Bonding an Awning ‘C’-Channel to my new motorhome

[Malcolm Greenhill]

I’ve just taken delivery on my new motorhome and had the dealer fit an Awning C-Channel to the side as I don’t want a wind-out Awning. I have a Kampa Air Ace Pro 400 awning which i used for the first time last weekend.

Unfortunately the C-Channel separated from the van above the awning front side wall. I suspect this is because the channel is 4m and so is the Awning. Consequently the downward pressure from the side wall pegs is exerted on the C Channel where it ends and is therefore at the weakest point of the bonding.

 

The Dealer used a Adhesive sealant from Würth called Glass Clear Adhesive Sealant.

 

This is no one in particulars fault so I’m happy to re-fit the channel despite the pain of having to remove the old adhesive using a toffee wheel.

 

I was advised that Sikaflex make a suitable sealant adhesive. Does anyone have an opinion about this compared to Würth or any other Adhesive sealants?

 

I intend to fit over length C-Channels to avoid the downwards loading being at the end point of the channel and hence the weakest bonding point. Again does anyone have an opinion about this potential remedy?

 

Many thanks is advance

[Derek Uzzell]

The specification of the Wurth product you mention is given here:

 

https://eshop.wurth.co.uk/Glass-clear-adhesive-sealant-ADH-GLS-MET-GLASSCLEAR-290ML/08932250.sku/en/GB/GBP/

 

SIKA, or Henkel Loctite, may market an adhesive/sealant that would be more appropriate for the task than “Glass Clear”, but Wurth may do that too.

 

SIKA, Henkel Loctite and Wurth all market a wide range of adhesives - the challenge is not so much selecting the right manufacturer, but selecting the most appropriate product. It might even be that - in your case - merely ‘gluing’ the awning C-channel in place might not be a practicable approach and that ‘mechanical’ fixings (eg. screws) might also be required.

[globebuster]

I'd say that the Wurth product used was not suitable - in fact the total opposite.

 

I suggest you go on the Sika [other brands are available] website - is the substrate this rail is bonded to painted aluminium or GRP/Polyester?

 

It will have a bearing on your choice, and whether a primer is required.

[Derek Uzzell]

Malcolm’s motorhome is a Rapido 8094DF (photo of example attached) so the bodywork’s outer skin will be polyester.

[Malcolm Greenhill]

That's it!

 

Unfortunately the awning light is right where the awning channel should be so the Dealer had to fit it at almost maximum height. Height range 2.5 - 2.65m, fitted at 2.6m The front wheels were half way up small Fiamma levelling ramps. This contributed to the problem, however;

 

I had an extremely comprehensive response from Würth's technical department;

 

The glass sealer is probably not the best product to use due to the downward force applied, this product only has a shore hardness of 38 so it is more flexible than strong.

 

1. How do I remove the Glass Clear Adhesive sealant? Do I use a ‘toffee-wheel?

 

Yes you will have to use mechanical removal, a toffee wheel will cause less damage to the gel coat but may take some time to remove all the sealer.

 

2. The rail is under considerable downward (lateral) pressure where the side walls of the awning are pegged down. This is always at either end of the rail where there is only a bonded length in one direction therefore at a relative weak point. When replacing the rail would it be beneficial to fit a longer rail so there is a longer bonded length either side of the maximum downward force.

 

A longer rail will distribute the load better so if you can extend the rail this will also help with the distribution of the downward force.

 

3. Did the aluminium rail fitter use the correct product when bonding the rail? Is there a more suitable product. Another product called Sikaflex has been mentioned to me.

 

Probably not, they may not have known the required strength needed to hold the rail to the body once the awning was pegged down, cleaning the area and contact points correctly is also extremely important as well to make sure you get the best bond.

I would suggest something with a higher shore hardness but not something that will dry ridged as this will crack if it has no flexibility at all, so I recommend using our MS Adhesive Sealant 0893 225 1 (white) , this is an MS polymer base the same as the glass sealer that has been used but with a shore of 60 which will make it a lot stronger.

 

https://eshop.wurth.co.uk/Adhesive-and-sealant-MS-MS-ADHESIVE-AND-SEALANT-WIT-310ML/08932251.sku/en/GB/GBP/?VisibleSearchTerm=0893225&CampaignName=SR001

 

 

4. I noted that the thickness of the Glass Clear Adhesive sealant left on the motorhome is approximately 1mm. Your website states;

“A minimum adhesive layer thickness of 3 mm is recommended to harness the benefits of thick-coat bonding”.

When refitting the rail would it be beneficial to use a thicker bead?

 

3mm is recommended to make sure that when pushed down a good amount of product is distributed and makes good contact points along both substrates. You can apply a larger bead, this will extend the curing times but I would not apply more that 5mm as the more sealer between the two substrates can also cause a weak spot as you want all 3 areas to take the strain of the downward force.

 

[Malcolm Greenhill]

Globebuster, you are absolutely correct. See Würth's response in my last post

[Malcolm Greenhill]

Update.

 

The dealer, now armed with the feedback from Würth, is collecting my MH (300mile round trip), will be removing the remaining C-Channel section and refitting a complete, longer, new channel using the correct bonding agent.

 

They will also be attending to some other minor remedials at the same time.

To quote Jamie Lawson's lyrics, "I wasn't expecting that"

[mjay]

I bought an airbeam awning for our Bailey and asked for a rail to be fitted while having my last hab.check and was advised that the grp/insulation/grp sandwich that the body is constructed of may seperate in high winds with the weight of the awning attached so didn't bother just to be on the safe side.

[monique.hubrechtsgm]

if you have read my comments about this carefully, you should be aware that bonding a c-rail, or using the c rail of the existing awning is not good practice to put a Kampa of that size.

[monique.hubrechtsgm]

you can scew a c channel to a proper fiixed awning. The answer as you stipulated is just Nonsens.

[globebuster]

mjay has a valid point.

 

I would not expect the outer polyester to be more than 1.5/2mm thick, and indeed 'loading' a small area could well create delamination from the sandwich construction.

 

If there is no frame or reinforcement located within the mounting area any mechanical fixing will be pointless and useless, and almost certainly undermine the integrity of the outer skin.

 

 

Perhaps tight under the top capping that runs the length of the van would be a better point to locate the rail [if that's viable] clearly they'll be a bit more 'meat' and torsional strength.

 

 

If bonding only I would suggest Sika 292 BUT I would absolutely use a primer - probably Sika 210 T

 

 

Even the best sealants are only as good as the correct procedure recommended for the substrate/material concerned.