# Drilling GRP any tips?



## lifeson (Sep 13, 2010)

I have ordered a cycle rack for my MH which I am going to fit myself.
This is going to involve drilling through the back panel of the MH    
Any tips for drilling holes through GRP panels?
I should imagine slowly, apply masking tape to the area to avoid slipping but any more tips greatfully received.


----------



## Chudders (Jul 5, 2008)

Never had the bottle to do it myself. Your suggestions seem to me to cover the safe drilling. I couldn,t bring myself to do it. Inside the vehicle it needs spreader plates to spread the load and a length of metal tube between the inner and outer skins to prevent compression when tightening the bolts and it all got to complicated and risky for me.
Good luck with the fitting.
Dave


----------



## ched999uk (Jan 31, 2011)

I think you need to start with a very small drill and work up to the size you want.

Note: I have only ever drilled fibreglass on a 1970's Reliant Scimitar and that fibreglass was thick (8-10mm).

Good Luck.


----------



## brillopad (Mar 4, 2008)

Measure 4 times drill once,

Dennis


----------



## ramblingon (Jul 15, 2009)

Use a tiny pilot drill first then get someone to support the inside with a lump of wood while you drill the correct size -let the drill bit do the work.

Below -not the same construction I know but useful information just the same..
http://www.pedelecs.co.uk/forum/electric-bicycles/4172-fitting-bike-rack-motorhome.html


----------



## ched999uk (Jan 31, 2011)

As Dennis said PLUS check out what is behind the panel, the depth and where all your cables and pipes are!!!!


----------



## peribro (Sep 6, 2009)

I'm sure this has been discussed before but do you have the "map" of the load bearing panels? I know that when I bought my Autotrail, the dealer was not prepared to fix a cycle carrier as they hadn't at that time received the details from Autotrail of where the load bearing panels were and hence where they could drill.


----------



## StewartJ (Nov 20, 2009)

Agree with all other posters start with small pilot drill and work upwards. I would stick masking tape down to panel and mark centres for holes on it this will prevent drill slipping/skidding and damaging surface. Use sharp drills to prevent edge chipping. 

Once you have small hole through as you use bigger drills drill halfway from each side if going all the way through again to prevent chipping on inside facings.

Stewart


----------



## Penquin (Oct 15, 2007)

I agree with the above tips and would add to masking tape a washer on first so that you stay within that - GRP is fairly soft from my experience and it drills easily using a bit designed for metal and NOT pushed through.

Start with a VERY small pilot hole (2mm) then gradually open up in 2mm steps. I found if you tried to use too big a bit it (a) skidded and (b) shredded the GRP sideways somewhat. Sharpness is very important.

DO check carefully what is inside if you can - both for supporting components and wires/pipes etc - although not so likely on the rear except for the wires to lights/cameras etc.

Do make sure that you use e.g. Sikaflex to seal as bolts go through - a decent seal now will prevent problems later. And don't forget the spreader bars inside.......

Also beware of tightening too much - you do not want to distort the GRP so sleeves around the bolts are useful if they are available.

Hope those extra hints help,

Dave


----------



## sheringham (Mar 24, 2006)

Agree with all that has been said before.
If you know a plumber or have the old fashioned hollow tubular hanger I suggest that you cut a number of pieces approx 30mm ( or determine the depth with your first tentative drill) long to insert into the panel through which the bolts will pass to connect onto the spreader plates. You will need 8, (each 8mm ID ) of these for the job. Seal well in and out before you tighten everything up and before completion. The masking tape (6 x 6 ") on each hole will also cater for the squeezed out sealant so that you dont get gunge over the surfaces.
With care there is little to worry about! 
I have had 2 Mhs and on each I have fitted both bike rack and omnistor/fiamma awning.

Ron


----------



## Techno100 (May 8, 2010)

Doesn't really matter as the brackets will more than amply cover any chipping and no one will know when it's lathered in Sikaflex for ever more.
Not a chip in sight


----------



## Techno100 (May 8, 2010)

Likewise today an 82mm hole and 4 small one's, what's to see? Show it who's boss 8)


----------



## Penquin (Oct 15, 2007)

Looks like a job well done, you had better reward yourself with a small amount if suitable refreshment of your chosen kind! :lol: 

Well done, once you pluck up the courage it's fairly easy material to work with,

Dave


----------



## Techno100 (May 8, 2010)

:lol: Like it's been said already the main thing is to drill in the right place 8O then a brand new 6mm bit no need for smaller one's :roll: 
A good variable speed battery drill will start nice and easy and won't run off on GRP it's too soft unlike drilling a ceramic tile.
With the wall being an average of 40mm thick the main problem is keeping your holes straight i.e. at 90 degrees to the surface. One solution is to use a piece of 2x2 hardwood. Drill a 6mm hole through a piece on a vertical pillar drill so you're sure it's square, then use it as a drill guide placed against the van wall.


----------

