hi i have an 88 Ke station wagon with a roof aproxximately oooo say 2 and i bit Metres long and when i listen to music albeit enthusiastically it resonnates..... if i hit a small pot holl it sounds like it will bend .. suggestions to ease this , not limited to dynamatt

obviously dynamatt, anything that will add mass to the roof will help, metal ect or any kind of bracing should help aswell.

how well would 3mm~9mm MDF work

I dont think it would really work all that well. The roof isn't completely flat and straight, parts do curve, meaning getting the MDF to stick will be difficult. Attaching the MDF is also something that will have to be considered.

Whereas deadening in general should stick and be able to mould to the shape of the roof, which is a good thing.

ok s/ding seems to be the goer now , should i cover the entire roof or concentrate on the worst part.........

Depends how much you want to spend? If you can afford it something like 2x bulk packs should get rid of any flexing you have I would imagine, would easily get a couple of layers.

If you don't want to spend a huge amount, focus on the areas that are the worst for flexing/resonating/weakness and put a few layers on there to add some more mass to it.

If I read it correctly, you have a large open roof area that easily flexes when you play music yeh? So its not exactly very stiff?

If so, then dynamat will make it considerably worse off, not better. The problem you have is the roof is fairly thin, and it uses its internal tensile strength to maintain shape. By adding mass to the roof (which is what you will be doing with the dynamat) then you'll increase the tensile stress on the metal. The roof wasnt designed to take that stress, and will displace itself (bend). That = bad.

What you need to do is brace the roof, to remove the tensile stresses. Think of ribs. What this will do is increase the points the stress is supported (and therefore where the force = 0) and lower the overall stresses at the extremes. THEN you can apply dynamat to lower the resonant frequency.

MDF is a great cheap way to brace (think those balsa dinosaurs you had when you were a kid), but obviously the best is using tubing welded to the roof, made of similar metals. In the end though, cost will be the largest factor, and you're determination on whether its worth it or not.

i have spare 18 mm mdf would it work to make .. "ribs" similar to those in the back of ute with leather tops.. is that what you mean

go the mdf route with svrews and then also add bracing of 1x2s or sumthin betweem the mdf and the foof drill into the parts wre the roof brace is and fill the vo=ids with SPRAY FOAM INSULATOR works well for wall constuctions and huge splers why not a wagooooon

voids of what....