[NSRCA-discussion] Firewall Material

[Bob Kane]

I will add the reason I used polyurethane glue is it expands to fill all the voids.  End grain balsa will suck up a lot of epoxy or aphilatic resin. The resulting structure is very strong, light, and "low tech".

In my case, the Hyde mount spread the load out enough on the front side of the firewall so no extra reinforcement was necessary.  I added 3/32 plywood disks approx 5/8" diameter to act as a hard points for the blind nuts. These were simply glued to the 1/64 plywood on the backside of the firewall. 



Bob Kane
getterflash at yahoo.com


--- On Thu, 1/28/10, J N Hiller <jnhiller at earthlink.net> wrote:

> From: J N Hiller <jnhiller at earthlink.net>
> Subject: Re: [NSRCA-discussion] Firewall Material
> To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
> Date: Thursday, January 28, 2010, 11:32 AM
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> Tim unless
> absolute lightest weight is a factor a simple balsa-ply
> laminate as bob
> describes works very well, low cost, simple and made from
> readily available material. 
> 
> I first
> started doing this 25 years ago usually on large scale
> airplanes where I wanted
> more rigidity and flatness than 1/4" aircraft ply
> offered as well as a
> wider edge for gluing. I've used end grain balsa but
> feel it isn't worth the
> trouble if end grain hard points are inserted where bolts
> pass through, which
> requires a little prior planning. I generally use dowel
> (poplar if I can find
> it) for hard points because it's easy to cut a round
> hole through the balsa
> sheet core with a sharpened brass tube, although spruce
> block would work as
> well. Internal hard points give the blind nut points
> something to lock into
> eliminating the need for an external backer or
> reinforcement. I believe the
> balsa sheet is actually better than an end grain balsa core
> when thin surface
> material is used as it offers better support against
> dimpling under stress. I
> just used slow set epoxy for laminating, clamping the
> 'sandwich' between two pieces
> of 3/4" plywood or weight it down on the
> workbench. 
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> I don't
> have a paint booth so I still build wood airplanes and use
> iron on paint. 
> 
> Jim Hiller
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> -----Original
> Message-----
> 
> From:
> nsrca-discussion-bounces at lists.nsrca.org
> [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of
> Pascoe,Tim [Burlington]
> 
> Sent:
> Thursday, January 28, 2010
> 7:29 AM
> 
> To: General
> pattern discussion
> 
> Subject:
> [NSRCA-discussion]
> Firewall Material
> 
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> I’m
> working on a pair of Genesis’ for next season. In the
> past, most of my
> airplanes have been wood, and while I have some experience
> with composite
> airframes, I’m far from being an expert. I’m
> ready to put in the firewalls, and
> I’d like some suggestions as to what the best
> material will be for this. I’d
> like to keep the weight down (don’t we all), and was
> wondering if laminated
> carbon/balsa panels such as those available at the
> Composites Store (http://www.cstsales.com/carbon_sandwich_panel.html)
>  are worth it, difficult to work with, etc. Also, do
> panels like this
> require some special reinforcement where the bolts go
> through? Special epoxies
> for adhering to the fuse, etc.? Or should I just be using
> aircraft grade
> plywood?
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> Any
> suggestions would be great.
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> Tim
> Pascoe 
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> -----Inline Attachment Follows-----
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