Inserting/bonding threaded inserts to fiberglas?

[OneTon]

I know this isn't an automotive forum, but the apparent vast spectrum of knowledge here leads me to believe we could build a "Garage Journal" nuclear reactor if we all put our heads together.

Anyway...I'm installing a fiberglas rear deck (engine lid) on my 911. The lid already has threaded inserts in place for attaching the hood to the hinges. Unfortunately, the holes are in the wrong place (different year/model).

Matching up the hinges to the lid, I marked where the holes should be for the new attachments. There is plenty of fiberglas "pad" available where my marks are. I even have access to the backside if I wanted to do nuts/bolts (Note: There isn't enough room to install a shouldered insert from the backside).

Before I go the nuts/bolts route, I thought it would be neat/clean to use threaded metal inserts (similar to the items shown below, but not exactly). The existing inserts look like they were pressed(?) in place...do not appear to be glassed/glued in.

What is the correct procedure for installing threaded inserts to a fiberglas part?

 

[trbomax]

Those are used in die molded parts,and are molded in place. The right way is to put a tapping plate in the layup,then drill and tap it as reqd. In your case maybe well nuts are a possibility.I was in the frp open molding business for about 30yrs and on hoods,doors,deck lids, we would lay an aluminum or brass plate on the part after the last layer was rolled out,then cover it with a couple pieces of 2 oz matt to hold it in place.You could use cage nuts too,they are a square nut in a sheet metal "cage" that it blind riveted after being located.

 

[LEVE]

I've installed Helicoil inserts in my CJ7 Jeep's fiberglass body. I drill the hole, thread it for the insert and then drip resin into the hole. Once that's done I twist in the insert with a bolt (threads protected by grease) and let everything cure. When it's cured, I pull out the bolt... and the job is done.

 

[OneTon]

Those are used in die molded parts,and are molded in place. The right way is to put a tapping plate in the layup,then drill and tap it as reqd. In your case maybe well nuts are a possibility.I was in the frp open molding business for about 30yrs and on hoods,doors,deck lids, we would lay an aluminum or brass plate on the part after the last layer was rolled out,then cover it with a couple pieces of 2 oz matt to hold it in place.You could use cage nuts too,they are a square nut in a sheet metal "cage" that it blind riveted after being located.

It's too late to lay anything in the glas...the piece is finished.

Do you have pics of "well nuts" or "cage nuts"? Whatever I use must be inserted from one side. I do have some rubber-mount well nuts left over from a motorcycle fairing installation. Not sure if rubber (with steel inserts) is adequate for this application, though...

 

[OneTon]

I've installed Helicoil inserts in my CJ7 Jeep's fiberglass body. I drill the hole, thread it for the insert and then drip resin into the hole. Once that's done I twist in the insert with a bolt (threads protected by grease) and let everything cure. When it's cured, I pull out the bolt... and the job is done.

I looked at something similar. A threaded insert with external threads. Not sure if something like that would work loose though on a moveable panel like an engine lid...

 

[Lotek]

The nice thing about glass is that you can add to it without too much trouble, grind out a flat spot where you want the threaded fastener plate, glue the plate down, add glass over the plate. I would suggest using epoxy instead of regular resin, it will form a better mechanical bond to the original surface. Use cloth over the plate since epoxy does strange things to mat. West System works for me, there are others.

 

[trbomax]

It's too late to lay anything in the glas...the piece is finished.

Do you have pics of "well nuts" or "cage nuts"? Whatever I use must be inserted from one side. I do have some rubber-mount well nuts left over from a motorcycle fairing installation. Not sure if rubber (with steel inserts) is adequate for this application, though...

Sorry,no pics,but you could google it and get something. that was a while back when I was doing that,it was the shop in toledo,got rid of all of it in the mid 90's.

 

[GeorgiaHybrid]

Have you tried using nutserts?

 

[OneTon]

Have you tried using nutserts?

Haven't tried anything yet. Two questions: Aren't nutserts for metal? Do you need to insert them from behind? I only have access to the front surface.

 

[GeorgiaHybrid]

They are inserted from the front side and set with a device similar to a pop riveter. You can buy them in aluminum or steel and can be bought for the thickness you need to clamp the nutsert on.


Edit: Taking a look at this page, they suggest a washer under both sides of the nutsert to provide some additional bearing surface. I also think they make a large flange nutsert for use in soft materials.

Nutserts

 

[OneTon]

Edit: Taking a look at this page, they suggest a washer under both sides of the nutsert to provide some additional bearing surface. I also think they make a large flange nutsert for use in soft materials.

Nutserts

Hmmm...that might do it. Almost looks like what's in there now.

 

[v7guy]

clickbond has some nutplates that you can bond to fiberglass as well as adhesives to bond the plates, I've just recently come across their stuff. The reviews are good, but i've not personally used their products.

I have had a lot of success with Hysol 9430 to bond plates to fiberglass and carbon parts.

Either one of those products should do the job...

you do not want to go threading any kind of metal into the fiberglass. It'll never hold.

 

[Crank1]

In my job, I work on MV-22B Ospreys. The plane is mostly all composite and we have to attach things to it somehow. The majority of the wiring bundles are attached with what we call Clickstuds, with external threads, but some of them also have internal threads. And sometimes we also bond on nutplates. We use Hysol 9394 on a regular basis for bonding the two components together, the clickstuds come with fiberglass bases, and we bond them to fiberglass/carbon fiber with the 9394. Sometimes the only way to break the bond is by destroying the base of the clickstud, the bond is that strong. We also use the 9394 to fill holes in some of the damaged composites or act as a liquid shim.
I'll say this, we do have certain things threaded into composite parts on my aircraft, they are inserts that we attach fairings onto on the Proprotor. They are large threaded inserts which you thread into place, then you hammer locking tines into place to keep them from backing out... Of course the stupid people working on this aircraft install the wrong fasteners and find a way to Fu(k them up...

I'm sure this doesn't help you much at all, because the clickstuds and the 9394 are probably out of your price range for a simple job, but just passing on the information, you can put inserts in fiberglass, are they worth it, probably not, the are we insert it to is probably .5" deep and completely solid carbon fiber.

 

[OneTon]

Some good info. Thanks.

So, my second idea is nuts/bolts with a metal sleeve through the glass...?

I'm not holding a wing on a plane, just need to keep the hood attached to the hinges. The previous hood (also fiberglas) had nuts/bolts. It held fine for years, but looked crappy. I'm trying to clean things up on this install.

Edit: Just looked up pricing for the recommended Hysol products. Sounds like it can glue your nuts to your leg, but definitely too much $$$ for this project!

Those Click Bond fasteners look ideal, but there are so many to choose from. I'll have to stop by the local aircraft supply house to eyeball 'em.

 

[LEVE]

You could also fab a metal plate, drilled and threaded to match the hinges. Then glass that in on the underside of the hood, if you've got the room. That also wouldn't take much effort or cost. It would sandwich the hood between the plate and the hinges.

On my Jeep, I've made some 5/16" hold downs to hold down the hard top. I take an oversize washer, and weld a 5/16" nut onto it. Then I drill two holes in the washer and pop riveted the washer to the underside of the Jeep's tub lip. It's safe, cheap and works like a charm to keep the hard top on.

For your use you could fab something similar, even a threaded 3/16" plate and use stainless steel - tapered - flat headed bolts, countersunk into the glass, to hold the plate. Then the hinge would fit flush against the hood and bolts.

 

[OneTon]

There is no room between the hinge/hood as that would cause the hood to raise up beyond the body. I'd have to grind down what is there in order to make room for a plate. I'm trying to avoid grinding/glassing if at all possible. I'll try to get a pic of the inserts that are already in place. Those are what I'm trying to duplicate.

 

[mgilde13]

If it were me, I would glue the inserts in using 3M 08115 Panel Bonding Adhesive. It will bond two pieces of metal together stronger than a weld will and it has an even better bond to fiberglass. It has a 3500 psi sheer strength to be exact. It's the same stuff that holds your quarter panels, etc to your car.

 

[OneTon]

Yes, now that I've learned which inserts to use, I'm researching adhesives.

The Hysol stuff above sounds pretty damn strong, but it is also pretty damn expensive. I forgot about panel bonding adhesive (until you just mentioned it). My fiberglas fenders are bonded to the metal shell with it.

 

[JamieK]

Reread Leve's reply...

"You could also fab a metal plate, drilled and threaded to match the hinges. Then glass that in on the underside of the hood (where the nuts would go, if you've got the room. That also wouldn't take much effort or cost. It would sandwich the hood between the plate and the hinges."

And you wouldn't even need to glass it; just a dab of epoxy to hold it in plce till you got the bolts started.

 

[johno]

I know this isn't an automotive forum, but the apparent vast spectrum of knowledge here leads me to believe we could build a "Garage Journal" nuclear reactor if we all put our heads together.

Anyway...I'm installing a fiberglas rear deck (engine lid) on my 911. The lid already has threaded inserts in place for attaching the hood to the hinges. Unfortunately, the holes are in the wrong place (different year/model).

Matching up the hinges to the lid, I marked where the holes should be for the new attachments. There is plenty of fiberglas "pad" available where my marks are. I even have access to the backside if I wanted to do nuts/bolts (Note: There isn't enough room to install a shouldered insert from the backside).

Before I go the nuts/bolts route, I thought it would be neat/clean to use threaded metal inserts (similar to the items shown below, but not exactly). The existing inserts look like they were pressed(?) in place...do not appear to be glassed/glued in.

What is the correct procedure for installing threaded inserts to a fiberglas part?

Why not use something like that with west system epoxy?

 

[DavisonSpecials]

These "EZ-Points" may work, if you can limit yourself to 1/4-in or smaller fasteners. I have no experience with them, however. Since it says they are alodined, I assume they are made of aluminum. I don't really see them as much more than prefabbed metal plates - but they would save you the time of making your own.

http://www.aircraftspruce.com/catalog/hapages/ezpoint.php

You could achieve the "race" look by using hood-pins all around. They work great until you forget to install the clips. FYI: A fiberglass Camaro hood will achieve lift-off at about 35mph. Conveniently, Camaro t-tops allow for a perfect view of the hood as it flies overhead.

 

[EdT]

In a past life I had good luck installing knurled inserts as you have shown into FRP door assemblies on industrial equipment using 3M structural adhesive. Drill a hole so that the insert is a tight fit, apply the adheive to the inside of the hole and the outside of the insert and press it into place. After the glue is hardened, you can grind off the extra adhesive and make the insert flush to the surface if it's not already. This approach was neccesitated due to the "blind" nature of the holes with a cosmetic surface on the other side so through bolting was not an option. If the arrangement of the part allows you to run something thru from the back, you might want to look at "TEE" nuts. Just be sure that you have a way to get things apart should the need arise.