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  #11  
Old 06-29-2018, 08:40 AM
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JonJay JonJay is offline
 
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Originally Posted by Adam W View Post
thank you this has been reassuring and helpful

can anyone comment on the amount they lowered the top cowl to compensate for engine sag?
It is really difficult to determine how much, if any, sag you will get. Some don't sag at all. Some drop a bit.
In the day, folks felt it was a sense of pride to have as little gap as possible. Over time, vanity lost out over ease of use and folks started accepting a larger gap. The larger the gap, the less noticeable the sag will be, if it does sag. It is also much easier to put on and remove.
Others can chime in, but 1/4" gap would be an absolute minimum. I would accept more. I gapped to 1/8" on the top and 5/16" on the bottom hoping for the sag to even out to 1/4" gap. My engine never sagged. I still have the same gap, which frankly isn't noticeable unless you go looking.

As far as top alignment, I think it is important that the transition from the top of the cowl to the spinner makes a nice profile but it is also needs to be centered to the cowl. There is a bit of compromise here and the "gap" plays into how that looks. Sag doesn't come into play as much in regard to the profile unless it really sags a bunch.

I hope others can add to this.
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Last edited by JonJay : 06-29-2018 at 08:45 AM.
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  #12  
Old 06-29-2018, 09:07 AM
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RV6_flyer RV6_flyer is offline
 
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Originally Posted by RV7 To Go View Post
Can't speak to the latest cowls but I had about 2" to cut off the back of my cowls (2008 kit) with the standard extension. I would suggest no less than 3/8" clearance from the back of the spinner to the cowl. Any less and it becomes difficult to re and re the cowl. One of the guys who has built 8 or 9 RV's leaves 1/2" for this reason. I split the difference between Vans 1/4" and his 1/2" and did 3/8" which worked out ok. I had a 4 with a 3/16" gap and it was a pain getting the bottom cowl on and off. FWIW.
Al
20 some years ago, I built my RV-6 with 3/8" space between back of spinner and front of cowl. IMHO, that is the minimum space needed to get my cowl on and off.
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  #13  
Old 06-29-2018, 09:38 AM
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Carl Froehlich Carl Froehlich is offline
 
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Originally Posted by Wunderon View Post
Somewhat related, when drilling the top hinges to the cowl, is it best to hold the ‘slack’ out of the hinge due to the .090 pin‘s sloppy fit, or let it ride in the ‘middle’ of the hinge eyes where it wants to?

Seems like the cowl would end up loose if you don’t hold the hinge separated, but that might make it hard to put on and remove.
Another option, use 1/8” SS pins for the top cowl. You need to tapper the last 8” or so to .090” or so to make the curve. I did this and it eliminated the top of the cowl riding up on the hinge slack that you get by using the 0.090” pins.

The hard part is doing the tapper. I chucked up a lenght of 1/8” pin in the drill press and had it run on slow speed. I used a die grinder with a rotary file to make the tapper. Cleaned it up with some sandpaper then trimmed the length. The SS is tough - this took some time.

Carl
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  #14  
Old 06-29-2018, 11:51 AM
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Originally Posted by Carl Froehlich View Post
Another option, use 1/8” SS pins for the top cowl. You need to tapper the last 8” or so to .090” or so to make the curve. I did this and it eliminated the top of the cowl riding up on the hinge slack that you get by using the 0.090” pins.

The hard part is doing the tapper. I chucked up a lenght of 1/8” pin in the drill press and had it run on slow speed. I used a die grinder with a rotary file to make the tapper. Cleaned it up with some sandpaper then trimmed the length. The SS is tough - this took some time.

Carl
My neighbor did this as well Carl. He used a disk grinder and it went pretty quickly. Chucked up the rod in a drill as well. Good suggestion.
I just let mine ride up. Doesn't bother me a bit, but this is an easy "fix" if it does.
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  #15  
Old 06-29-2018, 11:52 AM
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Originally Posted by RV6_flyer View Post
20 some years ago, I built my RV-6 with 3/8" space between back of spinner and front of cowl. IMHO, that is the minimum space needed to get my cowl on and off.
I wish I had 3/8". Fortunately, the 5/16" I have is on the bottom.
It is a bit tricky but obviously doable. I like your recommendation. 1/4" is really tight.
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  #16  
Old 07-02-2018, 09:38 PM
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I’m having trouble visualizing how the cowl is ultimately supported in the front. Do the baffles end up supporting the weight of the cowl, with the hinges mainly holding position? Or, should I fit the hinges so that they support 100% of the cowl weight,
prior to installing baffles?

Should I remove my front supports only after all hinges are fitted?

thanks, I’m feeling dense,
dave
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Last edited by Wunderon : 07-02-2018 at 09:39 PM. Reason: clarity, heh
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  #17  
Old 07-02-2018, 09:44 PM
Kyle Boatright Kyle Boatright is offline
 
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Originally Posted by Wunderon View Post
I’m having trouble visualizing how the cowl is ultimately supported in the front. Do the baffles end up supporting the weight of the cowl, with the hinges mainly holding position? Or, should I fit the hinges so that they support 100% of the cowl weight,
prior to installing baffles?

Should I remove my front supports only after all hinges are fitted?

thanks, I’m feeling dense,
dave
The cowling is a self supporting structure. Between the hinges which hold it to the firewall, the hinges along the sides of the cowl, and the screws on the inside of the spinner, the cowl is supported all around and quite rigid. Neither the baffles or engine are part of the support structure for the cowl.
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  #18  
Old 07-03-2018, 07:05 AM
rocketman1988 rocketman1988 is offline
 
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...nor should the cowl be attached to the engine. One look at how much that engine moves will illustrate why...
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  #19  
Old 07-03-2018, 07:54 AM
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Thanks, makes sense.

Why I ask is that after I drill the top hinge, and remove the front supports, the front sags below where I want it on the spinner. This is prior to trimming the bottom cowl. Should I leave the front cowl supports in until after the cowl bottom and sides are trimmed and drilled?

thanks
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  #20  
Old 07-03-2018, 07:59 AM
BillL BillL is offline
 
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Originally Posted by Wunderon View Post
Thanks, makes sense.

Why I ask is that after I drill the top hinge, and remove the front supports, the front sags below where I want it on the spinner. This is prior to trimming the bottom cowl. Should I leave the front cowl supports in until after the cowl bottom and sides are trimmed and drilled?

thanks
Definitely keep the front in line with where you want it for the lower cowl fitting process. With just the aft hinge holding it, the sides will bulge out under it's own weight. Just make sure nothing is forced into place when final fitting. Taking the whole thing off and on a few dozen times is normal, at least it was for me.
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