Steps in Building a SCAMP sailboat
Links to all my scamp building pages.
My SCAMP build, Making a Mast
Cutting lots of strips for mast staves.
I'm getting ready to cut the mast staves and at the same time I'll cut the support strips. Scamp seams are built using a combination of stitch and glue and strips of wood that give a point of attachment to the thin plywood. Not quite chine logs but a framework of strips that add rigidity and increased gluing surface.
It took a bit of time to clear the table saw, set up an out table, make sure the blade was perfectly square and set up the feather boards and stop blocks.
Because I'm cutting 2x4 lumber down to thinner strips some wood will certainly warp as I cut and there is a real danger of binding and kick back. The feather board and stop blocks make the process much safer. I also cut in 2 swipes, this helps release the tensions.
I spent a couple of hours of quality time with my table saw and ended up with a large pile of strips. I've rough cut only the thickness of the strips, the width I'll do later. The support strips which will be used to support various parts of the sailboat such as the seat, are 20mm plus a bit for shrinkage and planing, the mast staves are 17 mm plus some for cleaning up and I have some extra planks of various ends at about 15 mm that I can glue up if I need more strips.
I'm using 8 feet lumber select grade. There are lots of small solid knots. I'll have to remove any large knot and scarf pieces together for the mast, time consuming but it works well. That's what I did for my Skerry mast and it has been rock solid. I used old knotty pine shelving. It was a sort of patchwork mast.
NOTE IN HINDSIGHT: It took quite a lot of time to glue the pieces together and IF you consider time it would have been cheaper to buy better wood. I just did not have easy access to it. In terms of strength the seams are good so I don't think I've compromised strength.
This lumber is mostly spruce. I can see that there is the odd board of other wood thrown in.
I've cut lots of extra so I can pick the better pieces and use the rest in other projects. I always seem to need bits of wood.
I'll plane them after a day so that they will have had a chance to warp if they plan to.
Cutting the pieces for the mast.
After planing the long strips, I set up the table saw to cut the notches. I don't bother cutting the width of the board because when I cut the notch the width will automatically be right
Instead of using the fence I clamped a board. It is easier to feed and some of my boards have slight warps and this makes it easier to cut.
The blade is at 45 degrees. I've checked and measured the width.
I'm using 2x4 x 8 feet and the mast is to be 16 feet so I will have quite a number of smaller pieces that will need to be joined. I don't want to have to set up to cut really long strips, everything gets complicated and I have to feed to the outside because I don't have 32 + feet. That's why I have a garage door in the shop. It's winter and it's cold so I'm using a comfortable 8 feet.
I cut a couple of test pieces and assembled them. I'm finding that the plans's 30 mm long gives me a slightly too large diameter. I guess that there is a bit of extra for sanding and finishing.
I set this up to cut the scarf joints. I will need many joints to get the full length and to cut out the bigger knots or flaws. I did this for my Skerry mast and it has held up beautifully even though it was made of softer pine. My boards are spruce for the most part.
The blade is at a slight angle and the jig holds the piece to be cut between 3 guide boards. The little clamp holds it while I slide the whole thing through the blade. It fits on top of the table saw fence.
The blade is as hight as it will go and this gives me a 6 to 1 scarf, or a bit more. This is not ideal but I used an even smaller scarf on the Skerry and got away with it so I'm confident this will work. The joints end up looking like curved lines in the round mast and actually look like wood grain so it blends in well.
There are many ways to cut a scarf joint but this will be very easy, safe and fast.
The joints should be staggered so that they do not weaken an area. It looks better too. I'm not sure that a joint like this weakens the board because the filled epoxy glue is stronger than the wood and I will be coating the mast with epoxy as well. I don't think the mast is expected to bend very much
I did a quick check to make sure the pieces fit and they are nice and flat and well cut.
Joining some of she shorter pieces. Since the mast is to be about 16 feet and I'm using 8 feet lumber, there are at least 3pieces for each stave. I've cut out any of the larger knots and that means many more joints.
This allows me to use lesser quality wood at the expense of having to take much time building the mast. There are no handy lumber yards near here so it's not easy to go shopping for nice wood either.
Now that all the cutting out of bad knots is done the putting together will go quickly. For a while I had stuff everywhere and not a surface to work on. I've spent some time and cleared sawdust and extra wood away.
Once I have all the staves cut out and lined up so there is no join at the same level, I will plane them so that the mast tapers when it is put together.
Detail of one of the joints. I've checked the ones I've done so far and they are all sound. I'm sure the joints are more sturdy than the wood. I don't think this mast is intended to bend so having stiffer joints is not an issue.
8 pieces 17 plus feet long ready to be slightly tapered. I'll probably use the belt sander. There are too many small knots and joints to use the bench plane.
After measuring the staves and cutting them even, I realized that I had mis-measured. I will be about 10mm short. Dang and Poot!
I clamped the bundle together and using the belt sander thinned out the staves to create the taper on the mast. It worked very well.
Now I'm bracing myself, a nerve wracking marathon glue session to put it all together.
I plan to put 3 pieces of wood inside the mast at vulnerable spots, the base, the top and where the mast touches the top of the cabin.
The core was cut from a piece of a pallet. I had to experiment to figure out the size for the top of the mast but I got it.
I made a glue spreader from a plastic bottle. I used one when I made the Skerry mast and it works really well. By leaning it you can control how much glue is left and the sides keeps the glue from going to the sides of the wood.
I measured out several glasses of epoxy what I could mix quickly as required. In the end I under-estimated how much I would need and had to measure some more.
I like to use a gram scale to measure the epoxy. It's fast and more accurate than I can measure by making marks on containers. The pumps are not as accurate I think. At least not the ones I had. I don't think it really makes much of a difference. In this case I'm using MAS epoxy and the hardener and resin are almost the same weight so there is not a significant difference if it is measured 2:1 by weight. How do I know, I tried both ways.
I put plastic under the mast parts, got my gloves, epoxy, thickeners, drill with bit, clamps, plastic ties, paint brush, baggies, scissors, tongue depressors, put some wood on the fire, chose some music, and finally took a deep breath.
The first part is easy, coat the V and the inside face with epoxy so it does not suck up the glue and starve the joints. No problem if that starts to kick off.
The next 2 hours are fast paced and insanely stressful, at least for me. I mixed epoxy, thickened it with silica and wood flour, squeezed in the V, spread it as best I could, and repeated this until I had all 8 strips, all 16 feet of them, done. I would change my gloves regularly.
NOTE: In Hindsight I would have been better to forget about my little spreader and line up the 8 strips V side up, and paint on the thickened epoxy into the 8 together, maybe clamping them temporarily side by side. There would have been more squeeze out when I assembled them but it would have taken less time.
Even though I'm using slow hardener, and the shop is not warm, I only have about 45 minutes of open time. I was getting close to this and had not even put the mast together yet, let alone clamped it.
Sorry I have no photos, I was working too fast and everything was sticky.
Some pipe clamps and many zip ties secure the mast.
When I made the mast for the Skerry I had a lot of trouble getting everything together. This time I was wiser. I had put bar clamps with the end making a fence sticking up and stopping the staves from falling off the table so I did not have to worry about both ends at once. I took the photo after removing the clamps and taking the sticky gloves off the workbench.
When I made the spars I actually made a few semicircular stands that help position the staves. That worked well too. My Page on making the yard for the SCAMP
I went to the top of the mast, and forced the staves in position. I did not worry about anything except getting the very end lined up. This was quite easy to do. I slipped in the core which I had covered with thickened epoxy all ready to go. I then slipped on a round of cut off plastic pipe to roughly clamp the end and put a pipe clamp on. I then went down to about half way and manhandled the staves till they were in position, slipped on a clamp and went to the spot where I had marked the position for the core piece at roof level and put in the core and put a clamp. The end was pretty much in position so I put in the bottom core and put on another clamp. I used the drill with a driving bit to tighten the pipe clamps
Now my time is getting short, my epoxy is just starting to get thicker and it's harder to get it to squeeze out, YIKES. It took a lot more force than it would have 15 minutes earlier. I eventually got the mast clamped. I used pipe clamps and plastic ties. I had not expected to need a lot of pipe clamps so I had to tighten with the pipe clamp, put on a couple of plastic ties and remove the pipe clamp and go tighten further down. I had a couple of spots that did not want to squeeze in and I used a bar clamp to push in the resisting stave. Once pushed in I could add a plastic tie or 2 and move on. Once in position the staves did not come back out so the plastic ties were enough to hold the mast in postion. I had prepared plastic wrap but that was not enough force.
I spent some time going up and down the mast, tightening the clamps, adding plastic ties and removing some of the squeezed out glue.
By this time everything is gummy, the screwdriver and drill are covered with epoxy and some sawdust, I am covered with goo and I'm a basket case. There are used gloves everywhere and my glue mixing table is a mess. The good news is that the Scamp mast is together. It is also quite straight with no significant bend.
The Bird mouth method of mastmaking is very forgiving and for the most part a mast will be fairly straight unless it was clamped very crooked.
I spend the next while checking that the mast is straight and that there is no obvious problems. I checked the level of the supporting table and various bits I had set up to support the mast and wedged in anything not quite right. I had lots of little wedges from the joints I had cut so that worked out well. I put a log on the fire so that the shop would be warm to set the epoxy and went back to the house with my drill hoping to get some of the goop off. I used vinegar, not great but it got some of it.
The next morning I took off the clamps and snipped the plastic ties. The epoxy has set and there is no obvious flaw. It seems quite straight too.
Using my smoothing plane I have started rounding the mast. I plan to gradually work around the the mast rounding it. There are a few small gaps where the epoxy did not squeeze out. I'll drip some epoxy and hope it fills any gap. I don't think there are many though.
This is what the mast looks after my first pass. I'm not being particularly careful at this point since I'm still roughing off the extra corner.After going around the mast once my plane is already starting to feel dull. Silica thickener is rough on a plane edge. I sharpened it and am ready to get back to rounding the mast.
I've been rounding the mast gradually using my smoothing plane. The shop is warm, I have nice music on and I'm just gradually rounding the mast. I'm up to my ankles in shavings. I'll collect these, they are good to start the fire.
By the end of the afternoon I have a roundish mast. I'll need to sand some more but it's not bad. I had some tear-out in a couple of spots while I was planing so the sanding should take care of that.
I've checked the diameter of the scamp mast and it's about 2mm over. I'm hoping that will come off when I sand.
It's a bit heavier than I had hoped. I'm not finished shaping it so it will lose some weight, and I can handle it.
I spent most of the day sanding the mast and getting the flats out. It is now as round as I can get it. I need to finalize the size. The mast turned out about 3 mm too thick in most parts.
I checked the weight and I'm just short of 17 pounds.
Today I will finalize the size. I checked and rechecked the diameter and took my newly sharpened plane and took off a very thin shaving all around. After a couple of hours of careful planing and sanding I'm very close to exact size and that's good enough for me. The mast now weight just under 15 pounds. It will put on a bit of weight with epoxy and varnish but I don't think I'll be much over 15 pounds completed. Compare that to my carbon fibre mast which is just under 4 pounds for a 15 foot mast.
The top of the mast is tapered slightly less than the plans call for. My wood is not high quality and I'm not happy thinning it too much. It's only a couple of mm larger than the plan. There is a core for about 8 inches. I like the end to be full to support any screw or attachment that goes on the top.
I used the drill press to make a half inch hole in the top of the mast. It's useful to have a spot to quickly tie things to.
I used files and sandpaper to smooth the hole opening so that it will not damage lines tied to it.
After trimming the bottom of the mast I sanded everything with a fine paper, vacuumed it really well and wiped any dust off. I paid particular attention to a couple of spots that did not have enough epoxy between staves.
I made up a thickened epoxy and filled any gap and a couple of tear out spots. I then coated the mast with a coat of un-thickened epoxy. I plan to put 2 or 3 light coats of epoxy.
Fast forward a couple of weeks. I've been making the centreboard but I've almost run out of epoxy so I have to wait till tomorrow. Noah has promised delivery. I had put a couple layers of epoxy on the mast but it took some time to harden because of the cold. It's nice and set and is not clogging sandpaper anymore.
It's difficult to make sanding look interesting. We all agree that it's important but not much happens. Maybe I'll make little piles of sawdust and measure how high they become.
Anyway, I'm getting ready to add a final coat of epoxy on the mast. This will be the third. I had a couple of drips and various imperfections. I put on some music and sanded away while Edit Piaf sang to me. I'm not doing a perfect sand job. This will happen after the last of the epoxy has set. I'll put a coat on tomorrow and then get the scamp mast ready for varnish. I've been warming the last of the Mas epoxy because it was starting to crystallize. All epoxy will crystallize in cold weather, I've had the same problem with East System epoxy. After warming up the epoxy is fine.
I've put 3 coats of epoxy on the mast and let it sit for a couple of months. I'm now back at it sanding the epoxy in order to start varnishing. Because epoxy is sensitive to UV it must be protected.
I'll be using Epiphane varnish but with a small amount of stain added to help blend in the various colours of the many strips.
I've moved on to making the spars.
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