Van's Air Force
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Developing New MLG Subfairings
- Thread starter Bob Axsom
- Start date
FlyerJumper
Well Known Member
Awesome. Anxiously awaiting the outcome!
PlaneBuilderBill
Well Known Member
MLG Subfairings
There was a guy years ago that sold add-on speed fairings similar to this for Grumman wheel pants....he called them "spats". The net effect was that very little of the tire was exposed....gotta land on pavement for sure. His name is Gene Plazak and he still has speed components for Grummans. He might be able to help...
Dallas Metroplex Aviation is owned and operated by Gene Plazak. 281-379-5430
There was a guy years ago that sold add-on speed fairings similar to this for Grumman wheel pants....he called them "spats". The net effect was that very little of the tire was exposed....gotta land on pavement for sure. His name is Gene Plazak and he still has speed components for Grummans. He might be able to help...
Dallas Metroplex Aviation is owned and operated by Gene Plazak. 281-379-5430
Not a Problem
This is such a custom fit for speed that each one has to be done individually. It isn't much of a problem just tedius. I did the nose gear already and the change in speed was remarkable. I do not expect much of a gain with the MLG sub fairings but I have to give it a shot.
Bob Axsom
This is such a custom fit for speed that each one has to be done individually. It isn't much of a problem just tedius. I did the nose gear already and the change in speed was remarkable. I do not expect much of a gain with the MLG sub fairings but I have to give it a shot.
Bob Axsom
These are for racing only
These are not practical for general use and could be dangerous in the wrong situation. Don't try this at home - the custom subfairings are for N710BJ and racing only. This and the nose landing gear subfairing thread before are only to show the idea, the implementation and the results. Then if someone wants to try this on their own for speed purposes only they can copy the process at their own risk. I have no intention of going into business. This amounts to conducting another experiment and sharing the information.
Bob Axsom
These are not practical for general use and could be dangerous in the wrong situation. Don't try this at home - the custom subfairings are for N710BJ and racing only. This and the nose landing gear subfairing thread before are only to show the idea, the implementation and the results. Then if someone wants to try this on their own for speed purposes only they can copy the process at their own risk. I have no intention of going into business. This amounts to conducting another experiment and sharing the information.
Bob Axsom
flyeyes
Well Known Member
Bob--I've thought about this in the past and wondered about making intentionally flimsy sub-fairings for a race.
What if you made the fairings out of pour-foam and "hard-shelled" them with micro? It seems that they would break away easily if contacted by a tire or the ground, but might last for a couple of (fast) flights.
Nice work BTW
That would address safety
I have an unwritten design requirement that no change shall have the potential for detracting from the airplanes appearance so I would not do that but it would do the drag reduction job and provide safety against fairing induced damage or nose over mentioned earlier. If you shape it right, so the so the interface angles between the fairing and the tire are small and the extension survives the first landing it probably will last a while. Don't let your tire pressure get low.
Bob Axsom
I have an unwritten design requirement that no change shall have the potential for detracting from the airplanes appearance so I would not do that but it would do the drag reduction job and provide safety against fairing induced damage or nose over mentioned earlier. If you shape it right, so the so the interface angles between the fairing and the tire are small and the extension survives the first landing it probably will last a while. Don't let your tire pressure get low.
Bob Axsom
Slow Progress 4-29-08
There is a lot of cleanup after laying up the first layer of a fiberglass part over airframe, tires and clay in an inverted close to the ground space. I have everything nearly ready for the second layer except sanding one of the subfairings but we have to prepare the plane for departure Friday morning for the race in Abilene, TX. Since the RV-8 that beat me at Texoma has dropped out, the pressure is reduced a bit. I plan to layup the second layer diagonally today then it will sit until next week before continuing.
Bob Axsom
There is a lot of cleanup after laying up the first layer of a fiberglass part over airframe, tires and clay in an inverted close to the ground space. I have everything nearly ready for the second layer except sanding one of the subfairings but we have to prepare the plane for departure Friday morning for the race in Abilene, TX. Since the RV-8 that beat me at Texoma has dropped out, the pressure is reduced a bit. I plan to layup the second layer diagonally today then it will sit until next week before continuing.
Bob Axsom
Unfortunately I made two mods at once
Unfortunately I made two mods at once because of a race and I do not have independent test results. My base line was raised from 177.8 kts to 181.3 kts at 6,000 ft density altitude using the U.S. Air Race Handicap procedure (www.us-airrace.org) and the National Test Pilot School spread sheet that John Huft and Kevin Horton provided. The other mod was the removal of the tail tiedown ring that had been enclosed in an aluminum streamlined fairing previously. The change was remarkable. My original fairing on the nose only, was the older flatsided model. Now the original fairing and the subrfairing makes the tire blend into the shape of the fairing. I do not expect the subfairings on the mains to make that kind of difference
Bob Axsom
Unfortunately I made two mods at once because of a race and I do not have independent test results. My base line was raised from 177.8 kts to 181.3 kts at 6,000 ft density altitude using the U.S. Air Race Handicap procedure (www.us-airrace.org) and the National Test Pilot School spread sheet that John Huft and Kevin Horton provided. The other mod was the removal of the tail tiedown ring that had been enclosed in an aluminum streamlined fairing previously. The change was remarkable. My original fairing on the nose only, was the older flatsided model. Now the original fairing and the subrfairing makes the tire blend into the shape of the fairing. I do not expect the subfairings on the mains to make that kind of difference
Bob Axsom
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5-10 08 Status
I cut the left subfairing in half and now have the third overlap layer curing on each side of the forward half. When I applied the first overlap layer I had a little bit of a problem trying to figure out how to get a contour conforming layer without a mold. I finally determined that if I hung the forward half of the fairing from a coat hanger so the 1" joint overlap layer was hanging down below the fairing half it would have no forces trying to distort it. It worked very well and of course the cured first layer provides the support for the second and third layers. I added the last two layers at the same time after the first layer was cured and trimmed.
I learned that Tom Martin has only a 3/4" ground clearance on his EVO Rocket fairings so I was way too conservative with my 1" which may be 1.25" after all of my trimming. Bringing it in high like that is really a bad mistake on my part. It puts the edge up where the tire gets fat with ground contact. It is better I think to have the upward and outward deformation up in the fairing cavity. This is for racing only of course. I simply don't have the energy to do all this work over right now but maybe next winter ...
Bob Axsom
I cut the left subfairing in half and now have the third overlap layer curing on each side of the forward half. When I applied the first overlap layer I had a little bit of a problem trying to figure out how to get a contour conforming layer without a mold. I finally determined that if I hung the forward half of the fairing from a coat hanger so the 1" joint overlap layer was hanging down below the fairing half it would have no forces trying to distort it. It worked very well and of course the cured first layer provides the support for the second and third layers. I added the last two layers at the same time after the first layer was cured and trimmed.
I learned that Tom Martin has only a 3/4" ground clearance on his EVO Rocket fairings so I was way too conservative with my 1" which may be 1.25" after all of my trimming. Bringing it in high like that is really a bad mistake on my part. It puts the edge up where the tire gets fat with ground contact. It is better I think to have the upward and outward deformation up in the fairing cavity. This is for racing only of course. I simply don't have the energy to do all this work over right now but maybe next winter ...
Bob Axsom
The Left MLG sub fairing installation
5-10-08 I went out to the airport and installed the left main subfairing. The installation went well but I still have to do some more work. Mainly I need to rivet on internal aluminum strips that will clamp the lower edge of the forward and rear halfs aligned. I did this on the nose gear subfairing but I though perhaps I would not have to do it on the mains (getting lazy).
More interesting is the measurements I took Without the subfairing and with the subfairing on the ground and in the air. My measurement methods were not the best but they provide some insight that I wanted to get with the small amount of time and tools available for the task. I will try to enter the data directly and if it isn't readable I will try another way.
First I measured the no subfairing weight on wheel (tire on ground)configuration then lifted it off the ground and remeasured. Then I installed the new subfairing with flight hardware and repeated the measurement process in reverse order.
The bottom of the tire extension below the fairing as viewed from the front:
No sub/ on ground = 2 5/16"
" " in air = 2 15/16"
Subfairing/ ground = 1 1/8"
" " / in air = 1/7/8"
Gap between front of opening and the tire:
No sub/ on ground = 7/8"
" " in air = 3/4"
Subfairing/ ground = 1/4"
" " / in air = paper thin
Gap between rear of tire opening:
No sub/ on ground = 15/16"
" " in air = 9/16"
Subfairing/ ground = 1/4"
" " / in air = paper thin
Gap between outboard side of tire and fairing opening:
No sub/ on ground = 1/2"
" " in air = 5/8"
Subfairing/ ground = 3/16
" " / in air = 1/4"
Gap between inboard side of tire and fairing opening:
No sub/ on ground = 1/2"
" " in air = 5/8"
Subfairing/ ground = 3/16"
" " / in air = 5/16"
Given that I was using file folder cardboard to transfer distances from the hardware to a 12 inch ruler with 1/16" markings, errors on the order of 1/16" are highly likely but from this exercise I learned that for this set of conditions the fwd and aft gap decreases in flight and the side gaps increase in flight.
There is more work to do before I get back the the right subfairing.
Bob Axsom
5-10-08 I went out to the airport and installed the left main subfairing. The installation went well but I still have to do some more work. Mainly I need to rivet on internal aluminum strips that will clamp the lower edge of the forward and rear halfs aligned. I did this on the nose gear subfairing but I though perhaps I would not have to do it on the mains (getting lazy).
More interesting is the measurements I took Without the subfairing and with the subfairing on the ground and in the air. My measurement methods were not the best but they provide some insight that I wanted to get with the small amount of time and tools available for the task. I will try to enter the data directly and if it isn't readable I will try another way.
First I measured the no subfairing weight on wheel (tire on ground)configuration then lifted it off the ground and remeasured. Then I installed the new subfairing with flight hardware and repeated the measurement process in reverse order.
The bottom of the tire extension below the fairing as viewed from the front:
No sub/ on ground = 2 5/16"
" " in air = 2 15/16"
Subfairing/ ground = 1 1/8"
" " / in air = 1/7/8"
Gap between front of opening and the tire:
No sub/ on ground = 7/8"
" " in air = 3/4"
Subfairing/ ground = 1/4"
" " / in air = paper thin
Gap between rear of tire opening:
No sub/ on ground = 15/16"
" " in air = 9/16"
Subfairing/ ground = 1/4"
" " / in air = paper thin
Gap between outboard side of tire and fairing opening:
No sub/ on ground = 1/2"
" " in air = 5/8"
Subfairing/ ground = 3/16
" " / in air = 1/4"
Gap between inboard side of tire and fairing opening:
No sub/ on ground = 1/2"
" " in air = 5/8"
Subfairing/ ground = 3/16"
" " / in air = 5/16"
Given that I was using file folder cardboard to transfer distances from the hardware to a 12 inch ruler with 1/16" markings, errors on the order of 1/16" are highly likely but from this exercise I learned that for this set of conditions the fwd and aft gap decreases in flight and the side gaps increase in flight.
There is more work to do before I get back the the right subfairing.
Bob Axsom
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New development thought
The side gaps of the sub fairings are disappointing. In thinking more about it I think I could just add fiberglass to the inboard and out board sides to extend them to a lower end point where the side growth of the tire on landing is lower and come closer to retaining a constant gap on the sides in flight. The profile would curve down from the front to the lowest point then curve back up to the rear of the opening. The front and rear gap dynamics are about perfect as is. If I were building a full fairing I would probably bring the lower surface of the part of the fairing behind the tire to a higher point then curve it down more to give a large surface tangent interface rather then an edge on to the tire interface.
Bob Axsom
The side gaps of the sub fairings are disappointing. In thinking more about it I think I could just add fiberglass to the inboard and out board sides to extend them to a lower end point where the side growth of the tire on landing is lower and come closer to retaining a constant gap on the sides in flight. The profile would curve down from the front to the lowest point then curve back up to the rear of the opening. The front and rear gap dynamics are about perfect as is. If I were building a full fairing I would probably bring the lower surface of the part of the fairing behind the tire to a higher point then curve it down more to give a large surface tangent interface rather then an edge on to the tire interface.
Bob Axsom
N941WR
Legacy Member
Hey Bob,
Do you want to work your magic on my -9? I wonder if I can run with the big boys AKA O-320 or bigger if I cleaned up the airframe.
The only problem is I'm stuck with a fixed pitched prop due to the O-290-D2. Well, that's not exactly true as the engine originally had a controllable (not fixed) pitch prop.
The question would be, as the airplane speeds up, I would need to upgrade the prop to match it.
Do you want to work your magic on my -9? I wonder if I can run with the big boys AKA O-320 or bigger if I cleaned up the airframe.
The only problem is I'm stuck with a fixed pitched prop due to the O-290-D2. Well, that's not exactly true as the engine originally had a controllable (not fixed) pitch prop.
The question would be, as the airplane speeds up, I would need to upgrade the prop to match it.
Operational Test flight Complete 5-15-08
I spent many hours over several days getting the subfairing to tire gaps as good as I could get them. This afternoon It was finally ready but the ceiling was 2,500 ft, much too low for the standard speed test method I have used on all my testing (6,000 ft density altitude required). However, it was fine for an operational test flight. The temperature was only in the low sixties (F) so it was not a stress test of braking effects. I will stay off of the brakes as much as possible with the subfairings installed to minimise heating risk. I taxied 2 miles to and from the runway, parked inspected MLG without removing the fairings and saw no problems. I am very anxious to conduct a speed test but that is probably going to have wait a little while. We are flying to St. Louis tomorrow and next week we are flying to Baltimore. With any luck I may be able to work it in next week before I take off the racing wing tips and reinstall the tip tanks and stock tips for the Baltimore trip.
Bob Axsom
I spent many hours over several days getting the subfairing to tire gaps as good as I could get them. This afternoon It was finally ready but the ceiling was 2,500 ft, much too low for the standard speed test method I have used on all my testing (6,000 ft density altitude required). However, it was fine for an operational test flight. The temperature was only in the low sixties (F) so it was not a stress test of braking effects. I will stay off of the brakes as much as possible with the subfairings installed to minimise heating risk. I taxied 2 miles to and from the runway, parked inspected MLG without removing the fairings and saw no problems. I am very anxious to conduct a speed test but that is probably going to have wait a little while. We are flying to St. Louis tomorrow and next week we are flying to Baltimore. With any luck I may be able to work it in next week before I take off the racing wing tips and reinstall the tip tanks and stock tips for the Baltimore trip.
Bob Axsom
Speed Test Results
I got up at 06:17 and the skies were clear and the winds were calm. By the time I got to the airport a half hour later some surface wind had picked up. I flew the test at 6,000 ft density altitude using the www.us-airrace.org handicap procedure and I evaluated the results using the National Test Pilot School spread sheet often mentioned by Keven Horton and recopmmended by John Huft. The wind was not steady enough to meet the 1 kt maximum variation per leg standard but I took the numbers and used them as close enough because my time is very limited by the changes I have to make in preparing the plane for our Baltimore trip. On the 000 track the 20 second interval speeds were 195, 195,193,194 and 195. On the 120 track the speeds were 202,200,200,200 and 202. On the the 240 track the speeds were 141,140,140,140 and 141. When I plugged 194.4, 200.8 and 140.4 into the spread sheet wth the track angles it computed the wind as 40.5 kts from 244.7 degrees and true airspeed of 180.8 kts. That is a disappointing 0.5 kt slower than it was before I installed the MLG subfairings. Depending of the errors in the testing, the speed may be the same with or without the MLG subfairings. The difference with the subfairing on the nose gear old style fairing was so amazing that I was hoping for some additional gain from subfairings on the new style MLG fairings but that just didn't happen. I will finish them, paint them and use them in races but they are just for show and any microscopic gain that could be hiding there.
Bob Axsom
I got up at 06:17 and the skies were clear and the winds were calm. By the time I got to the airport a half hour later some surface wind had picked up. I flew the test at 6,000 ft density altitude using the www.us-airrace.org handicap procedure and I evaluated the results using the National Test Pilot School spread sheet often mentioned by Keven Horton and recopmmended by John Huft. The wind was not steady enough to meet the 1 kt maximum variation per leg standard but I took the numbers and used them as close enough because my time is very limited by the changes I have to make in preparing the plane for our Baltimore trip. On the 000 track the 20 second interval speeds were 195, 195,193,194 and 195. On the 120 track the speeds were 202,200,200,200 and 202. On the the 240 track the speeds were 141,140,140,140 and 141. When I plugged 194.4, 200.8 and 140.4 into the spread sheet wth the track angles it computed the wind as 40.5 kts from 244.7 degrees and true airspeed of 180.8 kts. That is a disappointing 0.5 kt slower than it was before I installed the MLG subfairings. Depending of the errors in the testing, the speed may be the same with or without the MLG subfairings. The difference with the subfairing on the nose gear old style fairing was so amazing that I was hoping for some additional gain from subfairings on the new style MLG fairings but that just didn't happen. I will finish them, paint them and use them in races but they are just for show and any microscopic gain that could be hiding there.
Bob Axsom
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Alan Carroll
Well Known Member
Retest?
Bob - are you planning to retest in calmer conditions? 40 knots is a lot of wind, and I'd guess it could have changed over the time required for the test.
Bob - are you planning to retest in calmer conditions? 40 knots is a lot of wind, and I'd guess it could have changed over the time required for the test.
I agree
I am thinking about it because the same thoughts occurred to me. The wind speed according to the data was varying as much as 2 kts during two of the legs and 1 kt on the other. Also, the slowest leg was the last leg and there may have been a general wind speed increase in the time it took to fly the test. Reading between the lines I decided the speed is at least very similar to what I had before (0.5 kt less than previous high) and it deserves more exposure so I plan to see how they perform in the Rocky Mountain 150 next month and I will probably have them on for the AirVenture Cup Race as well. We are going to Baltimore in the morning and I spent the last couple of days taking the racing wingtips off and reinstalling the tip tanks and stock tips. So no testing can be done for a while. I plan to change the steps to a removable installation and reinstall the racing wing tips before the race at Denver and there may be an opportunity to get another same configuration test in before that race - we will see. I have to fill, sand and paint the subfairings before the race as well so time is tight. According to the www.sportairrace.org calendar of events, the Rocky Mountain 150 is on June 28, 2008.
Bob Axsom
I am thinking about it because the same thoughts occurred to me. The wind speed according to the data was varying as much as 2 kts during two of the legs and 1 kt on the other. Also, the slowest leg was the last leg and there may have been a general wind speed increase in the time it took to fly the test. Reading between the lines I decided the speed is at least very similar to what I had before (0.5 kt less than previous high) and it deserves more exposure so I plan to see how they perform in the Rocky Mountain 150 next month and I will probably have them on for the AirVenture Cup Race as well. We are going to Baltimore in the morning and I spent the last couple of days taking the racing wingtips off and reinstalling the tip tanks and stock tips. So no testing can be done for a while. I plan to change the steps to a removable installation and reinstall the racing wing tips before the race at Denver and there may be an opportunity to get another same configuration test in before that race - we will see. I have to fill, sand and paint the subfairings before the race as well so time is tight. According to the www.sportairrace.org calendar of events, the Rocky Mountain 150 is on June 28, 2008.
Bob Axsom
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