Rivet nut strength

[PETERPJERO1]

I am considering using rivet nuts in roof gutter to hold roof rack. 8 each side zinc plated steel to take 6mm bolts. Any experienced opinions would be greatly appreciated. My main concerns are strength & sealing against rust and moisture. NT

[Dicko1]

Not too sure about strength but 6mm is not a size I would equate with strength. Could you possibly go to 8mm. Maybe too large? I would also use sikaflx to make waterproof and also to act as an adhesive as well.. Dont use silicon.

[NFT5]

If I understand correctly you plan on replacing the existing factory rails. To do this you'll need to access from underneath, in which case you could use bolts, through rivnuts, as studs on which to mount your rack. Something like this would allow the use of nice big washers to spread the load with no risk of the rivnuts pulling out. Sealing up is easy with a little smear of sealant when assembling.

[PETERPJERO1]

re Rivet nut strength

I am cosidering each option. I know the nut & bolt option is the strongest but riv nuts may me ok with advantage of not having to remove hoodlining to remove rack mounts in the future. the riv nuts are 9mm to take a 6mm bolt. I'm not 100% sure they will fit in the gutter but my main concern is strength and sealing. Sealing me be better with riv nuts. I would fit the riv nuts from the top which would leave the thread part of the riv nut protruding underneath. It would take a stack of washers to take up space. But a good thought.

[sharkcaver]

I wouldn't go there myself. Its a disaster in the making. Apart from the small flange on the compressed rivnut, I just don't believe it will have the strength without pulling through. Washers may help, but it may just pull through the washer. Imagine what the consequences of loosing a roof load could be. Is trialling a rivnut worth that risk? And you have to drill a 9 odd millimetre hole to fit an m6 rivnut.

[GHendo]

When I installed my Rhino platform I also installed the Rhino tracks in the channels. The recommendation is to use 3/16” rivets which I did – installed with an air gun. I painted the holes with gal. paint first, then put sealant around each hole under the track as well. This makes for a very strong installation. If you want to remove the platform all that is left are the two tracks down in the channels. If you remove them you are going to have two open channels and you probably won’t still have to original covers for them.

Cheers

Geoff

[old Jack]

I would not be using Rivnuts unless you can guarantee they are 100% perfectly flush or slightly recessed from the roof surface and installed correctly and using a rivnut tool, because if they are proud of the surface then, even with sealant, you will be clamping down on the top of the rivnut and not the roof. This could lead to flexing and fatigue and the rivnut/hole in the roof failing. The only possible reason for using rivnuts is wanting to be able to remove the rails but this will be difficult if the correct sealant is used.

I would be looking at what size and type of fasteners the roof track manufacturer states to use. As Geoff stated Rhino recommends 3/16th dia rivets (approx 5mm dia) so increasing to 6mm dia maybe possible without weakening the rail but I would doubt if 8mm dia would be possible. Also the rail manufacturer will have worked out the correct fastener diameter and hole pitch so it is wise not to increase or decrease this too much.

It will be the sealant (Sikaflex neutral cure, automotive grade) that will provide not only the waterproofing but significant bond strength and resistance to vibration cracking so do not skimp on the quality and ensure the whole rail mating surface has a thin but sufficient coating, too much and the rail will distort when you put the fasteners in, too little and it will not be enough to do the job correctly.

If the roof lining has to come out to remove factory rails then I would be using stainless bolts, nyloc nuts and large diameter washers. If there are no rails then I would be using the blind rivets recommended by the track manufacturer, installed with a powered rivet gun or an industrial manual gun and not your normal hand "plier style" of rivet gun, unless you want to drop the roof lining and use bolts.

Correct preparation is the key to any good installation, make sure the holes are the correct size for the fasteners, drill under size then again on size as the hole will be rounder and less burring on the underside. Deburr both sides of the holes, a manual "hook type" deburring tool is best and will deburr blind holes. Deburring is critical as a hole which is not deburred is very likely to develop a fatigue crack radiating from the hole. Do not deburr so the holes become countersunk as this weakens the hole.

Painting the bare metal of the holes is also important, one step "killrust" paint is ok to use but prime and paint is better but takes longer as the paint must be dry between primer and paint and assembly.

Masking tape applied to the external roof surface, 3mm outside the edges of the track, will make the cleanup of the excess sealant easier and give a nice straight line and smooth finish.

Good luck.

OJ.

[PETERPJERO1]

re Rivet nut strength

Have decided to go with the bolts and nuts idea. A 9mm hole in the gutter may weaken it and the hood lining is ok to remove. So thanks for the input It's made me rethink .

Save