Scale Soaring UK

Is it me or is there a wide variation in density, even among supposedly the same brand and "type" ?

e.g. Bought a 4 pack of Jabalite 50mm insulation board (50mm thick polystyrene sheets) that were uniform white particles

https://www.diy.com/departments/jablite ... 643_BQ.prd

Then needed some more (I'm teaching myself to hotwire wing cores!) and they had the same brand, and apparently the same type / package name etc, but the contents were a mixed white / black particle. These seem to me to be lower density. The resulting cores seem more flexible too and visually, they seem to have more gaps between particles too...

rant /over.

Marc

Sorry to hear that Marc. I have noticed that the black/white beaded foam is very weak and breaks off in big lumps. I think it may be recycled stuff. So you'll be saving the planet, although your wings may fold.

I have made wings out of the black and white stuff and have had no problems. I have add problems with blue foam wings bending after veneering and also blue foam delaminate when using latex glue.

I've found the recycled white bead foam does vary in quality, I've bought batches where the black
bits are so hard it's impossible to get a good cut. Try and source virgin bead white foam if you can.

Better still is pink or lemon coloured XPS foam.

Like Roo, I've had problems with blue foam, though it's probably due to me not using it enough
to get my setup correct. I've heard that skimming the top and bottom 5 or 10mm off a block will
release the torsional forces inside so you don't get any twisting or bowing of the core.... not quite
sure how and why this works though!

My current stock is from Wickes ,It has the black blobs in it ,but I'm happy with the density .It has a blue "hue" to it and is quite firm ,perfect for large scale spans.
I guess it's a case of grading as you purchase ,much the same as you would balsa.
I used to cut the shiny surfaces off of blue xps blanks as they formed a meniscus of sorts ,where once the core was cut ,the surface tension would curl the blanks.

Paul W wrote: ↑25 Apr 2021, 11:05 I've found the recycled white bead foam does vary in quality, I've bought batches where the black
bits are so hard it's impossible to get a good cut. Try and source virgin bead white foam if you can.

Better still is pink or lemon coloured XPS foam.

Like Roo, I've had problems with blue foam, though it's probably due to me not using it enough
to get my setup correct. I've heard that skimming the top and bottom 5 or 10mm off a block will
release the torsional forces inside so you don't get any twisting or bowing of the core.... not quite
sure how and why this works though!

Thanks!

So, where to find the pink / lemon XPS? It that a local thing or mail order typically?

M

Try Sheffield Insulation or SIG.
They have branches all over the country.
Worth also trying local roofing contractors.
They often have offcuts that suit our requirements.
Hope that helps.
Mick

mjcp wrote: ↑26 Apr 2021, 12:27

So, where to find the pink / lemon XPS? It that a local thing or mail order typically?

M

As Mick says, try and track down a local insulation supplier. I've found one in the
past that gave me several sheets (which they'd cut incorrectly or were damaged)
in exchange for a contribution to their tea and biscuit fund.