MaxxFan Deluxe fitting puzzle

mrmoosehead

Active Member
Joined
Sep 28, 2020
Location
Ilkley, West Yorkshire
Something doesn't feel quite right. But I am probably over thinking things, as I am wont to do.
I have a MaxxFan 400mm version.

In all the documentation, the hole is supposed to be 400mm.
The flange fits flush to the surface.

But in all videos etc that I have seen - there is no overlap _inside_ the 400mm of the top mount or the unit itself.

But the top mount has a raised section that is about an inch wide before its aperture for the fan unit etc. This raised bit is 400mm aroudn the outside, but only about 350 internally.
It would be stupid to put that bit on the surface, as that would mean the rest of the flange was about 8mm off the surface. It would also mean only cutting a 350mm square hole.

So something doesn't add up. Anyone who has fitted these before shed some light?

Pictures to show.

2021-02-19 09.25.04.jpg 2021-02-19 09.25.10.jpg 2021-02-19 09.25.21.jpg 2021-02-19 09.28.57.jpg
 

Rixster

New Member
Joined
May 5, 2018
I am afraid I don't have very good photos with measurements, but here are a couple. It has been a year or so ago since I fitted mine but I think I just made a frame that fitted the fan and I then knew it was the right size. Then I bonded the frame to the roof, and then cut the hole accordingly. Personally, I would not cut the hole and then fit the frame.
 

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mrmoosehead

Active Member
Joined
Sep 28, 2020
Location
Ilkley, West Yorkshire
I am afraid I don't have very good photos with measurements, but here are a couple. It has been a year or so ago since I fitted mine but I think I just made a frame that fitted the fan and I then knew it was the right size. Then I bonded the frame to the roof, and then cut the hole accordingly. Personally, I would not cut the hole and then fit the frame.
Thanks. I wasn't going to cut first, ask questions later. It was just that edge inch or so that worried me, because I'd seen so many examples where I couldn't see that from underneath, or where it looked like people had cut a hole to the actual aperture, rather than around that edge bit.
If you see what I mean.
Anyways, your pictures confirm it as well. Thanks.
 

BigStevie

Active Member
Joined
May 17, 2017
Location
Highlands
I had sleepless nights wondering how I was going to successfully fit fiamma vents to the ribbed roof of the sprinter. I ended up making some steel frames with a 9mm vertical lip to compensate for the ribbing and welded them in!
 

egg-fried-rice

Active Member
Joined
Sep 28, 2020
Location
Lancashire
Here are some sizes to help you.

I no longer have the Maxxfan instructions but I think that the sizes Maxxfan say to cut are 356mm X 356mm. I increased this a little to 360 mm on mine to give me some wriggle room. Can you check this I could be wrong. Looking at your image with tape measure I think a 360mm X 360mm hole looks correct.

I also added a double layer of Mastic, some of the videos dont show this. They also dont always cover how to get the roof lining cut perfectly, I've seen videos of people doing this on the floor or a bench but it actually takes 1 min using a cheap router and the result is perfect. Do it after the fan is fitted

If you are insulating your van similar to mine, with 50mm celotex on the roof, then you need a wood frame thats 40mm thick. The frame hole size should be exactly the same as the hole you cut in the roof, in my case this was 360 X 360mm, the fan went it smoothly with bags of spare metal.

If all the above is a bit vague then I have made a set of step-by-step images on my website (its recent so you may not have seen it before), all the sizes are there. Sorry to post yet another link to this site (I am trying to avoid posting it) but theres just too much to type here.

Maxxfan Step by Step Images
 
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mrmoosehead

Active Member
Joined
Sep 28, 2020
Location
Ilkley, West Yorkshire
Hmm. There _are_ two sizes of maxxfan - 355 and 400
The 360mm on min means that 1" wide raised bit doesn't go through the hole. On one of your pictures, I can see that bit (the one saying " If you look carefully you can see a nice gap around the fan, this is were the internal cover sits ")

I suspect you have the smaller hole size.
 

egg-fried-rice

Active Member
Joined
Sep 28, 2020
Location
Lancashire
Hmm. There _are_ two sizes of maxxfan - 355 and 400
The 360mm on min means that 1" wide raised bit doesn't go through the hole. On one of your pictures, I can see that bit (the one saying " If you look carefully you can see a nice gap around the fan, this is were the internal cover sits ")

I suspect you have the smaller hole size.
Mine looks to be sat about half way or maybe less, over the edge section. But you may well be right.

mrmoosehead2.jpg

maxxfan.002.jpg
 
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mrmoosehead

Active Member
Joined
Sep 28, 2020
Location
Ilkley, West Yorkshire
350mm on the bit shown, so probably 340mm for the inner cover.
Hmm. Curioser and curioser.
Do you see the 1" wide bit I am talking about. The outer edge of that is 400mm square.
It doesn't look appropriate to have that sitting on the vehice skin because a) it has loads of gaps and wouldn't stick well, and b) the gap between the outer flange and the skin would be about 8mm high. You could put sealant in that, but the screws will pull it down. Maybe that is by design?

However, the instructions say to draw around that cowl for the cutting line, which implies that it does go like that.

I am beginning to suspect that different people have done it differently.
 

egg-fried-rice

Active Member
Joined
Sep 28, 2020
Location
Lancashire
350mm on the bit shown, so probably 340mm for the inner cover.
Hmm. Curioser and curioser.
Do you see the 1" wide bit I am talking about. The outer edge of that is 400mm square.
It doesn't look appropriate to have that sitting on the vehice skin because a) it has loads of gaps and wouldn't stick well, and b) the gap between the outer flange and the skin would be about 8mm high. You could put sealant in that, but the screws will pull it down. Maybe that is by design?

However, the instructions say to draw around that cowl for the cutting line, which implies that it does go like that.

I am beginning to suspect that different people have done it differently.
If your inner cover measures 340 mm across then we have the same fan. Maybe you can help me check my measurements. I believe Area A shown in the image should sit flush on the outside surface of your van roof with mastic in between. Area B should sit inside the van. Please check this and comment.


mrmoosehead5.jpg

maxxfanbase-002b.jpg
 

mrmoosehead

Active Member
Joined
Sep 28, 2020
Location
Ilkley, West Yorkshire
If your inner cover measures 340 mm across then we have the same fan. Maybe you can help me check my measurements. I believe Area A shown in the image should sit flush on the outside surface of your van roof with mastic in between. Area B should sit inside the van. Please check this and comment.
Yes! That is what i think. But to the edges of B is 400mm square
 

egg-fried-rice

Active Member
Joined
Sep 28, 2020
Location
Lancashire
Thanks I see it is 400mm, I am sure mine is the same.

I still think I cut the hole to 360mm so that more of the Maxxfan framework bedded into the mastic. You know its difficult to remember but I think I did this so that when it was tightened (screwed down) it didn't make the mastic too thin. I checked with Greg Virgoe this afternoon and he also cut to 360mm. There is a step of mastic on my roof and then the fan sits on top of it. If my memory serves me correct I put a single layer of mastic on Area B and at least a double layer on Area C. Use plenty of mastic it should not be too thin. Then finish the edges with Sikaflex 522.

I dont see a problem if you cut to 400mm, I think it would work fine.
 
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Sandbagsid

Active Member
Joined
Sep 16, 2019
When you cut the hole cover the roof area with dust sheets so the hot metal splinters don’t burn into the paint as after a month or so you will end up with rust spots everywhere they even get on the sides of the van . Voice of experience when I cut my fan hole in the roof cos no one told me lol.
 

Keith Alexander

New Member
Joined
Sep 6, 2018
Location
North Shropshire
A hint, Imho there is absolutely no need to drill the 20 odd holes through your roof for all the unnecessary screws.
Just use a decent sealant like PU40 and clamp it down it will never ever come unstuck.
It may take a few months but one of the bastards might leak eventually as I found out.

 
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