SHRINKAGE!!!

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Falling Jihad

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is it normal for my pep piece to shrink, cus it kind of did last night? i coated my pep'd chest piece last night with resin on half of the outside and it shrank when i checked it this afternoon. there is like a 1 inch difference in the bottom opening.

is the shrinkage b/c of how cold it is outside (20 degrees)?

i hope i dont have to start over.
 
It's kind of a given that the weather would be a contributing factor, however I think the major issue is that you're going about the whole resining process all wrong.

Granted, I've never resined/fiberglassed a Pepakura helmet myself (I'm constructing mine out of sheet styrene), but if I recall correctly you're supposed to resin the inside first, then the outside.

Please, anyone correct me if I've got that backwards. I wouldn't want to be giving inaccurate information. That wouldn't help anyone, LOL.

Also, keeping the general laws of physics in mind regarding heat expansion or vice versa, obviously if something gets cold it will contract. The extent to which it contracts is dependent on the difference in temperature. That would definately account for the issue you're now faced with.

My best advice for that would be to do your resining/fiberglassing work in the garage, as although the ambient temperature will still be somewhat less having it in an enclosed, yet large and still ventilated (due to the slight gaps along the garage door) area will probably reduce the risk of it contracting any further.

The temperature differential won't be quite so extreme in that case, and so would certainly help matters.

Considering the degree to which your helmet has already shrunk, though, it may be best to simply start over... :whistle:
 
i was working in a garage i opened the door so i wouldnt sufficate but i closed when i was done. do u think it would go bak to regular size if i brought it inside for a while to warm up
 
Hmm... I see.

It would stand to reason that by opening the garage door that brought the ambient temperature waaay down, which is why your helmet ended up the way it is.

Do you have a proper face mask for filtering out the fumes? If so, and you can keep the garage door closed, that may help. I would strongly suggest using a mask either way, as inhaling too much of those resin fumes can be harmful.

Maybe you could use a portable heater to heat the area around the helmet?

I wouldn't put it up too high, as then the resin would take forever to harden in such a humid environment, but that way, even if you have to open up the garage door for ventilation, when you close things up again and let it sit that would help compensate for the temperature differential.

Another thing I should also ask is, has the resin completely hardened at this point?

If not, it may be possible to reshape it by hand (I'd suggest wearing gloves if you do that), otherwise I don't believe simply bringing it inside to "warm it up" will do the trick.

Like I said before, though, I'm no expert with resining/fiberglassing as I've never done it. All I know about it is what I've read here on the forums.

You're welcome to try, though. Who knows, it could work...
 
SPARTAN II said:
It's kind of a given that the weather would be a contributing factor, however I think the major issue is that you're going about the whole resining process all wrong.

Granted, I've never resined/fiberglassed a Pepakura helmet myself (I'm constructing mine out of sheet styrene), but if I recall correctly you're supposed to resin the inside first, then the outside.

Please, anyone correct me if I've got that backwards. I wouldn't want to be giving inaccurate information. That wouldn't help anyone, LOL.

Also, keeping the general laws of physics in mind regarding heat expansion or vice versa, obviously if something gets cold it will contract. The extent to which it contracts is dependent on the difference in temperature. That would definately account for the issue you're now faced with.

My best advice for that would be to do your resining/fiberglassing work in the garage, as although the ambient temperature will still be somewhat less having it in an enclosed, yet large and still ventilated (due to the slight gaps along the garage door) area will probably reduce the risk of it contracting any further.

The temperature differential won't be quite so extreme in that case, and so would certainly help matters.

Considering the degree to which your helmet has already shrunk, though, it may be best to simply start over... :whistle:
Click to expand...
From the tuts I've read, outside first is fine. Perhaps it was the temp that changed the helmet size. Remember though, you can trim the neck portion of the helmet to fit you. In fact in almost all cases you need to. Its not noticeable on the final product from what I gather either.
 
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Ah, okay. Thanks for the correction there, Luke. Like I've said at least a couple times here, I'm not entirely "in the know" when it comes to resining/fiberglassing Pep helmets, LOL.

I went with an alternative construction method for mine, and so haven't brushed up on all those tutorials recently.

He's right about the trimming of the neck portion btw, FJ. If that's really the only part of it that's been shrunk, once you cut it down to fit your head it probably won't even be noticeable... ;)
 
Resin shouldnt shrink, maybe it's just your imagination.

But, other than that, you shouldnt resin at such cold temperatures especially since it's winter time.

Hot sunny days = good and fast cure time

Cold days = slow results.
 
did i say it was a helmet... im sorry i meant it was my chest piece that shrank. i do wear a niosh approved ventilator but my family has a refrigerator out there that gets alot of use so i dont want them breathing any concentrated fumes so i put the garage up just for their safety. i was way off about the size change it went from 44 in. to 39 in. im hoping that it was just the waist part that shrank b/c i was planing on cutting away the pieces under the arms.

But thanks spartan II for the help ill try and get a small heater for it next time.

Edit: Aob im kind of on a dead line and i need to have the whole suit mostly done by the summer for a movie im making so im stuck with working in these temps.
 
No problem, FJ. I'm glad I could be of some help, albeit in a limited capacity. Best of luck with your project, and here's to hoping you don't have to entirely redo what you're already put together... :cool:
 
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