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Balsa vs. Foam


David Pierce

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After some research, it is apparent that the e-glass is the structural strength (not core material) of the composite construction. Has anyone substituted balsa cores for foam cores, especially in the bulkheads and seats. Balsa is 1/2 the price of the foam and is easier to cut and prepare for layup. The analysis I read was the balsa was stronger than foam and lighter. Any thoughts?

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Balsa Rots

 

The Plane is a total system, strenghten one piece and you now direct forces to other areas that may need strengthening.

 

before i started building i figured i would modify and improve the design, more modern cores, etc, etc. read enough to learn that i am not capable of designing a whole new plane, well i am capable, if i want to spend years of learning and TESTING

 

get to building, the plans are great and they work

 

enjoy the build

 

Mike

maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build

 

i can be reached at

 

http://www.canardcommunity.com/

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Originally posted by Dave

After some research, it is apparent that the e-glass is the structural strength (not core material) of the composite construction. Has anyone substituted balsa cores for foam cores, especially in the bulkheads and seats. Balsa is 1/2 the price of the foam and is easier to cut and prepare for layup. The analysis I read was the balsa was stronger than foam and lighter. Any thoughts?

The cost of the foam in a composite aircraft is a minuscule %age of the cost of the aircraft. The foam in the wings is 2-4 lb/ft^3 - light to medium balsa is 7 - 12 lb/ft^3. You'd add a LOT of weight, you wouldn't be able to hot wire it, so good luck getting the shape right, and it would be susceptible to rot. Explain to me again (given that you've already admitted that the glass provides the strength) what an advantage of balsa as a core material might be? :-).

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I answered you with very little detail, when you start the building thinking, the first thing many do is to look for ways to improve the plane, or in my thinking(it was for me anyway) delay the build start.

 

OK lets look at the bulkheads

(and this is from memory so don't critisize me for imperfect memory or SPELLING

 

first bulkhead very tiny maybe 6x9

 

second bulkhead, most of it gets cut away, very little left to reduce weight

 

third buldhead 3"x30" 1/4 inch foam, not much there?

 

fourth bulkhead, instrument panel, 1/4 high density foam, very little of it left buy the time you install the instruments

 

fifth bulkhead, seatback, 1" or 3"4 inch foam, could make the change here, you would have to do testing to find the same amount of strength as the seat back

 

next set of bulkheads, landing gear supports, quite small and subject to extreme loads, you would have to be very confident to change these and they are also quite small with large areas of 25 or so layer hardpoints, not really much foam to substitute here

 

Outside if fuselodge,

 

1 exposed to weather, spelled ROT

 

2 are bent, balsa may not take the shape easily,(the bottom is 1" thick in SOME places

 

3 carved, my 6 day a week hobby is woodworking and i wouldn't want to carv the bottom edge out of wood, it is finicky enough out of easily cut and sanded foam

 

 

Wings, no way i would try to cut wings out of wood, it is a snap with the hot wire

 

nose, no way i would like to replace the easily formed nose with wood

 

Strakes/gas tanks, the foam here is both external and can be exposed to gas, wouldn't trust wood here eithor

 

In short, there is a 6x9 bulkhead you could easily replace in the nose with balsa

 

one last thing, each foam is used in it's spot for both it's strength and properties, gas resistant for fuel tanks

 

hot wire cuttable for wings

 

easily formed for nose

 

it is not just "foam" it is appropiate for it's use

 

enjoy the build

 

mike

maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build

 

i can be reached at

 

http://www.canardcommunity.com/

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I had only wondered about the internal buldhead not any structural parts. The only reason is that I am used to building R/C models and balsa is very easy to cut and shape. I thought that I might be able to save some time and weight. I am planning on using MDS 285, and want to build a light as possible.

I appreciate the ideas....thanks.

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ohhhhhhhh, thats another change needed to your thinking, ALL parts or almost all parts in a cozy are structural.

 

In doing my improve research, i talked to a gut that used honeycomb on an airplane(not a cozy can't remember the plane) he saved a whopping 10 pounds

 

enjoy the build

 

Mike

maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build

 

i can be reached at

 

http://www.canardcommunity.com/

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