Francis....first post! Thank you for joining in.
Do you recall the airspeed at which you found an 8" differential? Were the tube ends open, or did you add something to negate dynamic pressure?
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Help with measuring cowl pressure differential
- Thread starter lostpilot28
- Start date
Francis....first post! Thank you for joining in.
Do you recall the airspeed at which you found an 8" differential? Were the tube ends open, or did you add something to negate dynamic pressure?
lostpilot28
Well Known Member
Hi Francis, I'm just trying to learn, so bear with me...I'm sure if I'm wrong, someone will point it out. But, pointing the tubing aft in relation to the airflow would create a lower pressure at the opening of the tube, wouldn't it? And depending on where you placed the tubing you could get some pretty significant error based on that (false) pressure drop. 8" of water difference sounds pretty good compared with what others have seen. I just wonder if the results were skewed.
Sorry, I forgot to ask the test altitude. I'm guessing 3000~4000 ft?
Ok, I now have Lycoming cooling air charts for 320 and 360 parallel valve and 360 and 390 angle valve.
Three PDF files....download here:
http://www.perryhillauto.com/downloads/
Three PDF files....download here:
http://www.perryhillauto.com/downloads/
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Got it! Thanks Dan. Differential pressure instrument is on order and should arrive in a week or so (I hope).
lostpilot28
Well Known Member
Well, I got my Chinese digital instrument, and...I like it! It seems pretty well built for what I paid. I've played around with it a little, and it seems to work - although how well I can't say. Maybe I'll stick one of the tubes out the window on the drive home and see if it measures something. 
I'm ready to get this testing under way!
I'm ready to get this testing under way!
GrayHawk
Well Known Member
Well, I got my Chinese digital instrument, and...I like it! It seems pretty well built for what I paid. I've played around with it a little, and it seems to work - although how well I can't say. Maybe I'll stick one of the tubes out the window on the drive home and see if it measures something.
I'm ready to get this testing under way!
祝你好运, (some extra characters)
lostpilot28
Well Known Member
Thanks, Bill...I can use all the luck I can get. I often say "I'd rather be lucky than good".
Ok, let's see how accurate it is. Easy to do; tee the meter to a water manometer made from vinyl tubing and a yardstick. Make sure the static end for each meter is in the same location and oriented the same. Have your assistant hold the pitot tube out the window of your car and note the readings (you drive!). If accurate, the meter will read exactly twice the rise of the water in one of the tubes, or put another way, it will equal the difference in water level between the two legs of the manometer. Expect about 9" at 60 mph. At 85 you'll blow the water out of the tube
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lostpilot28
Well Known Member
Ok, let's see how accurate it is. Easy to do; tee the meter to a water manometer made from vinyl tubing and a yardstick. Make sure the static end for each meter is in the same location and oriented the same. Have your assistant hold the pitot tube out the window of your car and note the readings (you drive!). If accurate, the meter will read exactly twice the rise of the water in one of the tubes, or put another way, it will equal the difference in water level between the two legs of the manometer.
Couldn't I simplify that by just putting one end of each tube out the window and having the other end free inside? They should measure the same, no? less T's this way I think.
I dunno about you Sonny. I try to give you a triple cool, Dynamic Science Guy, zoom around in your sports car setup..... and you bitch about too many tees
As punishment I give you the boring, cheap, dirt simple no-tee method. You can do it over the kitchen sink. No worshipful assistant required. Just you and about 10 feet of 1/2" vinyl tube. Hook up as pictured, pour water in one end, measure the height difference and compare with the meter reading. Make sure the connection at the meter is air tight.
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longranger
Well Known Member
lostpilot28
Well Known Member
I dunno about you Sonny. I try to give you a triple cool, Dynamic Science Guy, zoom around in your sports car setup..... and you bitch about too many tees
As punishment I give you the boring, cheap, dirt simple no-tee method. You can do it over the kitchen sink. No worshipful assistant required. Just you and about 10 feet of 1/2" vinyl tube. Hook up as pictured, pour water in one end, measure the height difference and compare with the meter reading. Make sure the connection at the meter is air tight.
Ahh, c'mon, Dan...if I could do it the first way you mentioned, I wouldn't have needed to spend the $40 on the digital instrument!
GrayHawk
Well Known Member
I heard that Idaho just passed a new law: "No manometering while driving".Ahh, c'mon, Dan...if I could do it the first way you mentioned, I wouldn't have needed to spend the $40 on the digital instrument!
lostpilot28
Well Known Member
I would've gotten a ticket on the drive home from work today if that were the case!
Ahh, c'mon, Dan...if I could do it the first way you mentioned, I wouldn't have needed to spend the $40 on the digital instrument!
Seriously, we do want to know if the $40 digital is any good. Only way to know is to calibrate. In this case the standard is really, really cheap (water) and so is the apparatus.
Add a tiny bit of dishwashing liquid to the water to reduce surface tension.
The kitchen sink method is actually the better way. I just didn't think of it until after posting the first one
Fixed it for you (sorry, it's getting close to 5PM here on the west coast)...
That's funny....I don't care who 'ya are.
lostpilot28
Well Known Member
Hey Dan, that Tygon fuel line is apparently hard to get locally. You happen to have any alternate ideas for tubing?
Have you tried the hardware store? Our local Ace has clear vinyl tubing in a variety of diameters. It's a bit stiff when it's cold (like, oh, this time of the year) but softens nicely when threatened with a heat gun, or even hot water. I have made many manometers with the stuff. I wouldn't consider it fuel-safe, but I don't believe that's a criterion here.
I should note that the hardware store vinyl tube, while not fuel safe, is at least stable to 212°F; I've immersed plenty of it in boiling water- it softens (temporarily) but seems no worse for the wear. For the purposes of a temporary hookup under the cowling it should be adequate, but make sure it's well-clamped where it connects to anything.
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I bought Tygon at the local NAPA Auto Parts as "small engine fuel line" assuming vinyl tube would not handle engine compartment temperatures. Maybe it will. Cheap enough; why not give it a try?
Doug
Well Known Member
Good idea to use an ASI for the test. I have an u/s ASI I can calibrate in inches a use for my own tests. Thanks for the idea.
Also, 200kts is 26.68"h2o from other references.
Doug Gray
longranger
Well Known Member
You're welcome for the idea, Doug. I just used the formula of dynamic pressure equals density times velocity squared divided by two, reconciled the units to psi, then used an online units converter to convert to inches of water. From memory, I used an air density of 0.076 pounds mass per cubic foot, but that could be off a bit and account for the difference. Anyway, most ASI's I've seen are way off on the low end, so I'd recommend anyone doing this to calibrate whatever ASI they use against a water manometer.
When I did that table, I had no idea what a good differential pressure across the cylinders and baffling might be. It appears it's in the single digits of inches of water, so a lower range ASI might be more appropriate.
lostpilot28
Well Known Member
Let me know if you find some suitable tubing. I was thinking of checking Home Depot after work today...
Have not yet, but I will.
I've been finishing up new cold air ducting for my oil cooler.
Thanks Dan.
Only thing I could find at HD and ACE was Vinyl tube which was rated at only 175 F. We are not applying a lot of pressure to these tubes so they really only need to maintain their shape and not close up when heated above 175. I bought some for the water calibration test and will put a piece in my oven and see how it does up to 300 F or so.
Only thing I could find at HD and ACE was Vinyl tube which was rated at only 175 F. We are not applying a lot of pressure to these tubes so they really only need to maintain their shape and not close up when heated above 175. I bought some for the water calibration test and will put a piece in my oven and see how it does up to 300 F or so.
Instrument Calibration Results
Test Conditions:
Temp: 24.4 deg C (76F) (spec error is listed at 25 deg C)
Pressure Instrument Calibration Data
"H20 Measured "H2O Indicated error (ind-measured) inches % error
0.3065 0.3 -0.0065 -2.12%
0.701 0.7 -0.001 -0.14%
1.1895 1.19 0.0005 0.04%
1.83 1.84 0.01 0.55%
2.7415 2.75 0.0085 0.31%
3.6545 3.66 0.0055 0.15%
4.8695 4.88 0.0105 0.22%
5.745 5.77 0.025 0.44%
7.18 7.2 0.02 0.28%
10.13 10.15 0.02 0.20%
15.25 15.21 -0.04 -0.26%
16.84 16.77 -0.07 -0.42%
Set up the manometer as such:
Added a drop of dawn dish soap and a few drops of red food coloring.
Measured the water height with a set of calibrated digital calipers until reaching 10" and greater where I used an engineering ruler graduated in .01" increments. In truth a good deal of error exists in the measurement itself as finding the EXACT bottom of the meniscus to .001" is really a stretch as well as interpolating values less than .01".
Couple of points. You have to be very careful when connecting the rubber tube to the instrument to avoid squeezing the tube as it slides onto the terminal as it will pressurize the tube and lock this in as your starting point. Not a big deal but beware it is difficult to start at zero because of this. This became the first data point.
I allowed each point to sit for 3 minutes while tapping the tube to ensure all droplets found their way to the top of the water column. Surprising to watch the instrument register the value of a single drop of water! I'm sure using a bit larger diameter tube would have made things easier but using a syringe to inject the water worked really well.
This instrument has an avg function which may be handy for those readings which are certainly going to be fluctuating. I'll play with this and see how well it works.
Test Conditions:
Temp: 24.4 deg C (76F) (spec error is listed at 25 deg C)
Pressure Instrument Calibration Data
"H20 Measured "H2O Indicated error (ind-measured) inches % error
0.3065 0.3 -0.0065 -2.12%
0.701 0.7 -0.001 -0.14%
1.1895 1.19 0.0005 0.04%
1.83 1.84 0.01 0.55%
2.7415 2.75 0.0085 0.31%
3.6545 3.66 0.0055 0.15%
4.8695 4.88 0.0105 0.22%
5.745 5.77 0.025 0.44%
7.18 7.2 0.02 0.28%
10.13 10.15 0.02 0.20%
15.25 15.21 -0.04 -0.26%
16.84 16.77 -0.07 -0.42%
Set up the manometer as such:
Added a drop of dawn dish soap and a few drops of red food coloring.
Measured the water height with a set of calibrated digital calipers until reaching 10" and greater where I used an engineering ruler graduated in .01" increments. In truth a good deal of error exists in the measurement itself as finding the EXACT bottom of the meniscus to .001" is really a stretch as well as interpolating values less than .01".
Couple of points. You have to be very careful when connecting the rubber tube to the instrument to avoid squeezing the tube as it slides onto the terminal as it will pressurize the tube and lock this in as your starting point. Not a big deal but beware it is difficult to start at zero because of this. This became the first data point.
I allowed each point to sit for 3 minutes while tapping the tube to ensure all droplets found their way to the top of the water column. Surprising to watch the instrument register the value of a single drop of water! I'm sure using a bit larger diameter tube would have made things easier but using a syringe to inject the water worked really well.
This instrument has an avg function which may be handy for those readings which are certainly going to be fluctuating. I'll play with this and see how well it works.
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lostpilot28
Well Known Member
Ken, that's great...thanks for beating me to it! I managed to get some tubing at HD that I think will work. I had planned on doing this tomorrow (really), but now there's no need.
Bob...I'm not shocked at all. I've had pretty decent luck with most of the Chinese stuff I have. Granted, not all of it is great, but then again I can point to lots of tools in my garage or hangar that's not Chinese made that is cruddy. Sometimes a good deal really is a good deal.
Bob...I'm not shocked at all. I've had pretty decent luck with most of the Chinese stuff I have. Granted, not all of it is great, but then again I can point to lots of tools in my garage or hangar that's not Chinese made that is cruddy. Sometimes a good deal really is a good deal.
Sonny, you should still check yours. Bummer to spend time and money flying a test only to find out later the equipment was lying. Just do a gross check; agreement with the water manometer within 1/8" is plenty good for our purposes.
New shoes go a long, long way...
BTW..I checked for hysteresis by walking the water level back down from the highest point. Within measurement accuracy the hysteresis is negligible.
Vinyl tube heat test:
Oven Temp set to 300 deg F. Heat soak time 20 minutes.
Results: did not lose shape when flattened and released. When folded in half and released the tube returned to its previous shape with only slight permanent deformation. Attempted to pull tube apart through elongation but could not do so. 3" length of tube remained 3" at 300 deg
Oven temp 350 deg F. 20 min heat soak
Results: 3" tube ended up at 1.75" @ 350 within first 4 minutes. When squished flat with a fork it took 11 seconds for it to return to its previous round shape. When folded in half and released the tube remained bent at about a 90 deg angle.
Anyone have under cowl temp survey? I wouldn't be worried about in flight temps but rather after shut down.
lostpilot28
Well Known Member
Science can be fun
OK, guys. I did it...see the image below for my results. Ken is right about the measurement error being significant. At the hangar today I didn't grab my digital calipers, so I ended up using a ruler. Ouch. So, I was only getting within 1/32 accuracy, at best. Obviously, better tools would paint a more accurate picture...but, these results are reasonable (at least to me).
OK, guys. I did it...see the image below for my results. Ken is right about the measurement error being significant. At the hangar today I didn't grab my digital calipers, so I ended up using a ruler. Ouch. So, I was only getting within 1/32 accuracy, at best. Obviously, better tools would paint a more accurate picture...but, these results are reasonable (at least to me).
Wayne Gillispie
Well Known Member
Ken,
I have temp labels on all accessories. Temps have not exceeded 225F(min indicator dot) yet. I have only flown in 70F and below.
I have temp labels on all accessories. Temps have not exceeded 225F(min indicator dot) yet. I have only flown in 70F and below.
Thanks Wayne!
OK, guys. I did it...see the image below for my results. Ken is right about the measurement error being significant. At the hangar today I didn't grab my digital calipers, so I ended up using a ruler. Ouch. So, I was only getting within 1/32 accuracy, at best. Obviously, better tools would paint a more accurate picture...but, these results are reasonable (at least to me).
close correlation to my results..good news.
lostpilot28
Well Known Member
Time to resurrect another old thread. I started this thread with the hope of learning how to measure my airflow through the cowl so I could see if there was a problem, thus fixing it to lower my oil and CHT temps.
After following Bob's thread on modifying the exit, I read a post somewhere in there from an Aeronautical Engineer saying that adding the curved exit at the bottom of the firewall is the biggest thing you can do to improve cooling. Well, why didn't I notice before that Dan and some of the other guys have done this? No clue...but I decided to follow suit and see what happened. So after finishing my condition inspection last weekend, I added one (see pic below).
Had the chance to test fly today, but the OAT only got up to 60 (F). It appears (I'm still holding out final judgement for more testing) that both my oil and CHT temps have dropped. I'm going off of memory with Oil temps, but I'm pretty sure with today's OAT, my oil reading should've hit the mid 190's...maybe even 200. After 30 minutes I started some maneuving flight and it didn't go higher than 187...it actually sat in the low 180's most of the rest of the flight.
My CHT's appeared to be lower as well...They never went past the mid 350's, and in the past they would've been closer to 390.
Again, this needs more testing, but I'm optimistic. Last year when I brought this up, I only wanted to knock 10 degrees off my oil temps. Looks like this may have done that, and then some.
I'll report back later after more testing. Tomorrow is supposed to be hotter, so maybe then...
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This picture was before the addition of lots of high-temp RTV and aluminum tape to fill the gaps.
After following Bob's thread on modifying the exit, I read a post somewhere in there from an Aeronautical Engineer saying that adding the curved exit at the bottom of the firewall is the biggest thing you can do to improve cooling. Well, why didn't I notice before that Dan and some of the other guys have done this? No clue...but I decided to follow suit and see what happened. So after finishing my condition inspection last weekend, I added one (see pic below).
Had the chance to test fly today, but the OAT only got up to 60 (F). It appears (I'm still holding out final judgement for more testing) that both my oil and CHT temps have dropped. I'm going off of memory with Oil temps, but I'm pretty sure with today's OAT, my oil reading should've hit the mid 190's...maybe even 200. After 30 minutes I started some maneuving flight and it didn't go higher than 187...it actually sat in the low 180's most of the rest of the flight.
My CHT's appeared to be lower as well...They never went past the mid 350's, and in the past they would've been closer to 390.
Again, this needs more testing, but I'm optimistic. Last year when I brought this up, I only wanted to knock 10 degrees off my oil temps. Looks like this may have done that, and then some.
I'll report back later after more testing. Tomorrow is supposed to be hotter, so maybe then...
This picture was before the addition of lots of high-temp RTV and aluminum tape to fill the gaps.
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Pretty work Sonny. It's very much as Steve Smith advocated, rather than the larger "duct" style radius I and others are trying.
In addition to judging effect on CHT and oil temperature, you might want to do a three-leg top speed check. In theory the mod should have increased exit velocity.
In addition to judging effect on CHT and oil temperature, you might want to do a three-leg top speed check. In theory the mod should have increased exit velocity.
rvmills
Well Known Member
Sonny,
Nice work...looks very clean. Will be interested in your continuing test results. I've talked to Steve about this mod, and from the discussion, I believe the -8 radius is 2", and Steve felt a bit bigger might be a bit better. I've heard of two guys that build Super 8s in Oregon that use a radius > 2", and are happy with it (not sure of the exact dimension...trying to find out).
Your radius looks like perhaps 3"? Pretty much where I was planning to go. Need to get a new performance baseline with this winter's mods, then replace the old boost pump (on the FW) and gascolator (in the exit) to make room for a radius like this (already have the EFII pump on the shelf for that project). But I plan to follow your lead here!
I see the nutplates on the fuselage bottom...was wondering if you attached the top edge somehow (RTV to FW, etc)? I've also always wondered if covering the sides of radius would be beneficial...have any pics of the taped and RTV'd product?
Hey Dan, when you say your larger duct radius, do you mean your forward sloping bell? It fairs right into the top of the stock -8 FW radius, doesn't it? (Just trying to keep up!)
You guys are blazing some great trails...thanks! Lots of homework to do in this thread on the instrumentation set up. At the risk of sounding lazy (perhaps I am!) is there an exec summary of parts to make, parts to buy, placement of sensors, tube and wire routing, and the gauges you guys are using to display the data. I'm reading through to refresh and gain the background knowledge, but if you guys have a collaborative cheat sheet you are willing to share on set up and testing, I'd be most appreciative! If it needs to wait till after your comparative results are published, that's OK too. Very interested!
Cheers,
Bob
Nice work...looks very clean. Will be interested in your continuing test results. I've talked to Steve about this mod, and from the discussion, I believe the -8 radius is 2", and Steve felt a bit bigger might be a bit better. I've heard of two guys that build Super 8s in Oregon that use a radius > 2", and are happy with it (not sure of the exact dimension...trying to find out).
Your radius looks like perhaps 3"? Pretty much where I was planning to go. Need to get a new performance baseline with this winter's mods, then replace the old boost pump (on the FW) and gascolator (in the exit) to make room for a radius like this (already have the EFII pump on the shelf for that project). But I plan to follow your lead here!
I see the nutplates on the fuselage bottom...was wondering if you attached the top edge somehow (RTV to FW, etc)? I've also always wondered if covering the sides of radius would be beneficial...have any pics of the taped and RTV'd product?
Hey Dan, when you say your larger duct radius, do you mean your forward sloping bell? It fairs right into the top of the stock -8 FW radius, doesn't it? (Just trying to keep up!
)You guys are blazing some great trails...thanks! Lots of homework to do in this thread on the instrumentation set up. At the risk of sounding lazy (perhaps I am!) is there an exec summary of parts to make, parts to buy, placement of sensors, tube and wire routing, and the gauges you guys are using to display the data. I'm reading through to refresh and gain the background knowledge, but if you guys have a collaborative cheat sheet you are willing to share on set up and testing, I'd be most appreciative! If it needs to wait till after your comparative results are published, that's OK too. Very interested!
Cheers,
Bob
lostpilot28
Well Known Member
Thanks, fellas.
Dan, I definitely plan on more in-depth testing. I wanted to see some initial results for a couple (maybe 3) flights first just to determine if it even warranted more analysis. So far, so good. If the positive trend develops I'll do the 3-legged tests with pressure and temp sensors connected.
Steve, I was shooting for a bend radius of 2 inches, which is pretty much how they turned out...maybe 2-1/8. I used a one inch piece of metal tubing and taped the edge just like we do for the elevators and rudder.
Bob, the next time I pull the cowl I'll get some pictures with RTV and tape. I pretty much RTV's every seam because there were a lot of edges and tubes to go around (dang nose gear!)...but the aluminum tape helped smooth it out. I actually had to assemble it in the 4 pieces shown simply because it was so tight a fit. As for the nut-plates - I could've done that better by putting them on the curved metal, and simply countersinking the plate that's attached to the airframe. I would've been able to put the curved piece on TOP of my plate, thus not interfering with the cowl. Interference ended up not being a factor, thankfully.
Thanks for the kind words, guys...I really appreciate it. I'm hoping this small mod makes a big enough difference!
Dan, I definitely plan on more in-depth testing. I wanted to see some initial results for a couple (maybe 3) flights first just to determine if it even warranted more analysis. So far, so good. If the positive trend develops I'll do the 3-legged tests with pressure and temp sensors connected.
Steve, I was shooting for a bend radius of 2 inches, which is pretty much how they turned out...maybe 2-1/8. I used a one inch piece of metal tubing and taped the edge just like we do for the elevators and rudder.
Bob, the next time I pull the cowl I'll get some pictures with RTV and tape. I pretty much RTV's every seam because there were a lot of edges and tubes to go around (dang nose gear!)...but the aluminum tape helped smooth it out. I actually had to assemble it in the 4 pieces shown simply because it was so tight a fit. As for the nut-plates - I could've done that better by putting them on the curved metal, and simply countersinking the plate that's attached to the airframe. I would've been able to put the curved piece on TOP of my plate, thus not interfering with the cowl. Interference ended up not being a factor, thankfully.
Thanks for the kind words, guys...I really appreciate it. I'm hoping this small mod makes a big enough difference!
rvmills
Well Known Member
Thanks Sonny, sounds good. On the nutplates...I'm thinking your method may be better. The curve fairs the edge of the exit, and you can blend that back into the fuselage with RTV or the like at the trailing edge (if needed). Also, those nutplates could be a nice front anchor for a Vetteman-like after-body, as phase II of the experiment (perhaps). Always thinkin'
Cheers,
Bob
Cheers,
Bob
Yes. As Steve said, skin friction in the large bell may offset any gain due to the larger radius.
Most of the work is in fact learning how to do the setup. Plenty of false starts, leaky tubes, bad placements, and 'Huh?" moments. You can expect a setup summary in due course because it's best if everyone does it the same way.....making the results directly comparable.
rvmills
Well Known Member
Thanks Dan. Interesting on the first part. Skin friction versus all the engine mount and accessories getting in the mix...(not disagreeing, just more of that aero-black-magic stuff).
Excellent! Kinda what I was thinking, and why I asked (well that and laziness!
)Cheers,
Bob
Bob, My firewall fairing looks very similar. Kinda a 4 piece puzzle where the two outer pieces cover and close the ends.
I attached at the top via some holes strategically placed on the fire wall so that they drill through the firewall and into the support angle behind. Then just tap them 6/32 or 8/32 (your choice) and they can screw right into the firewall/angle. No nutplates necessary.
On the bottom flange, my radiused fairing goes above the flange so that the nutplates are in the fairing. Match drill the flange and fairing, countersink the flange and screw into the fairing/nutplate.
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rvmills
Well Known Member
Roger all that Gary...good work as well.
Did you somehow bevel the leading edge of the flange or put RTV in the little notch that is formed where the radius sits above the flange? Perhaps its in the boundary layer and not a factor, but the devil is in the details, and if that little edge is a "trip hazard" for airflow as it exits, it could reduce the flow attachment effect we are looking for. That could be true whether the radius sits above or below the flange (I thnk). The -8 guys have it good, in that the radius flows right into the ramp on the belly.
Here's a thought for adding the radius to a 6 or 7. Make a small lap joint inside the radius (full width), and have that sit on top of the flange at the firewall. The lap joint would contain the nutplates, and the radius itself would then be flush with the flange itself (and thus the belly of the plane).
The only issue I see with a either lap joint or the radius on top of the flange (Gary's method), is working around the rivets in the flange. I gues one could drill them out and reinstall after radius installation, or drill holes in the lap joint or radius to fit over the shop heads. How'd you do it Gary?
Thoughts from anyone on the lap joint? Overthinking it?
Cheers,
Bob
Did you somehow bevel the leading edge of the flange or put RTV in the little notch that is formed where the radius sits above the flange? Perhaps its in the boundary layer and not a factor, but the devil is in the details, and if that little edge is a "trip hazard" for airflow as it exits, it could reduce the flow attachment effect we are looking for. That could be true whether the radius sits above or below the flange (I thnk). The -8 guys have it good, in that the radius flows right into the ramp on the belly.
Here's a thought for adding the radius to a 6 or 7. Make a small lap joint inside the radius (full width), and have that sit on top of the flange at the firewall. The lap joint would contain the nutplates, and the radius itself would then be flush with the flange itself (and thus the belly of the plane).
The only issue I see with a either lap joint or the radius on top of the flange (Gary's method), is working around the rivets in the flange. I gues one could drill them out and reinstall after radius installation, or drill holes in the lap joint or radius to fit over the shop heads. How'd you do it Gary?
Thoughts from anyone on the lap joint? Overthinking it?
Cheers,
Bob
