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Lowrider LSA

I can definitely see the merits of grounding all avionics to a single bus, as well as the strobe light having its own, shielded ground. I have flown more than a few A/C that you could hear the strobe light pulses through the intercom. But nav/position lights (especially the low draw LEDs ) I dont think would cause interference.
Definitely a subject that I will be doing some more research on...
 
It's a no brainer on the grounds for the wing lighting; each light needs it's own separate ground wire. But than again I do have a wood wing so .............. Sorry; couldn't resist.
Marty57
 
You guys are fun to have around!!

Wrong,

I look forward to an update on your research!

......and a good night to all.
 
Stuck a wing on this morning for the first time.

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Very nice! I need to do the same soon. Maybe visitors will stop asking if your are building a helicopter; I get that question a lot.

Marty57
 
Thanks Marty!! Be sure to shoot some pix of your wings too and I wish mine was as light as yours!!
 
Just checking before I start welding on my prototype tail wheel...the king pin should lean forward at about 8 - 10*, right? I'm using a stainless 3/4" stinger and not a flat spring and initially will not be streerable but that can be added later...just playing with a design for now and trying to make it light.
 
Hmmm...no thoughts on king pin angle yet.

While I was waiting I pulled out 3 bathroom scales and weighed the fuselage in it's current condition...seats, landing gear, tailwheel parts, wheels, brakes, tires (6.00x6), tail...mostly done but some more items to be added. I know the bathroom scales are not perfect but they weight within a pound of each other and I left some tools in there to make up for whatever and here's the results:

Left Main: 84.8 lbs.
Rt Main: 81.8
Tail: 92.3

Total: 258.9 lbs

Wonder how that compares to a Cub frame or something like it?????
 
Thanks Glenn!

I'm kinda making this up in my head as I go...trying for a fairly tall tire and light weight.

Looks like from the pictures the angle is less than 10*...maybe 5 or 6*. I'm using bronze bushings instead of bearings with a rubber O ring top and bottom to keep dirt and water out and keep the swivel and grease clean. The bearings require a much larger chunk of steel and adds a lot of weight. My thought is the bushings are cheap ($3.50 each) and can easily be replaced at annual or if they become worn. The parts are all 4130 except for a grade 8, 3/4" bolt used as the king pin. The wheel is a 5" Matco and holds a 4"x11" tire.

Maybe I'll split the difference and use 8* forward tilt at the top.
 
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...the king pin should lean forward at about 8 - 10*, right?

I think you have it backwards. For some reason this site won't let me post a link but Google tailwheel shimmy. The top of the kingpin needs to lean back or vertical.

Doug
 
Hmmm....the pictures Glenn posted sure look to me like they lean forward at the top as well as others I've seen.

Here's an article I found:


Tail Wheel Shimmy
HIGH WINGS
Cy Galley
Most tailwheels will shimmy quite easly if
the design geometry is wrong (most are) or if the
friction device (Scott #3234, thrust plate- #4 of
diagram) is mis-adjusted or gets grease on it.
The first item, geometry is easy to
check. The pivot should be vertical, never
slanted to the rear of the aircraft. If the pivot is
slanted towards the front of the plane, it is O.K.
 
Google "tailwheel shimmy" again and read the article that's posted on back country pilot on the subject. It was written by Gilbert Pierce (Steve Pierce on this site is Gil's son). It explains the why of having a vertical or aft-slanted pivot point on the tailwheel assembly. Most people on this site (including myself ) consider the Pierce family to be cub (and any rag-wing taildragger) gurus.
 
Wrong,

I read that one and a bunch of others, most seem to suggest vertical is the answer so it makes sense to have the top leaning rearward when not loaded which I believe would make it move toward straight up as weight is added to the tail by loading the plane. I agree on the Pierce family too.

I welded the king pin this afternoon but I can cut it off and change the angle to give it a rearward slant. It's just a trial build anyway to see how it will workout and what I need to change in the final one.

Thanks for setting me "straight" as it were!!
 
I cut the king pin off and got a new bolt to play with. While I was out, I stopped by Wally Mart to pick up a few things and I checked out their the shopping carts and the front wheels lean forward at the top and they did not shimmy unless they were bent. No point being made here, just an observation.

I'm going to set up the king pin leaning to the rear about 8* and drop the yoke down a little lower than the one shown on Larry's pix above...got that from the shopping carts and other tail wheels I've seen. I'm also going to include a friction washer and see if that is necessary. Once I get it together, I'm going to attach it to the rear of a 4 wheeler and see what angle seems to ride the best. Since the tail wheel should not contact the ground until it's close to stall speed, I'll start to test at about 40 mph.
 
I cut the king pin off and got a new bolt to play with. While I was out, I stopped by Wally Mart to pick up a few things and I checked out their shopping carts and the front wheels lean forward at the top and they did not shimmy unless they were bent. No point being made here, just an observation.

I'm going to set up the king pin leaning to the rear about 8* and drop the yoke down a little lower than the one shown on Larry's pix above...got that from the shopping carts and other tail wheels I've seen. I'm also going to include a friction washer and see if that is necessary. Once I get it together, I'm going to attach it to the rear of a 4 wheeler and see what angle seems to ride the best. Since the tail wheel should not contact the ground until it's close to stall speed, I'll start to test at about 40 mph.
 
Think more like the king pins on the front axle of your pickup truck. They are leaned aft like we are discussing to avoid shimmy.
Someone once told me that it also had to do with gyroscopic procession. A force applied at right angles to a spinning disc acts 90* from the input of the force. The idea is that a positive castor angle applies a slight downward force when steering left or right, helping reduce shimmy. Whereas a negative castor angle would apply an upward force which could cause and/or increase shimmy.
 
Good explanation Wrong!!

I know you're out of the target area but keep your head down and powder dry!! An RCMP friend of mine used to work for the Sergeant at Arms at Parliment when they were stationed in New Brunswick...says he's a "top copper" and a good shot...glad he put a stop to the nonsense today!! God speed to the Corporal!!
 
I know this has been discussed before. I'm getting ready to paint my main gear legs and I wanted to get some thoughts on how to cover and fair the round tube to reduce the drag. I'm thinking just attaching some 1 1/2" alum angle front and rear on the tubes and covering it with fabric. There was some discussion awhile back about making ribs between the tubes to make it more aerodynamic...think it's worth the effort??
 
I think just covering the gear reduces a fair amount of drag. I have heard guys talk about changing the shape of the tubes to reduce drag if leaving them uncovered. Building the gear legs is in my near future and I was going to leave them uncovered but still on the fence. I wonder if anyone has tried using streamlined tubing to build them. Be better than adding weight with angle iron and ribs Im thinkin....
 
Of course if big tires (24" +) are in your/my future, then the shape of the gear, covered or uncovered probably wont make much if any difference in cruise speed....
 
I made extended and pretty stout gear and I couldn't find anything heavy enough in the streamline tube that was available. I'm giving up some drag with tires but I hope to make up for at least some of the drag with things like closed gear legs, strut fairings and maybe some work on the tail wires too. It won't be perfect but I hope it will help. I was looking at my quarter wave antenna today and wondered of it was worth doing also. I guess most everything that is made clean or "slick" will help some. Since I have alum skin wings, I'm thinking of doing the tail in alum skin instead of fabric but I'm not sure there is that much to be gained. I think it's easy to get carried away with this clean thing....and no...no wheel pants.
 
SKy,

I did search this and other forums and they all seem to support the need for streamlining on round tube. The most telling in my mind was the one you found above. This is the table from the report and it sums it up concisely but I can't seem to make it smaller and the site won't display it. The table is in your last ref above.
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The straight fairing is what I was thinking of using but the table clearly points to the use of ribs between the gear legs to make a streamlined structure out of the 2 gear legs.

I'm not excited about using soft materials for the streamlining since I will be flying off primarily gravel and sometimes high grass fields and mud and I'm concerned about what toll that may take on the fairings. I'm using ribs on the tail surface to make an aerodynamic profile and I'm thinking of using something like balsa or cedar to fair the back edge of control surfaces but they are only 3/8" tube on the trailing edge so I'm not sure how much gain there could be in that area.

Guess I'm looking for some thoughts on where else I can reduce drag.

BTW, I spoke to Ly-Con a few days ago and they speak very highly of their porting and the use of 10:1 pistons. I believe there is efficiency to be found in many places but streamlining may be the biggest bang for the buck.
 
...Guess I'm looking for some thoughts on where else I can reduce drag.
Take a close look at this picture for fairing ideas. There are a lot of them which in total added about 20 mph to the speed.
attachment.php

Post #25 http://www.supercub.org/forum/showthread.php?45012-Gear-leg-fairing&highlight=comanche+floats

There are lots of places where you can install fairings for drag reduction. Look at what Piper did on the PA-12. Lots of fairings, each doing just a little. This will be a time intensive endeavor.
 
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