|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

11-08-2007, 02:53 PM
|
 |
|
|
Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,357
|
|
Quote:
Originally Posted by Bob Axsom
I have a foam bulkhead glued in the aft end of the left MLG fairing and I plan to test fly it today then commit to doing them all or tearing this one out.
Optimally I will get a yaw to the right and a slight increase in speed.
|
A yaw to the right would certainly be a sign of less drag from the left wheel pant. But, it is quite possible that the total drag in the yawed condition (or from the deflected rudder if you push on it to zero the ball) could be higher than it was when the two wheel pants had equal drag. So don't be discouraged if you can't see a speed increase, or if you measure a speed decrease.
If you've only modified one side, I think the resulting yaw will be a better indication of an improvement than any change in speed.
|

11-08-2007, 06:25 PM
|
|
|
|
Join Date: Mar 2005
Posts: 5,685
|
|
I test flew this afternoon
I hate when this happens. I reinstalled the left MLG fairing with the bulkhead in the aft portion only. There was no difference that I could detect in flying the plane. The speed at 6,000 ft density altitude using my USAR haddicap procedure and the NTPS spreadsheet for calculation with MAP = 25, RPM = 2730, leaned for best speed was 177.4 kts. That is 1.3 kts faster than my test on the 6th of November after sealing the strut hole in the NLG fairing but it is 0.4 kts less than the previous test after I reduced my wingspan by 3 feet. Intuitively, I don't think this will make the plane fly faster but it is not demonstrably slower either. In fact it is about a half a knot faster than the average of the two previous tests. My belief is that this is just another point in the error range of the test method but I can't take a chance (Mike Thompson are you lovin' this). SO ... I brought all three fairings home and I will install the bulkheads and fillets tonight then take them to the airport for fitting tomorrow. Then I should fly another test to get a speed for the whole mod shape. If it is good I will take them off and bring them home again for fiberglassing. If the results are not good I will cut out the foam and spend the little time remaining before the Rocket 100 race next week washing and waxing the plane (which I would like to be doing now instead of squeezing it in at the last minute).
Now, back to work.
Bob Axsom
|

11-08-2007, 06:52 PM
|
 |
|
|
Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,357
|
|
The CAFE Foundation flight tests showed more than a 2 kt increase in speed on their Mooney from a wax job. Maybe you should spend more time waxing, and less time adding more weight to those wheel pants.
Mind you, I get the impression that their Mooney really, really needed a wax job. Your paint is probably in better shape then theirs was, so the potential gain is probably less.
|

11-09-2007, 06:02 AM
|
 |
|
|
Join Date: Feb 2006
Location: Pagosa Springs, CO
Posts: 130
|
|
Kevin, I have long held the theory that because the Mooney is a laminar flow airfoil (well, more than our fat wing birds, anyway), it would respond more to the wax job than one of ours.
That said, I think a clean bird goes faster anyway. At least it looks like it goes faster. I think.
|

11-09-2007, 09:41 PM
|
|
|
|
Join Date: Mar 2005
Posts: 5,685
|
|
The Foam is in all three fairings
Plan to test fly tomorrow.
Bob Axsom
|

11-09-2007, 09:45 PM
|
 |
|
|
Join Date: Sep 2006
Location: Townsend, Montana
Posts: 3,179
|
|
Got my fingers crossed for ya'
__________________
Retired Dam guy. Life is good.
Brian, N155BKsold but bought back.
|

11-09-2007, 10:45 PM
|
|
|
|
Join Date: May 2006
Posts: 24
|
|
Two other options for later with more time...
Bob,
I really love reading all about all your never-ending quests for less drag/more speed. I have thought about the air blowing in and out of the wheel pants too. I think there are two options:
1.) Seal the opening between the tire and the wheel pant with brushes as someone has suggested. I'll only add that a series of small paint brushes with the handles cut off might be just the ticket. Or....this is thinking outside the hen house...use feathers to help seal the area.  Or feathers and brushes.
2.) Cover the bottom of the tire completely with a nice smooth fairing. This would be like a landing gear door in it's complexity. It would probably be just as tough to fit as a whole canopy. My thoughts were along the lines of something made with unfinished balsa wood. Because the human element enters here. Let's imagine that you made nice smooth covers that covered the tires in flight. They sealed well with the wheel pant and they were smooth and transitioned well with the wheel pant curves. Let's say they produced the desired drag reduction/speed increase. Now you won the race it's time to bring her in and....oops you forgot to retract the tire covers up out of the way. You touch down and hopefully you built these to tear away with very soft shear pins or pop rivets or similar easy tear away construction.
I'm thinking you just left a mess of balsa slivers and tooth picks all over the runway.
I actually want to try the second retractable cover idea. Just getting a good mechanical means to open and close is the challenge. I also thought that using small tabs and aerodynamic forces to cause it to flip up/open and down/closed might also be possible.
Now quit reading all the posts. Go wax the plane and think about good race flying techniques.
__________________
I'm just grateful to be here.
|

11-10-2007, 01:21 PM
|
|
|
|
Join Date: Mar 2005
Posts: 5,685
|
|
Test Flight?
The ceiling was too low to get in a formal test. I did buzz around at ~ 3,000 dodging clouds and SkyVenture Cessnas east of Drake field. The general conclusion I made was it is good enough to go ahead with the fiberglass bulkheads over the foam. It looked quite good actually - a raw single observation three way average at 3000 pressure altitude was 181.6kts. I don't have anything to compare that with and there was no real test method involved. Still, I think I'm on to something.
Bob Axsom
|

11-11-2007, 03:08 PM
|
|
|
|
Join Date: Mar 2005
Posts: 5,685
|
|
New thought
The foam bulkheads have all been glassed and will be cured tomorrow. Weather permitting I will squeeze in a test flight.
I'm sure you have thought of something and as the idea is implemented a refined idea emerges that was not even conceivable in the original state of things. OK, here it is. I now have these confined areas around the tires in all three fairings. It would not be difficult to install a containment ridge around the bottom of each fairing. An inflatable device could be installed there to seal the gap between the fairings and the tires in flight. I'm not sure how the nose wheel will react in flight but you could just apply the brakes to stop the mains before inflation. You would need at least one valve to control the inflation state and a pump (maybe a hand pump) for inflation. The plumbing would be simple if you didn't have fiberglass strut fairings already installed.
Bob Axsom
|

11-12-2007, 06:40 AM
|
 |
|
|
Join Date: Mar 2006
Location: Bloomsburg, PA
Posts: 273
|
|
Thanks Bob
Bob,
I just wanted to say that I have really enjoyed reading your messages. You have put forth a remarkable effort to gain more speed. Sharing your ideas from conception to implementation and testing has been really fun to read. Thanks for making the effort to share this with us!
Jim
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 03:45 AM.
|