Firewall hole?
09-17-2009, 06:43 PM
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Firewall hole?
Ok this will sound too easy to guys who have run gassers, so excuse the newbie question. I fly glow a lot and am working on my first gasser, a 50cc Extra 330L. In my glow planes the firewall always has a round hole for the gas tank neck to fit into, or at least for the various fuel lines to pass through. My 330L does NOT have a hole in it. Do I need to drill one for the tubes to pass through, or can I pass any tubes over or under the firewall? Pic shows my DL 50 on the firewall. If I make a hole, should it simply be big enough to also fit control rods to connect to those two bellcranks above the tube nipple? Thanks. Jon
09-17-2009, 06:57 PM
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RE: Firewall hole?
This picture was taken to show the muffler bracket but it also shows the fuel line and choke control rod holes in the firewall. The throttle rod is hiding behind the standoff, it too is a hole just big enough for the rod to pass through.
I hope this helps.
I hope this helps.
09-17-2009, 07:58 PM
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RE: Firewall hole?
Really you just need a hole large enough to fit your control rods through. its easy to just drill one large enough to fit everything through since you have a rear mounted carb. Either way it wont hurt your plane but I prefer to keep my fuel lines as direct as possible. With gas planes your carb has a pump so you can mount your tank near your CG without affecting how your engine draws fuel.
Bottom line - you dont need to drill a big hole but it might be easier to drill one larger hole using a forsner bit or a hole saw vs. several smaller holes for your push rods.
Bottom line - you dont need to drill a big hole but it might be easier to drill one larger hole using a forsner bit or a hole saw vs. several smaller holes for your push rods.
09-17-2009, 08:18 PM
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RE: Firewall hole?
You might want to ensure there is some breathing room at the carb intake. Looks pretty close to the firewall in the picture. I'm not sure what your engine manufacturer recommends. I make sure I have about an inch or so.
09-17-2009, 08:18 PM
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RE: Firewall hole?
ORIGINAL: maukaonyx
So I see the hole that pre-existed in your firewall was not even used...there is tape over it?
So I see the hole that pre-existed in your firewall was not even used...there is tape over it?
Yes, the hole is taped over to keep the inside of the plane clean and cooler.
I find it better to have small holes and use the firewall as support for the control rods and fuel line.
A little more work to place the holes in just the perfect location but worth it, I think.
But, what do I know, it's my only gas plane.
09-17-2009, 09:38 PM
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RE: Firewall hole?
ORIGINAL: propchief
You might want to ensure there is some breathing room at the carb intake. Looks pretty close to the firewall in the picture. I'm not sure what your engine manufacturer recommends. I make sure I have about an inch or so.
You might want to ensure there is some breathing room at the carb intake. Looks pretty close to the firewall in the picture. I'm not sure what your engine manufacturer recommends. I make sure I have about an inch or so.
The instructions are pitiful, and don't say anything about clearance behind the carb, nor how to hook up the controls. BUT, I am using the stand-offs that came with the engine and they provide 1/2" clearance between the firewall and the carb. Jon
09-17-2009, 09:39 PM
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RE: Firewall hole?
Yup prop chief has a point which is why I go for the single larger hole. Fits all your control rods, fuel line, and lets your carb get more air just in case. Honestly taping over the opening won't make much difference at all. I have flown my planes 28-41% like this (many have an open designed motor box) with zero problems.
You might gain a few more RPM's on the high end if your carb can get more air. I cant tell how far it is from the firewall in the pix. Anyways I think it would be easier to go with a single larger hole.
You might gain a few more RPM's on the high end if your carb can get more air. I cant tell how far it is from the firewall in the pix. Anyways I think it would be easier to go with a single larger hole.
09-17-2009, 09:41 PM
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RE: Firewall hole?
ORIGINAL: airborneSGT
Yup! Plus I am not talking smack. I fly a lot of gas planes if you read my posts.
Fly PAU!!
Yup! Plus I am not talking smack. I fly a lot of gas planes if you read my posts.
Fly PAU!!
Did you recognize my plane as a PAU Extra 330L? Actually it is I think a BME plane sold by AKModels, but exactly the same as PAU except for color scheme. I think. I bought it when I missed out on the PAU clearance of their 330L a couple years ago, but found this one at AKM. Jon
09-18-2009, 04:07 PM
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RE: Firewall hole?
Jon-
The DA manual says
On my plane I bored a hole in the firewall and epoxied the bottom dome from a Coke can to get the required clearance. The clearance spec is met and there is no open hole to the interior of the plane. I have an offset hole through the firewall large enough for the sensor wire and spark plug boot. I have noticed no trouble with crud getting into the plane.
Stan
The DA manual says
Make sure the carburetor has adequate clearance near the inlet to allow an unobstructed airflow into the carburetor. If the carburetor is located in front of a former or firewall, be sure there is at least 1" (25mm) of clearance from the carburetor inlet. If there is less than 1" clearance, make a hole larger than the carburetor inlet diameter in the former or firewall.
Stan
09-18-2009, 04:34 PM
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RE: Firewall hole?
wow the carb is really close to the firewall.... i think you need to dril a 1" hole over there at least. Dont forget to put washers there on the stands off and back of the firewall.
