Below deck bowsprit

I'm interested in putting a retractable bowsprit mounted below deck. The boat is under construction and I think now would be the time to consider doing this. I'm prepping the main hull for the inner layup so nothing on the inside. I tried searching on here and the web but didn't turn up much in the way of a diy install. I'd prefer fabricating the sprit and tube myself. Any guidance on how to approach this would be greatly appreciated.
Thanks.

 

Is this for the trimaran that you mention in this thread?
Built up bow question https://www.boatdesign.net/threads/built-up-bow-question.66339/

 

Bajansailor it's the same one. Once the layup is done I'm going to address the forestay chainplate.

 

Pic of the bow bulkhead and the bow design from the plan sheet. The anchor locker ends at station 1 which is 53" aft of bow at dwl. The few pictures I could find use that anchor locker bulkhead for the tube attachment. The bow bulkhead is about 4.5" outside width.

 

For a DIY below deck tube install you are probably looking at DIY engineering as well. While I know several manufactures make deck mounted extendable spirts, there needs to be something to take both the inboard thrust and downforce on the heel. That means foundations for the WT launch tube inside the hull. Unless you are planning an un-stayed carbon pole like modern rigs, you will need to go back to the old methods; which means guys and bob stay. While also a good book to have around, The Riggers Apprentice has good chapter on spars and loadings; as do Skene's and Chapelle's works. For a more modern (although for larger vessels) rule set there is the DNV rules.
https://rules.dnv.com/docs/pdf/DNV/ST/2016-12/DNVGL-ST-0412.pdf
https://rules.dnv.com/docs/pdf/DNV/ST/2021-11/DNV-ST-0411.pdf

 

Thanks for the reply. The diy examples I've found used the aft bulkhead of the anchor locker for the launch tube and I believe that would work here. I'm installing a g10 cross tube at the waterline so a bob stay could be used. My understanding was you'd need that for upwind. No whiskers so an unstayed sprit.
I've got the rigger's apprentice I'll look at the spar section
How do you determine the projected length? Too far can negatively affect the balance. Does some amount of lead need to be preserved?

 

Ok, so you are going to set an asymmetric or Code Zero? On a hoisted flexible roller? Is the hoist point above the fixed fore/jib stay?
FWIW, I'd make the hoist parallel to the forestay with a gap between so as to pass the flying sail without having to drop it to gybe. YMMV.

 

Asymmetric and code zero. The masthead has a bail above the forestay. I'll get a pic.

 

Pics of masthead. Thinking about it how do I determine if the bail is strong enough for a code 0?