywood.  The second photo shows the stitches from the outside of the hull.  A hole is drilled in each of the plywood panels about a 1/4 inch from the edge.  The wire staple is pushed though and working from the bow to the stern the wires are tightened by twisting to bring the hull in to shape.   DSC_0069 (2) (Medium)

I have started to tab the hull which means that I am adding fillets between the wire stitches and applying a 2 inch square pieces of fiberglass cloth over the joint of the panel edges. The third photoDSC_0068 (2) (Medium) shows completed tabs with peel ply which is added to smooth out the epoxy so there is a smooth finish.  The peel ply is easily pulled off taking the excess hardened epoxy with it.  By removing the excess epoxy this way I have greatly reduced the amount of sanding that I need to do.  Sanding epoxy is the bane of stitch and glue boat building.

Scarfing Demonstration

February 8th, 2016

Last Saturday I gave a plywood scarfing demonstration at RiversWest Small Craft Center (www.riverswest.org).DSC_0039 (Medium)

Plywood normally comes in 4’x8′ sheets or the metric equivalent of 1220mm x 2440mm.  In boat building, we often need longer sheets of plywood to work with and the most cost effective way to make plywood longer is to cut a scarf joint, usually in a 1 to 8 ratio.  For a 6mm (~1/4inch) thick plywood the scarf would be 48mm long or just under 2 inches.  DSC_0041 (Medium)To cut the scarfs for the Candlefish 13 I used the John Henry Scarfer which is a jig that bolts to a power planer; in this case a Makita 1902 3 1/4 inch wide planer.  DSC_0049 (Medium)The scarfer runs on long the edge of the support piece and a the work bench top and by adjusting the number of shims the angle of the cut is controlled.

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I set the planner to cut only 1/32 inch so it took 5 passes to cut the scarf.  It takes longer to setup than to cut the plywood.  DSC_0047 (Medium)

Once all the scarfs are cut I then cleaned them up with my #6 joiner hand plane.  The next step is to epoxy the plywood sheets together.  When done properly the joint is just as strong and almost as flexible as the plywood.

All Stitched Up

February 4th, 2016

All_Stitched_Up (Medium)After two tries the stitching is complete.  There was a scare because the strakes would not lay properly on the molds.  It turns out that the designer, Sam Devlin, added some space between the bulkheads and the strakes intending for the gap to be filled with wood filler and epoxy.  To make the strakes fit fair with the molds I added 5mm spacers (1/4 inch underlayment) which mostly worked.   The strakes fit molds #3 and #4 fit very well with just a little offset at the upper chime and a bit more offset with molds #1 and 2.  It is nothing that I cannot live with considering home much blood but no tears into the boat.  The wire to stitch the hull are sharp and my hands look like I have been fighting with the cats.

The next step is to tab the hull.  That means going under the board and put neat epoxy on the seams.  The neat epoxy will soak into the end grain of the plywood and I won’t have epoxy starved joints when I add the fillets.  Neat epoxy means there is no fillers added.  The second step is to add fillets between the wires.  The filleting material is 2 parts colloidal silica 2 parts low-density filler, and 1 part high-density filler mixed with epoxy until it is a peanut butter consistency.  It is squeezed into the joints and the smoothed over.  Finally the fillet is brushed with more neat epoxy and then a fiberglass square is put over the fillet anchor the joint.  Once the epoxy sets up I can remove the wires and the hull will retain its shape so I can sheath the exterior of the hull in fiberglass and epoxy.

I intended for the Candlefish 13 to be 13′ 10″ long.  Somehow the boat ended up at 14′ 1″ long.  Where did those extra 3 inches come from?  Once the hull is turned over I will measure again and see if I made a mistake in measuring.

Building Jig

January 31st, 2016

CF13_Building_Jig (Medium)The Candlefish 13 build has reach a major milestone; the completion of the building jig.  Early in the build I had cut out the forms and the transom then  put them aside.   I had also built the supports for the forms although I had build the supports for bulkhead #1 too wide and I had to cut it down.  With the strakes that I had just completed before finishing the building jig I am now ready to start stitching the hull.  First the two bottom strakes go on and I need to make sure they are in the correct location and they lay properly on the hull.  There will be a lot of measuring to make sure the hull is symmetric.  I have been measuring 3 and 4 times to make sure that I have avoid any errors and I have also been measuring from a common point to avoid error accumulation.

The Scary Part of Boat Building

January 12th, 2016

The scariest event in boat building is the cutting out of the strakes (planks). Making and gluing the scarfs is second. When it comes time to cut out the strakes I have already spent many dollars on high grade marine plywood, completed the scarfs and lofted the strakes onto the plywood. One little slip of the circular saw and all of that time and money is gone.IMG_20160111_152431104 (Medium) Fortunately I only made one little error in cutting out the planks that will be easy to recover from. A little epoxy and fiberglass will cover up the error.

I had raised the building platform in anticipation of cutting out the strakes. I had covered the platform with plywood and 1 inch Styrofoam sheets. The foam won’t wear on the blade or interfere with the cutting of the strakes. I reviewed the layout and made sure I knew what side of the line to cut on before I started cutting. When cutting on the outside of the circular saw I could stay just outside of the line; when cutting on the inside of the circular saw I stayed away from the line to avoid cutting inside the line. I was cutting both the port and starboard strakes out at the same time so to keep them aligned I put pallet screws in each end and the middle. You can just see them in the picture. The holes will be filled later.

Since the two stakes are screwed together it made it easier with the spoke shave and belt sander to clean up the saw cuts. The upper strake is done and once I am done with the other two I will clean the garage, sorry boatshop, again so I can assemble the building forms.

Scarfing Plywood

January 9th, 2016

Work interfered with my boat building again but I did manage to assemble the building platform and scarf the plywood.  The 4 sheets of 4ft x 8ft x 6mm plywood are turned in to two sheet of approximately 4ft x 16ft by 6mm plywood.  plywood_scarfing_glueup (Medium)The short edge of the plywood is planed down to a 1 to 8 taper so that when the two sheets are epoxied together they retain their strength and flexibility across the joint.  In the middle of the two sheets of plywood you can see a batten that was screwed through the 6mm plywood the to 12mm plywood below.  If everything works out right in a few days I will remove the clamps and screws to check the joint.  I am using West System #205 fast harder that cure wells in the cold garage.  The time to cure to full working strength is 2 to 7 days so I can mark out the planks and cut them out next weekend.

On the Second Day of Boat Building

December 24th, 2015

On the Second Day of Boat Building…   The transom template has been cut out but I made a mistake on one of the cuts and put the saw on the wrong side of the line. That little mistake resulted in the transom being off by 1/8 inch. Out came the biscuit joiner so I could glue the cutoff back on so I could then cut it off again only on the correct side of the line. Little mistakes take so long to fix. Error Avoidance is a process where errors are avoided my making doing the right thing easy and doing the wrong thing hard. After I mark out the transom I use colored pencil, pink in this case, to make where to make the cuts. The idea is not to cut drafting lines by mistake. The process has worked perfectly on the four molds and only one mistake on the transom.cf_13_frame (Medium)

I borrowed a John Henry planer-scarffer attachment and planner to cut the scarfs for the 6 mm plywood in which four sheets of 4 x 8 plywood will be joined end to end to make two sheets of 4 x 16 plywood. Actually the joined sheets will be 15 feet 10 inches but that is close to 16 feet. I made some test cuts with the scarffer and after a few tries it worked ok. I see that I still need to refine my setup to get better scarfs. I also epoxied the test cuts so I could do destructive testing to see strong the joint will be.

One of the changes from Sam Devlin’s plans is to replace bulkhead #4 with a laminated frame. I was planning on cutting the frame from White Oak but when I went to my wood pile I could only find Red Oak which is not used for boat building. I managed to find some off cuts of Khaya, an African mahogany to use instead. The building of the jig, cutting of the strips 1/8 inch thick took one evening and I epoxied the frame the next morning. I ran out of 3 inch deck screws so my wood blocks to hold the frame down did not work as well as I would have like. The strips were 15/16 thick but when I am done the frame may be only 11/16 thick instead of the 3/4 inch thickness that I was aiming for. We will see what the thickness is when I clean up the frame.

On The First Day of Boat Building

December 21st, 2015

cf_13_molds (Medium)On the first day of boat building… I made the molds for the Candlefish 13 build; finally after months of planning the build has finally started. I snagged some molds from a fellow RiversWest member who was going to throw them out. The plan was to use them from jigs or something since they were made from 1/2 inch MDF. The Candlefish 13 is a smaller board so I was able to cut the old molds down to what I needed.

The Candlefish 13 as designed is 13 feet 4 inches. Mine will be a candlefish 14 at 13 feet 10 inches by increasing the bulkhead spacing by 4%; the beam is not changing. I am also replacing the plywood bulkhead #4 with a laminated frame made from Mahogany; in the same method used by Joel White in is Nutshell and Shellback designs. The plans have plywood frames as part of the bulkhead and those will be replace with Alaskan Yellow Cedar.cf_13_prifile (Medium)

Tomorrow I hope to start cutting the bulkheads and transom.  I will most likely make a pattern for the transom to make is easier to cut out and check the dimension.  It is so easy to make a mistake so I am checking my measurements twice.

 

Looking A Little Blue

June 3rd, 2015

I have started to paint the pram.  The sides are an off white and the bottom and ribs are Largo Blue.  I am using Interlux Brightsides one-part polyurethane and it is very easy to use.  Looking_BlueI am using the roll and tip method to get a very nice finish.  Roll and tip is where the paint is applied with a foam roller then brushed out to remove orange peel.  On the bottom between the runners I used a foam brush and then the paint brush to smooth it out.  The Largo Blue is a bit more blue than I was expecting but it does look good.  Once the painting is done on the inside I will install the inwale, seat riser, stern knees and fore deck.  These will be painted before installation and then touched up.  I am really hopping to have the boat in the water by the end of the month.