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reinforcing motorbox/firewall

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Old 04-02-2008, 04:15 PM
  #26
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Default RE: reinforcing motorbox/firewall

Metallica,
I am not sure what kind of pilot you are or how you fly your panes, but let me reassure you that an engine box reinforced with tri stock made of balsa or spruce, will handle pretty much everything you could throw at it...IF it is done correctly. The addition of carbon fiber or fiberglass is added weight and not really necessary...an insurance policy perhaps, but not really necessary.
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Old 04-02-2008, 04:53 PM
  #27
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Default RE: reinforcing motorbox/firewall

I tend to agree. What I don't agree with is reinforcing the inside of the engine box. As I stated before, the load is outwards, not inwards. If you didn't have a ply overhang on the outside of the firewall to fill with some tri stcok a couple of small (3/4" x3/4" x3") pieces of aluminum 90 degree angle bolted on the outside would be better than adding a bunch of wood inside. It used to be a pretty common method of setting engine boxes before arfs were the rage. You could do the same at the engine box to forward fuselage bulkhead if you truly thoght you needed it.

More than one way to do the job, but all of the better ways will be done at the outside of the box. Think about that and the stress forces a little before debating it. All you have working for you on the inside is the strength of the glue. The balsa does nothing.

However you decide to fly YOUR plane, enjoy to the best of your ability. The other guys won't be there to help build or fly, so do however you want to and have fun.
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Old 04-02-2008, 05:47 PM
  #28
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Default RE: reinforcing motorbox/firewall

thank you Pat, and everyone else with helpful input, now i have a better idea of what we are going to do. [sm=thumbs_up.gif]
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Old 04-07-2008, 02:09 AM
  #29
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Default RE: reinforcing motorbox/firewall


Quote:
ORIGINAL: Pat Roy

I tend to agree. What I don't agree with is reinforcing the inside of the engine box. As I stated before, the load is outwards, not inwards. If you didn't have a ply overhang on the outside of the firewall to fill with some tri stcok a couple of small (3/4" x3/4" x3") pieces of aluminum 90 degree angle bolted on the outside would be better than adding a bunch of wood inside. It used to be a pretty common method of setting engine boxes before arfs were the rage. You could do the same at the engine box to forward fuselage bulkhead if you truly thoght you needed it.

More than one way to do the job, but all of the better ways will be done at the outside of the box. Think about that and the stress forces a little before debating it. All you have working for you on the inside is the strength of the glue. The balsa does nothing.

However you decide to fly YOUR plane, enjoy to the best of your ability. The other guys won't be there to help build or fly, so do however you want to and have fun.
I agree.
I think the SD planes already used aluminum angle wrapped around the outside of the box on both sides. If not, then that is definitely an option for a bulletproof box.
Regardless, I have yet to rip a box apart on any of my recent giant scale ARFs and I fly my stuff hard sometimes, too. I don't think Metallicajunky really needs to do anything above and beyond what SD recommends, even or his flying style, whatever that may be. I would be more worried about snapping wings apart WAY before ripping an engine box apart.
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Old 04-07-2008, 02:20 AM
  #30
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Default RE: reinforcing motorbox/firewall


Quote:
ORIGINAL: Pat Roy

I tend to agree. What I don't agree with is reinforcing the inside of the engine box. As I stated before, the load is outwards, not inwards. If you didn't have a ply overhang on the outside of the firewall to fill with some tri stcok a couple of small (3/4" x3/4" x3") pieces of aluminum 90 degree angle bolted on the outside would be better than adding a bunch of wood inside. It used to be a pretty common method of setting engine boxes before arfs were the rage. You could do the same at the engine box to forward fuselage bulkhead if you truly thoght you needed it.

More than one way to do the job, but all of the better ways will be done at the outside of the box. Think about that and the stress forces a little before debating it. All you have working for you on the inside is the strength of the glue. The balsa does nothing.

However you decide to fly YOUR plane, enjoy to the best of your ability. The other guys won't be there to help build or fly, so do however you want to and have fun.
I agree.
I think the SD planes already used aluminum angle wrapped around the outside of the box on both sides. If not, then that is definitely an option for a bulletproof box.
Regardless, I have yet to rip a box apart on any of my recent giant scale ARFs and I fly my stuff hard sometimes, too. I don't think Metallicajunky really needs to do anything above and beyond what SD recommends, even or his flying style, whatever that may be. I would be more worried about snapping wings apart WAY before ripping an engine box apart.
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