Airfoil for 50ccm

[sairaghi]

Hi,
I am planning to build a scale trainer with a wing span of 2.30m (7-8 kg) and I am evaluating different airfoils. The wing cord is about 400 mm and it will have 15% thickness. I was thiniking to use a semi-symmetric airfoil to be able to perform some basic acrobatic.
To me it seems a good choice the NACA 2415. What do you think? Do you have better suggestions?

Thanks Stefano

[Texas Buzzard]

Hi,
I am planning to build a scale trainer with a wing span of 2.30m (7-8 kg) and I am evaluating different airfoils. The wing cord is about 400 mm and it will have 15% thickness. I was thiniking to use a semi-symmetric airfoil to be able to perform some basic acrobatic.
To me it seems a good choice the NACA 2415. What do you think? Do you have better suggestions?

Thanks Stefano
.................................................. .........................................
w.s.= 230 cm & chord = 40 cm
That wing will have an Aspect Ratio of 5.0 .... 230/40 = 5 That is a very Low Ratio for a Trainer Type. Aspect Ratios of at leat 6 and even up to 7.5 will give much better flight caracteristics. Most 0.40 cu in powered trainers have a wing span of from 58 to 70 inches and a chord of 11 to 12 inches from front to back of wing (chord). So a 60" spand and an 11" chord has A.R. of about 5.5....to me that is more of an aerobatic plane.

15% thickness is very thick but it will fly! Lots of volume for strength of spars, eh? The NACA 2415 is an airfoil that many builders of full sized experimental planes used in the 1960's to 1980's. It is a good slower speed airfoil and will lift a lot of weight. I you don't mind slow speeds then us the NACA 2415. Personally I would thin it out a bit to a NACA 24 12. But HEY, give it a fo....it will fly.

Also I would make the wingspan divided by the chord to be at least 5.5 more if I could manage it. I like an A.R. of 6 for trainer types or Ariel Photography airframes. Do you have to fly in those MOUNTAINS? EEEEEEEK!

[Brandano]

Usually the higher the AR, the snappier the stall. Low AR wings tend to "mush" rather than really stall.

[sairaghi]

Hi, what I would like to build is a swiss semi-scale trainer (pilatus p3, http://www.p3flyers.ch/). The 40 cm cord is the root cord (sorry for that inaccurate value). The mean cord is 357mm: the aspect ratio should not be so bad!
I choose the 15% to be as scale as possible (like the original). I am searching an airfoil that allows me to fly the airplane at a moderate low speed (for a scale model is usually a good thing) but also allows me to perform some basic aerobatics (like the orginal P-3).

You confirm me that the naca 2415 could be a good choice. An other option that I am evaluating is the naca 63(2)A-015. Less max lift, more drag but also less moment (cm0).

Stefano

.................................................. .........................................
w.s.= 230 cm & chord = 40 cm
That wing will have an Aspect Ratio of 5.0 .... 230/40 = 5 That is a very Low Ratio for a Trainer Type. Aspect Ratios of at leat 6 and even up to 7.5 will give much better flight caracteristics. Most 0.40 cu in powered trainers have a wing span of from 58 to 70 inches and a chord of 11 to 12 inches from front to back of wing (chord). So a 60" spand and an 11" chord has A.R. of about 5.5....to me that is more of an aerobatic plane.

15% thickness is very thick but it will fly! Lots of volume for strength of spars, eh? The NACA 2415 is an airfoil that many builders of full sized experimental planes used in the 1960's to 1980's. It is a good slower speed airfoil and will lift a lot of weight. I you don't mind slow speeds then us the NACA 2415. Personally I would thin it out a bit to a NACA 24 12. But HEY, give it a fo....it will fly.

Also I would make the wingspan divided by the chord to be at least 5.5 more if I could manage it. I like an A.R. of 6 for trainer types or Ariel Photography airframes. Do you have to fly in those MOUNTAINS? EEEEEEEK!

[HugePanic]

Clark-Y ????

[BMatthews]

The link to the P3 gives me a 404 error.

I would try to aim for a much lighter weight than 7 to 8 kg. Even with a low aspect ratio and the resulting bigger wing area a far more suitable weight would be at most 5 kg. More like 4 kg would be much better and 3.5 kg would be near optimum for aerobatics of any sort. At 7 to 8 Kgs it would be a car with a propeller and flat things out the side and not an airplane.

From the specification of weight I am going to guess that you have not built or flown very many model airplanes. You may want to look at some other more successful options before trying to design your own model. Or at least do more studying on what sort of specifications you need to aim for that are more in line with successful design practices.

[vintage1]

The link to the P3 gives me a 404 error.


Try http://www.p3flyers.ch/

[sairaghi]

I think would be quite difficult to build a plane 2.30m (90") that weights 3-4 kg. The extreme aerobatic airplanes weights 7-8 kg. For a scale like model I found 8 kg a good optimistic weight.

Stefano


The link to the P3 gives me a 404 error.

I would try to aim for a much lighter weight than 7 to 8 kg. Even with a low aspect ratio and the resulting bigger wing area a far more suitable weight would be at most 5 kg. More like 4 kg would be much better and 3.5 kg would be near optimum for aerobatics of any sort. At 7 to 8 Kgs it would be a car with a propeller and flat things out the side and not an airplane.

From the specification of weight I am going to guess that you have not built or flown very many model airplanes. You may want to look at some other more successful options before trying to design your own model. Or at least do more studying on what sort of specifications you need to aim for that are more in line with successful design practices.

[BMatthews]

I think would be quite difficult to build a plane 2.30m (90") that weights 3-4 kg. The extreme aerobatic airplanes weights 7-8 kg. For a scale like model I found 8 kg a good optimistic weight.

Stefano

Ah... I think you're right. While I'm fairly comfy with metric my brain muddled up the sizes to weights on this one. I was thinking of the old pattern models that used to come in around 8 to 9 lbs and were around 70 inch span. I did the conversion in my head and figured that you were aiming at too heavy for the size. But for a 90 inch model 15'ish lbs would be about right.

[vintage1]

I think would be quite difficult to build a plane 2.30m (90") that weights 3-4 kg. The extreme aerobatic airplanes weights 7-8 kg. For a scale like model I found 8 kg a good optimistic weight.

Stefano

It is very possible with good design: An open structure, slow model should be around 10-15lb, or 3-4.5kg.

Mind you for a gas model you need some hefty structure around the engine.

[ZAGNUT]

because of an andy lennon article some 15 years ago i've been using the eppler 197 on all my sport planes ever since with very nice results, especially when compared to all the flat bottom profiles i had tried up till then. whether or not there is something better i don't know and probably wouldn't bother looking anyways as i have a huge selection of aluminium foam cutting templates for the 197 that i've accumulated over the years...




dave