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  #21  
Old 10-03-2017, 07:33 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by rvator51 View Post
Front fin on no 2 is about 1/8 in deep. Used washer in back of no 3 cylinder. All four cylinders run about same temp.
Do the bypass ducts and #2 and #3 will come down big time.
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  #22  
Old 10-03-2017, 07:55 PM
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Ok, I will make the bypasses and see what happens.
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  #23  
Old 10-03-2017, 07:59 PM
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Not wanting to drag up old discussions, but I see a lot of folks chasing the "gotta stay below 400 deg F" at all times or ??
I personnaly have no issues letting mine go to 410-415 for short durations of a few minutes but rarely see that even in the hottest weather when heat soaked. That is still way below continuous operating specs let alone red line.
I have never had the need to climb out at 70kts. I see no advantage to that when best rate is significantly higher. It would be rare you would ever need to do that in an RV. We climb so well, lower the nose, cool things off if you need to.

I see a lot of folks adding complexity and cost to their machines based on poor understanding, or misinformation.

I have "fixed" two machines "cylinder cooling issues" with timing adjustments.

So, define what is a problem to your own definition, understand it, then address it as needed. If you "need" cowl flaps, or just think they are the answer, know that you are adding some weight, complexity, and cost. If that is justifiable to you, that is all that matters.
However, if I see an RV with cowl flaps, the first thing I am going to ask myself is "what else is wrong here". Maybe nothing, but I am a betting man....
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  #24  
Old 10-03-2017, 08:06 PM
Timberwolf Timberwolf is offline
 
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Quote:
Originally Posted by rvator51 View Post
Ok, I will make the bypasses and see what happens.
Do you have any pics or can you point to any posts that show these ducts for the cylinders? I've seen them referred to a few times in posts, but haven't seen exactly what kind of duct you guys are referring to.
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  #25  
Old 10-03-2017, 10:30 PM
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DanH also has some good ones, but this one should start you down the path:

http://www.vansairforce.com/communit...ght=CHT+solved
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #26  
Old 10-04-2017, 06:01 AM
Timberwolf Timberwolf is offline
 
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Thanks Michael, makes sense. I thought the reference was to a fiberglass duct mounted to the top cowl, which is why I couldn't find much info on it.
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  #27  
Old 10-04-2017, 08:55 AM
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Whole lot of debate over nothing.

If a fella wants to cover all bases during construction, rather than waiting until after test and break-in to judge temperatures, well, why not?

The Vans mantra is balanced performance, an airplane with a wide operating range that does all things pretty well. A builder can make choices which add to the range (go faster, stall slower, etc), and remain in accord with the mantra if his modification does not subtract from performance elsewhere (for example, go faster, stall faster).

Here the subject is cooling. The ideal approach, when incorporating changes early in the build, is to widen the cooling range at both ends.

How? Assume the builder wishes to use something like Nimmo's doors. Determine the additional exit area provided by one door. Section the stock cowl exit so as to remove fixed exit area equal to that one door. Now install two doors.

The result is one door area less than stock in cold cruise, and one door area more than stock in hot climb. That should be a useful range addition given stock inlets, baffles, etc. Frankly, if it won't cool with one additional door area, yes, there are other issues.

The concept can be applied multiple ways, and with system mods the cooling range can be extended even further.

RV-8 stock exit. Compare with below. (Yes, the pipes had to be modified):



Don't really need doors. Instead build swappable exit panels for hot and cold seasons:



Very small fixed exit (on right, above), installed for winter:



Even less fixed exit area....



....with low drag variable exit area:

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Last edited by DanH : 10-04-2017 at 09:04 AM.
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  #28  
Old 10-04-2017, 12:35 PM
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... Dan, you are an artist! Your work is a work of art. Thanks, Allan..
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  #29  
Old 10-05-2017, 10:46 AM
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MikeyDale MikeyDale is offline
 
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I live in West Texas and did install an Anti-Splat Cowl Flap. I do not need it most of the time but it sure is nice to have when I do. It adds very little weight and is easy to install. Better than opening up the exit area and creating more constant drag in my opinion!
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  #30  
Old 11-27-2017, 01:48 PM
Guyfly47 Guyfly47 is offline
 
Join Date: Mar 2010
Location: South Haven, MI
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Default Missing pictures wanted

If Dan or anyone else has these missing fotobucket pictures , Id very much like to see them. Im fighting high temps and have done the basics of plugging holes in baffling. I have resorted to leaving the close out panel for the nose gear off in order to get enough air through the cowl. I need to do more and was about to resort to a cowl flap.
Thanks,
Eric

Quote:
Originally Posted by DanH View Post
Whole lot of debate over nothing.

If a fella wants to cover all bases during construction, rather than waiting until after test and break-in to judge temperatures, well, why not?

The Vans mantra is balanced performance, an airplane with a wide operating range that does all things pretty well. A builder can make choices which add to the range (go faster, stall slower, etc), and remain in accord with the mantra if his modification does not subtract from performance elsewhere (for example, go faster, stall faster).

Here the subject is cooling. The ideal approach, when incorporating changes early in the build, is to widen the cooling range at both ends.

How? Assume the builder wishes to use something like Nimmo's doors. Determine the additional exit area provided by one door. Section the stock cowl exit so as to remove fixed exit area equal to that one door. Now install two doors.

The result is one door area less than stock in cold cruise, and one door area more than stock in hot climb. That should be a useful range addition given stock inlets, baffles, etc. Frankly, if it won't cool with one additional door area, yes, there are other issues.

The concept can be applied multiple ways, and with system mods the cooling range can be extended even further.

RV-8 stock exit. Compare with below. (Yes, the pipes had to be modified):



Don't really need doors. Instead build swappable exit panels for hot and cold seasons:



Very small fixed exit (on right, above), installed for winter:



Even less fixed exit area....



....with low drag variable exit area:

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