Fibreglass / GRP panel trailer cutting for access panel

[Harry44]

Hi guys,

I use a 14ft blueline box trailer for transporting my small classic mini around, to make strapping it up a bit easier i have ordered a pair of custom access doors to fit into the front of the trailer. Wondering what the best way to cut the GRP is, i have the usual air saw (which i think is my go to) reciprocating saw, multi tool cutter and jigsaw.

Wondered what people have used in the past and if any advice can be given, i have to cut around a 800x350mm rectangle in each side, then bond and bolt the panel in. Made of aluminium with white covering so will look good and the rigidity in the panel. Owned the trailer for quite a few years and its been great for transporting project minis around but now i want to make some changes to keep the finished cars a bit safer in there.

 

[Bullet2012]

Chances are it is some sort of sandwich construction, either grp over plywood or most likely grp over foam.
personally I would cut both the inner and outer skin with a 1mm slitting disc and then use a jigsaw on the core.
a jigsaw will probably be the tool to use on its own .
Use masking tape on both sides of the area to be cut, use the tape as the centre of the cut.

 

[hotponyshoes]

Depends how neat younwant the finish,
On horse box sides I pop a couple of homes in opposite corners with a spade bit then jigsaw around with a rough blade just inside the line.
Then drop a template over and run around with a guided router bit.
Blow off with the air line then brush with epoxy resin to seal.
If I am likely to be in there again I run around with fibreglass tape while the epoxy is still tacky.
Drop the door/hatch in the hole, drill the holes through the outer skin, masking tape around then remove and refit with sealer putting a blob of sealer in the screw holes as well.

 

[Fastdruid]

1mm slitting disk works very well. Just ensure you have the correct PPE. Fibreglass itself is pretty safe, if a bit irritating. The dust from cutting or grinding though is nasty stuff, wear a good mask, googles and long sleeves etc.

 

[addjunkie]

1mm disc last time I did it. But masked up to try to avoid cracking gelcoat around the edge.

 

[James1979]

As above slitting disk, 1mm or 0.8. Also agree with PPE. I got covered last time I did anything like that. Hate to think what it’s like in your eyes.

I’ve never had much success with anything that reciprocates. It seems to shatter the material if you’re not extremely careful. May just be me mind!

 

[Fastdruid]

I’ve never had much success with anything that reciprocates. It seems to shatter the material if you’re not extremely careful. May just be me mind!

It seems to work well if you've got a good "brace" on the material to stop it vibrating around. On something that isn't that stiff or can flap about it doesn't seem to work very well.

 

[James1979]

As the op doesn’t mention a grinder I’m assuming he’s only got what’s mentioned. Out of that lot a multi tool would be my choice. If you run the blade at 45 deg they don’t snag so much.

If you used the jigsaw or recip saw I wonder if you could bolt a bit of sacrificial ply to it and cut through the lot to stop it vibrating?

 

[hotponyshoes]

If you are doing it on the trailer just get a mate to push against the panel to stop it vibrating.
A multitool is a bit slow but will be fine for a one off job.

 

[addjunkie]

If using a recip saw Id use a metal cutting fine toothed blade.

 

[hotponyshoes]

I'd be wary of a rip saw, if it jumps on you at best the foot will mark the panel, more likely it will crack a big lump of the skin off.

 

[Barking Mat]

Angle grinder, every time & Ppe.

Get trailer well level with a spirit level, marker pen, on the bottom of spirit level.

Set squares, so it's straight, grinder time.

Wipe edge with sand paper, line up access panel, Mark holes, remove panel, drill.

Wipe with acetone, bead on inside lip of panel, silicon sealant or p.u.

Assemble, wipe off excess goo, before it sets.

If you don't have an angle grinder, go beg , borrow or buy one.

My thoughts, how we do boat windows...

 

[Barking Mat]

Nice trailer and inspection panel incidentally.