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  #21  
Old 11-02-2019, 04:36 PM
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RV7A Flyer RV7A Flyer is offline
 
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I noticed the post above that mentioned tying down the tailwheel. I seem to recall from a few years ago where some guys were doing that to their planes and doing full power run-ups for some reason or another (comparing amount of power or something like that), and ended up damaging their fuselage by bending that bulkhead back there...

An awful lot of airplanes out there that have done their engine break-ins "the old-fashioned way"...by flying.
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  #22  
Old 12-29-2019, 03:07 PM
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Default Engine cooling shroud

I built a shroud and here's how it looks. More pics on the blog post. I'll hopefully test it tomorrow to see if the engine stays cool during break-in.

http://www.rv8.ch/engine-cooling-shroud/

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  #23  
Old 12-29-2019, 04:19 PM
TShort TShort is offline
 
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I looked over your blog post as well.

I assume for break in on the ground you'll run at high (full?) power; do you think the clecos will hold? That would make me nervous. Perhaps in order to store flat you could secure some of it with nylocks and screws or bolts?
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  #24  
Old 12-29-2019, 11:25 PM
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Default Clecos

Quote:
Originally Posted by TShort View Post
I looked over your blog post as well.

I assume for break in on the ground you'll run at high (full?) power; do you think the clecos will hold? That would make me nervous. Perhaps in order to store flat you could secure some of it with nylocks and screws or bolts?
I think they will hold, but might switch to pop rivets anyway - I have lots of spares. I know a guy that flew with his front skin clecoed on, which gave me confidence that they will hold.

While taking a shower last night I realized I should have just used hinge to fit the pieces together - that would hold securely, look nice, and be easy to fold. Oh well - next time!
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  #25  
Old 12-30-2019, 05:48 AM
TShort TShort is offline
 
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Quote:
Originally Posted by rv8ch View Post
I know a guy that flew with his front skin clecoed on, which gave me confidence that they will hold.
On purpose??
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  #26  
Old 12-30-2019, 10:55 AM
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Default Ground run

Did a few runs today with the shroud - couple of things I learned:
  • the engine moves *a lot* - the shroud was of course trying to keep up with the engine shaking, and struggling. When the engine was not shaking during higher RPMs, all was fine.
  • The airflow caused the top to bulge up several inches - this is very stiff 2mm (~0.075") aluminum sheet - very thick - I'll add some angle tomorrow
  • the cooling was much better - I was getting close to 360 with no shroud, during some 2-3 min ground tests, and today the max temp I saw was 265. Perhaps too much cooling. OAT was about 3°c. (38°F according to the GRT EFIS)
  • I could not bring myself to bring it up to 2700 RPM - max I hit was just under 2000 - I was quite terrified that if something broke lose I would launch into the air like a scud missile. This baby wanted to take off! I will add a second strap to the tailwheel.
  • I will add some additional strength to the shroud - the math says it's fine, but the idea of that thing breaking loose and slamming into the windscreen didn't seem pleasant.
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  #27  
Old 12-30-2019, 10:58 AM
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Quote:
Originally Posted by TShort View Post
On purpose??
Yes - pretty amazing - it flew fine he said.
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  #28  
Old 12-30-2019, 11:04 AM
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Just a thought, but how about a single piece of aluminum that is bent into a half pipe that is bolted to each side of the engine similar to what you have now? No seams and you could cut it so that it creates a cone.
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  #29  
Old 12-30-2019, 11:59 AM
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Default single piece shroud

Quote:
Originally Posted by Zuldarin View Post
Just a thought, but how about a single piece of aluminum that is bent into a half pipe that is bolted to each side of the engine similar to what you have now? No seams and you could cut it so that it creates a cone.
I think this is a great idea.

You could probably do it with with flexible enough sheet, and some good geometry to cut out the shape flat and then just install it. With the amount of cooling I seem to be getting, sealing it up tightly at the back does not seem to be very critical.
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  #30  
Old 12-31-2019, 03:42 AM
svyolo svyolo is offline
 
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I don't think a whole lot is critical. Except maybe being strong enough so that it doesn't fly apart and damage the very expensive stuff right behind it.

Think hurricane force winds.
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