PocketShip.net

The pocketship prototype and the manual shows a bobstay without a turnbuckle. I'm wondering how proper bobstay tension is achieved with that arrangement especially since the bow eye's exact location is a little "up for grabs" too. Any thoughts?

The Bowsprit flexes slightly when the mast is raised so the bobstay tension is actually achieved with the jib halyard, or in my case the spinnaker halyard has been repurposed for raising the mast. Just make sure the bobstay isn't loose to the point of sagging when you make it up. Watch out for the back stays being to loose too since the mast makes a 16" lever that's really good at breaking things if the back stays don't stop it where they should.

Chris

But, without a turnbuckle how does one actually adjust the bobstay tension to get it to what it should be when tensioning the jib halyard? Am I over thinking it?

Yes, the harder you pull on the halyard the more tension you're putting into the bobstay. The purpose of the bobstay is to prevent the bow sprit from flexing upward from the force of halyard. The jib halyard is actually doing the job of the fore stay in most boats. With any tension on the halyards you won't be able to attach the bobstay since the bow sprit will flex upwards and the bobstay will be to short. Because of the way my boat is rigged with the spinnaker halyard permanently used to raise the mast from the cockpit the bobstay won't reach it's pad eye if I don't uncleat the halyard first. Even with the mast down. Ounce all the tension is off the end of the bow sprit the bob stay clips right on and tightens up when the mast starts getting hoisted up.

Take care,

Chris

As a follow up to this.

I purchased the sailing hardware package which included a pre-made bob stay. I had already installed the bow eye in a location that I derived from the plans (after a lot of calculations a measuring). When I went to attach the bob stay it was about 1" too short. I added a 1 1/2" shackle I had laying around and it resulted in a slighly slack bob stay. I could deflect the bob stay about an inch before I could feel tension. After I raised the mast and tightened the jib halyard I rechecked the bob stay and it was drum tight. The slight flex of the bow sprit easily took up the tension of the bob stay. Then I went sailing!

Bill

Mine that was supplied in the hardware package was way too short also. It looked like to me the cable was measured to the correct length before the eyes were made. Then after the ends were folded over the result was too short. Thinking back I believe the length should have been 4 feet.

This all kind of gets to what I was asking in the OP. It seems there are three variables that must align for proper set up and that getting them all right on the first try is a bit of a trick.
The variables are: Bow eye location, bobstay length, and bowsprit "steeve" (angle). A change in any of these affects the final fit. A turnbuckle would allow a little "wiggle room." On the other hand I like the tidiness of the arrangement without a turnbuckle.

It seems odd to me that the bobstay in the sailing hardware package could be exactly the right length to reach from bowsprit to the bow eye. There is no way that I can see to get the bow eye in exactly the right position. Nothing about it in the manual (or did I miss something?). On Sheet 4 of the plans I measured a straight line from the spot where the breasthook meets the topside panels to the top bolt on the bow eye, inside the front compartment. I had to draw extensions from those points to make it work. That's the measurement I used to place the top hole for the bow eye, and it looks about the same distance from the waterline on the plans.

I say "about;" there's all sorts of room for error here, e.g., the panels don't curve exactly the same on every boat, I may not have drilled my hole exactly perpendicular to the stem, plan sheets expand and contract, etc., etc. And on top of all that I had to do the measuring while lying on the BH2 opening and reaching through a small hole in BH1! That I got it as close as I did is a minor miracle. I'm not to the point of installing the bobstay, but I'll be very surprised if it fits out of the box.

I measured three times and cut once, and my bobstay was STILL the wrong length. Not sure how that happened. I bought a longer shackle too. The forestay/jib halyard pulls the whole system into tension like everybody said.

How much slack is acceptable in the bobstay when it's at rest (no jib halyard tension)? Mine has about 1/4" of play between the bow eye and the bobstay shackle with no halyard tension. Is that okay?

Just for comparison, in John's video of getting the pocketship ready to sail it looks like he has quite a bit of slack in his bobstay before tensioning up the jib halyard.