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Old 04-30-2018, 05:42 PM   #11
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Thanks for the insightful comment.
If you would have actually read the entire post, there was no mention of using it for bikes. but yeah.

Quote:
Originally Posted by Jeffrey View Post
If you think I'd trust my $7.5K bike to a piece of tape on the roof, you've been smoking too much cheap wine.
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Old 04-30-2018, 06:15 PM   #12
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Originally Posted by rean1mator View Post
Thanks for the insightful comment.
If you would have actually read the entire post, there was no mention of using it for bikes. but yeah.
I think he is responding to your original question asking if anyone else has used VHB tape to mount racks to their roof. He uses his racks for his bike so for his purpose that would not have been secure enough or worth the risk....

I tend to agree almost regardless of purpose for the racks. Just bolt them down and you won't have to second guess yourself.
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Old 04-30-2018, 06:28 PM   #13
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VHB Tape to mount Thule Tracks

I was actually just at my local independent everything and hardware store today and was talking with the owner about this stuff (heís a car guy, knows my rig and lots of others with expedition type vehicles) and said a friend had just purchased an Earthcruiser whoís done a bunch of research into the product including correspondence with 3M, and is planning on using it on his roof to secure tracks as drilling into the top would void the warranty. I believe he said it was to hold a kayak, with absolute confidence from 3M for the application.
Following proper protocols with regards to surface prep and the ambient temperature during and after installation of this product is important to follow. I was told that heating up the surfaces being worked on and heating the 3M tape just prior to contact will significantly help in the adhesion process. Itís also important to make sure the ambient temps once adhered to remain above a certain temp for a period of time to allow for proper cure to occur.
Thereís also a local solar installer that came up with a solar panel mounting foot that uses this stuff too.


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Old 04-30-2018, 08:29 PM   #14
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Looks ok for locating, I don't know about sealing performance. Anything I put on the outside of the van is going to be through bolted (preferably with stainless steel bolts and nylocks), and bedded down with something real sticky. I'll probably loop a safety cable through it to boot.
I'm responsible for my load when going down the highway.
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Old 04-30-2018, 09:33 PM   #15
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Just post a sign that says "Roof rack is attached with tape" in your rear window and you'll never have a tail-gater again!
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Old 04-30-2018, 11:08 PM   #16
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I just re-read the first post and caught a detail. The bottom of the track is plastic, but surely the main track is metal, right? You gotta ask yourself, "How is the plastic attached to the metal, and do I think it's as strong a bond as my VHB when the engineers at Thule knew the plastic would be sandwiched between the metal rail and the roof by screws?"

Sorry but I have never seen one of these tracks in person.
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Old 05-01-2018, 01:22 AM   #17
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These pics will give you an idea of the Thule tracks. The plastic piece slides into the metal track extrusion. The plastic piece has groves that are captured by the metal track.( See the third picture) It is not a "tight" fit and the plastic slides very easily. As you can see in Pic 4, the track comes with holes drilled every six inches and the plastic piece has matching holes. The cross sectional view will show you the bottom of the metal piece is not flat and the wide center flat section is about 1 mm above the outer edges. The bottom center flat is 1/2" wide and the two outer surfaces are 1/8" wide. Overall width of the track is 1 5/8". (Pic 2) Hope that helps, let me know if I can get any other info you might need on the tracks.

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Old 05-01-2018, 08:42 AM   #18
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I've used various flavors of VHB tape on many projects for work; and it is amazing stuff.

One question for the doubters on this thread...have you ever used the stuff or played with it?? It's shear strength is quite high......the failure mode I would be most concerned with is the foam failing in tension; although for roof rack loading things are pretty much in compression, except for washboard fire roads and perhaps some amount of lift from wind.

I've got a small electrical pass-through box adhered to my PH roof with VHB, works great...been up there for a couple of years. I reworked the box a couple of years ago and had to remove the old tape....best way is slicing the foam with a razor then cleaning off tape with solvent like acetone.

With tape, it's all about surface area....
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Old 05-01-2018, 10:35 AM   #19
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Thanks for the pics, Ray. I've considered using track like that, rather than mounting to the drip rails. Don't really want to drill a bunch of holes in my roof either without being really sure of myself. Which is also why I've researched the VHB question a little bit.

VHB is in its element if used to attach a broad, flat panel, when you can cover a significant amount of area with tape, to support the weight of the panel. Not so much for heavy loads that attach at a few points. When you take a system that was designed to work with screws, which can handle thousands of psi, and substitute tape, which can handle single-digit psi, without changing anything else, you're setting yourself up for failure. In OP's application he is changing something, in that he's covering as much area as he can, but I just doubt that it's enough.

Re Boywonder's question: yes I've used VHB for stuff around the shop -- mounting signs and whatnot, as well as action camera mounts (which I've seen fail just from a motorcycle helmet sitting in the sun -- tape just lets go), and I know how strong it is. I know that 0.26 psi design stress is underrating it significantly - for short term loads. Think dynamic loading like braking and going over bumps. It's the long-term load with temperature taken into consideration that drives 3M's 0.26 psi recommendation.

BTW 0.26 psi is what I worked out when converting from SI units in the paper I linked earlier. I've seen literature for the American market stating "4 square inches of tape per 1 pound of load (0.25 psi)," but I couldn't find the link when I looked yesterday.

Sure, at any given moment, the tape might be stressed to 50 times 0.25 psi, or 12.5 psi, and not fail. That's because the failure mode to be concerned with for "permanent" applications of VHB is creep, which takes time at load, and happens faster at higher temperature. Creep is the same phenomenon that explains why the pressure sensitive adhesive "wets out" the substrate over the course of 24 hours after application. 3M's guidelines state that you should try to achieve 15 psi in the tape during application to get the process going.

You can see this for yourself quite easily if you take a piece of scotch tape and set it on a smooth surface like glass or plastic where you can see the interaction going on between the tape's pressure sensitive adhesive and the glass. Don't press it down hard like you normally would but just set it there and poke a few spots close together with your fingernail. You will see the tape "connecting the dots" by itself between the spots that you started. This is what's going on with VHB in the hours after you first apply it.

From what I've gathered, 3M's biggest market for this product is architectural facade, like steel panels on a skyscraper. 0.25 psi is what 3M recommends so that the weight of the panels is supported indefinitely. If you exceed that stress you start risking failure due to creep. The wetting out process reverses due the the sustained load and the tape peels off at a much lower stress than what it can handle for a transient load.

I'm not trying to scare or discourage OP; just trying to provide info so he can make an informed decision.

[Edit]: Found the link to the data sheet with more detailed info on 3M's website.

https://multimedia.3m.com/mws/media/...-vhb-tapes.pdf

See p. 7, "Use the right amount of tape."

When I said their biggest market was architecture, that was probably wrong. They're selling VHB to many markets like consumer electronics, signs, etc.

A more accurate statement would be, "Their most safety-critical market is architectural facades." When you absolutely can't tolerate a 100 pound piece of sheet metal falling off the 80th floor...
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Old 05-01-2018, 12:14 PM   #20
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Here are a few related links......and one more point.....if the VHB holds the rack on the paint........the paint also has to hold the rack on to the primer and the primer has to hold the rack on to the metal substrate.....

https://sprinter-source.com/forum/sh...ad.php?t=50688

https://sprinter-source.com/forum/sh...ad.php?t=36186

https://sprinter-source.com/forum/sh...ad.php?t=36137



I don't have time to read all of these so YMMV
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