Reinforcing fixing points for door cards

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Alan_M
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Reinforcing fixing points for door cards

Post by Alan_M »

A quick question for the engineery type folks.
While I have my doors apart I want to reinforce the points where the screws attach the door card as the holes are so large the screws just drop out. Rather than just using fibreglass as originally which in time probably end up the same, I was thinking of sandwiching a thin piece of aluminium between the current door shell and new fibreglass - so how thick/thin aluminium do I need to give a good long lasting purchase for the self tapping screws?

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Re: Reinforcing fixing points for door cards

Post by Woogiebloke »

Hi
Always good to improve fixings etc. while working on an area.
Self-tapping screws in the GRP isn’t always great - I’ve found the thin steel originals will rust as well as wear the fixing.
I have found using slightly higher gauge & stainless works on the low-stress fixings okay. Not sure thin alloy would be better than GRP in this - probably need some kind of plate washer etc. then the problem becomes how to retain that fixing to the panel. (Pain if it spins in place when trying to remove) You could scuff the GRP and Epoxy something in place?
In areas where repeated disassembly is required I have occasionally drilled the hole oversize and made a bush (Rawplug style) to accept the screw and protect the GRP. Using small Well-nuts can be useful in places but the receiving panel usually needs a very oversize hole.
Hope this is useful - good luck
Chris

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Re: Reinforcing fixing points for door cards

Post by Excel SA »

I'm not sure there are enough fixing points in the door card either, nor are the ones there in the right orientation.....the plastic on mine is cracking at the top where it hangs onto/over the door skin. Having the speaker mounted to the door card doesn't help either I don't think, and if I'm not mistaken there is only one screw from the bottom up into the door skin in that area.

My doors had multiple holes nest to each other that had been progressively been enlarged over the years, have been closed up for now on the driver's side while I wait patiently for a clever answer to this!

I think it's too easy to strip a threaded hole in fiberglass, a threaded insert in plastic may work and can be replaced easily if overtightened as used in most cars these days? Maybe adding in an extra fixing point under the cover that the door light switch pushes on - assuming that's what it's for....black button bit in the pic below (the other side has a red one...)

Image

Neil.

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Re: Reinforcing fixing points for door cards

Post by Pete Boole »

I've just added several layers of fibreglass and added more fixing points as Neil suggests. A stainless screw into 1/4" of fibreglass is going to be fine. If you want to add metal I'd use 1.5mm stainless bonded in place using epoxy. Make the stainless strip long enough so that it cannot spin completely if it comes unstuck (with the right epoxy and prep this will never happen!). Screw the self tappers into the strip before bonding - to cut the threads - less stress on the fixing later.

Pete

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Re: Reinforcing fixing points for door cards

Post by HC180 »

A rubber Rivnut with brass insert works well.
https://www.ebay.co.uk/itm/272929984585 ... %3A2334524

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Re: Reinforcing fixing points for door cards

Post by Pete Boole »

HC180 wrote:
Wed Sep 15, 2021 20:37
A rubber Rivnut with brass insert works well.
They do until the screw gets corroded into place and then they are a real pain! I remember spending hours trying to get the fairing off a Honda which used them :(

Pete

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Re: Reinforcing fixing points for door cards

Post by MetBlue »

I've replaced the screws with M4 hex head cap screws on my door cards.
Epoxy bonded an Ali plate 4mm thick into the door and tapped M4. Now all very secure and with some copper slip on the screws, I'm hoping they will be easy removable when needed (Aluminium is a lot easier to work than Stainless 😊).
You must us low profile cap screws though because there is little room between the door seal and the door card.
Tony
What goes together.... Must come apart.

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Re: Reinforcing fixing points for door cards

Post by Alan_M »

Thanks for all suggestions and experiences. I’ve decided to go for the stainless option. I’ve ordered some 1.5 mm stainless plate. I will use pieces and shape as the fixing points are close to angles and bind these in with fibreglass. Then when rebuilding the door I will drill some pilot holes to match the door cards and fix with stainless screws.

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