Multihull compression post base

This might be a basic question, but for the life of me I cannot find any information regarding the connection between the bridgedeck and the compression post of the mast. I have seen that in many production cats the compression post is not tied to any bulkheads, but are rather just going straight through the saloon. How to they dispurse the load under the floor?

Cheers.

 

From your description I assume you are referring to a trimaran?

 

No, catamarans

 

What catamaran are we talking about? Look on Multihull structure thoughts thread C1o6 pdf's and spindrift 37 pdf's for some hints. But there are many techniques for dispersing loads. Some of the latest french cruising cats are using "furniture" and longitudinal underwing stringers to spread the load.

 

Both Sunreef 50 and Lagoon 50 have compression posts running through the center of the saloon, apparently pushing the force right into the bridge deck.

 

Builder45 Look up a cat from Mike Waller TC670. It will give an idea of how large cat designers handle the loads. There is a russian web site about the build of a TC 670 that shows many detailed build photo's (2 photo's attached). The mast compression appears to go thru the middle of the cabin at the front of the central daggerboard case. But the front of the Double bunk (on left side photo) attached to the daggerboard case has a small cross beam attached and under the underwing has several very deep fore and aft underwing stringers that attach to the fore and aft cross beam structures. The Richard Woods design site is down at this moment but in the plan update section is a plan update for a Flicka 35 cat cross beam shows the beam under the front of a seat. The beam goes between the inner gunnels. Big french cat designers know how to discretely disperse the loads along and across the wing deck structure. It doesn't need to be very deep just very well designed.

 

oldmulti, thank you so much, explains a lot!

 

Hi Builder,
I was going to see some greater loads of the mast to my bridgedeck or cabintop,..with my aft-mast design. In most cases I chose to make sure I got one of the major bulkheads involved. My mast base was going to involve a junction of the a vertical face of a major bulkhead with both the horizontal faces of both the bridgedeck and the cabin top.

In this discussion, Aftmast rigs??? https://www.boatdesign.net/threads/aftmast-rigs.623/page-23#post-414479
I wrote, "My masthead backstay then passes over an aft jumper strut that redirects its force down to the base structure supporting the mast.

[IMPORTANT NOTE] This backstay that originates at the masthead DOES NOT reattach to the base of the mast itself, but rather to a structure of the vessel, …and preferably to the structure that accepts the compression loads of the mast to the vessel.]


There was another instances where I was proposing to place a mastaft rig onto a kit boat design called the Solitary 40. This is the 'mast base' I was proposing for that conversion,..

 

Here is that Solitary Cat with original rig, then mastaft one...