Hood firewall pin cracked fiberglass?

[MonstaS4]

Seems like I'm fighting a loosing battle with bodywork at the moment. Started installing rivnuts for the hood firewall pin mounts today and seem to have come up against defect in the gelcoat and or fiberglass.

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The first rivnut seemed to pull up way further than the rivnuts just installed on the other side, then on the last pull of the second rivnut, i started to hear cracking which continued for a minute or so where I was left with a couple of large cracks. You can see in the second pic that the defect is raised on the corner. It also seemed like the aluminium bonded behind/within the glass was only covering half of the 3rd hole.

Any suggestions on what to do here? I suspect I'm going to have to cut out that 'face' that the rivnuts are installed on and glass in a new one as there's something NQR in behind there.

[wallace18]

I use aluminum rivnuts when I am going into fiberglass. You can get them from McMaster-Carr. Best to drill out rivnut, patch cracked area and redrill using aluminum. IMO.

[MonstaS4]

Thanks Wallace, will do. I've used 'plus' nuts in places where I know there's no aluminum reinforcing which has worked well so far, but I've stuck with the FFR supplied rivnuts elsewhere.

I'll see if I can source some aluminum rivnuts. Unfortunately, no McMaster-Carr here in Australia.

[wallace18]

Thanks Wallace, will do. I've used 'plus' nuts in places where I know there's no aluminum reinforcing which has worked well so far, but I've stuck with the FFR supplied rivnuts elsewhere.

I'll see if I can source some aluminum rivnuts. Unfortunately, no McMaster-Carr here in Australia.

Here is a link. you can order on the internet.

https://www.mcmaster.com

[FF33rod]

If you do want to order from McMaster Carr and are not a US resident, have a company name/address ready. They will not ship internationally to individuals.

Steve

[wrp]

How did this work out for you? Wallace is a very experienced builder. I have been screwing with the hood for years. Made a complete mess out of the mounting. The hollow part of the hood is full of failed rivenuts. Looking at the mess one night I figured there had to be an easier way. I took the hood off and stood it against the wall nose up. I then went into the backside of the area, after marking where I wanted the mounting holes to be, and inserted an aluminum plate. I had first drilled the fiberglass so I could mark the plate. Then I drilled the holes in the plates and went back and bolted the hinges to the plate, sandwiching the entire fiberglas area you are showing cracked. I will confess I could have done a neater job cutting the fiberglass but on the front side of it, no one will ever see it un less they are checking with a mirror. With all the Gen1 hood hinge difficulties I have been happy with the results. The hood is solid. I would recommend this to anyone who has put a few miles on their Hot Rod and find the need to adjust or tighten the hood hinges resulting in the rivenuts failing.

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[MonstaS4]

I haven't had much opportunity for 'shed time' lately. I have managed some investigative surgery and it looks like the glass was wafer thin at this point. Maybe 1 layer of mat behind the gelcoat, then an aluminum insert backed with maybe 2 layers of mat. The ally insert was also too small and hence I missed it completely with one of my holes.

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I'm not sure on the best way to repair it. I'm thinking of laying up 3 layers on the bench and let it go off, then cut it to size and insert it from behind and epoxying it in. Then grind the front back a little and lay another 2 layers over it from the front. Epoxy in an aluminum backer then use a plus nut instead of a rivnut. I'm open to any suggestions though.....my glassing experience is close to 0.

I didn't have any trouble with the hood hinge or striker rivnuts WRP. When drilling, I could see plenty of thinkness along with an aluminum insert. Maybe early hoods didn't have this aluminum insert?

[wrp]

No they had the plate, I’ve just had the hood on and off so many times and so many others have tried to fiddle with it the aluminum plate was like swiss cheese. Sort of a similar situation to yours. On that one I would either replace the plate and class over the bottom and side or just lose the Rivenuts and run a bolt straight through the new glass and the old plate, use a pretty large washer and tighten it down. I have had no problem with the striker at all

[Dodgeman]

No they had the plate, I’ve just had the hood on and off so many times and so many others have tried to fiddle with it the aluminum plate was like swiss cheese. Sort of a similar situation to yours. On that one I would either replace the plate and class over the bottom and side or just lose the Rivenuts and run a bolt straight through the new glass and the old plate, use a pretty large washer and tighten it down. I have had no problem with the striker at all

Here are the ones I have been using in the hood and trunk lid.
https://www.mcmaster.com/90186A213

Bob

[cob427sc]

There are some special rivnuts made for installing into plastic and fiberglass which have a larger head. On a similar problem, I used a steel plate and welded on nuts for the bolt locations, then glassed the plates into location. Think it was on a GTM but can't remember where. Also early roadsters did not have the aluminum plate where the optional hood hinge located (changed in later versions) and I used this same fix there after the rivnuts kept pulling out. The steel plate makes it easy to fabricate and won't rust when it's incapsulated with the fiberglass.

[wrp]

I like the welded nuts, I would think that you could just get a thick enough piece and thread it though. My Hot Rod Kit, built in 2008-2009, number75 definitely has an aluminum plate. I have drilled it enough times to know for sure. I was curious and went out and looked and yep there is an aluminum plate there. I assume on roadsters you are talking about the cobra roadsters?142427

[cob427sc]

Yes early Gen I roadsters. I believe by Gen II they had added an inner liner to the hood and provided a mount location for a hinge. The Gen I were just an outer shell fiberglass which some of us modified by adding an internal aluminum layer.