Here's how i installed a solar panel to my caravan.

Bought a 40 watt solar panel off ebay for £130 delivered, size is approx  .6 x .6 mtrs square, 2 slot board brackets from B & Q  .6 mtrs long ( £10.98 each ), some 2 core flex 10 mtrs long ( £6.50 ), some 6.0mm cable clips ( £1.99 ), tube of Sikaflex 291 ( 10.49 delivered ).

The correct brackets for fitting solar panels are imo very expensive for what they are ( £50 ), i think
the ones I've bought ( shelf brackets ) look much better and are made of aluminium instead of plastic.

First i drilled two holes on the sides of the panel where the brackets would fit, being careful where i drilled so not to damage the panel.
( one hole shown ).

Now i placed the bracket against the panel and marked the position of the holes, thro the ones i'd just drilled in the panel.

( one hole shown in the bracket )

I applied a bead of sealant along the line of the screw holes, then screwed the brackets to the panel.

Note: solar panels need at least a 10mm gap under them, so they can dissipate heat, the shelf brackets allow for this.

Next i soldered the wiring to the panel, note i marked plus and minus after checking with a multi-meter,
then realised it was marked on the plastic box, you may just be able to see the markings if you make the
picture bigger ( click on it ).

Fitting the panel to the roof 

The area where the panel would be stuck down was first cleaned with meths, then very lightly rubbed
 with scotchbrite, and final cleaned again with meths.
The shelf brackets were treated the same, clean, rub down, clean.

Now a good amount of Sikaflex 291 was applied to both brackets.

Panel is now stuck down ( note; i lifted it up a couple of times to ensure the sealant had good contact
with the roof surface ).
Then added a bead of sealant along the edge of each bracket.

I drilled a hole for the cable from inside the wardrobe, and deburred the aluminium skin where
the drill broke thro. Then cleaned, scotchbrited, and final cleaned the area. 
Next feed the cable into the caravan and fixed with cable clips.

Only when the cable was fixed did i apply a good amount of Sikaflex 512 ( haven't added this to the cost as
i already had some in the shed ).

I then cable clipped the cable down to the floor and around to the charge controller.
Note you need to have the charge controller connected to the battery BEFORE you connect the solar panel,
failure to do this could damage the charge controller.

Well there you have it, i hope it may be of some use to anyone wanting to install a solar panel,
i will be adding a 80 watt panel in the future and will use the same method, but will include 2
side brackets to support the longer panel.

atb

Wizard

Link to solar information  Leisure_power_advice_center

Caravans_and_motorhomes_with_Solar_Panels