Roadster Hood Fastener Choices

[Jim S]

I'm looking for ideas on how to fasten the roadster hood to the hinges other than using the 3/16" rivet method FFR recommends. For painting and maintenance, I would like to be able to easily remove the hood without drilling out / re-installing rivets.

What I would like to use is M5 pan head bolts. I know McMaster-Carr has rivet nuts specifically for use in fiberglass. Unfortunately, the rivet nut's uncompressed length is about 1/2" longer than the depth of the pocket at the hinge mounting location. Does anyone know of a M5 rivet nut with about a 1/2" uncompressed length? I'm not stuck on an M5 size. Anything from 3/16" to 1/4" would be fine. So would M6. I think M4 is a bit too small.

What have others done? Would a regular rivet nut hold in fiberglass? I have thought about trying a regular rivet nut but if it doesn't hold, getting it out usually enlarges the hole quite a bit leaving a mess to deal with.

Could you share your ideas / solutions?

[michael everson]

There is an aluminum plate in that area. I have drilled an tapped the holes with no issues.
Mike

[CaptB]

After building a MK IV, the weakest engineered part is the hood hinges (most everything else is ok). I'm sure there are a lot who would disagree with that however, I did tap and rivnut it in but it did not do well with that. Suffice to say the end result was a pain but it is way more than what is probably needed. We anchored studs in and we have nuts that hold it on. If I had any recommendation for FFR, it would be to come up with a better hood hinge set up. That's my .02 cents and it's exactly worth that!

[rich grsc]

Bond & rivet the mount to the hood. To remove the hood, take 2 bolts out of each side of the hinge arms.

[edwardb]

Bond & rivet the mount to the hood. To remove the hood, take 2 bolts out of each side of the hinge arms.

X2. Have done three Roadster builds that way. Bonded with HSRF and then the kit rivets. They won’t be coming off but still easy to remove the hood via the pivot bolts. Completed before paint so the mounting brackets are body color. Nice clean look. Did the gas strut attachments the same way FWIW.

[phileas_fogg]

Do NOT use regular riv-nuts in fiberglass. They will crush the material & pull out, leaving you with oversized holes to fix. Do as rich & edwardb suggest.

https://thefactoryfiveforum.com/showthread.php?45350-Help-me-fix-my-hood


John

[Jim S]

I have to admit, I was concerned about any fastener holding the hood. Maybe a bit of belt and suspenders... I think I will drill and tap the aluminum plate as Mike suggested (Thanks Mike. I didn't realize there was a plate in this area) and also bond it.

Thanks for the inputs / ideas guys.

[Jeff Kleiner]

After building a MK IV, the weakest engineered part is the hood hinges (most everything else is ok). I'm sure there are a lot who would disagree with that however, I did tap and rivnut it in but it did not do well with that. Suffice to say the end result was a pain but it is way more than what is probably needed. We anchored studs in and we have nuts that hold it on. If I had any recommendation for FFR, it would be to come up with a better hood hinge set up. That's my .02 cents and it's exactly worth that!

I'll disagree with a caveat--- the engineering is good but the suggested execution isn't ideal. Throw away the wave washers, use flat washers of the proper I.D. and thickness for the shoulder bolts and the hinges will work flawlessly for years.

Except for a few times when I've done cars that the owner has either tapped as Mike mentioned or bonded the brackets I always use rivets (be careful of the length). I did get one in that had rivnuts that were not holding and simply spun...loosely. that was a real mess.

Jeff

[CaptB]

I'll disagree with a caveat--- the engineering is good but the suggested execution isn't ideal. Throw away the wave washers, use flat washers of the proper I.D. and thickness for the shoulder bolts and the hinges will work flawlessly for years.

Except for a few times when I've done cars that the owner has either tapped as Mike mentioned or bonded the brackets I always use rivets (be careful of the length). I did get one in that had rivnuts that were not holding and simply spun...loosely. that was a real mess.

Jeff

You said it better, the execution here is the key to the problem. The hinges themselves are fine and how it opens and closes it great.

[rich grsc]

I absolutely prefer the bracket bonded and riveted, then painted body color. The rivets are just to hold the hinge in proper alignment till the bonding is cured. I have done two that way, and if I ever do another, thats's how it will be done.

[Bill Elliott]

So is the epoxy simply put between the bracket and hood to act as a glue essentially?

[edwardb]

So is the epoxy simply put between the bracket and hood to act as a glue essentially?

Adhesive bonding in addition to the kit provided rivets. Not epoxy though. 3M Marine High Strength Repair Filler (commonly referred to as HSRF on here) is a vinylester product that matches the resin the FF bodies are made from. Highly recommended for very strong bonds.

[rich grsc]

HSRF is a very good product, but I think it's expensive. There are many other bonding products that will work for this use that's less $$. Check boat repair companies, such as West Marine.

[Jeff Kleiner]

If you’re going to bond the brackets (I don’t but won’t try to talk you out of it) remove the gelcoat from the surface of the hood as well as any powder coating on the bracket. Better yet grind a little rough surface “tooth” on the back side of the metal bracket.

Jeff

[edwardb]

HSRF is a very good product, but I think it's expensive. There are many other bonding products that will work for this use that's less $$. Check boat repair companies, such as West Marine.

Rich -- Agreed. That stuff is like liquid gold. After always been relatively easy to obtain, went through a period some months ago where no one had any. But it's back if you shop around. Has always been expensive, but has gotten more so. It's the only thing I've ever used when bonding to the body. But I scraped the last bit out of the can I had when I finished my truck build. Hoping not to need any more for now. My main point was to use something that's compatible with the vinylester body. Hardware store epoxy is likely not the best. Boat repair companies are a good suggestion.