Can/should you cut holes after PMF-ing?
Posted:
Thu Sep 16, 2021 1:30 pmby Fractangle
From what I've seen on here, the general process is to cut holes (doors, roof vent, etc) in the foam body before applying PMF. However, I'm trying to plan my build to be incremental - I want to be able to add a skylight or a 2nd door or whatnot later. Could I just cut a hole in already-PMFed foam, apply a strip of PMF around the cut edges, and not suffer the wrath of the waterproofing and/or delamination gods?
Re: Can/should you cut holes after PMF-ing?
Posted:
Thu Sep 16, 2021 2:32 pmby linuxmanxxx
Holes for windows and doors need framing for attachment and strength. Water inside is the enemy more than anything and the cloth coming loose and peeling is more a strength issue than leaking so it would be best to wrap over the holes but at least do strips.
You get a lot of strength in a completed closed structure but it's still foam and cloth.
Steve
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Re: Can/should you cut holes after PMF-ing?
Posted:
Thu Sep 16, 2021 5:23 pmby ghcoe
I have made cut outs on walls that were already PMF'd on one side and both sides. Here is a door I cut out recently.
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- 20210821_164728_HDR s.jpg (401.83 KiB) Viewed 608 times
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- 20210821_164734 s.jpg (339.83 KiB) Viewed 608 times
- #3
- 20210823_122607 s.jpg (354.78 KiB) Viewed 608 times
Just make sure you cut out the pattern correctly or you may have some issues.
Re: Can/should you cut holes after PMF-ing?
Posted:
Fri Sep 17, 2021 9:26 pmby Fractangle
Interesting - thank you for the pictures! Have you had any problems with the cut edges of the PMF wanting to shrink away from the cut edge of the foam?
Re: Can/should you cut holes after PMF-ing?
Posted:
Sat Sep 18, 2021 11:49 amby ghcoe
Fractangle wrote:Interesting - thank you for the pictures! Have you had any problems with the cut edges of the PMF wanting to shrink away from the cut edge of the foam?
No. Most of the shrinking is from the initial lay up.