Note on the following post:
Graphite Dave put together an install post a while ago here:
https://sprinter-source.com/forums/showthread.php?t=15278&highlight=orton+diy+fan
In that post he included a PDF file that is extremely helpful, along with his idea of re-enforcing the fan. I'm following Dave's lead completely. This was all his great idea
Thanks Dave!
That said, I'll continue with writing in my "way too much details that nobody cares about" fashion
******************************
How to install a Maxxair Fan:
Episode 1: Preparation
So tomorrow is the big day.. cutting a 14" square hole in the roof

to install the Maxxfan. I worked for a while this evening getting things ready for tomorrow so that my "exposure" time when the van is cut open is minimal.
Making sure I have all the stuff I need (I'd hate to have to run to home depot with a hole in the roof

)
Butyl tape, primer (to prime the metal after I cut it - re-sealing the paint), masking tape (to hopefully keep the primer from getting where I don't want it), OSI sealant (for my second layer of waterproofness) and a caulking gun, Dynaflex 230 (for my 3rd layer of waterproofness:
The maxxfan includes a little plastic lip that goes in the hole, and then that lip bolts to the roof and the fan bolts to the lip. You can see that mounting lip in this photo I've posted before:
The issue with a Sprinter is that the roof is a whopping 1/8" thick. Not thick enough to bolt the fan frame to. So the solution is to build a 3/4" wooden frame that'll go inside the van and the fan will bolt to it. I just made this one out of 3/4" by 1.5" pine:
I threw away the woodscrews the fan came with for mounting and got all stainless hardware with nylon lock nuts:
The next potential issue is that over time, the plastic frames of RV vents/fans tend to weaken with age and then crack around all the bolt holes.
I really do want to (in a perfect world, knock wood) keep this thing for 10+ years... and I don't want to have to redo the roof vent (or develop leaks) in that time. Solution? An aluminum reinforcement strip all the way around on top of the stock plastic mount (as per Dave's idea)
First I cut two 17" pieces and two 12" pieces:
Then drill holes 3/8" back to line up with the holes in the plastic.
The four corner holes are 9/16" back (as per Dave's PDF):
and voila!
This is how things will go on the van:
My aluminum on top, then the plastic stock mount, then my layer of butyl/goop/etc, then the roof of the van, then the wooden box on the inside of the van. Then bolt it all together (I hope!).
I still have to around the corners of the aluminum and make it fit/look nice.
The Plan:
So! In the morning, if everything goes to plan I will...
spray the aluminum strips I made with the white primer.
create a 14" square template out of some light masonite.
use the masonite as a template to get the hole exactly where I want it.
Drill each corner with a small drill bit.
Drill each corner with a 7/8" hole saw to give me nice rounded corners that are tangental @ exactly 14".
Cut the square out.
Lightly sand the edges, tape off, and spray with primer inside & out.
Let primer dry.
Go around the edge of the hole with 320.
Go around the 320 with butyl tape.
Put the plastic mounting frame in the hole.
Go around the mounting frame with OSI.
Put my aluminum strips over the mounting frame.
Squirt some 320 in each bolt hole and then insert the 16 bolts.
Bolt the wooden frame up to the 16 bolts from the bottom.
Squirt some 320 on each bolt head to make sure every bolt is completely waterproof
Let it set up for a while.
Insert and mount the maxxair in the hole.
...then I'll try and figure out how to wire it up and make it work
(sorry.. I wrote all of those steps for myself to reference when I'm doing it

).