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Discussion Starter #1 (Edited)
Biting the bullet and installing a MaxxAir 6200k on my medium height Transit this weekend. I've reviewed a million posts and mostly have it sorted. However, I have a few questions about fastening that no one seems to really address.


Caveat - I'm using Hein's roof adapter and installing in the back in that tight space between the roof ribs. I'm not using an underside framing strip inside the van. Or not planning to unless someone convinces me otherwise. I know Hein's interior adapter will not work in the space I'm installing it.


Q's:


1. How many fasteners did you use that fully penetrate the roof through the flange? Full penetration attachments all around the mounting flange seems like overkill and I'd prefer to limit the number of holes I drill into roof.

2. The most likely water intrusion point on the roof is the drilled fastener holes along the gutters (sides of the flange/vent, as opposed to the front and back of the flange/vent). If you're not drilling through the roof skin on all holes around the flange can I avoid the gutters (sides) and simply penetrate the skin in the front and back of the flange to avoid roof penetrations in the gutters?

3. If you didn't do full penetration fasteners all around the flange, did you still use the remaining flange holes to attach the flange solely to the Hein adapter?

4. Did you use sheet metal screws or nuts/bolts (or some combination of both?).

5. Did you use rubber washers above the roof mount flange or below against the underside of the roof skin? Seems like a good idea given the flex in the van when in motion and that the weak point in the roof mount is the flange (which appears likely to crack over time).

6. Any reason to put a squirt of silicone into the drill holes that penetrate the roof skin before screwing them in? I've only seen where folks apply it the top of the screw head but in other applications (construction primarily) it's considered good practice.





If it matters or you're interested, I'm using 3M Windo-Weld under the Hein adapter and planning to cover the whole flange post-install with Eternabond.



Thank you!
 

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Discussion Starter #3
I'd install wood frame inside. You'll need something for your ceiling and the internal fan trim to fasten to. 1"x2" battons (3/4 x 1 1/2") work perfectly

For your wood frame, did you just use the fasteners coming through the roof to secure it? That's what it looks like anyways.



BTW, that's a first rate build out. Nice work! Mine is much more amateur hour looking.
 

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For your wood frame, did you just use the fasteners coming through the roof to secure it? That's what it looks like anyways.



BTW, that's a first rate build out. Nice work! Mine is much more amateur hour looking.
Yep, I used all the factory mounting locations through the sheet metal into the frame. You'll need longer screws than provided to get good purchase if you use Hein's adapter. I used butyl tape and 3M 5200. No leaks. I purchased Eternabond to go over everything, but never bothered to install it. I guess I will if it ever decides to leak ;)
 

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I used butyl tape to level it and put one screw in the center of each long section into the sheet metal. Then, Eternabond on all four sides, covering all the screws/screw holes.

It is solid.
 

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I glued Hein's adapter to the roof and screwed the fan to the adapter. No screws through the roof. It's still there after 3 years.
 

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I glued Hein's adapter to the roof and screwed the fan to the adapter. No screws through the roof. It's still there after 3 years.
I used window weld for both sides of the adapter and put lap sealant on after everything cured. no holes/screws at all.
 

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I've done 2 fan installs using Hein's adapters.

On the first, I used window weld as he recommended. It's nasty stuff. In order to get a great 'bond', it needs the activator that's used when they do a window install using that stuff.

On the second fan, I used 3M 4200 fast cure marine adhesive. 5200 is great to use also, but is a more permanent adhesive. Both are urethane based adhesives as is the window weld from NAPA. The cost is about the same.
Make sure you get the "fast cure" 3M adhesive if you use it, not the regular cure which will take a week to harden. The 4200 or 5200 fast cure will be firm in an hour, and solid as a rock the next day. It's messy stuff no matter which one you use.

I also added supports from the rear cross rib, to the next one forward. You'll see the sheet metal is extremely thin and flimsy and really doesn't offer much support. I'm glad I did. Like the other poster said above, you'll need material on the inside of the roof that will allow you to attach the plastic trim piece once the fan is installed. The last thing you'll want is a flimsy foundation that will move, warble, or vibrate when going down the road. Do it right the first time.

I glued the fan adapter from Hein first, and let it cure overnight. It was solid the next day. MAKE SURE you scuff the paint with scotch brite, or 220 sand paper before gluing the adapter to the roof top. After that, put your upper fan flange in place, mark the holes, remove the fan flange, drill them (right through the adapter and metal roof)

Then, apply the butyl tape over the topside of the adapter. Place the upper fan flange back on top and fasten it securely with sheet metal screws. FYI the butyl tape will ooze ouf on the sides and also sag on the inside, especially when the sun heats things up.You don't have to use silicon caulk with the screws, but it can't hurt either. You don't need any leaks.
After it's all secured, I also applied GE Silicon II to the whole top side of the upper flange as well as the outside of the adapter where it meets the rooftop.
Overkill... yeah. Who cares? I don't want any leaks...

Good luck.
 

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1. How many fasteners did you use that fully penetrate the roof through the flange? Full penetration attachments all around the mounting flange seems like overkill and I'd prefer to limit the number of holes I drill into roof.
If you use adhesive or VHB tape rather than butyl tape then screws at the corners will be enough. We provide those with our adapters.

2. The most likely water intrusion point on the roof is the drilled fastener holes along the gutters (sides of the flange/vent, as opposed to the front and back of the flange/vent). If you're not drilling through the roof skin on all holes around the flange can I avoid the gutters (sides) and simply penetrate the skin in the front and back of the flange to avoid roof penetrations in the gutters?
We do not experience any leak points using our adapters when all screws are used and penetrate the roof. Just make sure to drill pilot holes through the adapter and metal. And apply membrane sealant over everything as final step.

3. If you didn't do full penetration fasteners all around the flange, did you still use the remaining flange holes to attach the flange solely to the Hein adapter?
Best if all screws penetrate both adapter and metal roof. We have an offset adapter (thick on one side due to slope of roof) on our van and not all screws go through. It has been on for 4 years and no sign of coming loose.

4. Did you use sheet metal screws or nuts/bolts (or some combination of both?).
Sheetmetal screws are fine. Some have used bolts/nuts. Just do not over-tighten so butyl is squeezed out and vent flange is depressed around head of fastener. Just snug is best.

5. Did you use rubber washers above the roof mount flange or below against the underside of the roof skin? Seems like a good idea given the flex in the van when in motion and that the weak point in the roof mount is the flange (which appears likely to crack over time).
No rubber washers are needed. Membrane sealant over the top of everything will prevent leaks. Check and renew as needed. We have not experienced any cracked adapters.

6. Any reason to put a squirt of silicone into the drill holes that penetrate the roof skin before screwing them in? I've only seen where folks apply it the top of the screw head but in other applications (construction primarily) it's considered good practice.
Again not needed but if it feels good do it. You can use a dab of windoweld for this.

Thank you for using our patent pending adapter. You may be overthinking this a little. No need to get carried away with the install. We have seen it done in a number of ways and never hear of leaks.

All the best,
Hein
DIYvan
541 490 5098
 

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Some are happy using tape to hold the fan in place. Im the opposite side of that coin.

Fast cure 5200 to glue heins adapter in place, butyl tape to seal the fan mount to the adapter. Thru bolt/nuts thru the fan mount, heins adapter,van skin, and a wood fame on the inside. The wooden frame is glued to the skin on the inside usind 5200. As someone noted, you’ll need the interior wood to attach your celind to anyway.

My fan was installed away from any ribs so the wood was used in part to stiffen things up. The butyl tape will enable you to remove/replace the assembly if ever needed.

I also used strips of 1/8 x3/4 aluminum on top of the fan mount to prevent possible cracking of the fan mount plastic. Others have done the same. Or just use fender washers and dont tighten too much.

Finally, dicor self leveling sealant over the bolt heads and aluminum strips.
 

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Some are happy using tape to hold the fan in place. Im the opposite side of that coin.

Fast cure 5200 to glue heins adapter in place, butyl tape to seal the fan mount to the adapter. Thru bolt/nuts thru the fan mount, heins adapter,van skin, and a wood fame on the inside. The wooden frame is glued to the skin on the inside usind 5200. As someone noted, you’ll need the interior wood to attach your celind to anyway.

My fan was installed away from any ribs so the wood was used in part to stiffen things up. The butyl tape will enable you to remove/replace the assembly if ever needed.

I also used strips of 1/8 x3/4 aluminum on top of the fan mount to prevent possible cracking of the fan mount plastic. Others have done the same. Or just use fender washers and dont tighten too much.

Finally, dicor self leveling sealant over the bolt heads and aluminum strips.
Nearly identical to my install from this weekend, everything went great, didn't use the alu strips on top but I can see why you might want them. I had washers on both sides and used the lightest torque setting on my drill with nylon washers inside.
 

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Some are happy using tape to hold the fan in place. Im the opposite side of that coin.
Anyone with experience trying to remove Eternabond tape will already know that it is probably easier to rip out the fan that is attached with sheet metal screws, lap sealant, and glue than it would be to dislodge one held in place with that stuff. :D

Eternabond was designed for commercial roofing applications, sealing seams and perforations on flat roofing materials for large buildings, and has an expected lifespan of thirty years or so. Many (most?) RV manufacturers have forgone traditional lap sealants in favor of Eternabond for their OEM assembly applications. It is sold in RV stores for doing roof repair. The only thing it won't stick to is Silicone.

Traditional lap sealants have plagued the RV industry and owners with problems that Eternabond tape addresses. Those traditional sealants must be inspected annually for cracks and deterioration. Eternabond's most frequent use in RV repair is application directly over cracked and leaking lap sealant as a permanent repair.

I chose the product that the industry leaders are using today, rather than what they used before finding a better way to do it.

Either method provides more than enough adhesion and weatherproofing for the application. It is only a matter of how much time and various products a builder wants to employ in achieving their goal. Choosing the product for the job should be based upon knowledge and understanding in order to select the most effective one for the application, including any periodic inspection and maintenance that might be required.
 

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I could see using the tape in place of the 5200 to stick the adapter down as I would not expect it to ever need to be removed. But I can see the potential to need to replace the fan mounting flange or the fan body itself. Eg, a branch or hail damages them. Thus the desire to use butyl tape between hein's adapter and fan fan mounting flange and the dicor over the top of it all. Ya, dicor sealant is a mess and needs to be inspected once in a while. But if the tape is used in place of the butyl or dicor, then you will have an issue if you need to replace anything.

A major drawback to the 5200 and dicor, esp. if you are a pro trying to get a customer's vehicle in & out of the shop, is they require time to setup before moving on the the next install steps. I'd expect that is a major reason the tapes are used in lieu of adhesives that have a cure time by the pros.

Ahh, so many ways, so many choices.
 

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A major drawback to the 5200 and dicor, esp. if you are a pro trying to get a customer's vehicle in & out of the shop, is they require time to setup before moving on the the next install steps. I'd expect that is a major reason the tapes are used in lieu of adhesives that have a cure time by the pros.
Well, ease of installation and fast turn-around for the customer are certainly good reasons. Add to those the fact that they won't have to look at a tape job for another thirty years.

As opposed to all the hassle you pointed out that is involved with installing the other product. A product that must also be inspected annually and re-applied, not if, but when it starts cracking in the sun.

Yeah, there are a plethora of reasons the pros will usually choose the product that best serves both them and their customers. That is what makes them pros, isn't it?

Lap sealant will work just fine, for a while. Heck, a builder may only have to reapply it once or twice more before it is time to retire their van. ;)
 

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Discussion Starter #15 (Edited)
First off, thanks everyone for the tips, advice, etc., especially Hein who responded to a few text questions as well. In hindsight I do think I was overthinking it - probably a result of working in the construction industry where I spend my days cleaning up the mess caused by improper weatherproofing...

Final install went as follows with a few comments, if anyone is interested:

1. Windo-Weld to attach Hein's adapter to the roof. Hard stuff to work with, this was a pain. Maybe 4200 is a better option?

2. Hein's adapter. Worked great.

3. Butyl tape b/t adapter and mounting flange

4. Sheet metal screws through all 16 holes, all penetrating the roof. Given how thin Hein's adapter was along the front/back, I was not confident I could securely attach a screw to it so I chose to fully penetrate all fasteners through the roof. Ultimately I think this was best, as it will distribute the stress more evenly along the flange to reduce the likelihood of it breaking and it allowed me to evenly press the butyl tape for an even seal around the entire flange.

5. Eternabond all around. Hard to apply perfectly because it sticks like mad the second it touches anything. I figured out some more efficient ways to apply it after the fact but hopefully I'll never need to use it again... It's bomber and should never leak.

The only true issue I had was that the mounting flange and the vent itself don't actually sit flush together - one corner is raised a bit. This made screwing the vent to the mount difficult and it still doesn't seat perfectly true. The mounting flange looks perfectly flat and the rubber gasket is fully set in place so the bottom of the vent must not be truly plumb and square. Unless it leaks it obviously doesn't matter...

This was by far the most stressful part of my build out and I'm really happy to have it done. Thanks again all for the advice,
 
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