I've just about run out of projects to do to our 11 year old 1997 Bailey Pageant Champagne , so have been thinking about updating it slightly.
The light vent over the sink and cooker is looking very sorry for itself. The fly screen has black dots all over it, and the light shade looks very grubby. I did think about renewing the flyscreen (have tried washing it etc), and also changing the top light shade. Both items would cost about half what it would cost me to get a Mini Heiki 400(mm) roof light/vent.
The Heiki would look much better and give far more light. The 400 model is a direct replacement for my 400x400mm existing vent.

• I went with W4 mastic and Sikaflex 512 on the leading edge!
• The main reason I used some 512 was that the front of the vent sticks out further than the rest.
• I had used 32mm on the front of the vent, and 19mm on the rest of the edges.
• I then surrounded the hole in the roof with 19mm to give a double seal.
• This left a slight gap at the front that although water tight, could have caused problems in the future. I should have used 32mm on the leading edge of the hole...DOH!)
• I just used 512 to fill the gap, and to make sure the leading edge will be water tight when towing.
• The old vent came out a treat, and I found that meths didn't work on the old mastic and white spirit did.
• The total job took me about an hour and a half, which includes laying everything out to packing the tools away etc.
• The cupboard nearest the vent will not open fully without touching the vent casing.
• I plan on either rotating the door, or making it drop down.
• Or I will have to fit kitchen fridge door type hinges that drop down slightly when opened etc.
• Worst case I will fit sliding hinges!

First shot shows the ladder used. The dust sheet was to protect the awning rail

This was the old and black spotted roof vent

You can see how the vent has aged

The first thing to do is unscrew the old inner surround

You can now see the caravan roof and wooden surround

Outside, you need to carefully cut around the old mastic

Once done, you can gently prise the old roof vent up

This will leave a lot of the old mastic that needs scraping off.
An old wooden spatula will help!

White spirit will dissolve any remaining mastic.
I used plenty of kitchen roll to wipe off the excess.

Once all the mastic was removed, I used some Fenwick's caravan cleaner to clean the entire area.
I then used some Meth's to give the area around the vent a final clean. Use plenty of kitchen roll to make sure no residues remain.

I test fitted the vent to make sure it would fit.
I then got two rolls of W4 mastic. (19mm/32mm)

I used 32mm roll on the leading edge, and 19mm on the remaining three. Make sure you over lap the corners. Before fitting the vent, I also put an extra seal of 19mm roll around the caravan's hole. (To create a double seal)

I then dropped the Mini Heki into the hole, making sure the gaps were even each side. The vents hinge faces the direction of travel etc.

Inside, the vent is ready to receive the inner surround

Next two pictures show the inner surround fixed to the top vent. I had to cut 4mm of each lug before fitting.

I fixed each screw lightly before tightening them all up. I crisscrossed each screw to make sure of an even spread of pressure.

I noticed that there was a gap at the front due to me using 19mm to seal the caravan hole. I should have used 32mm like I did on the vent!
It was actually sealed, but looked like a gap.

Inside the final covering shroud was fitted, and all looked well

Here's the final inside shots showing the blinds...

Well that's it folks. It took about an hour and a half, and cost about £90 for all the parts.
It has made a big difference to the light inside the caravan, and the vent allows a lot more hot air to vent on the sunnier days and when cooking!