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Improve Fit of Upper Cowl

 
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Joined: 26 Feb 2007
Posts: 429

PostPosted: Mon Jun 25, 2012 7:53 am    Post subject: Improve Fit of Upper Cowl Reply with quote

Barry S.,

From your pictures it looks to me that the nose bowl does not fit very well. Maybe it was messed up when they did the split on it. It looks like the nose bowl fit could be improved.

Pictures attached below. Note the horizontal seam where the upper cowl door meets the lower cowl side. Extend an imaginary line on this seam toward the prop. You should see that the nose bowl seam is no where near that imaginary line. It is down significantly and it is not parallel. I think this is part of the cause of your gap on the top corner where the cowl door should rest on the nose bowl corner.

In addition, another source of the misalignment is that there is no spacing at the nose bowl seam.
When the nose bowl is cut for the split STC there is material lost with the cut. The pictures show that there is no gap at the cut. The cut surfaces were laid on top of each other without any gap and the screws were placed to hold it there. This would be where to start a fix. You might close your gap at the corner by moving the screw holes to hold a gap here. As a result the seam will have a gap. You could fill the gap with epoxy if it gets unsightly.

After the nose bowl is fit properly if there is still a gap one could build up the fiberglass in the corner where the problem gap is. You could also use a shrinker on the aluminum upper cowl door in that corner if you think it has been stretched. But that is the last resort as it may crack.

Regards,
Ned


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bkspero



Joined: 23 May 2012
Posts: 17

PostPosted: Tue Jun 26, 2012 5:12 am    Post subject: Re: Improve Fit of Upper Cowl Reply with quote

Now you're getting my hopes up, again.... Gary had convinced me that either I be happy with what I have, or buy a Jaguar cowl. So I decided to be happy.<G>

Seriously, I see what you mean. I had gotten a private email from another person before I posted the photos and he speculated on this cause. I think his words included something like "...instead of using a thin kerf sawblade, some mechanics use a chainsaw and remove way to much material. Then when they reassemble it gaps show up in the cowl corners...he was exaggerating but makes the point". I'll ask my mechanic what it would take to adjust the screws to insert a ca. 1/16" gap. That could be enough to correct the fit in the front, as it is only a problem on one side and by only a small amount. He would need, I think, to adjust the position of the upper cowl about 1/8"-1/4" towards to passenger side to even out the fit, though. Don't know if that is possible. I presume that a 1/16" gap wouldn't cause any functional issues. As you can see, the plane is serviceable, but not a showpiece. So I don't think I'll even see that small a space in the split.

Still leaves the larger gaps in the back. Guess I will continue to live with those.

Thanks for the input.

Barry


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PostPosted: Tue Jun 26, 2012 9:36 am    Post subject: Improve Fit of Upper Cowl Reply with quote

The back of the cowling: A lot of cowlings don't fit well in the back; mostly from damaged doublers on the cowling. Spot welds break, the doubler cracks, you name it. You can buy another upper cowling, have it installed, strip it, alumi-prep it, prime it and paint it the base color, install it, line up the stripes, remove it and paint the stripes. Odds are it won't match the rest of the plane . . . but, it MIGHT fit better.
The front of the cowling and the nose bowl: If you just do the nose bowl, you might want to consider where the stripes are. If you open up the gap on the cowling, the stripes won't line up. Then you'll have to get the nose bowl repainted. You could get another nose bowl, you could get a LoPresti nose bowl (RJ, here's your chance, jump in at any time). Regardless of which way choose, some painting is involved.
You're using a dollar to chase a penny.
On-the-other-hand, it is your dollar. And, putting money back into circulation does help the economy. So, who knows, the dollar you spend could help your mechanic buy groceries. That, in turn, helps the kid bagging groceries. It helps the teller who rings it up. It helps the store owner. It helps the truck driver bringing groceries to the market. It helps the toll both operators who check the weight of the trucks. It helps the petroleum industry for the fuel used by the truck. It helps the truck driver. It helps everyone involved with the truck. It helps the grower in California who owns the orchard. It helps the Mexican picking the fruit. He helps his family in Mexico. They produce drugs that end up on the streets of New Jersey. Which in turn, . . . .
You could single handedly change many lives. Or, you could just fly your plane.
Thank you, everyone, for letting me express my thought process. It was really a lot of fun.
From: bkspero <bkspero(at)gmail.com>
To: teamgrumman-list(at)matronics.com
Sent: Tuesday, June 26, 2012 6:12 AM
Subject: Re: Improve Fit of Upper Cowl


--> TeamGrumman-List message posted by: "bkspero" <bkspero(at)gmail.com (bkspero(at)gmail.com)>

Now you're getting my hopes up, again.... Gary had convinced me that either I be happy with what I have, or buy a Jaguar cowl. So I decided to be happy.

Seriously, I see what you mean. I had gotten a private email from another person before I posted the photos and he speculated on this cause. I think his words included something like "...instead of using a thin kerf sawblade, some mechanics use a chainsaw and remove way to much material. Then when they reassemble it gaps show up in the cowl corners...he was exaggerating but makes the point". I'll ask my mechanic what it would take to adjust the screws to insert a ca. 1/16" gap. That could be enough to correct the fit in the front, as it is only a problem on one side and by only a small amount. He would need, I think, to adjust the position of the upper cowl about 1/8"-1/4" towards to passenger side to even out the fit, though. Don't know if that is possible. I presume that a 1/16" gap wouldn't cause any functional issues. As you can see, the plane is serviceable, but not a showpiece. So I don't think I'll even see that small a space in the split.

Still leaves the larger gaps in the back. Guess I will continue to live with those.

Thanks for the input.

Barry


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