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Panel fasteners


ianboag
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My J200 - being a few years old - has the fairings and covers and things held together with PK screws. Whenever I take off a cover for maintenance or inspection or whatever I end up putting bigger screws into some of the holes because they have grown a little on me.

 

This problem can't be unique to me as Jabiru now uses some kind of self-tapping threaded inserts instead of PK screws. I'm told they cost about $4 each which seems a tad steep.

 

Does anyone know what they are called in the non-aviation world and/or where they can be obtained? Alternatively can anyone comment on the suitability of Rivnuts (or any other sort of fastener) for this job? Captive nuts would probably work but seem a bit over the top.

 

IB

 

 

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Are you thinking of the same thing as the thread that's in behind the front cowl lower screws? If so they came with the kit and there's crap-loads of them in there. I have heaps of spares and I could put some in an envelope for you. They are a small piece of thread in a fitting that you have to attach with rivets and you need to countersink the holes for the rivets. Does this sound right?

 

When I have your problem I sometimes put in some epoxy glue to shrink the hole back up again.

 

 

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They are a small piece of thread in a fitting that you have to attach with rivets and you need to countersink the holes for the rivets. Does this sound right?

Thanks Brent. That's what I was referring to as a "captive nut" - not quite what I wanted here. The rivet/countersink drama is a bit more than what I had in mind.

 

Have a look at a new Jab and you'll see the rather neat inserts I am looking at. Imagine if all those PK's that hold covers on were replaced with M4 screws going into metal (aluminium) threads. The inserts holding the threads are self-tapping but I'm told the way they get mounted is by drilling a suitable hole and epoxying them in. (If there is such a verb as "to epoxy" .....)

 

Here are a couple of pix ...

 

 

 

Cheers IB

 

 

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I don't have any of those and they do look handy. I wonder if they would last well in terms of securely fitting them - better than just screws I guess.

 

 

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I wonder if they would last well in terms of securely fitting them - better than just screws I guess.

They are what Jab supply in the kit now. I borrowed these from a local building a J230.

 

 

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I'm a bit new to all this fastener stuff but there's a helpful supplier here (in Auckland) who is answering my questions so he might sell me $25 worth of them. Good ole Internet.

 

Nutserts are a Rivnut. I think they would work fine and the 25c unit cost is a big plus - I'm slowed down a bit by the apparent need for a $125 setting tool that I would probably never use again. I may of course be able to borrow one. Working on it ....

 

I have to say that Rivnuts (Nutserts) look to me as if they would be just as good as captive nuts but a whole lot cheaper to buy and easier to install. They must be OK for some aircraft things because Spruce sell them.

 

IB

 

 

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On the other hand - at $NZ10 each (give or take a bit) Dzus fasteners are not quite there for this application. I need 50-odd to replace the PKs. $500 - choke. Aside from the price I think they would be overkill - the PK's do a reasonable job (I haven't had any fall out) and I'm just looking to tidy things up a bit.

 

 

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Ian,

 

I cut some squares or circles of fibreglass a few millimetres thick and glued them on the inside of each existing hole with epoxy and floc. Clamp overnight with a spring clamp and redrill hole the next day to the appropriate size for the self tappers. The extra meat for the screw to bite into has worked well. They stay tight and are amazingly cheap.

 

Regards

 

Jeff

 

 

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Another method of making the original self tappers used for making fairings more secure is simply to drill the holes out slightly then mix some flock and epoxy(araldite) and push it into the hole aiming for a bit of a lump on the inside.

 

Normal preparation of sand-papering the area, cleaning it with acetone and applying a thin layer of epoxy before the main job will make the plug more secure.

 

Allow to cure.

 

Re-drill the hole to suit the self tapper.

 

Perhaps use a slightly longer self tapper than the original.

 

I bought extra captive nuts as used for securing the various hinge pins and used them where ever possible instead of self tappers - eg for joining two parts of a fairing.

 

 

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Thanks for all the suggestions. It's a bit of an indictment on Jabiru after-sales that so many of us have encountered this problem and bunbled our way through it. Especially as they have come up with a solution that they are using on new planes.

 

Personally I think I'll be going for the Nutsert solution. I might even just glue them in without to clinching.

 

IB

 

 

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Fasteners

 

The free and free post "Aircraft Spruce & Specialty Co." catalogue has many different fasteners listed with photos and often with explanations of how to use them and in what situation.

 

All the fasteners mentioned in the previous posts are listed and priced.

 

The Spruce catalogue has over 700 pages of aircraft related parts and equipment listed and priced.

 

It is often able to supply Australia from the west coast or east coast of the USA in about a week with certified or uncertified materials and equipment.

 

 

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Thanks Ross. I haven't seen the fasteners that Jab now use (threaded self-tapping inserts as in the previous pix) in the Spruce catalogue or anywhere else.

 

I think I'll buy the Rivnut tool - I'm not a mechanic. My experience has been that I can usually manage things OK with the right tool but I make a mess with shortcuts. I've seen how one can lash one a Rivnut setter with a bolt and a washer but I dunno .....

 

I decided about shortcuts after I had tried to crimp wires - my hangar mate strips wires with a knife, crimps them with pliers and makes a neat job. I have to use a wire stripper and a reasonable crimp tool.

 

IB

 

 

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I highly recommend you DO NOT USE RIVNUTS.Both wing fairings on the C47's I work on are held on by rivnuts and we are forever replacing them.If you get even a small amount of corrosion on the end of the fastener the rivnut will spin as it jams [the friction of the swag is all that stops it from rotating unless you get the one with a notch] and you cannot get it of other then having to drill it out. Been there and done that. You may wish to look at how surf ski foot straps are held in place Cheers T87

 

 

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T87

 

I'm always happy to take advice from people who have already solved the problem. At 62 years old and living a long way from a beach (and the NZ North Is south-west beaches are pretty crappy anyway) ....... it's a bit of a chore for me to find a surf ski to look at :-) So how are they attached anyway?

 

ModPi

 

What's the superglue for?

 

IB

 

 

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I personally like anchor nuts ,Dzus and camlocks, but I repaired my sons surf ski foot strap the other day and it had an SS insert which needed to be re-epoxied which looked a bit like a rivnut with spikes around it so as to give it grip once the whole thing was epoxied in place. I have no idea what they are worth or where to get them. Cheers T87

 

 

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