Deano642

Anyone have an suggestions on how best to reinforce the firewall on the H9 Funtana 90? I'm installing a Saito 1.80 and I'm a little concerned about the strength of the stock firewall.

So far I was only planning on using some balsa tri-stock on the inside corners. I did see another thread where someone used servo screws and epoxy to "pin" the firewall - But I'm not convinced that's the best way to go.

Also..I think the Funtana's internal structure (around the firewall) comes pre-treated (fuel proofed). I don't know how that would factor in to the ideas of reinforcing the firewall.

I am open to suggestions....Thanks for the help

Deano

pettit

My Feedback: (23)

Drill 1/8" holes through the fuselage sides into the center edges of the firewall. Make the holes about 3/4" deep.

Use 1/8" dowels as pegs all around.

I would suggest at least 4 on each side, or more if possible

Secure them with yellow glue. It'll swell up the dowels and make for a tight dit.

Now just try to pull the firewall off the plane.

You can also add triangle stock but remember that lots of epoxies won't stick to cured epoxy.

Deano642

Thanks....

I checked the thickness of my firewall and its only 1/4 inch....Would you still advise using the 1/8 dowels or would you go smaller ?

Deano

pettit

My Feedback: (23)

I'd use the 1/8" dowels, but you gotta drill the holes absolutely straight into the firewall.

If you can find some 3/32" dowel stock, use that, but use as many as will fit.

Space them maybe 3/4" apart

dmcmike

My Feedback: (14)

I've used piece of bamboo skewers (look for them at the grocery store) in place of dowels. they're about 1/16 in diameter, and very tough! Just do what Dick said, pin the firewall. 1/4" should be plenty thick.

pettit

My Feedback: (23)

I also have used those bamboo skewers. A pack of 100 is about a dollar, and they're each about 1 foot long.

They're stringy and don't cut cleanly with a razor saw, but you can score them with a sharp Xacto blade all the way through.

But the ones I used are just about 1/8" in diameter.

I'll have to look for the smaller ones.

Deano642

Excellent....I just found some bamboo skewers in the house. Would you still use wood glue with these or epoxy??

Thanks
Deano

pettit

My Feedback: (23)

Either one, but wood glue is a lot less messy to clean up.

Plus, 99.9% of the strength comes from the shear strength of the dowels, not from the glue holding them in place.

91zulu

My Feedback: (2)

you could also put the tri-stock and glue it with either Goop or Gorilla glue. either one adhere to almost anything. and is very strong. With the Gorilla glue you would have to find a way to hold the tri-stock tight to the corners, because when the glue expands it will force it out. What I do is use small screws from the front to hold it in place.

dmcmike

My Feedback: (14)

use white glue or something similar for the dowels (or skewers), and maybe add some hardwood triangle stock around the firewall instead of balsa.

Deano642

Thanks all....I flew it today with the 1/8 dowels and tri stock on the inside corners...It feels REAL sturdy and flew like you wouldn't believe....I don't normally post reviews of my airplanes, but this one is worth mentioning.

Thanks for all the help and suggestions.
Deano

dmcmike

My Feedback: (14)

that shouldn't come loose... looks good!