As mentioned previously, I will be getting a pattern kit sometime soon. Now, I'm thinking about the Firewall and servo tray.

What recommendations are there for a lightweight and strong Firewall? I have CF cloth easily accssible, and was wondering if a Balsa sandwich would work(YS 140)?

I was also thinking of getting some Hybraid Fabric for the servo tray, to add some color. How do these Hybraid Fabrics compare with normal CF Cloth? Also, where can I find a Honeycomb Nomex Sandwich, like those supplied by PL Prod?

Thanks,
Alex

Dont try to skimp on the fire wall. Especially if your going to run a banger in it. 5/16" or 1/4" AC ply and use glass or carbon fiber fill in the fillets on both sides of the firewall. For servo trays use hardwood cross members or lt ply with a double under the screws. The aramid colored fiber woudl look neat. Hardwood if your using pull/pull setups.
Now if your talking a completely built up composite firewall then go for it. You could use 1/4" end grain cut balsa sandwiched inbetween heavy weave of C.F, uni-directional if you have it. By using end cut balsa it is stronger and will absorb the resin making it even stronger. I dont think it would be much lighter though.

my .02 worth.....

Make some samples and compare weights before you decide. A friend just did this in a nomex plane and the lightest was 3/16 aircraft ply.

Anthony

My nomex/carbon firewalls on my Vector weighed 9 grams 1/4" lite play firewall for it weighed 40 grams, carbon/balsa weighed in at 18 grams, 1/8" lite ply weighed in at 18 grams, and the carbon/nomex is as strong as any of them.

How did you layup this 9 gram firewall? I am definatley interested in that as I am about to set the engine in my Prophecy.
I guess it doesnt sound like much wieght. 9 grams is about 3/8 of an oz and 40 grams is about 1.5 oz. But in the big scheme of things if you look at it as a percentage of reduced wieght in everything you add or build it can all add up in a hurry.
10 to 15% on 80% of the parts of your 11lb airplane equals about
1 to 1.25 lbs equals better performance.
I stand corrected....

Wayne

Chad,

Do you have the pictures of the Firewall, and how you prevent crushing of the Honeycomb?

Would be interested in how you lay up your plates, since I may be able to get Honeycomb Nomex here.

Thanks

We are using nomex in our fuse's as we lay them up on the sides back to the tail group. We have been able to effectively eliminate the rearward formers and still have a stiff fuse.

I have a pic on my website of the servo trays which are the same layup as the firewall, when I get home I will post more that I have on my local drive.

http://members.shaw.ca/patternwest/technical/ch.htm

It is important to use the correct cell size to help prevent crushing, but the pictures I have at home describe how I keep it non-crushed better. I saved probably in the neighbourhood of 4 ounces on my Vector, and have a much stiffer mounting for my servos.

If you guys are interested, I can make this for you, I have all the stuff here to do it finding nomex of the correct weight and size in quantities that are small is tough from my experience.

Anyways will post more later, work calls

As promised pics of what is going on

This one is showing an aluminum fitting that we made to support the plate. The part of the fitting that is in the plate takes up the compression loading from the bolt, and the larger diameter that sits outside takes up the thrust load and the torque loading on the glue in shear (minimal). These can be made of a peice of dowel and a ply disk, the bolt runs all the way through the fitting.

another shot

yet another

and some more

ok last one I promise

How many layers of CF cloth are there on each side? It doesn't look like more than 2. Very creative and innovative solution . I'm going to try this on a smaller plane with some 1/8" nomex core I have. I built composite landing gear a couple years ago with 1/8" nomex and CF. Very light and extremely stiff. I've worked in composites professionally for 3.5 years, building models with it for 12 years; way back before gassers went main stream with composites
ps: that hybrid stuff is nice but beware that you aren't getting dyed nylon instead of dyed Kevlar (aramid). The nylon hybrid's color fades less in sunlight but also sands like cr@p (worse than the kevlar).
Just for fun (and school credit), I built a coffee table out of 3/4" nomex honeycomb, CF layed up on glass and cleared, soft maple legs and edges. Whole table weighs 9 lbs.

Troy,

I see from your table photos that you forgot to seal the gaps between the legs and the table. This could result in flutter during high speed dives, and a lack of control authority when close to the stall.

Still at 9 pounds, it should hover nicely with a 1.20. With the landing gear as it is, grass fields shouldn't be a problem either.

Nice work!

Hi,

On my two tornado that I'm currently building, I have used a Nomex Carbon Fiber for the Firewall (1/4), the floor is Carbon Nomex (1/8), so is the Tank support, and the Throttle/Mixture will be the same, but the Rudder servo will be Carbon Fiber Nomex (1/4).

The plate for the fixed gear is End balsa Carbon Fiber(1/4).

Hope this help Daniel Dupont

Beware end grain balsa has zero bending strength, make sure it is supported.

It is just a single layer of cloth, as you probably know the strength even from one layer is pretty high for this application. The only place I didnt use it (well I did but it didnt work out well) is the landing gear.