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Old Jul 23, 2010, 12:22 PM
If it floats....sail it!
FoamCrusher's Avatar
Elk Grove, CA
Joined Sep 2002
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Airfoil Selection?

Based on Mike Smart's recollection that the airfoil was probably an E-193, and not being familiar with that foil, I started doing a little Internet research on it. My thought was that since the plane does not qualify for NOS, the laser cutter will make the ribs with any foil section we choose, and a lot has happened in the understanding of TD plane wing design since the 1980's when Mike selected the E-193, would there be a better shape to use now?

From what I have read, it is relatively simple to select the top 5 or so choices based upon the intended performance envelope, but after that it is person preference defended by a great deal of ego.

If the build group is interested and since we will not be sending out the rib cutting instructions for a little while, can we have a discussion about the relative merits of building original versus using a different foil section? We probably all have very different flying conditions and building experience and therefore different needs, and the price break on the laser cutting probably applies to having all the sets cut to the same foil, so if this idea is too far out, I understand. However, since we all will be investing considerable resources in the build, I thought the idea is at least worthy of discussion. Perhaps Mike can offer his opinion about which one he would use now with the perspective of 25+ years.

Other candidates for foils could be a Clark Y, MH 32, S 3014 (a favorite of Skybench Aero's Ray Hayes) and the familiar SD 7037. A bit more complex build could use Mark Drela's combinations of AG series used on the Allegro and Bubble Dancer http://www.charlesriverrc.org/articl...t-airfoils.htm. I offer this link http://www.gliders.dk/clark_y.htm as an interesting reference source for one person's opinion regarding a few comparisons.

FC
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Old Jul 23, 2010, 01:43 PM
Making wood fly since 2007
Windependence's Avatar
USA, MN, Rochester
Joined Mar 2008
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Hi FC,

I asked Mike this same question in an email earlier this year. I believe I said something like, "If you were to design the Raven 3M today what airfoil would you use?" his reply to me was that he really liked the overall performance of the original airfoil but..... that he may use the SD 7037 today.

Now that being said I will state that, without a doubt, I am the last person in the world you want to get airfoil advise from. Any airfoil will have its pluses and minuses. Perhaps the more knowledgeable members out there can offer us some insight. The design specs are listed earlier in this thread so, given that information, let the airfoil discussion/debate/argument begin. My only opinion is this, the Drela airfoils are very fine airfoils but I think they may add significant complexity to the build. Carbon caps, kevlar wraps and solid shear webs seem the norm when they are used. That level of complexity may push some builders away from the project.

Wayne
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Old Jul 23, 2010, 02:23 PM
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Watertown, WI 53098
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Quote:
Originally Posted by Windependence View Post
Hi FC,

I asked Mike this same question in an email earlier this year. I believe I said something like, "If you were to design the Raven 3M today what airfoil would you use?" his reply to me was that he really liked the overall performance of the original airfoil but..... that he may use the SD 7037 today.

Now that being said I will state that, without a doubt, I am the last person in the world you want to get airfoil advise from. Any airfoil will have its pluses and minuses. Perhaps the more knowledgeable members out there can offer us some insight. The design specs are listed earlier in this thread so, given that information, let the airfoil discussion/debate/argument begin. My only opinion is this, the Drela airfoils are very fine airfoils but I think they may add significant complexity to the build. Carbon caps, kevlar wraps and solid shear webs seem the norm when they are used. That level of complexity may push some builders away from the project.

Wayne
I'd go with the original, but that is me...
I'd say let the ones that would like a different airfoil to make them on their own... But hey, that is me and will have to live with what ever you all argue about... I've hear/seen arguments over airfoils before and will look away until I get notified as to when to send in the funds for the order... The rest of you enjoy the debate...
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Old Jul 23, 2010, 02:28 PM
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Aylesbury, Buckinghamshire, Great Britain (UK)
Joined Jan 2000
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I would probably use the SD 7037 or MH-32, I'm not a fan of the Clark Y. However, I believe the SD 7037 & MH-32 work best with camber changing flaps & ailerons, so flap-less the E193 may still be a reasonable performer.

Mike
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Old Jul 23, 2010, 04:41 PM
Making wood fly since 2007
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USA, MN, Rochester
Joined Mar 2008
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Ah... Mike brings up an interesting point. The newer airfoils are designed with camber changing in mind. So here is a question for all of us to ponder. If I am not going to ever implement flight modes, what are the benefits of the newer airfoils? It is one thing to deploy flaps for landing purposes, it is quite another to configure trailing edge settings for thermal, launch, and cruise.

I'm not taking sides here just asking the question.

Wayne
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Old Jul 23, 2010, 10:04 PM
AMA 3959
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United States, CA, San Jose
Joined Oct 2002
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I am leaning toward getting in on this build as you guys are getting the balsa dust in my old veins going. Now as far as airfoils, hhmm, I think it has to do with how you are going to build the Raven, I currently fly a Sagitta 900 in woodie class with like, I belive an eppler foil, on it works great. I also have an Artemis moldie with the 7037 and it really works great due to the camber adjustments I can make. So basically I guess I am saying the airfoil best to use is how you are going to build it, I am leaning toward the gull wing RES version so the stock airfoil would work for me. But anybody thinking of a full house version would want the 7037. just my 2 cents worth.

Al

p.s were do I get the plans? Mike? OHH no I may be hooked
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Old Jul 23, 2010, 11:23 PM
Making wood fly since 2007
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USA, MN, Rochester
Joined Mar 2008
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So let's try this, I will contact Bob and ask him to contact Tony, the laser cutter guy, with this request. Would it be possible to have a choice of laser cut airfoils for this plane? Either the original one or one suited for full house camber. The worst he can say is "no", the best he can say is "no problem builders choice"

Lets give some discussion to what the second airfoil option should be. It may be fun to have both airfoils and make two sets of wings, one for full house and a second poly wing for RES, both fitted to the same fuselage.

Wayne
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Old Jul 24, 2010, 04:50 AM
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Aylesbury, Buckinghamshire, Great Britain (UK)
Joined Jan 2000
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Quote:
Originally Posted by alstrahm View Post
I am leaning toward getting in on this build as you guys are getting the balsa dust in my old veins going. Now as far as airfoils, hhmm, I think it has to do with how you are going to build the Raven, I currently fly a Sagitta 900 in woodie class with like, I belive an eppler foil, on it works great. I also have an Artemis moldie with the 7037 and it really works great due to the camber adjustments I can make. So basically I guess I am saying the airfoil best to use is how you are going to build it, I am leaning toward the gull wing RES version so the stock airfoil would work for me. But anybody thinking of a full house version would want the 7037. just my 2 cents worth.

Al

p.s were do I get the plans? Mike? OHH no I may be hooked
PM sent,

Mike
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Old Jul 24, 2010, 09:22 AM
Blueplaidcanard flyer
sdy. ny
Joined May 2007
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Except for sticking a motor in the nose I think I'll just build it stock.If I had room to set up the highstart I might even skip the motor.
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Old Jul 24, 2010, 09:38 AM
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UK, Coventry
Joined Aug 2005
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You could look at the SD6080. I had a 100s model with it that flew a treat. One desciption I heard for it was 'like an updated E193', which is why I chose it. On an unflapped wing I would definitely consider it again.

Martin H
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Old Jul 24, 2010, 09:53 AM
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Watertown, WI 53098
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Plans Arrived...

The plans arrived...
Total cost was $17.19 US Dollars...

Comes with an Instruction Manual... (5 pages - text only - no pictures)
There is also an option on the plans for Foam Wing Construction...
KA
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Last edited by KickAce; Jul 24, 2010 at 10:17 AM.
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Old Jul 24, 2010, 10:36 AM
The Lone Blue Plaid Flyer
Bob Cook's Avatar
Seattle
Joined Jan 2003
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Hi Guys,

I'll get a hold of Tony the lazer guy, and ask him about doing the wing in other air foils. I tend to think he will do it but there may be some charge for that. The program he has now in his computer, is for a D box sheeting only on the wing. If your going to do something other than D box sheeting you need to tell him so he can change the program. I'll write him and let you know what he says.

Bob in Seattle
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Old Jul 24, 2010, 04:16 PM
The Lone Blue Plaid Flyer
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Seattle
Joined Jan 2003
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Hi Guys,

I wrote Tony and will let you know as soon as I hear from him. He does travel and so there might be a bit of a time lag.

Bob in Seattle
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Old Jul 24, 2010, 04:23 PM
Making wood fly since 2007
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Joined Mar 2008
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Hi Bob, Thanks for getting in contact with Tony about this. It never hurts to ask.

Wayne
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Old Jul 24, 2010, 04:30 PM
The Lone Blue Plaid Flyer
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Seattle
Joined Jan 2003
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I really don't think it will be a problem, as long as folks are willing to pay for his service. If I ever build one of my own design, I'll have him do the ribs for it. It's a small price to pay for accuracy where it's really needed.

Bob in Seattle
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