Suggestions for Engine cover core material for B25

[ianupton]

I removed the waterlogged core material today from my 1962 B25 engine cover.

I probably removed about 50 lbs of wet rotten material.

What should I use for new core?

I was thinking 1/2" corecell (foam) on the sides and 3/4" on the top.

I'll put the sounddown on top of that.

Am I on the right track?

Ian.

[CaptPatrick]

Ian,

Corecell will do fine. I used Klegecell on "Buddy Boy", pretty much the same stuff, just different manufacturer.

In order to get a true structural composite sandwich, glass over the exposed surface, (after bonding in the foam), with a layer of 1208 biaxle cloth. Without the layer of fiberglass the top of the box will have a fair amount of flex, eventually leading to delamination of the foam.

Get a faily true & flat surface to work on and use heavy weights when bedding down the foam. Notice that I added two more stiffeners on Jim's boxes. When all glassed in, it becomes far more rigid that the original boxes. I did the bedding with the boxes down on the concrete floor.

Be sure to carry the glass well onto the exposed areas of the engine box...

Br,

Patrick

[ianupton]

Thanks.

With as waterlogged as it was, it was quite a bit more rigid than it is now.

She's 'floppin in the breeze'.

1 layer of 1208 is sufficient?

Ian.

[CaptPatrick]

Ian,

One layer was all I felt necesary for Jim's, but you can add more layers if you like. The more you add, the stiffer it'll become...

Compressive stiffness builds faster with thickness of the core.

Br,

Patrick

[ianupton]

How much resin should I buy for this? I will be able to figure out pretty easy how much glass I'll need, but how much resin will a yard of 1208 or 1708 suck up?

It looks like corebond only comes in quantities larger than I need. I'm planning on mixing my own with cabosil and poly resin. This should be OK correct?

Ian.

[CaptPatrick]

Ian,

Different amounts of resin are required to wet out different forms of fiberglass.

For example, one gallon of resin will wet out approximately the following
amounts of fiberglass:

40 square feet of 8 to 10 oz. cloth
50 square feet of ¾ oz. mat
30 square feet of 1½ oz. mat
35 square feet of 24 oz roving

based on that, 1708 & 1208 will be about 38 square feet per gallon. In the event successive layers of glass are laid up before previous layers have gelled, the coverage will be greater.

Don't skimp on your resin purchase though, better to have too much than not enough... Your most ecconomical volume for resin will be 5 gallon pails. Kept tightly covered in a cool dark place the shelf life can be as much as 6 months. If you only have a gallon left over in a 5 gallon pail, transfer to a new 1 gallon can to keep the container atmosphere to a minimum.

Also figure on about a 10% - 15% waste of your dry fabric through cutting and fitting.

Br,

Patrick