I did a lot of research online before I tackled this project. There is a wealth of information on building octagonal spars and other blogs and videos on using a birds-mouth cutter. The only thing I did not find was a spar that was tapered on both ends. I found a few projects where the pole was tapered in one direction so there was no reason to believe that it could not be done to both ends.
I chose Port Orford Cedar because it was cited on a few blogs as an excellent material for Spars. Unfortunately what I was able to find was fairly new growth so I was careful in my design and construction of the project to ensure maximum strength.
In the photo you can see the initial milling of the Port Orford Cedar into individual staves. The size is rough and the length on my starting material was 14ft.
I chose Port Orford Cedar because it was cited on a few blogs as an excellent material for Spars. Unfortunately what I was able to find was fairly new growth so I was careful in my design and construction of the project to ensure maximum strength.
In the photo you can see the initial milling of the Port Orford Cedar into individual staves. The size is rough and the length on my starting material was 14ft.
I needed to build a spar roughly 22ft long so I had to make many long scarf joints to get the length I was looking for. The Photo on the right shows my initial rough Cutting of the 12" long Scarf joints. I laid out the cut and then quickly sliced through the material with the band saw. Later in the process I trimmed the scarf joint clean and crisp for maximum face grain glue up.
Here you can see the rough Scarf joint cut on all the boards. This step did not take very long. It was important to lay out all the cuts on the whole spar before hand to make sure all the joints are well staggered.
On the right you can see the jig I constructed to perform the finish cut of the scarf joint using a router for a perfectly smooth face for gluing. The initial set up was time consuming but I could perform the cleaning of each joint in about 5 to 10 min. The only issue I had here was when the end of the board would peal up from the bottom as I milled down to the last 32nd of an inch. Thankfully I milled all my material an 1/8th to 3/16ths oversized to account for these kinds of issues.
Here you can see an example of a clean and crisp scarf Joint which is 12" long. This was in preparation for the glue up.
I used west systems epoxy to glue all the scarf joints. This allowed for a long open time and resulted in a massively strong scarf joint. On the right you can see the gluing and clamping of 5 out of 10 scarf joints.
Once the scarf joints were glued and cured, I proceeded to mill them down to final thickness and width. This posed a challenge because working with 22' long staves was a first for me. They were so long I had to use the "Tailgate Infeed" from my truck into the planer and out the other end way into the shop. It worked though, and I had nice crisp, clean joints after the milling removed all of the imperfections from my jig setup.
The next step was to taper both sides of each end of each stave. I needed to remove only 7/16th of an inch on either side. This definitely required a jig. Here you can see the setup, tapering with a skill saw. This proved to be quite accurate compared to several other techniques I was considering. I had to taper each piece 4 times. With 8 staves that ended up being 32 tapers. Ugh. I had some problems at the beginning due to the fact that my skill saw was out of square and cutting an angled taper. PROBLEM! I fixed it eventually but this resulted in issues that showed up in the final glue up preparation.
I was concerned with the transition from straight octagon to tapered octagon. So after the tapering process I clamped all the staves together and eased the transition from straight to tapered using my hand plane. I took off a lot of shavings but in the end I think this step was superfluous because the taper was so gradual.
Cutting the birds mouth on the shaper with a 45 degree bit was more of a challenge due to the fact that the tapered ends were so small. They were rolling into the shaper bit instead of staying flat on the table. I solved this issue by screwing blocks of cedar to the sides of the staves and then running them through the shaper feeder this way. This worked but resulted in screw holes that showed up when I started to round the tapered ends of the spar. Ugh. They mostly disappeared and were not that structurally important as they were filled with epoxy in the glue up process. They just looked unsightly.
I was initially going to build a solid core for the straight portion of the spar but the amount of material needed would have added a great deal to the weight of the spar as a whole. So instead I decided to mill the parts for an interior octagon to fill the central portion of the spar and add strength. On the left you can see the Octagon Core. This was extremely helpful in that it gave me a practice round in preparation for the major glue up of the entire spar. It also showed me that there were some cumulative errors that made the parts not fit perfectly together. As if some of the cuts were not correct, resulting in a slight gap. That was OK due to the thick and gloppy nature of the epoxy. Still it encouraged me to buy a filler for the epoxy that effectively turned it into peanut butter. Perfect!
The Birds Mouth seen from the end, lovely. If you can't see the imperfection I will point it out. The top right joint is slightly open but all the other joints are nice and tight. I think I will have to find out why that occurred the next time I use this bit.
The picture on the left shows the preparation for the glue-up. It was well worth going through the process. It showed that the cumulative error was great enough that I had to do something about it. I believe that part of the cause was the slight angle cut into the tapers on the first few rounds of cutting the taper with my skill saw. I removed the staves and hand planed all the stave sides square. Then I reassembled the whole spar a second time and found significant improvement. But it still wasn't perfect. Why, I do not know for sure, but it was close enough to call it good. A 1/32nd gap on two joints was not going to ruin the spar, especially with the type of epoxy I was using.
I wanted to make sure that the spar was glued up perfectly straight so I set up my laser to make sure. Again this was in preparation for the glue up.
My friend Carlos came over to help with the glue up and it went very smoothly. I did have to clamp with hand clamps and then tighten the hose clamps in a slow methodical process all the way down the spar. But I had time and the end result was a great glue up. In the picture you can see that it was "Totally Clamped Dude!"
The client, who is pictured to the right decided that he wanted the ends rounded but the central portion left octagonal. This made it easier but the rounding of the ends was still pretty challenging. I did not take it very seriously and the result was something that looked nice and round but in reality was not. I made a small hand tool to show me where to cut another facet in the octagon. I made the tool in a sloppy fashion and then used it in a sloppy fashion. Here I am admitting to all my mistakes. That is OK because really, I kick butt! I used my electric hand planer and cut down the high point and effectively made 16 facets on the rounded ends. Then I cut the next high point and made 32 facets on each end. At this point it was time to sand so I purchased several sanding belts and did what the client is doing here for about 3 hours. Talk about a core workout. It kicked MY butt. So I asked the client if he wanted to get a good core workout. He was excited about it so he went to work for about an hour, sanding the 32 facets round. It looked great when we were done but I knew that it was not perfectly round. I will have to think of a more accurate solution next time.
Here you can see one end tapered and rounded. Looks nice doesn't it?
The mahogany plug at the end of the spar was a royal pain in the arse to make. I spent almost 4 hours trying to figure it out. I eventually did but I had to repeat the process 5 times to get it right. I had to mill a perfect tapering octagon that stuck out of the end just an inch or two. Here you can see the end of pole with mahogany plug. It looks great. It better!
The client was happy with the final delivery of the Spar. I think that I made exactly what he had in mind. It cost a little more than we initially estimated but the result speaks for itself. A 22ft long tapered octagonal spar!
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