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Author Topic: wing thickness?  (Read 16246 times)

Alan Hahn

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Re: wing thickness?
« Reply #50 on: November 09, 2009, 03:28:59 PM »
It might be interesting to open a thread on "how to fly slowly". Not sure which sub-forum it would make sense in. Maybe the Open forum would be best.

I know I don't feel comfortable with lap times much above 5.1 to 5.2 s--typically I am flying on lines up to 64 feet handle to center of plane. That is with glow or electric. Basically I just don't feel like it will make it over the top.

I am always amazed to see some planes just pull over the top--I wouldn't have thought they would make it.

Offline Erik Janssen

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Re: wing thickness?
« Reply #51 on: November 10, 2009, 02:28:14 AM »
I have just received my copy of Profili2 a software where you can compare different profiles. I selected 4 profiles and compared the outcome.

The NACA has the lowest drag, the CAP the lowest increase but a wing load limit.
The GOE has a higher drag in level but seems to match the NACA 0018 in the maneuvers.

This leads to the conclusion that the Eppler 479 works best in the maneuvers and if I want to increase drag in level flight I have to increase wing area.





Offline Claudio Chacon

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Re: wing thickness?
« Reply #52 on: November 10, 2009, 05:43:17 AM »
I have just received my copy of Profili2 a software where you can compare different profiles. I selected 4 profiles and compared the outcome.

The NACA has the lowest drag, the CAP the lowest increase but a wing load limit.
The GOE has a higher drag in level but seems to match the NACA 0018 in the maneuvers.

This leads to the conclusion that the Eppler 479 works best in the maneuvers and if I want to increase drag in level flight I have to increase wing area.






Erik,
Can you please draw the polars of this two attached airfoils for me ?
This is a .jpeg image. Please let me know if this is OK for Profili or if I have to send you the documents with .dxf or .dwg extensions.
Your help will be much appreciated.

Thanks!
Claudio.

Offline Erik Janssen

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Re: wing thickness?
« Reply #53 on: November 10, 2009, 09:25:26 AM »
Profili comes with a database of profiles, I cannot import a drawing. So if you have a name of the profile or something that comes close I can make a comparison

Profili is cheap, for an encouragement fee of 10 euro's you'll get a code to use it. The professional versions are more expensive.

Offline Claudio Chacon

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Re: wing thickness?
« Reply #54 on: November 10, 2009, 09:31:19 AM »
Profili comes with a database of profiles, I cannot import a drawing. So if you have a name of the profile or something that comes close I can make a comparison

Profili is cheap, for an encouragement fee of 10 euro's you'll get a code to use it. The professional versions are more expensive.

OK.
Thanks anyway.

Offline John Miller

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Re: wing thickness?
« Reply #55 on: November 10, 2009, 11:41:10 AM »
I find the Profili information interesting. I use Compufoil for my wing and airfoil lofting requirements, but the Eppler 479 is not in my database. The Eppler 169 is though, and when the percentage of thickness is set to the same percent, looks almost identical to the NA63A modified I use. I'm beginning to believe that both are very similar in performance as well.

Claudio, your airfoils most resemble the NACA 4 digit airfoils. Possible around 0022 -0024. Performance may wind up being in the same league as the NACA 0018, with the advantages, and drawbacks associated with the thicker high point.
 H^^
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Offline Erik Janssen

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Re: wing thickness?
« Reply #56 on: November 10, 2009, 02:25:25 PM »
I found the E169 in Profili, the NA63A is not in this database. Seems to have even lower drag in alpha.

This should flow easily through the square maneuvers, do you have that experience?



Offline Serge_Krauss

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Re: wing thickness?
« Reply #57 on: November 10, 2009, 02:32:48 PM »
Erik,
Can you please draw the polars of this two attached airfoils for me ?...
Claudio.

If you have enough of the coordinates to enter by hand, Profili will put your wing section in it's library, draw it, and draw relevant graphs from XFOIL. If these are known, non-proprietary sections, they might already be in the Profili library.

Stephano has been very good about encouraging and helping with its use. For instance, he first sent me a password the day I e-mailed him, allowing me to send the $10.00 later.  I don't know whether it's still a $10.00 donation, but it is very inexpensive for what you get. You should just do a Google search for "Profili" and find his site - it comes right up. Then e-mail him and obtain the program. I've used it a lot, even verifying that XFOIL sees the wing section that John Miller and I like as being a bit better than the NACA thick 00xx sections for my particular use. It will modify any profile in several ways and will draw comparisons of profiles and polars by drawing or graphing in different colors on the same grid. Finally, even the basic version will draw up ribs with sheeting and spar holes/recesses for tapered and elliptical wings, even when the wing sections change from root to tip; so it's a great help in building wings. There really isn't any reason not to just go ahead and get Profili, if you like what it does. There will probably be no real waiting, and it's easy to use. If your section is already in its library, you might even get your polars completed in a few minutes by sometime tomorrow.

SK

Offline John Miller

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Re: wing thickness?
« Reply #58 on: November 10, 2009, 02:57:50 PM »
Yes Erik, That is my experience. It also does not seem to get upset with turbulence easily, offering good penetration without inducing the stall at our speeds and usage.

Both I, and Serge, have been using the NAC63A and modify it by moving the high point forward to about 25%. When so modified, it seems very similar to the E 169 with it's normal high point at 26% of chord. I have been using a thickness between 18 and 20% on most of the designs I use it on.

You may want to increase the thickness of the E-169 from 14+% to the same range and re-compare.

I hope that Serge will use Profili and compare the E-169 and the NAC63A modified. I'd really like to see where we're going here.

 H^^
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Offline Erik Janssen

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Re: wing thickness?
« Reply #59 on: November 11, 2009, 12:48:13 AM »
Very interesting profile. When I increase the thickness to 20% it shows more drag in level but less in alpha. I kept the highest point at 26% and reduced Re a little to see if that matters a lot.

The drag in level matches the thicker profile, very interesting.

This is a candidate for my next wing.

Have you got experience with the blunt trailing edge?


Offline Igor Burger

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Re: wing thickness?
« Reply #60 on: November 11, 2009, 03:46:40 AM »
Guys, you want fly square figures "easily" at cl=1?   VD~

Offline Erik Janssen

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Re: wing thickness?
« Reply #61 on: November 11, 2009, 04:23:40 AM »
I cannot follow your remark, can you explain?

Offline Claudio Chacon

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Re: wing thickness?
« Reply #62 on: November 11, 2009, 06:32:18 AM »
Well guys, I have my Profili installed and a nice set of polar graphics of my airfoil. Now, there's a problem:
I don't know what they mean or how to read them ???!

Can you please help me on this one?
Many thanks and sorry for my ignorance on this matter.

Regards,
Claudio.

Offline John Miller

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Re: wing thickness?
« Reply #63 on: November 11, 2009, 07:19:36 AM »

Have you got experience with the blunt trailing edge?



I've been using a 1/8" squared off trailing edge for years. No problems experienced.
Getting a line on life. AMA 1601

Offline Serge_Krauss

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Re: wing thickness?
« Reply #64 on: November 11, 2009, 08:15:22 AM »
I hope that Serge will use Profili and compare the E-169 and the NAC63A modified. I'd really like to see where we're going here.
 H^^

John-

I'm just quickly skimming through here while struggling to get my club newsletter finished today and bowing fiddle parts for orchestra tomorrow. This looks very interesting, and I'll try to do it as soon as I can get free, but I'm swamped for the day. I have posted some low resolution (to meed Leonard's 50Kb restriction) Cl vs alpha graphs comparing it (flapless  and with stationary flap) to a comparable NACA 00xx section, but I will have to re-do more legibly and add the new section - not hard, but I have to get some serious effort into this newsletter for now. I'll check back in, when I resurface!

SK

Alan Hahn

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Re: wing thickness?
« Reply #65 on: November 11, 2009, 09:10:11 AM »
Well guys, I have my Profili installed and a nice set of polar graphics of my airfoil. Now, there's a problem:
I don't know what they mean or how to read them ???!

Can you please help me on this one?
Many thanks and sorry for my ignorance on this matter.

Regards,
Claudio.

Claudio,
I will attempt to explain, but will probably need to be corrected by others.

So what you are looking at are the coefficient of lift and drag (Cl and Cd) for different angles of attack (alpha). There are mainy ways to plot this stuff. So on the plot of Cl vs Cd, the curve is generated for different values of alpha. SInce this is a symmetrical airfoil, when Cl=0, alpha equals zero. My guess is that the ends of the curves are just the maximum and minimum values of alpha you see on the graphs which show Cl vs alpha directly.

But in the more general case, what does it mean. We have been debating here and there about thick wings, and making sharp corners, and so I think the direction of the argument is to see what airfoil gives the most lift with the least amount of drag at a high angle of attack (alpha), like you would see in a corner. In this case you would want an airfoil that has a high Cl and low Cd value near the ends of the Cl vs Cd plot.

However these plots do NOT include flaps, so maybe they are not completely relevant to the discussion--unless you are flying a non-flapped plane.

Hopefully Serge will fill in the flap question!

Ok, I am ready for the corrections! H^^

Offline Igor Burger

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Re: wing thickness?
« Reply #66 on: November 11, 2009, 05:44:28 PM »
Claudio, (and Erik as well) ... as Alan wrote, those plots are not usefull for maneuvering since they do not iclude flaps. There is no way to make a corner at lift coefficient close to 1 at our wing loads and speed we fly at.

Real analyze must be done with conjuction of elevator. Means 0 flaps and 0 AoA, then it must go by more and more AoA and more and more corresponding flaps deflection. Not so easy task.

That my orriginal statement which started this debate is, that as low as possible drag at high AoA and lot of flaps and as high as possible drag at 0 AoA and no flaps. Then we must include induced drag, prop thrust at actual speed, curvature of airflow etc. It is relatively lot of math.

Then we have to consider influences of changing airfoil moment to the controlling by elevator, bumps on lift polar (cl to alpha) if there are any. It is not so easy to play a numbers game and to say "that is the best airfoil" just by eyeballing of one or two numbers or polars.

However main meaning of those polars was in Alans post, it gives at least some imagination about the airfoil.

Offline Claudio Chacon

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Re: wing thickness?
« Reply #67 on: November 12, 2009, 05:04:33 AM »
Alan, John, Igor, thanks a lot for the input guys.
I understand now, it's much more complicated than I thought.
With so many variables in the equation, we can use those graphics as a mere starting point and that is it.

Thanks again,
Claudio.

Offline Igor Burger

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Re: wing thickness?
« Reply #68 on: November 12, 2009, 07:06:12 AM »
Yes, in any case you can see what modiffication makes what effect. So just add flaps to your airfoil and play with it, you will see :-)

Offline John Miller

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Re: wing thickness?
« Reply #69 on: November 12, 2009, 08:36:12 AM »
Igor has developed an airfoil, using a lot of information, that seems pretty good. Perhaps he'll share it once more.
Getting a line on life. AMA 1601

Offline Igor Burger

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Re: wing thickness?
« Reply #70 on: November 12, 2009, 10:08:58 AM »
this is what I use on latest "MAX"


Offline RandySmith

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Re: wing thickness?
« Reply #71 on: November 12, 2009, 11:10:44 AM »
SV-11 Rib profiles root tip, I tried many many airfoil shapes..too many planes\wings  too little time  ::)

Offline Erik Janssen

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Re: wing thickness?
« Reply #72 on: November 12, 2009, 11:32:53 AM »
Interesting profiles,

I finally managed to figure out which profile I use. The Sky Writer profile I am using with great pleasure in bad weather conditions is very close to the E169 profile at 17,5% thickness.

My .46 model conversion is 1750 gram and has 40 dm2 wing area, originally it was Super Tigre .46 powered and 1600 gram at the 1984 WCh. I still remember Bob Hunt giving me compliments on the consistency of the bottom maneuver line.

Later I used this profile on a 1660 gram .51 model with a wing area of 44 dm2, this flies more stable and does great hourglasses.

I'll probably keep this profile and change the thickness to 20%


 

Offline John Miller

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Re: wing thickness?
« Reply #73 on: November 12, 2009, 11:53:32 AM »
SV-11 Rib profiles root tip, I tried many many airfoil shapes..too many planes\wings  too little time  ::)

Randy, you've a good airfoil on your designs. I've studied it in the past, and believe it is very very close to what I've found to be the NAC63A modified, or, now I must add the E-169.

Your tip 'foil shows what the root would look like with the length shortened, high point moved forward a little, and a few percent thicker to control tip stalls.

Good penetration in turbulence, over the blunter 4 digit airfoils, due to the smaller radii at the nose. H^^
Getting a line on life. AMA 1601

Offline John Miller

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Re: wing thickness?
« Reply #74 on: November 12, 2009, 12:11:10 PM »
Interesting profiles,

I finally managed to figure out which profile I use. The Sky Writer profile I am using with great pleasure in bad weather conditions is very close to the E169 profile at 17,5% thickness.

My .46 model conversion is 1750 gram and has 40 dm2 wing area, originally it was Super Tigre .46 powered and 1600 gram at the 1984 WCh. I still remember Bob Hunt giving me compliments on the consistency of the bottom maneuver line.

Later I used this profile on a 1660 gram .51 model with a wing area of 44 dm2, this flies more stable and does great hourglasses.

I'll probably keep this profile and change the thickness to 20%


 

Erik, It looks that you have a good leg up on this aspect of stunt design. Notice Igors airfoil carefully. As I remember, he did a lot of work on it with many plots, and studies. This one had the least problems with the use of flaps. Interestingly, at least to me, there's a passing resemblence to the stock NA63A. No modifications at all. I may be wrong on this, but I seem to have been told one time, that the NAC63A was a laminar flow airfoil.
Getting a line on life. AMA 1601

Offline RandySmith

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Re: wing thickness?
« Reply #75 on: November 12, 2009, 02:35:42 PM »
Randy, you've a good airfoil on your designs. I've studied it in the past, and believe it is very very close to what I've found to be the NAC63A modified, or, now I must add the E-169.

Your tip 'foil shows what the root would look like with the length shortened, high point moved forward a little, and a few percent thicker to control tip stalls.

Good penetration in turbulence, over the blunter 4 digit airfoils, due to the smaller radii at the nose. H^^


Hi John

Yes that is why the tip rib station look as they do, I have never had any luck with making the root into a farther forward high point, that has hurt, not helped performance, and I have not had any tip stall problems with any of the SV airfoils


Below is the VECTRA airfoil, thinner but never had any problems carrying weight, or any stall problems even in very high altitudes and very hot humid condidtions
This is the airfoil I used in My Vectra and in Bill Werwages P-47, some people call it the Geo Bolt airfoil

Regards
Randy

Offline RandySmith

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Re: wing thickness?
« Reply #76 on: November 12, 2009, 02:53:00 PM »
These 2 are  the NOVAR , and Evolution airfoils, many people have used this on, it is slightly lower aspect ratio with 1\2 inch more chord 30 sq in additional to the large SV ships, and is 1\4 inch thinner, but still retains its roots from the  SV design series.
This wing has proven very good in turbulant conditions, This was developed in the early 90s with many many talks with Bill Werwage, I took the SV airfoil shape out  very very slightly to the design shape of Bill's  USA-1, in hopes of getting a little better wing in high winds and turbulance but still retaing  the high performance high lift ability of the SV series
All of the SV series are very good in winds and hi heat\humidity , but we all keep looking for more  ;D

The 2 drawings below is not to scale, the tip rib is about 2 inches shorter than the root

Randy

Offline John Miller

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Re: wing thickness?
« Reply #77 on: November 12, 2009, 03:45:15 PM »
You can see the family resemblance with all these airfoils. I'll bet that when I take the airfoil I like, which seems almost identical, and alter the percentage of thickness, to match your examples, they will also be close to what you have at the same percentage.

In my experience, these are great airfoils. They work, and I've gotten repeatable results, as you have.

As you said, we always look for "more bettah". H^^

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Offline Howard Rush

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Re: wing thickness?
« Reply #78 on: November 12, 2009, 04:56:27 PM »
This is the airfoil I used in My Vectra and in Bill Werwages P-47, some people call it the Geo Bolt airfoil

Possibly the only airfoil to beat Igor's at the last world championships.
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Offline John Miller

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Re: wing thickness?
« Reply #79 on: November 12, 2009, 05:27:58 PM »
Hmmmm. of course the pilot doesn't matter, right? LL~
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Offline Howard Rush

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Re: wing thickness?
« Reply #80 on: November 12, 2009, 05:45:56 PM »
Lots of other stuff matters, particularly team management.
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Offline John Miller

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Re: wing thickness?
« Reply #81 on: November 12, 2009, 06:07:55 PM »
True enough Howard. I can't agree more, but of course, it's also good to get oneself the best tools as well.

I'm reminded that a flintlock, and a M-60 are both firearms, but what a difference..... LL~
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Offline Erik Janssen

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Re: wing thickness?
« Reply #82 on: November 13, 2009, 07:19:09 AM »
They are exactly the same, a near hit is a total failure for both. I cannot afford to choose a wing profile that does not work so I decided to stay on the safe side and use the E169 profile at 17,5%. In order to keep future options open I am building the plane without fainings and big flat fuselage sides so any profile will match. The wings bolt on from the side.

The tail section was built in depron, only 14 grams.

Offline John Miller

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Re: wing thickness?
« Reply #83 on: November 13, 2009, 08:18:09 AM »
Erok, please keep us posted on your progress. I think you've made a good choice. One question, are you including the chord of the flaps when figuring percentage of thickness?  H^^
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Offline Erik Janssen

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Re: wing thickness?
« Reply #84 on: November 13, 2009, 12:52:29 PM »
I use the profile as specified, so 17,5% is as profili draws the profile.

I start with the root profile for a 295 chord, cut away the last 40mm and add a 10mm TE before sheeting the wing. So effectively the chord then is 295 - 40 + 10 = 265.

For the tip I use 245 - 40 + 10 = 215

I will keep you posted on the progress.

Offline Brett Buck

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Re: wing thickness?
« Reply #85 on: November 13, 2009, 10:32:46 PM »
On a stunt design with a w.s. of around 55" how thick should the high point of the root rib be if the cord length (not including flap measurement) is 10.000"? And same question for tip rib of 8.375" . Also hinge line distance of 17" would be about right?  Power supplied by ST 46 with bristunt ABC P&L set and head supplied by same (might try saito 40 also later )

    I think you guys have covered most of the airfoil possibilities as far as thickness goes. But based on some recent experience, I think that it makes almost no difference if you don't get the first 3/4" or so right. The "as delivered" ARF Strega is has a hugely thick wing, far more than even I had considered using, OK wing loading (about the same as my NATs airplane) and relatively large flaps. But the leading edge is pointy and it won't fly even mild corners, even at sea level and reasonable temperatures, without being on the edge of stalling.  Blunt it a little, and no problem. As described here:

http://www.brodak.com/files/file/Strega_Building_Wing_Instructions.pdf

    It's essentially as Al described in his 1973 AAM stunt column - if it comes to a point (say, less than 1/8" LE radius) it "buffets" (i.e. stalls) in the corners, and you can fix it by sanding back through the sheeting to the underlying LE wood and rounding it off. 

     I also think the other issue is the "departure angle" of the leading edge shape. The ARF Strega airfoil also seems to be designed to fair smoothly into the 1/4 square at about a 45 degree angle, essentially going straight back at 45 degrees until it needs to start turning to fair in with the high point. Sort of like conformally mapping the Nobler airfoil with the x ordinates not scaled, and the Y ordinates scaled by 150%.

    Point being, no matter what you do to the rest of it, if the LE radius isn't sufficiently blunt, you're going to have problems.

     And before anyone jumps on me for jumping on ARFs again, or Cardinal/Tsunami/Stregas, I would note that the Vector 40 and the T-Rex "Bradleymobile" ARFs don't have the same issue at all - Brad's being particularly blunt, not quite to "Intimidation"/"Excitation" standards, but noticeably blunter than most.

    Brett

Offline RandySmith

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Re: wing thickness?
« Reply #86 on: November 14, 2009, 12:39:10 AM »
 " I think you guys have covered most of the airfoil possibilities as far as thickness goes. But based on some recent experience, I think that it makes almost no difference if you don't get the first 3/4" or so right. The "as delivered" ARF Strega is has a hugely thick wing, far more than even I had considered using, OK wing loading (about the same as my NATs airplane) and relatively large flaps. But the leading edge is pointy and it won't fly even mild corners, even at sea level and reasonable temperatures, without being on the edge of stalling.  Blunt it a little, and no problem. As described here:
"
Brett
You are Exactly correct , the LE is very important, as is the hingelines, that is why the SV airfoil look like this...
, this size wing should not be any sharper than about the radius as a dime, or depending on the thickness maybe a little blunter
I have a guide printed on most of my plans that can be cutout and used as a template for getting the  LE radius correct. It also needs to be consistant across both halves of the wing panel LEs

Regards
Randy

Offline john e. holliday

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Re: wing thickness?
« Reply #87 on: November 14, 2009, 07:43:16 AM »
Randy,  is that the center and tip ribs? 
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Offline John Miller

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Re: wing thickness?
« Reply #88 on: November 14, 2009, 10:00:04 AM »
I feel I need to apologise to Howard for my playful, flip, answers to his recent posts. It was jousting in fun.  H^^
Getting a line on life. AMA 1601

Offline RandySmith

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Re: wing thickness?
« Reply #89 on: November 14, 2009, 02:09:38 PM »
Randy,  is that the center and tip ribs? 

Hi

Yep that is the  center and tip for 1 of the  SV  wings

Randy

Offline Howard Rush

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Re: wing thickness?
« Reply #90 on: November 15, 2009, 10:30:27 PM »
I feel I need to apologise to Howard for my playful, flip, answers to his recent posts. It was jousting in fun.  H^^

Aw, John.  I can't expect to have the monopoly on playful, flip answers.
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Offline Bradley Walker

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Re: wing thickness?
« Reply #91 on: November 16, 2009, 04:23:42 PM »
I would note that the Vector 40 and the T-Rex "Bradleymobile" ARFs don't have the same issue at all - Brad's being particularly blunt, not quite to "Intimidation"/"Excitation" standards, but noticeably blunter than most.

The Bradleymobile uses the Saturn airfoil.  Which is what I call my "thin standard" airfoil.  I believe it is the perfect compromise in the slightly lower aspect ratio T-Rex (I mean Bradleymobile).  I was particularly adamant with the factory that the front of the airfoil must perfect match the plans.  They did not disappoint.

Viewed in CAD all of these airfoils start looking alike, at least from the Hunt and SV series.  Randy's SV airfoils are about 3/32" thicker top and bottom than the Saturn airfoil (if blown up the same chord).  The Saturn airfoil was supposedly derived from Billy Werwage.  The Saturn airfoil looks suspiciously like a Genesi/Legacy/Buccaneer airfoil.  As Brett said, these are all not way off the Imitation airfoil (which is a favorite of mine also).

I would not go thicker than Randy's airfoil.  There is no need.  Just adds weight, drag, etc.

I would suspect the Saturn airfoil is similar to PT airfoil also.

"The reasonable man adapts himself to his environment. The unreasonable man adapts his environment to himself, therefore all progress is made by unreasonable men."
-George Bernard Shaw

Offline RandySmith

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Re: wing thickness?
« Reply #92 on: November 16, 2009, 07:34:59 PM »
""Randy's SV airfoils are about 3/32" thicker top and bottom than the Saturn airfoil (if blown up the same chord).  The Saturn airfoil was supposedly derived from Billy Werwage.  The Saturn airfoil looks suspiciously like a Genesi/Legacy/Buccaneer airfoil.  As Brett said, these are all not way off the Imitation airfoil (which is a favorite of mine also).""


Hi Brad

To be accurate..one of the SV airfoils is 3/32 thicker, The  SV airfoil system lets me plot many adjustable sizes of the STuntcraft airfoils, by sliding up and down the scale of  SV  rib stations R-2 - R-16, there are 18 avalible Stations for the SV foils, more if I want
So there are SV wings that are thinner, the  same, and  thicker than the Saturn.

Regards
Randy

Offline Howard Rush

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Re: wing thickness?
« Reply #93 on: November 17, 2009, 05:12:21 PM »
I would not go thicker than Randy's airfoil.  There is no need.  Just adds weight, drag, etc.

How do you figure a thicker airfoil adds weight?
The Jive Combat Team
Making combat and stunt great again

Offline Igor Burger

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Re: wing thickness?
« Reply #94 on: November 17, 2009, 05:24:04 PM »
looks like the air in the wing weights 1oz  VD~

Offline Bradley Walker

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Re: wing thickness?
« Reply #95 on: November 17, 2009, 05:26:15 PM »
How do you figure a thicker airfoil adds weight?

More wood...
"The reasonable man adapts himself to his environment. The unreasonable man adapts his environment to himself, therefore all progress is made by unreasonable men."
-George Bernard Shaw

Offline Howard Rush

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Re: wing thickness?
« Reply #96 on: November 17, 2009, 05:44:39 PM »
I'll pass that along to the structures guys at work.  They had it backwards.
The Jive Combat Team
Making combat and stunt great again

Offline Brett Buck

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Re: wing thickness?
« Reply #97 on: November 17, 2009, 08:12:18 PM »
More wood...

   Hey, crazy and maybe impossible idea - if you cut away the wood in the middle, it doesn't weigh anything.  And the wood at the edges might not have to be as strong, either, so maybe make it thinner or softer. Why, it's almost as if the thicker you make the airfoil (or the cross-section any other part), the lighter it is for a given stiffness, or, can be stiffer for the same weight. If only we had known that back in the 80s, we could have started making our wings thicker than aerodynamically necessary just to gain rigidity. And what great luck, in a startling coincidence,  it just so happens that we have such powerful engines the associated drag could easily be overcome. My God, we could have even told people about all this and why in print since 1979 and on the internet dating back to 1995 on the old Compuserve and RCO  C/L forums and published plans in magazine utilizing that effect.

   Alas, if we had just thought  of this, it would have been possible to win innumerable big contests against guys trying to build the same old 60-70's design ideas with 50's engine and prop technology lighter and lighter and with shinier and shiner finishes. They may never have realized that our airplanes always seemed in trim and were more controllable because the added stiffness permitted far more consistent control responses, even without 3000 flights per year of practice.  They might not have even figured out what we were doing, or didn't believe us,  so they couldn't take advantage of it. They might even come to the conclusion that the whole thing was rigged!

      I am sure glad none of that ever happened.

     Brett

Offline Bradley Walker

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Re: wing thickness?
« Reply #98 on: November 18, 2009, 05:48:22 AM »
Touchy touchy...  

I thought you used foam wings...  The thicker the wing the more sheeting required and the heavier the core.  

The thicker the wing they higher the surface area.  Even with an I-beam the middle beams and the capstrips would all be longer.

I never said that thicker wings would not be stronger...but to what end?  How strong do they need to be?

PS:  Every time you go on one of your rants about how the design of stunt airplanes has reached some consensus and everyone has conceded that you are correct, I am reminded of the great Al Gore.  I am also reminded that you keep getting beat by guys doing stuff you don't do, in fact they are beating with stuff you say *will not work*...  Since your method works for you, it does not make everyone else an idiot. 


« Last Edit: November 18, 2009, 08:48:34 AM by Bradley Walker »
"The reasonable man adapts himself to his environment. The unreasonable man adapts his environment to himself, therefore all progress is made by unreasonable men."
-George Bernard Shaw

Offline Steve Fitton

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Re: wing thickness?
« Reply #99 on: November 18, 2009, 08:58:26 AM »
   
   ...Alas, if we had just thought  of this, it would have been possible to win innumerable big contests against guys trying to build the same old 60-70's design ideas with 50's engine and prop technology lighter and lighter and with shinier and shiner finishes. They may never have realized that our airplanes always seemed in trim and were more controllable because the added stiffness permitted far more consistent control responses, even without 3000 flights per year of practice.  They might not have even figured out what we were doing, or didn't believe us,  so they couldn't take advantage of it. They might even come to the conclusion that the whole thing was rigged!

      I am sure glad none of that ever happened.

     Brett

At first, I was going to ask how we got from airfoil thickness to sarcastic conspiracy theories, but, I've decided to make some popcorn and sit back and enjoy it instead.  These are rising(sinking?) to the level of some of the Ted Fancher/Al Rabe "debates" S?P
Steve


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