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Building Tips and technical articles. => Building techniques => Topic started by: Matt Piatkowski on December 16, 2015, 11:40:40 AM

Title: Density of the styrofoam for custom made wing cores
Post by: Matt Piatkowski on December 16, 2015, 11:40:40 AM

Hello,
I would like to know which styrofoam to buy to cut the customized wing core.
What is the lowest density that will allow to build reasonably strong and stiff ~60" wing with 22% airfoil with full 1/16" balsa sheeting.
The wing geometry resembles the Max Bee wing?
Thanks,
M
 

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Mark Scarborough on December 16, 2015, 11:53:16 AM

the standard is 1 pound VIRGIN foam

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Matt Piatkowski on December 16, 2015, 12:40:18 PM

Hi Mark,
I understant it is 1 lbs./ cubic foot.
Am I correct?
M

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Tim Wescott on December 16, 2015, 01:15:32 PM

Yes.  "1 pound" means 1 pound per cubic foot.

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Fredvon4 on December 16, 2015, 01:44:50 PM

Matt the 1 lb per cubic foot is what we all want

tough to find, my buddy in San Antonio has a source but always has to weight the billets and select the ones he wants...all are virgin (not regrind) EPS but a wide range of weight as delivered to the supplier

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Dave_Trible on December 17, 2015, 02:57:41 PM

Might be sure it's closed cell bead foam.  Most plastic supply houses should have it.  Do a Google search for a supplier near you.

Dave

Title: Re: Density of the styrofoam for custom made wing cores
Post by: Howard Rush on December 17, 2015, 03:37:40 PM

Quote from: Matt Piatkowski on December 16, 2015, 11:40:40 AM

What is the lowest density that will allow to build reasonably strong and stiff ~60" wing with 22% airfoil with full 1/16" balsa sheeting.[?]

One hollows the wings, typically after they're sheeted.  I've found expanded-bead polystyrene foam as light as .7 lb./cubic ft.  I don't know whether thick light stuff would be stonger or stiffer than thin dense stuff having the same weight.

Speaking of thin stuff, let me know where one can get Herex in North America.

Title: Re: Density of the styrofoam for custom made wing cores
Post by: phil c on January 09, 2016, 03:52:05 PM

Ask for EFS foam, if they make/stock it.  External Finishing System.  It's spec'd for gaudy housing with stucco and lots of fancy trim.  Mainly the spec makes sure that all the beads are firmly stuck together and it is a uniform .95+/- lb/cuft.  It does make a difference.