[Rhodes22-list] Continuing compression post saga

[ROGER PIHLAJA]

Hi Matt,

Once the compression post is in place, the cabin roof flexing will stop.  FRP is very strong in compression.  But, it is not very strong in flexure.  The denting you are observing is a kind of flex failure called “oil canning”.  The name comes from the old time oil cans where you flexed the bottom to dispense oil.  The only concern I have is possible cracking when you force the dent out of the cabin roof.  All I can say is, install the compression post and keep an eye out for cracking around the mast tabernacle.  If you see cracking, fix it right away to prevent water intrusion and core rot.

Roger Pihlaja
S/V Dynamic Equilibrium
1978. Sanford, MI

Sent from my iPhone

> On Jun 29, 2024, at 5:45 PM, Matt Wilson <mwhornblower at gmail.com> wrote:
>
> Thanks Roger. You are an amazing resource!
>
> We could not find any evidence of rot with tapping on the fiberglass. It
> all had a very sharp pop sound.  No dull thuds and no apparent  squish or
> movement.
>
> If there is rot there, would the fiberglass start to crack since it is now
> getting compressed?
>
> Matt
>
>> On Sat, Jun 29, 2024 at 4:01 PM ROGER PIHLAJA <roger_pihlaja at msn.com> wrote:
>>
>> Hi Matt,
>>
>> The shoal draft keel has so called internal ballast.  In the picture, you
>> are looking at the top of the internal ballast.  The ballast consists of a
>> slurry of lead shot and Portland cement.  This slurry is poured into the
>> ballast cavity and allowed to cure.  Once cured, this composite ballast
>> material is very strong in compression.  I recommend you run your new
>> compression post down to the top of the ballast and thru bolt it to the
>> wooden stringer.  The thru bolt will prevent the bottom of the compression
>> post from moving around no matter how bad the sailing conditions get.  Make
>> the compression post long enough such that it must be forced into position,
>> not a slip fit.
>>
>> Do you have rot in the core of your cabin roof?  If yes; then, that must
>> be fixed first.  This fix depends upon the cabin roof being incompressible
>> and rot in the core will invalidate this assumption.
>>
>> Roger Pihlaja
>> S/V Dynamic Equilibrium
>> Sent from my iPhone
>>
>>>> On Jun 29, 2024, at 4:11 PM, Matt Wilson <mwhornblower at gmail.com> wrote:
>>>
>>> The boatworks guy didn’t really think there was much rot. It all sounds
>>> solid. FYI
>>>
>>>> On Sat, Jun 29, 2024 at 3:03 PM Matt Wilson <mwhornblower at gmail.com>
>> wrote:
>>>> Hi everyone,
>>>> Per my boatworks guy’s advice, I have started working on installing an
>>>> additional compression post as mentioned in some posts on this list.
>> After
>>>> cutting away the floor next to my original off set post, I have found
>> this
>>>> 2x(4?) on edge supporting the original post.  This 2x4 appears to be
>> half
>>>> submerged into some kind of cement like substance. Can I use this 2x4
>> and
>>>> or cement to support an additional post?
>>>> I hope the picture shows up
>>>> Thanks again,
>>>> Matt Wilson
>>>> Hornblower II
>>>> White Bear Lake, MN
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