Firbreglass Pod - Fasteners

[bobthebuilder]

I have a banana pod. It is of the two piece variety, whereby the top panel can be removed with the instruments.
The top panel is fastened to the bottom "box" by means of nine wood screws on the sides. Two of these screws have stripped.

What is the best way to fix this?

I had two ideas, either reinforce the edges with fibreglass tape on the inside. A bit messy, but it will work, or drill the existing holes out and fit Riv-Nuts. Will these crack the fibreglass?
Also, with Riv-nuts, will the bolts be prone to vibration?

Does anyone have a better idea?

[James Bentley]

Bob

A rivnut will work well but you must insert it into an oversized thin metal plate first

Most rivnuts are designed to grip in a substrate of 1 to 2mm, your fibreglass is obviously thicker than that so it won't 'hold' properly

the metal plate with the rivnut is now bonded into the fibreglass from behind using a structural adhesive, remember to open up the hole in the pod so that the raised head of the rivnut is flush with the outside. The result is a very neat way of attaching a fastener into a composite material, we do hundreds of them in this way every week

if you are worried about the screw loosening with vibration, use Loctite 243 on the threads when you reassemble the structure

243 is a low yield thread locker and is very resistant to vibration

need any more help, contact me

James

[bobthebuilder]

Nice idea, thanks James.
I'll make up some aluminium backing plates.
What structural adhesive do I use, got a brand name?
Can I get it from the hardware store?

[James Bentley]

Bob

Unfortunately not available at the hardware store, Pratley two pack epoxy in a tube will work but it tends to be brittle as it ages

AMT in JHB, 0113924232 sells structural epoxy in small packs- speak to Jo and tell him I referred you! He is doing his LSA licence and very willing to help aviators!

We use methylmethacrylate structural adhesives for our application, fantastic performance with minimal preparation required, but expensive! There is nothing to compare once you have used this material

Plexus sold by NCS resins, they have branches all over SA. Pack size is large but if you have a lot to do maybe worth it.

Scott Bader have just launched a new range under the Crestabond label, it has the most incredible performance of all the adhesives we have ever used but comes at a price. They also make an adhesive known as Crestomer that will be totally unsuitable for your application so please do not buy it, it is good in other areas but not metal to composite bonds.

You will be totally amazed at what can be done with adhesives these days, the technology has improved so much in the last few years, we "glue" together some huge composite sections in total confidence without fear of failure

Good luck!

[bobthebuilder]

Thanks for the advice James.

I have bought a few things from AMT before and will give them a call. I dealt with a lady named Kim I think. (British accent)

What line of work ar you in James?

[James Bentley]

Hi Byron

I have a composites and metal fabrication company

our scope of work is quite varied which has afforded me the good fortune to meet and work with some very interesting people over the years

will be travelling to Gauteng next week and can bring you some of the "super glue" if you have't already ordered some already

James

[bobthebuilder]

Thanks for the offer James, but I want to get this sorted out quickly, and will go through to AMT today.