Sunday, 2 February 2020

Bowsprit

I'm trying to figure out how to hold my bowsprit on. The standard bowsprit for navigator is a rectangular block of wood, which is bolted to the kingplank with 9mm (3/8") bolts.

I've made a 60mm dia round bowsprit (more pirate-like), which doesn't really lend itself to just bolting down. Here it is being held on Elena in the approximately correct position by my extremely patient husband:

The observant will also notice I've modified my winch mount a little to get it to work better. I flipped it over and cut down the pieces for the bow roller, making it a little more compact. Then I mounted it a little further up the post. Now I don't have to remove the winch and haul Elena forward on the trailer to fit her in the garage. The last little bit is to undo the front bolt of the hitch and rotate that out of the way, giving me an extra few cm. I've been looking online and have found drawbar pivots, so I could even conceivably cut the drawbar just forward of the winch post and extend it half a meter or more, then simply spin the front section of the drawbar out of the way when needed. Of course then the jockey wheel would need to go behind the winch post, but that's doable.

Back to the topic at hand though, I thought a heel socket and gammon iron were the way to go, something like:

However getting these in just the right size is a bit of an ask. These sort of things are really made for much larger boats. I could fab something from lots of bent and welded plate, but it just wouldn't look that pretty. Truth be told I wasn't entirely hapy with the way my fabricated mainsheet eye turned out.

So I thought perhaps combining some bronze straps over Jarrah bases was perhaps the right go. I could even angle things so the screws through the deck and into the king plank are angled, making them really hard to pull out...

Building that starts with cutting out the strap. I bent it in the vice by simply ruling nine lines across the piece, and bending each ten degrees.

I cut out the heel iron base from jarrah, and cut a flat spot into the deck to mount it. The deck looks reasonably flat, but there's actually quite a pronounced curve:

When mounting, I added a pair of 10g 1.5" screws under the bowsprit. This means the iron is held down wy a total of eight 10g screws into the king plank.

I further reduced the diameter of the heel end of the bowsprit to provide a more positive engagement to the heel iron. In use I expect the forces to be back and down on the bowsprit, due to the tension in the bobstay. Wind loading on the jib will be back and up. So there will be significant backward forces at the heel, meaning the bowsprit could slip back through the heel iron. The step in the sprit ensures this won't happen. The photo shows the sprit partially inserted, highlighting the step.

Finally a picture to show the whole thing.

I had entertained notions of fitting the bowsprit in the parking lot prior to launch, but really it's just not going to work like that. The front of the sprit comes well forward of the trailer, plus the winch gets in the way of the bobstay. So I think really the only way to go will be to insert the bowsprit and the bobstay once Elena is in the water.

Now onto the gammon iron, which can be a little simpler as it really only needs to ensure the sprit can't move from side to side, and doesn't have any upwards forces to contend with.

By leaving the top of the gammon iron open, installing the bowsprit should be fairly easy. Just drop it in the gammon iron and seat the heel into the heel iron, then tension the bobstay.

1 comment:

Chespearl said...

Great to see you working and posting on Elena again. That's a very elegant solution for mounting your bowsprit.
Brian