Willja67
Contributing Member-
Content count
174 -
Joined
-
Last visited
Posts posted by Willja67
-
-
the Kitfox curving cowl that kind of makes you think you are going crooked when you aren't, and worse yet, just the opposite. JImChuk
I haven't made up my mind about my cowl or firewall shape yet. I was planning on just duplicating the round top. I'm going to be sitting in the middle so that's not an issue, but is a flatter topped cowl more advantageous even when sitting in the middle?
Dude i just figured out how to quote!!!!!! Sorry im real slow on a computer. Hahahahaaaaa
I sure like the cowl my bluefox has, was told is a real earlie cowl, but havent ever cn it to much, anyone have any info on it?
Willja67 what did u do with the cowl u made to fit ur bird? U not useing that with the
It was a good practice run. Way too many mistakes. Showed me what I needed to do different/ better for the next attempt.
Edit for the who didn't see it I started building a new cowl for my model 1
-
the Kitfox curving cowl that kind of makes you think you are going crooked when you aren't, and worse yet, just the opposite. JImChuk
I haven't made up my mind about my cowl or firewall shape yet. I was planning on just duplicating the round top. I'm going to be sitting in the middle so that's not an issue, but is a flatter topped cowl more advantageous even when sitting in the middle?
-
The Europeans are or were switching some of their comm frequencies that were the same as ours. So a lot of folks especially gliders are having to install new radios. That means they're selling the old ones for pretty reasonable prices. I bought a Becker comm unit that fits in a 2 1/4" hole for around $250 i think, been several years since i bought it. It came with a wiring harness with headset jacks and ptt. Not sure if the supply has dried up, but worth looking into.
1 person likes this -
Btw I have had some experience with the legal system. Almost 12 years ago I got in a wreck in my bosses pickup. Totally my fault. Problem was that even though i had permission from my boss to use the truck for any work related activities he only had it insured as a private vehicle. Id driven it 90-100 times in the 8 months I worked for him, but as soon as he realized what that was going to do to him he started lying about it. Fortunately for me I had called him from the site of the accident and hadn't tried to drive off. He tried to convince the cops to arrest me for stealing his truck. Fortunately for me the cops recognized what was going on and refused, they even tried to give me a heads up without coming out and saying it. Also fortunately for me, my bosses partner told a way different story than my boss(both recorded and transcribed) so they ended up looking like idiots. That didn't stop a 4 year long legal battle between his insurance company and mine over who should pay for it. Eventually it was sent to arbitration and I think my insurance company won. If you can call it that. I'm sure they didn't recoup the costs of the 4 year legal battle. If things can get that dirty over $10k worth of vehicle repairs I have no doubt they can get even more nasty over a dead husband. Maybe I would win in the end but I shudder to think of what my financial situation would be afterward.
-
Everyone chooses where to take their risks. "I'm not going to stay in bed" I'm going to complete my highly modified kitfox and then hopefully fly the crap out of it, which i would think qualifies as trying to live life to the fullest. If i choose to stay away from what I consider would risk liability that's my choice.
-
Well you guys have talked me out of it. I don't plan on ever selling it but if I do it'll be in pieces. Just doing too much that increases the liability exponentially.
There has never been, nor is there legal grounds for a liability suit in selling an experimental aircraft, I have consulted an aviation attorney on this. Destroying a good airplane out of fear of liability is being ignorant of the facts.
I can't honestly offer any proof other than "read/ heard about" etc but Ive listened to arguments on both sides about someone's attorney saying the EAA's sellers release of liability is iron clad and others saying their attorney says it's a joke. My personal belief is that it depends on how good your lawyer is and perhaps how many palms get greased. In this litigious society we live in its hard not to be paranoid.
-
I'm going to be doing some work on my fuel tanks with ProSeal. Ive heard that you can get a quart of it from vans for about the same price as a pint most anywhere else. That'll be more than i need for the fuel tanks I think. I also have the pvc leading edges to install and the fuselage stringers. Just wondering if the proseal will do it all satisfactorily?
-
On thanks
-
Sorry, mostly talking about lexan, but there are a few of the 5/32" or maybe 3/16" rivets that hold the butt ribs to the tabs on the fuselag.
My firewall was held on with little screws not rivets so I'm also considering what to use to secure the new firewall with. Probably stainless, but the screws made taking it apart nice and easy.
Basically any type of rivet needed in the fuselage. About the only thing being done to the wings is recovering so no rivets needed there, except for the rib tail hangars, but that info is provided in the service bulletin.
-
I'm getting my ACS shopping list together and trying to figure out what rivets to use. In reviewing the manual it gives the length and diameter so that's not a problem but mostly it just says "aluminum" rivets. On the ACS site there are Cherry N rivets and Cherry Q rivets and each type comes in 2 different aluminium alloys. My gut feeling is that it really doesn't matter much but if you guys know better please let me know. Thanks
-
I'm looking for windshield material and reading what I can find before making my choice. I was going through the build manual and specifically the service bulletins and found something really interesting. Can't remember which one but I think #43?
It was about the windshield on the model 4 speedster. It stated that originally .118 poly was used for the windshield but it cracked too easily so they recommended going to .090 poly. Certainly the speedster has a higher Vne than 100mph? After all I've read about windshields starting to buckle around 100 mph I have to wonder if the angle the windscreen leans back at and perhaps the way it is supported at the bottom contribute significantly to its ability to not buckle? I'm going to be building a whole new cowling and changing the shape of the windscreen a little(nothing drastic) and wondered what the thinking was on this?
-
Or he can't fly it as a sport pilot. (just speculation) No turbo allowed. Sounds like an awesome deal to me.
I'm not trying to cause problems here just curious as I had never heard about tubos not being allowed in light sport. This was the first link that came up in a search for "turbos in light sport aircraft"
https://www.aopa.org/news-and-media/all-news/2014/january/21/tecnam
There were more articles than just that one referencing turbos in light sport aircraft. So the question is do you have a reference to a FAA reg that supports your statement?
-
I'm prepping the fuselage to get bead blasted and powdercoated. I'm also removing every single little tab that I don't think I'll use. For instance i removed the throttle mount in the middle of the instrument panel and cable the reverser.
I already cut off the knobs that the original bungees wrapped around. Now I'm wondering if i can remove the tubes marked in red? Since the bungees aren't there anymore I don't see a reason to keep them. Is there?
-
Well you guys have talked me out of it. I don't plan on ever selling it but if I do it'll be in pieces. Just doing too much that increases the liability exponentially.
-
My father is a pretty good mechanic, much better than I am and he can't stand having anyone else touch his vehicles. He's not a very trusting soul when it comes to his babies. That rubbed off. Although not being as good as he is and living a significant distance away means I've had to trust my truck to a shop. That's been difficult. Hopefully i can pick it up in the next few days and I'm going to be holding my breath for quite awhile to see if they did it right.
And yes I know I can assist in the inspection if I find an A&P who agrees to that. I think I already have one lined up.
-
BTW, how do you know that there aren't feds that read this forum??
i realize i used the words devious and so forth. I really do want to do this legally. I was just hoping there was some way to work through the system to achieve that objective. Ive read other comments about people who managed that. Maybe it was a case of "my uncle's cousins, former roommate". Which means "absolutely nothing" You can ask a dozen different government officials about a subject and get a dozen different answers. Somewhere there might be an official or individual like me that came up with a creative solution. And it's not necessarily about the money. At one point in time I was enrolled in A&P school but dropped out. It would be nice to be considered as an A&P even if only for a single aircraft. But I absolutely hate and despise paperwork so if there is a way to get the repairmans certificate it's probably more work than I'm willing to do. That's one of the reasons I never went back to school. I couldn't stand the thought of dealing with the FAA paper work day in and day out.
-
Build a "new" plane from parts.
ok, that's an idea. Ive read that you're required to have a bill of sale for a kit so verification can be made that you did more than 50% of the work. I have a bill of sale for an aircraft with an airworthiness certificate and an N number. Not sure how to jump through that hoop.
-
Where I live there's quite a few restricted areas, SLC class bravo and other hazards so I consider a gps and tablet as mandatory minimum equipment. Also i just watched this video this morning and they talked about how the ga accident rate has gone way down largely because of the new adsb weather services.
You have to be careful because there's a 20 minute lag in the weather info but still it gives a good picture of what's around you. You also get TFR and other info. Which could well save you a ride in a police car if the president makes an unplanned stop in your area(if the fighters don't shoot you down first).
This reciever is one of the cheapest I know about: https://crewdogelectronics.com/products/stratux-ads-b-dual-band-receiver-aviation-weather-and-traffic-ahrs-waas-gps
And it has a backup ahrs so if for some reason your other instruments go on the fritz.
I love the situational awareness it provides. I'm somewhat directionally challenged and this helps with that alot.
-
Ok guys I'm hoping there are some devious souls among you that know how to fight officaldom.
I'm stripping my plane down to the last nut and bolt, installing a new engine and a whole lot of other major and minor alterations. I recently got in contact with the local DAR to make sure I dot all i's and cross all t's. I also asked if I could get the repairmans certification since I'm taking the plane down to roughly a quick build state. This was his reply:
"Amateur-built Repairman certificates can only be issued on original certification. In your case, it is being changed from the original configuration but not being re-certified. So, the answer is you will need an A&P to perform annual condition inspections."
Ive read other comments I think on this board, about those who have managed that feat. So where are the loopholes?
-
He usually answers pm's pretty quick. And he'll probably see this soon as well.
-
I don't remember where I found it, but I downloaded a copy of Harry Riblett's book, GA Airfoils. This book has the coordinate points for the GA30U-612 airfoil that is used on the Kitfox.
Here are the points in an excel doc and a disorganized cad drawing with those points plotted out. I thought I had a drawing with the Avid undercambered and speed airfoils, as well as the riblett airfoil all plotted out in a cad drawing, but I am not able to find it.
Although I am hoping to get the early model kitfox airfoil coordinates, this is helpful.
-
Wilja67, I have only analyzed the Avid STOL airfoil, and don't have coordinates for any KF section. Is that what you want?
Yes, I was hoping to get the coordinates for the KF 1-3 airfoil. Until recently I assumed the Avid A model and the KF1 airfoil were the same. And I also assumed that the airfoil you analyzed was the same one(looked like it at first glance). I read something somewhere that stated the KF airfoil is a little thicker than the avid? I'm not familiar with Avids since I have concentrated on learning about kitfoxes since that's what I have.
If the Avid airfoil you analyzed is basically the same airfoil just thicker I can scale the thickness in my CAD program to get the correct airfoil.
-
There are some interesting posts in this thread from a few years ago on extending the leading edge. May find it interesting. JImChuk
www.avidfoxflyers.com/index.php?/topic/4125-leading-edge-extensions/#comment-34447
Thanks, i hadn't seen that. I'm even more glad now that I bought it. I know I'm not going to win any races in a KF1 but I do operate at high density altitudes and any increase in climb performance will be welcome. And if i pick up a couple mph and can lower my throttle setting for a lower fuel burn so much the better.
-
I was curious about the Avid STOL airfoil, so made some calculations using an inviscid panel method code. The results are interesting.
We aerodynamicists tend to do everything we can to remove scale, or physical size from consideration. For example, we divide the wing’s lift by everything it’s proportional to: wing area and dynamic pressure, to get a lift coefficient. The dynamic pressure is just the difference between total pressure, that measured with a forward-facing Pitot tube, and freestream static pressure Pfs, that of the air at that altitude away from the influence of the airplane. It turns out that at our speeds this difference is ½rVfs2, where r (Greek r) is the air density. What’s great about total pressure is that it’s constant almost everywhere, except in regions of flow separation or where viscous effects are important, like right next to the surface, in the boundary layer. Bernoulli would say that this means that in locales where local velocity is high, pressure will be low, to preserve the total pressure: Pt=Ps +½rV2.
We talk about the pressure distribution around a body in terms of a pressure coefficient, Cp, which is just the difference between local pressure on the body’s surface and freestream pressure divided by the dynamic pressure
(Cp = (p-pfs)/½rVfs2). When local airspeed, say, over the wing, goes up, pressure coefficient goes down. That partial vacuum on the upper surface is a lot of what keeps us afloat so-to-speak. But y’all already knew that!
So just for fun, I looked at not only the STOL airfoil shape, but a version for which a straight line defines the lower surface. This is what Manu (Efil01) has on his Avid. It has more camber than the speedwing airfoil, since the upper surface is more curved. Here’s a plot of the airfoil shapes.
The first thing I looked at was the pressure distribution at takeoff, assuming the landing gear arrangement allows a maximum angle of attack of no more than 8 degrees, relative to the max length line (here the x-axis). Taller main gear or a smaller tailwheel would help here. By the way, the plot seems to chop off the trailing edge of the airfoil. That’s just an artifact of what was plotted; the inviscid panel code used for the computation plotted the “control points” which are midway between the defining points. I’m just being lazy here, so I beg your forebearance.
So here’s what the Cp distribution looks like at takeoff:
Per aerodynamics custom the Cp is plotted upside down, with negative values going up the ordinate, not down. The blue is the original airfoil, the red is the flat-bottomed version. At 8 deg AoA, the flat-bottomed airfoil delivers 7% less lift than the original version. As you can see, the lower surface has positive pressure on it in both cases. The upper surface features an overspeed right at the leading edge, perhaps the consequence of having too large an angular range for the round shape of the front spar tube, with a rather abrupt change in the surface curvature. Note also that the upper surface, with its overall overspeed, contributes about 2.5 to 2.8 times as much lift (area under the curve) as the lower surface.
Still, the slowing down of the airflow on the upper surface is relatively gradual, which is a good thing (Thank you Dean!). Note also that the lower surface flow is accelerating as it goes back towards the trailing edge. However, the effect of the under-surface camber is about a 40% increase in nose-down pitching moment for the STOL section vs the modified shape. All that camber is like flying around with the flaps down. Yes, it gets us off of the runway faster, since with taildragger gear we’re angle-of-attack limited on the ground, and yes, it delivers glorious in-flight visibility over-the-nose. But this is one of the great things about the Junkers-style flaperons: The camber can effectively be increased for takeoff & landing, but that dang nose-down pitching moment can be banished by pulling flaps back up for cruise. Having the wing and tail not fighting each other lowers the induced drags of both and allows us to cruise more efficiently, and faster.
O.K. now, so what do the Cp plots look like in cruise? I ran both airfoils at CL=0.5, a typical cruise value. Here’s what showed up.
A bit different looking, eh? That giant -Cp spike at the leading edge is on the lower surface! Does the flow stay attached after that steep recovery? Do we need to VG the lower surface? Tufts would tell the tale. I’ll bet some of you have already done this. Note how much milder it is for the flat-bottomed modification. By contrast the upper surface has it easy. So it looks like our friend Manu will have a sweet-flying airplane!
One caveat here: these calculations did not include the boundary layer or any of its effects on the outer flow, and were incapable of modelling any flow separation. In subsonics, everything affects everything, so these results, while indicative of what’s going on, are not accurate to the nth degree. I also did not include any effects of the flaperon, assuming it was neutral, not lifting upward or downward. Retired, I don't have a tool available to model the flaperon too.
Turbo, i recently bought the pvc leading edge from Kitfox and am working on a template to mount them onto my wings. I downloaded the template that Dholly has posted to this site and imported it into my cad software just to see how accurate it was. The drawing needed to be scaled considerably to match the 2.5" spar and its for a KF4 wing. I'm hoping you would be willing to share your coordinates for the airfoil so I can generate a accurate template and create a pdf that will be much more accurate than the jpeg file. I will happily post that to this site when I'm done.
1 person likes this
Yeeehaaaa!!! New Gear is On!!!!
in Kitfox I
Posted
For you guys running the cub style cabane gear, how much vertical travel do you guys limit your wheels to? I figure that I could have almost a foot of travel if I do a wheel landing and still have a couple inches before i smack the prop.