MDF plywood for sides

[rwelp]

I have read as many posts as I could find for sides of a teardrop. Does anyone have any opinions for using plywood with an mdf core for sides of a teardrop? I can get 4x10 sheets of birch ply but it is has an mdf core.
Rob Welp

[caseydog]

That should be good and stable, but how is the weight?

CD

[halfdome, Danny]

MDF core basically is used so the underlying veneers don't telegraph to the top finish veneer. It's used for table tops and other interior applications. That said, if it ever gets wet it will swell up. I'd avoid using it if possible. I use a MDF & ply core panel for the carcass of my galley cabinets just because I have lots of 24" rips left over from a prior job. It's well protected from the elements. You can spline plywood veneer sheets together and if your making a Woodie do the lattice work to hide the joints. Danny

[eamarquardt]

IMHO MDF is good for filling up dumpsters! It is inordinately heavy and has little strenght!

Cheers,

Gus

[rwelp]

That should be good and stable, but how is the weight?

CD

MDF core basically is used so the underlying veneers don't telegraph to the top finish veneer. It's used for table tops and other interior applications. That said, if it ever gets wet it will swell up. I'd avoid using it if possible. I use a MDF & ply core panel for the carcass of my galley cabinets just because I have lots of 24" rips left over from a prior job. It's well protected from the elements. You can spline plywood veneer sheets together and if your making a Woodie do the lattice work to hide the joints. Danny

IMHO MDF is good for filling up dumpsters! It is inordinately heavy and has little strenght!

Cheers,

Gus

I am planning on insulated sandwiched walls and using 1/4" ply so weight shouldn't be too much of a factor. I can scarf join 2 sheets of 5x5 sheets of baltic birch ply for about the same price as a 4x10 sheet of mdf core ply. As a woodworker the only thing I use mdf for is jigs. The thought of using it for exterior walls didn't really appeal to me. I just wanted some other opinions.
Thanks,
Rob

[whitefishpoint]

mdf doesn't take fasteners well.

http://www.cnczone.com/forums/archive/index.php/t-25126.html

[wannabefree]

MDF has several problems -
1 -- it's heavy, and strength to weight ratio is very low
2 -- it will sag on the horizontal
3 -- screws will pull out of it easily
4 -- it is more like a compressed sponge than wood. Just add water, and watch it swell!!

#4 is the big problem. MDF has a place, but kitchens, bathrooms, and teardrops are not among them.

[madprinter]

I used MDF for my front shelfs around my A/C and fridge. It was'nt totally finished and has no paint. The moisture from the A/C made it swell and now I see surface mold. Its got to go. I would be very leary of using it for anything else in an outdoor setting. Good luck with your build and keep us posted as to your progress.

[afreegreek]

I've never seen plywood with an MDF core but there are several types of sheet goods made with MDF outer plies. most are veneer core others are wood strand or OSB core. the MDF serves as a smooth base for laying up veneer, plastic laminates, metal laminates on, or to paint. as others have mentioned MDF is weak in some respects compared to veneer core plywood and is heavy.

MDF is Medium Density Fibreboard. it's wood fibre (pulp) just like they make newsprint from. what determines it's suitability for exterior purposes is the adhesive it's made with.. there are MDF products made specifically for exterior or high moisture applications as well as fire retardant applications however the type of composite sheet you mention is very unlikely to have that adhesive used in it's manufacture. so I would stay away from it.