Re: [AlbinVega] Compression Post. Anyone done it?

[reefmagnet]

A compression post is impractical as it would restrict access to the
forward section of the boat imho.

My solution was to replace the original uprights with new ones that
basically wedged between the compression beam and the floor. I made a
support out of heavy gauge stainless steel angle iron that mounts to the
inside of the compression beam and transfers any load to the uprights.
Technically these uprights don't transfer the load directly to the keel,
however it would have taken only minor modifications to do this. Basically
I could have cut out the inner liner with one of those fein style multi
tools to expose the keel / hull and then built up a pad for the wooden
uprights to compress against.

In the end I decided against mounting directly to a pad at the bottom of
the hull, because as I saw it the compression beam bends over time because
it is unsupported in the centre. Basically, the design
is fundamentally sound, excepting that the compression beam develops a
central downwards set over time from the load it supports. My solution
reinforces the wooden beam with the steel brace and transfers loads that
would otherwise deflect the compression beam to the wooden uprights which
in turn transfer the load to the bulkheads as per the original design. The
tight fit between the compression beam and inner floor pan is really only
there to prevent any minor downwards movement.

I've only had this arrangement for a year so far, but it seams to be
holding up. If I was to become concerned to the point of making the
ultimate support for the mast, I think I would fabricate a stainless steel
arch running along the back (forward facing side) of the compression post
that in turn joined to stainless supports running adjacent to the wooden
uprights down the backside (forward facing) sides of the bulkhead to pads
mounted directly to the hull.

Here's a link to my mod:

Photo by ReefMagnet

Photo by ReefMagnet[Non-text portions of this message have been removed]

 

[pjacobs55]

Jeff,
Interesting that you'd transfer the mast loads to the floor. I've heard of another Albin model (the Ballad, with a keel-stepped mast) that when the mast step rusted away the downward pressure from the mast actually started to split open the hull from the downward forces. Subsequent production used a stainless mast step ... end of problem.

From part of the "Vega Owner's Repair Manual" by Sidney Rosen

http://www3.telus.net/sailing/Mast_Beam.pdf

that states, in part:
"The principal idea is that all the vertical load shall be transferred to the hull via the bulkheads on either side. The function of the two "posts", one on either side of the opening between the cabin and the fo'c'sle, is only to prevent the bulkheads from buckling (i.e. bending forward or aft under the pressing load). These posts must not transfer any load directly to the hull, since the hull is not fit to take such a concentrated load. Consequently, one should make certain that the posts do not touch the hull by cutting away some mm at the bottom if necessary."

Peter
www.sintacha.com

 

[reefmagnet]

Peter, agreed. The standard design uses the bulkheads to transfer loads to
the hull. The upright posts are both responsible for transferring the bulk
of the load on the compression beam to the bulkhead and also ensure the
bulkheads don't buckle under loading. I do however think the hull could be
made to support a compression post however on the proviso that suitable
pads to distribute the load were constructed. My previous boat used a
combination of compression post and bulkhead to transfer the mast
compression so I would have no doubts something similar would work on a
Vega. Having said that, I don't see the need for such an arrangement -
hence why I didn't use it - as I think the main cause of compression beam
problems on the Vega is simply the result of sag induced on the compression
beam over time (aka like a steam bending effect) rather than the exceeding
of some critical load point. Fix the sagging issue and the standard setup
works.

 

[lewills30]

Peter,
Looks pretty darn good. Someone pulled my engine and plugged the shaft. I saw you sawed down this area and saw a brass sleeve? Is there a water tight fitting which glasses in to the area you sanded? The prop shaft is installed into the brass fitting...yes? Do you have any pictures of this being completed?
Thanks,
Larry


________________________________
From: Peter peter@...
To: AlbinVega@yahoogroups.com
Sent: Tuesday, April 9, 2013 9:27 AM
Subject: [AlbinVega] Re: Compression Post. Anyone done it?





Jeff,
Interesting that you'd transfer the mast loads to the floor. I've heard of another Albin model (the Ballad, with a keel-stepped mast) that when the mast step rusted away the downward pressure from the mast actually started to split open the hull from the downward forces. Subsequent production used a stainless mast step ... end of problem.

From part of the "Vega Owner's Repair Manual" by Sidney Rosen

http://www3.telus.net/sailing/Mast_Beam.pdf

that states, in part:
"The principal idea is that all the vertical load shall be transferred to the hull via the bulkheads on either side. The function of the two "posts", one on either side of the opening between the cabin and the fo'c'sle, is only to prevent the bulkheads from buckling (i.e. bending forward or aft under the pressing load). These posts must not transfer any load directly to the hull, since the hull is not fit to take such a concentrated load. Consequently, one should make certain that the posts do not touch the hull by cutting away some mm at the bottom if necessary."

Peter
www.sintacha.com

 

[lewills30]

In my line of work, we transfer heavy loads over openings of all sizes. If I was to or asked to do a load transfer on this opening, I would box the entire opening. A SS plate on the floor, tied to SS box tube or c-channels at the compression beams , tied to a radiused SS c-channel at the head . All C-channel would cup, or fit over the existing system...leaving the builders design in place. Deflextion would be reduced or compression would be changed. I do wonder if the builder in his design used the entire structure of the boat to carry the designed loads...we use a system for this same movement called a moment connection. Which isolates the loads to a given area, somewhat like the builders design of transfering loads to numerous points. Just a thought.