General Question-Gas engine Fits Entirely Inside Cowl
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General Question-Gas engine Fits Entirely Inside Cowl
Hi all-
I am in the process of mounting a DLE 20 on a Spacewalker II (Seagull 120).
The entire engine as well as the muffler fits completely inside this very large cowl.
I realize I will need to do something about cooling air and will punch some holes strategically where they won't spoil the plane's looks, but what about the exhaust. Should I get an extension and extend the exhaust so that it is outside the cowl? Is it good enough to just put a hole in the cowl in the general area?
Your thoughts would be appreciated.
Thanks-
Larry
I am in the process of mounting a DLE 20 on a Spacewalker II (Seagull 120).
The entire engine as well as the muffler fits completely inside this very large cowl.
I realize I will need to do something about cooling air and will punch some holes strategically where they won't spoil the plane's looks, but what about the exhaust. Should I get an extension and extend the exhaust so that it is outside the cowl? Is it good enough to just put a hole in the cowl in the general area?
Your thoughts would be appreciated.
Thanks-
Larry
#2
RE: General Question-Gas engine Fits Entirely Inside Cowl
I would want the exhaust just outside the cowl. You are still pushing very hot exhaust and it could burn or discolor the aircraft.
#3
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RE: General Question-Gas engine Fits Entirely Inside Cowl
I would make sure it exited outside the cowl as well. Often times the standard exhaust comes out in a rather "unfortunate" spot when considering the scale appearance of the plane. That's what drives the "wrap around" exhaust system sales. They nearly always allow for a much cleaner exhaust installation, leaving the outlets centered somewhere just ahead of the firewall. They're also a tad less offensive when it comes to noise.
#4
RE: General Question-Gas engine Fits Entirely Inside Cowl
Your strategically placed holes in the cowl might not spoil the model's looks but might also not do much in helping to cool the fully enclosed hot engine. You need to have a front opening that allows incoming air to pass around and over the cylinder head and an exit opening approx. 3 times larger that the inlet to allow the hot air to escape quickly.
Karol
Karol
#5
RE: General Question-Gas engine Fits Entirely Inside Cowl
Cut yourself 3 or 4 half inch wide slots so they bloe across the head and a big hole down under close to the firewall on the bottom to exit the air. It makes a big difference in temps. Just adding a spinner to my butcher bird made the temp go up about 30 to 40 degree's in no time flat
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RE: General Question-Gas engine Fits Entirely Inside Cowl
Just punching holes or slots is a very haphazard way to go about it, and likely to fry your enclosed engine. To get air blowing, you need to set up a pressure difference. Then you need to guide that air over your engine.
See http://www.prme.nl/forum/viewtopic.php?t=148 for cooling requirements and solutions.
See http://www.prme.nl/forum/viewtopic.php?t=148 for cooling requirements and solutions.
#7
RE: General Question-Gas engine Fits Entirely Inside Cowl
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
#8
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
#9
RE: General Question-Gas engine Fits Entirely Inside Cowl
Your thinking is pretty much like putting the cart before the horse, as the one overheating condition you see might cost you an engine.
Karol
Karol
#10
RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: Truckracer
???? The first illustrations clearly show air exit area at the bottom rear of the cowl. It also illustrates how airflow tends to flow right past this exit without producing any negative pressure in the area .... so there is little air extraction from the cowl. The airdams produce low pressure behind them allowing for hot air extraction. Pretty simple really. can't see any reason to challenge Pe's logic on this and in fact thank him for publishing this some years back. Such a simple thing that works so well ... especially if coupled with the suggested baffles.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
ORIGINAL: unclecrash
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
#11
RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: karolh
Your thinking is pretty much like putting the cart before the horse, as the one overheating condition you see might cost you an engine.
Karol
Your thinking is pretty much like putting the cart before the horse, as the one overheating condition you see might cost you an engine.
Karol
#12
RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: karolh
Your strategically placed holes in the cowl might not spoil the model's looks but might also not do much in helping to cool the fully enclosed hot engine. You need to have a front opening that allows incoming air to pass around and over the cylinder head and an exit opening approx. 3 times larger that the inlet to allow the hot air to escape quickly.
Karol
Your strategically placed holes in the cowl might not spoil the model's looks but might also not do much in helping to cool the fully enclosed hot engine. You need to have a front opening that allows incoming air to pass around and over the cylinder head and an exit opening approx. 3 times larger that the inlet to allow the hot air to escape quickly.
Karol
#13
RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
The first pics DID NOT LOAD when i first clicked on the link. RCU bugs maybe The only cowl pic up was the round radial pic.
ORIGINAL: Truckracer
???? The first illustrations clearly show air exit area at the bottom rear of the cowl. It also illustrates how airflow tends to flow right past this exit without producing any negative pressure in the area .... so there is little air extraction from the cowl. The airdams produce low pressure behind them allowing for hot air extraction. Pretty simple really. can't see any reason to challenge Pe's logic on this and in fact thank him for publishing this some years back. Such a simple thing that works so well ... especially if coupled with the suggested baffles.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
ORIGINAL: unclecrash
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
#14
RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: pe reivers
Just punching holes or slots is a very haphazard way to go about it, and likely to fry your enclosed engine. To get air blowing, you need to set up a pressure difference. Then you need to guide that air over your engine.
See http://www.prme.nl/forum/viewtopic.php?t=148 for cooling requirements and solutions.
Just punching holes or slots is a very haphazard way to go about it, and likely to fry your enclosed engine. To get air blowing, you need to set up a pressure difference. Then you need to guide that air over your engine.
See http://www.prme.nl/forum/viewtopic.php?t=148 for cooling requirements and solutions.
#15
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
A friend has a 33% yak no baffles runs fine. He has been flying it for years. Wonder why yours needs one. All Im saying is Im not going to create something till I find a reason to do it. If I have a lean condition then I will trouble shoot it. But Im not going to create more problems for my self.
ORIGINAL: unclecrash
The first pics DID NOT LOAD when i first clicked on the link. RCU bugs maybe The only cowl pic up was the round radial pic.
ORIGINAL: Truckracer
???? The first illustrations clearly show air exit area at the bottom rear of the cowl. It also illustrates how airflow tends to flow right past this exit without producing any negative pressure in the area .... so there is little air extraction from the cowl. The airdams produce low pressure behind them allowing for hot air extraction. Pretty simple really. can't see any reason to challenge Pe's logic on this and in fact thank him for publishing this some years back. Such a simple thing that works so well ... especially if coupled with the suggested baffles.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
ORIGINAL: unclecrash
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
Looks good nice baffle, lets all run out and baffle our engines. Seems to me the cowled engine has no exit area on the rear so I guess if you don't let the air out of the cowl you would need to baffle it to get as much of it to run around it to cool it. I for one willnot waste my time till I see a overheating condition. Go fly have fun and see what the engine does, with the 3 to 1 rule, then if needed ad a baffle.
I don't baffle most of my engines but I do make sure the airflow is through the cylinder fins and that there is provision for air extraction. I've been asked more than once why my Yak has that baffle plate in the front of the cowl. Most of the time people just walk away wondering *** after my explanation. They ask the question but really don't want a real answer. Oh well, their loss!
This whole baffle, airflow, cowl pressure discussion goes right along with the problems some people have with Walbro carbs and their need for a vent line from the diaphram cover plate. In many cases, the Walbro problem is telling you there is a pressure problem in the cowl. It is just a symptom of a greater problem and not a problem with the carb at all.
Yes, I have seen (and flown or owned) many planes without any sort of baffles. But as I have learned more about our engines and their environment I prefer to use at least some of the basic principals necessary to prevent problems. The fact that I don't use full baffles is just pure lazyness on my part.
#16
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrashBut the 3 to one rule PE has pretty much shot down. You might make a high pressure area
In big round cowl installations I regularly see where the whole 3 to 1 thing is reversed where the whole front of the cowl is wide open but there is only a small hole for air to sort of escape. Sort of like a sauna for the engine to live in!
#18
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
Truck do you have any pics of how you do your setup, like to see how others do stuff. I like simplicity.
Truck do you have any pics of how you do your setup, like to see how others do stuff. I like simplicity.
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
But the 3 to one rule PE has pretty much shot down. You might make a high pressure area
ORIGINAL: karolh
Your strategically placed holes in the cowl might not spoil the model's looks but might also not do much in helping to cool the fully enclosed hot engine. You need to have a front opening that allows incoming air to pass around and over the cylinder head and an exit opening approx. 3 times larger that the inlet to allow the hot air to escape quickly.
Karol
Your strategically placed holes in the cowl might not spoil the model's looks but might also not do much in helping to cool the fully enclosed hot engine. You need to have a front opening that allows incoming air to pass around and over the cylinder head and an exit opening approx. 3 times larger that the inlet to allow the hot air to escape quickly.
Karol
In a sound design, a 1:1.2 rule will function perfectly. Only because of cooling problems did that rule change to 1:2, then to 1:3, and nowadays even to 1:4. Changing the ratio bypasses the real reasons for bad cooling, so be my guest, try it out for yourself. You can always sell the engine on the bay.
#21
RE: General Question-Gas engine Fits Entirely Inside Cowl
Wondering why on the one example it has like the whole bottom cut out which probably is around 1 to 4 and yet it shows it as not being effective at letting the air flow out the bottom.
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RE: General Question-Gas engine Fits Entirely Inside Cowl
Air must have a reason to flow. That reason is pressure difference. No pressure difference No flow. Amount of flow is depending on the amount of pressure difference. Pulling air through a restriction like engine cooling fins needs extra pressure difference.
Large holes by themselves do not cause air to flow.
Large holes by themselves do not cause air to flow.
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RE: General Question-Gas engine Fits Entirely Inside Cowl
Well Larry !!! I have the same set up next in line for the bench !!!
about a week or 2 away befor I start on it !!!!
P/M me when you get it going need to know what way to go !!! Thanks Larry
about a week or 2 away befor I start on it !!!!
P/M me when you get it going need to know what way to go !!! Thanks Larry
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: unclecrash
Wondering why on the one example it has like the whole bottom cut out which probably is around 1 to 4 and yet it shows it as not being effective at letting the air flow out the bottom.
Wondering why on the one example it has like the whole bottom cut out which probably is around 1 to 4 and yet it shows it as not being effective at letting the air flow out the bottom.
Pe is 100%correct re the cooling baffles. If you don't use baffles you still need a low pressure zone but also a large inlet area.
Pressure and area create force. Youneed sufficient air pressure from the front to push air out the bottom of the cowl without baffles.
No baffles works in some cases because the inlet area is large enough to drive the pressure difference.
its a case of either do baffles or don't and certainly do not blank off the front of the cowl as some people erroneously do.
#25
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RE: General Question-Gas engine Fits Entirely Inside Cowl
ORIGINAL: TimBle
its a case of either do baffles or don't and certainly do not blank off the front of the cowl as some people erroneously do.
its a case of either do baffles or don't and certainly do not blank off the front of the cowl as some people erroneously do.