Bury nuts in fiberglass

I'm looking for product names to look for.
I'm working on an instrument for a customer, and he's having me do the
whole-system design. This means I'm out of my comfort zone and playing
with mechanical issues.
It needs a big outer case (well, four feet long, by nine inches by two).
I'm thinking of doing the outer case from fiberglass for a number of
reasons, not least of which because I'm familiar with its
characteristics, and the instrument is going to be used on or near bodies
of water including salt water.
I'll need to attach things to this outer case. My current thinking is to
used buried studs and/or nuts, and use thumb-nuts and thumb-screws to
actually attach the bits. I'm assuming I want to use brass or stainless
hardware for corrosion resistance, and I probably want to take some pains
to match alloys.
McMaster is failing me for appropriate hardware. I'm finding thumbscrews
and thumb-nuts, but I'm not coming up with good candidates for nuts that
I can bury in the fiberglass. I'm assuming that the case will be a two-
part assembly that's glued together; nuts that can be buried in one side
and then captured in the gluing-up process seem to be the best notion to
me, but if someone with actual experience has alternate suggestions, I'll
listen (I may not _take_ your suggestion, but I'll certainly _listen_ and
_think_
about it).
So -- suggestions? I'm probably wanting some 4-40 or 6-32-ish sized
ones, and some 10-24 (or 1/4-20). The bigger ones may work better as
studs, with thumb nuts. I'm pretty sure that I want nuts for the little
ones, unless that presents severe difficulties.
Reply to
Tim Wescott
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5052 aluminum is fair for a marine environment, and it welds easily. It doesn't machine as well, but it is possible to machine it too. That might be an alternative for your shell. It can be drilled and tapped, but again it can be a little finicky. 6-32 into 5052 would scare me, but I have done it. 10-24 and 1/4-20 should be fine. I have heard 4-40 is easier than 6-32, but I have not done it.
I'm not sure about embedded nuts in glass, but stainless t-nuts are available. Usually they are used in wood by driving them into the opposite side as you are bolting from. If you do an encapsulated wood and fiberglass design I am sure It would work, but I am not sure how long it would hold up in your environment. In boat building they usually bolt through rather than into glass or glass composite. The holes are sealed during the bolt through assembly process. Occasionally screws are shot into glass, but they are very low load applications, and the holes are sealed from one or both sides as applicable.
Is your fiberglass plan for a sprayed or laid up shell in a mold, or do you plan to use some form of a core? Or both? Fiberglass boats for example use all of the above. A shell is sprayed into a mold, a core is added for strength, and additional glass is sprayed and/or hand laid. I imagine if your layup is heavy enough to handle any loads you probably can embed t-nuts with a stuf already in them to provide a hole for your machine screw later, (if you can find the right sizes) but it might be a tricky process. I am sure a mold release would be needed on the stud.

Reply to
Bob La Londe
Regarding your subject line, this is not to be recommended. They can get awfully swarthy that way, and they are impossible to scratch.
A simple supporter and cup will do.
Reply to
Ed Huntress
Depending on how thick this case needs to be you might want to think of a composite construction. Use something like thin plywood for a core and install either stainless nut-serts or T nuts into that panel, then use marine grade epoxy and glass mat to make it waterproof. The wood gives you some structural strength and will hold the inserts in position. Don't forget to insert the proper screws coated with release agent so that the threads are clean. Another option would be to install the insert into a piece of expanded stainless sheet and embed that. That would give you more surface area. Probably not needed with the little fasteners but might be for the larger ones.
And lastly, If this will be a continuing item, you could take a piece of stainless and make a girdle that has the holes drilled/tapped in the correct places and glass that in.
Now that you've asked this bunch, Try dropping a note to Randy at gofastfiberglass AT comcast DOT net He builds 'glass scoops, body parts and more for some of the fastest vehicles out there. He can probably give you a better idea.
Reply to
Steve W.
Well, if you can spread the stress to an internal metal plate (glass over it) or sandwich the fiberglass between two plates, you can then drill and mount rivnuts in said metal plate(s). There are also adhesive attach points (you see 'em for locking down plastic box computers) that could work without making holes in the fiberglass.
Reply to
whit3rd
Spae-Naur in Kitchener Ontario carries all kinds of press in and mold-in thread inserts. One manufacturer is AVK Industrial Products. Dodge makes some good ones too. Then there is Barb-Sert, and E-Z Lok 240 or 260 series
Call Spae Naur at 1-800-265-8772 and ask to talk to one of their application people. They are a MAJOR industrial fastener distributor in Canada - a long way from the auto uphostery shop (Spaetzel and Naurman) they started out as in the twenties or so - who found getting the little hardware required for the job was difficult in Canada, and started stocking and distributing things like trim clips, window track seals, fender welting - and on and on to what they are today.
(Still run by the Spaetzel family today)
Reply to
clare
A comment. If you make "fiberglass" enclosures for outdoor use try to have them made with "jell coat" which is the outer colored layer of a fiberglass lay up. You can paint them with two part paint but the jell coat provides better UV protection.
Buried studs would likely be a stronger solution. Depending your design you could make then with a length of stainless all-thread. Cut to length, a right angle bend then bond them into the container. A 6-32 nut would a far less secure fixture in the fiberglass.
Depending on the use, you might be able to simply drill and tap the fiberglass and screw a coarse thread screw directly into the fiberglass. Or even a sheet metal screw. If, for example, it was a screw to hold a component in and would never be removed and replaced.
You might have a look at Click Bond as they seem to specialize in what you want.
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Reply to
John B.
I think the type of thing you're looking for is shown here
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Reply to
David Billington
Exactly. More generally, the OP should ask his question in a fiberglass boat building forum, as there are no doubt many practical issues to be dealt with to get a reliable mechanical assembly.
Joe Gwinn
Reply to
Joe Gwinn
Joe Gwinn wrote in news:060620151010414419% snipped-for-privacy@comcast.net:
Boats frequently simply have nuts glassed in, or the fitting is bolted up then the nut is glassed over. For greater reliabilty, wrap the nut or bolt head in several turns of properly wetted out glassfibre tape and wait till its reached a 'green' cure before glassing it into place. If possible use epoxy resin. If glassing in a nut, *ALWAYS* use a brand new bolt with an undamaged thread to locate it, with a very thin coat of a suitable mold release (preferably one that will liquify if the bolt head is heated e.g. parafin wax) on the thread.
The epoxy manufacturer "West Systems" has several articles and how to guides for "hardware bonding".
With the appropriate reinforcement moulded in place, simply helicoiling blind holes may be satisfactory.
Remember, stainless on stainless galls very easily so for frequently removed fasteners, use a bronze nut on a stainless bolt or stud, with a corrosion control grease.
Reply to
Ian Malcolm
Thanks. This is an excellent start, but the UK part is a bit of a barrier for this Oregon boy.
Reply to
Tim Wescott
Your responses made it clear that I left out an important part: the case will be made with two or three fiberglass bits, glued together and finished. I'm envisioning the fasteners going into the top piece, then getting captured by the bottom piece, or perhaps some inner third piece.
Reply to
Tim Wescott
Yes, of course :-)
(but, how do you pronounce "jell" as in "jelly" and "gel" as in "gel coat" ? :-)
Reply to
John B.
It was just a pointer to the sort of things that are available. I've dealt with that company and knew they sold them, I'm sure when you look you can find lots of similar suppliers in the US.
Reply to
David Billington
The usual scheme with molded fiberglass is to (hopefully) build a mold that does everything in one fell swoop. Failing that, two parts that fit together as they come out of the mold. Cutting and trimming little bitty pieces and gluing them in and maybe coming back the next day to laminate a little cloth over them to make them stronger is a time consuming process and results in "things" that aren't all the same and bits that fit "Thing #1" probably won't fit in "Thing #2".
Reply to
John B.
Sounds messy and nasty. How many are you making? Vacuum formed PVC and option?
Could the instrument be made to fit inside existing PVC extrusion or pipe profiles?
Reply to
just_me
Well, Gel is actually a shortened version of the original. The gelatinous coat, is the original term. Called that because it is a thickened coating that you apply to the mold prior to starting the actual lay-up process. It's job is to smooth the finish, provide color and UV protection and to keep fibers from surfacing.
another oddball trivia item from the past....
Reply to
Steve W.
Thank you very much for your expertise. My family has been making car parts out of fiberglass since 1957, so we may actually have some clue of how the stuff works.
Reply to
Tim Wescott
And had you told us that at the beginning I wouldn't have offered the suggestion :-)
Reply to
John B.
A bit snarky Tim?
Reply to
just_me

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