Awning Rail

[Robmac]

I am fitting an awning rail (c-type) hopefully tomorrow if the rain has stopped by then. It is for a Fiamma Caravanstore xl which is an awning in a bag weighing roughly 10kg. I intend to stick it using Sikaflex 554 (thanks Bill @Fisherman) but as a belt and braces solution I also intend to put a stainless steel bolt at each end of the 3 sections of C-rail.

My question is, should I try and isolate the bolts from the rail with maybe a plastic washer or similar in order to avoid galvanic corrosion? I have seen these rails fitted before on Youtube where people have not done so but don't know if there were long term effects.

 

[wildebus]

I am fitting an awning rail (c-type) hopefully tomorrow if the rain has stopped by then. It is for a Fiamma Caravanstore xl which is an awning in a bag weighing roughly 10kg. I intend to stick it using Sikaflex 554 (thanks Bill @Fisherman) but as a belt and braces solution I also intend to put a stainless steel bolt at each end of the 3 sections of C-rail.

My question is, should I try and isolate the bolts from the rail with maybe a plastic washer or similar in order to avoid galvanic corrosion? I have seen these rails fitted before on Youtube where people have not done so but don't know if there were long term effects.

Not sure if you need the washers, but .....

A suggestion for you if you were not planning on it anyway ... Use something to make sure the sections of rail stay PERFECTLY lined up to each other as the sikaflex cures. There is very little tolerance on the rail profile when sliding in a caravanstore or anything else for that matter in and it goes from one section to the next and the slightest misalignment becomes a major pita.

 

[Robmac]

Not sure if you need the washers, but .....

A suggestion for you if you were not planning on it anyway ... Use something to make sure the sections of rail stay PERFECTLY lined up to each other as the sikaflex cures. There is very little tolerance on the rail profile when sliding in a caravanstore or anything else for that matter in and it goes from one section to the next and the slightest misalignment becomes a major pita.

Yes I was going to use a 6mm drill bit (I think it's 6mm) in the rail to keep the sections aligned if that makes sense?

Thanks.

 

[merl]

I am fitting an awning rail (c-type) hopefully tomorrow if the rain has stopped by then. It is for a Fiamma Caravanstore xl which is an awning in a bag weighing roughly 10kg. I intend to stick it using Sikaflex 554 (thanks Bill @Fisherman) but as a belt and braces solution I also intend to put a stainless steel bolt at each end of the 3 sections of C-rail.

My question is, should I try and isolate the bolts from the rail with maybe a plastic washer or similar in order to avoid galvanic corrosion? I have seen these rails fitted before on Youtube where people have not done so but don't know if there were long term effects.

Honestly dont know Rob! Galvanic corrosion is like a black magic mystery! I guess your body is steel the rail is Ali so using stainless bolts is either going to cure the issue or make it worse!
I suppose the rail will be electrically isolated from the steel body by paint and Sika so your idea of a plastic washer would maintain that insulation BUT the bolt would probably touch the Ali inside the hole as it passes through so you'd need something like a short piece of heatshrink on the bolt thread where it passes thru the Ali or a special plastic washer like this below which is used when fixing a transistor to a heatsink without electrically connecting them together.

Google Image Result for https://cpc.farnell.com/productimages/standard/en_GB/SC20281-40.jpg

I think they accept M3, probably not as large as you anticipated using but probably more than strong enough considering it's probably not needed anyway and more for peace of mind AND would look quite neat.

 

[SquirrellCook]

It's having a gap or absorbent materials that makes a difference with dissimilar metals.
If your using Sikaflex, make sure to put some in the hole and over the screw threads.

Mark

 

[Scotia]

Is the galvanic corrosion not caused by zinc ?

 

[Robmac]

Honestly dont know Rob! Galvanic corrosion is like a black magic mystery! I guess your body is steel the rail is Ali so using stainless bolts is either going to cure the issue or make it worse!
I suppose the rail will be electrically isolated from the steel body by paint and Sika so your idea of a plastic washer would maintain that insulation BUT the bolt would probably touch the Ali inside the hole as it passes through so you'd need something like a short piece of heatshrink on the bolt thread where it passes thru the Ali or a special plastic washer like this below which is used when fixing a transistor to a heatsink without electrically connecting them together.

Google Image Result for https://cpc.farnell.com/productimages/standard/en_GB/SC20281-40.jpg

I think they accept M3, probably not as large as you anticipated using but probably more than strong enough considering it's probably not needed anyway and more for peace of mind AND would look quite neat.

Thanks Merl. I was considering something like the washers with inserts like you show in your link, there is a trader near me who has every sort of nut, bolt, washer you can think of. I've bought from him many times and no matter what I've asked for he always seems to have it in stock.

The roof itself where I am fixing the rail is some sort of plastic composite so there won't be a problem there so that seems an ideal solution and would keep the bolt head and the thread away from the aluminium. It's probably not needed but being a boating man I have seen the effects of Galvanic erosion and it can look unsightly.

I was in a lock on the river once and there was a steel narrowboat next to an aluminium narrowboat - basically creating one big battery with the lock water as the electrolyte. In patches you could see small bubbles being discharged from the hull of the aluminium boat - not good!

 

[Robmac]

Is the galvanic corrosion not caused by zinc ?

Don't think so Sam. Zinc is a very un-noble metal and is used for sacrificial anodes. So in my case the awning rail being less of a noble metal than steel would become the anode.

 

[SquirrellCook]

Is the galvanic corrosion not caused by zinc ?

For galvanic corrosion to take place you need to form a battery. Hence avoiding having an absorbent material between two dissimilar metals.

Mark

 

[merl]

For galvanic corrosion to take place you need to form a battery. Hence avoiding having an absorbent material between two dissimilar metals.

Mark

Told you it was mysterious and black magic

 

[Robmac]

Told you it was mysterious and black magic

I've decided to go with blind Rivnuts Merl (also known as Well nuts), they seem an ideal solution. I do have a Rivnut gun but won't need it for these. Due to the internal structure I won't be able to get to the back of the bolts inside the van but using the blind Rivnuts I won't need to and the bolts will all be isolated from the aluminium.

 

[merl]

Perfect solution Rob, I've seen them used on 'top fix' toilets where you cant access the back of the bolt but didn't realise they were available in multiple varieties.
Interestingly, as soon as I saw the part in the video which showed that the 2 parts are isolated by rubber and vibration isolated to some extent I immediately remembered that I'd recently needed exactly that property when I was fixing something quite recently and had to rack my brains trying to remember what it was.......I then recalled it was my Sureflow pump! Ours is fixed onto the wall creating the toilet and it resonates through the van a lot when the pump runs, I took a look at the original fixings which have a rubber grommet between the pump and the wall but obviously vibrations are still transmitted via the fixing screw so I'm going to check and see if I can get 4 of these fixings and give them a try, I reckon leaving them only semi tight could work well.

 

[Robmac]

Perfect solution Rob, I've seen them used on 'top fix' toilets where you cant access the back of the bolt but didn't realise they were available in multiple varieties.
Interestingly, as soon as I saw the part in the video which showed that the 2 parts are isolated by rubber and vibration isolated to some extent I immediately remembered that I'd recently needed exactly that property when I was fixing something quite recently and had to rack my brains trying to remember what it was.......I then recalled it was my Sureflow pump! Ours is fixed onto the wall creating the toilet and it resonates through the van a lot when the pump runs, I took a look at the original fixings which have a rubber grommet between the pump and the wall but obviously vibrations are still transmitted via the fixing screw so I'm going to check and see if I can get 4 of these fixings and give them a try, I reckon leaving them only semi tight could work well.

In the case of the awning rail Merl they should also help to prevent water ingress although I will use a sealant as well.

 

[merl]

Be careful Rob, I don't know if you've done anything similar before but silicone sealant makes rubber extremely slippery, if the 'bung' has ANY potential to pop out then you may regret applying it liberally, maybe just a very thin bead between the body and the front flange only?

 

[Robmac]

Be careful Rob, I don't know if you've done anything similar before but silicone sealant makes rubber extremely slippery, if the 'bung' has ANY potential to pop out then you may regret applying it liberally, maybe just a very thin bead between the body and the front flange only?

A very good point Merl. I may then just put a dab under the flat under-surface of the dome head stainless bolts I intend to use although I think there is little chance of seepage down the thread - or I could just use Blue Loctite?

 

[merl]

A very good point Merl. I may then just put a dab under the flat under-surface of the dome head stainless bolts I intend to use although I think there is little chance of seepage down the thread - or I could just use Blue Loctite?

A bit on the thread deffo, just don't 'Bartle' a load over the rubber.
Bartle.... Brilliant eh

 

[Nabsim]

Weird things awnings. I got mine and a roof kit to suit my van and the awning (Thule Omnistore wind out). 4.5mtr awning needed 3 aluminium roof plates of varying sizes. All fitted as per Thule instructions then we lifted and slid the awning onto the roof plates to find it’s only held in place with 3 self tappers. Was a little doubtful but thought they probably knew best and ran with it. Been on a few years now and no sign of movement even though I have trimmed a few trees and hedges with it.

 

[Pudsey Bear]

I've decided to go with blind Rivnuts Merl (also known as Well nuts), they seem an ideal solution. I do have a Rivnut gun but won't need it for these. Due to the internal structure I won't be able to get to the back of the bolts inside the van but using the blind Rivnuts I won't need to and the bolts will all be isolated from the aluminium.

They are what Swift use to fix the exterior top light on my van, I'd not want to put a lot of weight on them though.

 

[QFour]

Mondal Pop Rivets would work. Stainless and Aluminium will corrode away the aluminium. If the side of your MH is aluminium stainless will happily corrode that as well over time.

 

[trevskoda]

Mine is like this, i coated the back with silicone and used a marine grade rivets as my van is alloy, so no black magic will happen.