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Old 10-17-2011, 09:32 AM   #1
Rivet Master
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1973 27' Overlander
1972 29' Ambassador
St. Paul , Minnesota
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ProDex between new floor and frame? Comments?

I have the opportunity to lay in prodex to completely laminate the underside of the flooring before bolting it to the steel frame, kind of like how the factory did the original fiberglass floor insulation.

I could increase the number of fasteners to better clamp things down - doing this would insert about a .15-18" gasket to insulate and quiet floor squeaks, creaks, pops while walking inside the trailer.

If I focus on any one spot it seems to not be tough enough, that it may crush at the fasteners, but when spread out over the eight-foot spar/outrigger lengths it might not be too giving.

About the worst I see is long-term the floor could have some 'wave' to it inbetween floor bolts, tiny but noticeable - and the outer edges would have to have multiple glue stripes of vulkem to keep water from penetrating.

Anyhow - just tossing the question out for comment!


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Old 10-17-2011, 11:13 AM   #2
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I have heard of some newer trailers that had issues with water collecting and sitting between the underside of the floor and the insulation. Completely hidden from sight, you would never know it was wet until you put your foot through the rotten floor. If you do use this it might be a good idea to cut it into strips instead of using a full size piece, so there are lots of places for moisture to escape.

Rich the Viking

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Old 10-18-2011, 03:05 PM   #3
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Comments and insights requested!

Understood about water being verrrry sneaky, thanks Viking!

From the prodex site:

"High compression recuperation. It takes back 97% of its form after applying a load of 11 PSI (It does not collapse)"
"With a pressure of 6 PSI Prodex compresses just 6%. When the load is relieved it takes back its initial shape."
I find the #12-24 screws as exerting 1140~ pounds axial force at a torque of 48 in/lbs on the screws shaft itself, an area of .036" - this translates to roughly 13 psi clamp force on the surrounding circular inch (3.14/.036=87; 1140/87=13) which is right in the ballpark for prodex; the narrowest metal bolted face is 1-1/4" and the widest is 2"...

I am guesstimating the foam will compress 75-80% from the original 0.197" (5mm))... So I see the need for a wafer stand-off to get a true structural clamp w/o the prodex inbetween in certain places - say the middle of each outrigger and one at each end of the spar sections, each wafer having a height of 0.15"; and of course the shell-to-floor clamps will be w/o prodex.

The entire length of the main ladder frame runners has zero fasteners, they are all on the lateral frame parts - here is where the prodex sandwich will really quiet the creaky floor by allowing the length-wise sway to be hushed up...

The 48 in/lbs as dry torque comes from Pratt & Whitney Torque Chart.
The use of maximum wet torque number in dry torque application intentional.

Axial force comes from
Bolt Torque Calculator - Engineers Edge

I just got off the phone with Insulation4Less after being hung up on when... 1) I had to be ask three times for them to speak loud enough to be heard, and 2) when they interrupted my project description by asking repeatedly for me to define 'laminate' from my just-spoken phrase 'I want to press-laminate prodex between my trailer floor and the steel frame'... and then the four other hang-ups when I requested to speak to Jonathan's supervisor or offered to help work through angst the supposed helpline tech was fabulously impacted with.

A quick reverse-directory address look-up gave me another land line to their shop and I learned it is nothing more than a small 'drop' shipping operation next door to a UPS retail store, that 'Jonathan' was having another bad day, and their tech support means reading 'not recommended' and hanging up if the discussed use veers from the boilerplate already detailed on their website. Anyhow - its always shameful when the Bosses' (insert relation) throws tantrums.

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Old 10-18-2011, 05:27 PM   #4
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Put it on top of the floor, and lay your flooring on top, works great.

Let the air keep it dry below the floor/frame
'77 Sovereign Intl 31' CB
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