Bob_Belville

Laminar Flow Wing and disturbed flow

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While I generally agree that drag is more important than power, I’ve done a lot of speed testing in my F and I know th ~.75” of manifold pressure I get from opening the ram air is worth a good 3 or 4 knots.  Are you sure your engine is running strong and all the compressions are good?  I had a barely noticeable exhaust valve wobble and I first noticed the speed loss.

 I have done speed tests at different weights and it definitely makes a noticeable difference, but really takes several hundred pounds of weight to make more than a knot or two.

Honestly though, probably a rigging issue since all the surfacs were just off, stripped, painted, balanced, put back on.  That’s the most likely.

Edited by Ragsf15e

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Extra point for M. E.!

Looks like getting the 5 kts back is going to take many small steps...

Each building on top of the next...

Precision rigging would be an interesting step... more engineering than artistry.

Adjusting levels of paint... that requires precision paint skills...

Best regards,

-a-

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39 minutes ago, Ragsf15e said:

While I generally agree that drag is more important than power, I’ve done a lot of speed testing in my F and I know th ~.75” of manifold pressure I get from opening the ram air is worth a good 3 or 4 knots.  Are you sure your engine is running strong and all the compressions are good?  I had a barely noticeable exhaust valve wobble and I first noticed the speed loss.

 I have done speed tests at different weights and it definitely makes a noticeable difference, but really takes several hundred pounds of weight to make more than a knot or two.

Honestly though, probably a rigging issue since all the surfacs were just off, stripped, painted, balanced, put back on.  That’s the most likely.

Compressions:

Mar. 18: 79/80; 79/80; 78/80; 78/80.

Feb. 17: 78/80; 78/80; 78/80; 78/80.

Dec. 15: 79/80; 78/80; 77/80; 78/80. 

Oct. 14: 78/80; 76/80; 77/80; 77/80                (fresh engine reinstalled after Triad overhaul - prop strike.) 

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7 hours ago, Bob_Belville said:

Thanks Lance, we are working on the aileron. With a straight edge across the yokes the right aileron is level and the left is down about 1/4". Lynn is going to check behind me and check with the rigging boards. He may need to tweak the adjustment even though we do not believe the painter could/would have messed with the adjustment. 

The rigging, particularly the subtle bending of the trailing edges of ailerons and rudder, is on going. As several here have noted this is no doubt a factor.

But I started this thread to get ideas from this august mob about the paint issue and possible fixes and I've received several useful ideas.  

Be sure to check that all of the shim washers are installed between the aileron pushrod aft rode end bearing and the aluminum fitting on the aileron.  Without them the rod end can move laterally on the bolt shank allowing the aileron trailing edge to move up and down.

While on the subject of shim washers, make shire that all of the elevator and rudder fittings have the required shim washers installed.  It is quite common to lose the washers when flight controls are removed.  If they are missed the fittings on the stabilator trailing edge get bent when the hinge bolt is tightened.

Lyn will know where to look.

Clarence

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2 hours ago, M20Doc said:

Be sure to check that all of the shim washers are installed between the aileron pushrod aft rod end bearing and the aluminum fitting on the aileron.  Without them the rod end can move laterally on the bolt shank allowing the aileron trailing edge to move up and down.

While on the subject of shim washers, make sure that all of the elevator and rudder fittings have the required shim washers installed.  It is quite common to lose the washers when flight controls are removed.  If they are missed the fittings on the stabilator trailing edge get bent when the hinge bolt is tightened.

Lynn will know where to look.

Clarence

Thanks Clarence! I'll ask Lynn to double check all. @AGL Aviation

The aileron fit to the wing seems tighter than previous, I've assumed thinker paint... wonder if your shims affect that fit...

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4 minutes ago, Ragsf15e said:

Good in March, I guess my thought is, how are they now?  

March was annual inspection after which the plane went to the painter. I've only flown 35 hours since and I have not had any reason to check compressions. Lance Keve and I took our airport manager to JNX to pick up a friend's Cherokee 6, we were at gross and climbed to 7000' just fine. 

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I'm guessing you could achieve the same ridges with a vinyl wrap - why not try a wrap in similar configuration on a friends plane. Do some pre and post speed tests.  Should be an easy theory to prove/disprove.  

I wouldn't  touch the paint until I proved it was causing the issue - my 2 cents - best of luck. 

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