Lowest Cost, Acceptable Foam For Core?

The problem with this is that you are hand laminating so the slits will not get filled with resin.
Also I think it will give you problems when lifting out and rotating the half hulls as the deck will be too floppy.

 

I would fill them from the outside, if I could find any. The compression on the inside part of the blocks is so great, the slits become invisible. There is perfect contact between every single block of balsa (on the inside) due to the complex curve of the deck. There aren't any slits inside at all. Only very very small ones on the outside where the scrim acts to hold the slits extremely close, in contact, actually. I'll take some pictures when I get to that stage. There really are no slits to fill. Take some scrim balsa and bend it the wrong way. It turns into a solid sheet of balsa.

I'll have to think about the floppiness.

So you have balsa, bonded to skin on one side and scrim on the other. This should be as stable as any foam core. The issue might come when you go to remove the scrim. Then it may become floppy, I'd think.

 

We would wet the sheets laid over a drum scrim side down before placement.

 

Problem solved!

War Whoop: How many boats have you built?!? 1000??

You seem to have the answer to every single problem a builder runs into.

 

Sir quite a few,Good luck.

 

Thanks for the help. I gotta try out the rep points thing for that.

 

Cat,Thank you!

 

Here's a good description of how to work with scrim/block balsa:

http://www.corematerials.3acomposites.com/uploads/tx_abdownloads/files/Guidelines_Balsa_komplett.pdf

 

Hmmm... my balsa supplier (NidaCore) said the scrim is designed to stay in the laminate, not be peeled off.

 

They change the design of the scrim now? so it measures "0" in cross section? The problem is it's presence aside from whatever it is made from, raises the laminate off the core.

The answer is NO you do not have to remove it ,but I have seen failures that can be attributed to it's presence.

 

thanks for posting that Catbuilder. helpful stuff

 

Glad that helped, Charly.

A warning or anyone new to foam. You can DIE using it. I got some pretty bad hydrogen cyanide poisoning this week. Not bad enough that my systems were failing, but bad enough to make me very sick.

If you heat Corecell (or Divinycell) up to thermoform it and overshoot the ideal temperature, it will release hydrogen cyanide - the same gas used in the concentration camps of WWII and used in gas chambers in the US for executions. It's a pretty rough thing to breathe.

Read the MSDS on foams before you use them. They can be deadly if you were to breathe a lot of the gasses let off - and you die in moments from complete cardio-pulmonary system collapse. All it took was melting one single sheet as I was thermoforming it to make me very sick. It came on within minutes of the thermoforming.

I was not successful using a heat gun, but was successful using a radiative quartz heater. However, you cannot heat Corecell over 180F without a chance of releasing hydrogen cyanide. Same for any of the foams, I believe, but possibly with different temperatures.

Be careful out there. I'm done with this hazmat BS. I'm buying a supplied air respirator today. I though epoxy was supposed to be bad. Nobody ever mentioned foam can KILL you, while epoxy is just a sensitizer.

 

I used really good powered respirators "MSA" problem is they draw air from a belt mounted unit,The switch to a fresh air mask is night and day,just another hose but you get used to the thing and learn not to tangle it or yourself in the air supply.

 

I heard the good old styrofoam also releases cyanide gas as well when burned.

 

Yes Kevlar is nasty when burned as well, LOL they go up in toxicity not down.