Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Boot plywood deck - soundproofing

Hello all,

I’m replacing the plywood deck in the back of my 2 seater plus 4. I was doing battery work (moved it from right to left side to better balance, adding a cutoff switch), and the 1/2” thick sheet just seemed a bit ‘minimalist’. I have a nice 3/4” slab to put there. I know it won’t make an enormous difference but I was wondering what people thought about putting a layer of some soundproofing sheet on the underside?

Might keep some of the road noise down. Won’t make the car quiet by any means but knocking off some decibels can’t hurt.

Has anyone done this? The beefier plywood alone will help, but thought question was legit enough to get TM opinions.

Cheers,

Nelson

I had a related idea -- with a bit of modification to the tool area you could maybe try a sheet of plexiglas (acrylic sheet) ? That way you could occasionally remove the carpets and check what's going on (preferably not while driving.....!). I have a good local supplier and I'm contemplating getting him to cut a piece for my Roadster using the existing ply as a template.

My 4/4 had an axle ratio changed. Unfortunately it is well known that they “whine” a bit. So stuck some sound proofing material (metal sandwich sticky black stuff in the middle) under the cover board & down the front board. Plus both sides of the battery access panel. Then using carpet foam type underlay cut to same shape as the rear carpet. Finally the carpet. Whilst you can still hear the axle at some speeds with the roof (hard top)on. You can not hear it roof down.

I've used "Dynamat" beneath the boor "floor"on two 370Z Coupes which are notorious for road noise, most of which comes from the Bridgestone tyres. Subjectively there was a reduction in the road noise but the biggest reduction came from changing to Dunlops.

If you stick something below the board, ie 'wet side' make sure it's a closed cell material or it will potentially soak up a lot of water (and weight) down there.

The idea of a thicker board will help too, as the thin 1/4" stuff the factory uses tends to resonate

Changing to a thicker and stiffer sheet of plywood could introduce knock on effects viz the high tech plywood locking rings would need amendment, the carpet stud fasteners would no longer fit and extracting the sheet itself may become interesting.

How about a rug laid over the carpet if noise is an issue.

Interesting idea Peter - I'll stick with Plywood for strength/soundproofing.

Max - is the Dynamat waterproof? Jon's right, if I put it on the bottom of the plywood, it's exposed to my differential and the ground and must be waterproof.

Chris - not an issue for me, my car is a 1966 Plus 4. The plywood hooks under two metal brackets near the spare tire, and on the edge near the seats has two wood screws. that's it, very low tech! My new deck will have a hole for my cutoff switch key, and I'm mounting the switch beneath the plywood on a bracket of stainless steel - so that I can take off the plywood and not have to disconnect the switch.

-N

I just have extra custom made floor mats for driver and passenger. There was a link posted on TM a few years back to the eBay seller. Black carpeting with red trim, they suited my car but had to be cut down and re-trimmed, an expensive exercise as advertised for a Plus 8. They do protect the OE carpeting and offer some sound reduction though.

On the decking the well laden custom aluminium tool tray adds enough weight to deaden any panel reverberation.

I cut a 17 mm thick PVC backed coir door mat to shape as tailored floor mats, something I have seen done in Dutch owned classic cars.
Practical, sound deadening &, I think, looks good. I would do the same on boot floor - if a 1985 4 seater had a boot floor!

A coir mat big enough for all four footwells cost £14.50.

Thanks all. I have plus 4 logo carpets from Morgan Spares, they look great. Was thinking of the boot deck because it’s pretty large, and is basically one thin piece of wood between the ground and our ears.

Has anyone tried this stuff: dynadeck. Looks good but not cheap - the 3 foot piece is US$220.