Sprucedeuce

I acquired a Jack Stafford Super Minnow recently and I plan to build it for plain old sport flying. It has a foam core wing which is great, I love them I cut a lot of them myself on my own custom made Variac powered equipment. Here's the problem, The foam wing core that comes in the kit was designed for pylon racing in the late 60's early 70's and it has unusually thin outboard section with an undercamber at the tip, I mean really thin, the cores are approx. 1/8th inch at the ends. Downloading a three view drawing revealed that the full scale plane had a symmetrical airfoil of conventional thickness along the span. I am thinking that for sport flying I should cut a new core that mimics the full scale plane because this will never see a pylon race and I'm a little unsure about the special racing wing for just knocking around the club field, can anyone offer me advice on this subject, many thanks.

All Day Dan

My Feedback: (5)

You can't beat the NACA four digit airfoils for sport flying. I have had continuing success with the 2415 and 0015. Dan.

geezeraviation

My Feedback: (3)

I agree with All Day Dan, you don't want the thin racing wing for sport flying,
Doc

jaka

Hi!
I would use the wing...All it takes to have a good flying sport model is light weight! The wing airfoil isn't that important how it looks.

Truckracer

My Feedback: (19)

Well as an old pylon racer from the 70' and 80's, I built and flew several of those old Minnows. Later on I even flew some of the retired planes as sport models when improved racer designs came along. You can cut and build a different wing but for the most part, the thin under-camber tipped wing will fly quite well as is. I've even seen them flown in a couple of pattern contests back in the day and they did quite well. As the trend went away from that highly washed out, under-cambered tip airfoil, I use to cut wing cores with a different tip airfoil for racing as the old design was a fairly high drag wing. I reduced the amount of washout by half the amount or so and the tip airfoil was copied from a Prather Little Toni racer that was so popular at the time. The root airfoil remained untouched and the tip airfoil became symmetrical.

I still have one of my late 70's planes with the modified wing hanging on the wall in my basement. (Photos attached) This particular plane has a fiberglass fuselage but for the most part it is just the Stafford plane slimmed down a bit. They were just quicker to build with the aftermarket fiberglass fuse. The original wing had the under-cambered airfoil. I could probably trace the modified airfoil if you are interested.

These old pylon planes have excellent handling characteristics and will slow down quite well for landing though you have to learn how to slow them down. Just darn good old planes overall!

With today's lighter radio equipment, it isn't hard to build these planes lighter than the weights they use to fly at. I still have a Prather F-1 Little Toni kit and hope to find the energy to build it one day.

For those who are not familiar with these planes, the full scale planes were named Little Toni, Ballerina, Cosmic Wind and Minnow at various times in their existence

Sprucedeuce

I want to thank you for the reply, that is a gorgeous plane. Thank you for the insights In was hoping to hear from someone who actually had experience with the way this particular wing flew. It looks like I was on the right track as far as changing to a more conventional airfoil. I think I will use a fully symmetrical section. I thought the Minnow was related to the Midget mustang but Wikipedia said it was designed and built by Tony Levier and some Lockheed spooks. I am leaning towards doing the Cosmic Wind markings, I have a brand new Fox 40 with one of the extended quieter tilt up silencers that's going to tuck in right under that cowling blister like it was meant to be. I wonder if anyone would be interested in the cores from the kit since I'm not using them. Des Moines is a neat town, I live in Tulsa. It was nice hearing from you, if you ever need a core cut holler at me I 'll do it for the cost of the foam and shipping.

Sprucedeuce

Thank you for replying, I see you are the MVVS guy, I have never owned an MVVS but I have always thought they looked like they would be excellent engines, they look very robust and sensibly designed.

Truckracer

My Feedback: (19)

One advantage of going to a normal airfoil section toward the tip is a thicker aileron. On some of the original wings, the ailerons got sorta thin out there and were prone to flutter. Several tricks were used to keep the flutter under control but most of these became unnecessary with additional aileron strength.

Keep a bit of washout in the wing and don't go too think on the airfoil section on the tip and you should have an enjoyable plane. If it were mine, I'd probably stay with a 10% to 12% section out there. This is common for many aerobatic designs these days.

One of the original full scale planes, Cosmic Wind #5 is on display at the EAA Museum in Oshkosh if you ever get up that way.

Sprucedeuce

I found the coolest site called airfoiltools.com that has an extensive library of foils, but what's really neat is a feature called airfoil plotter that allows you to enter parameters like the chord you desire and mods to the airfoil like thickness etc..., also you can have it allow for sheeting when it draws the foil, and you can use your printer to make a full size drawing that can be used to cut a template. I settled on a naca 0010, it just looked right when I laid it over the plan, it also seemed to be very similar to the three view that I have. It's an inch an 1/4 at the root and 3/4 at the tip. Should I go thicker at the tip? or does this sound like it will work fine. I appreciate your help.

HighPlains

My Feedback: (1)

The Minnow was designed back at a time where the airplanes were not very fast, and were heavy due to the crude radios available. My racing partner back in the 80's dug up a Minnow for another buddy to get his feet wet in F1, and while it flew, it was not all that great. The under-camber was something that was best left to WW1 aircraft and free flight models.

If you want to cut new cores, I would use the SD6060 section with no washout. Adding a bit more area also helps, especially if you are flying at altitude. Easy to do by adding a few more inches to the length of each core. Also do not delete all the dihedral. While the original kit design had quite a bit, some is necessary to prevent adverse roll with rudder input.

Truckracer

My Feedback: (19)

Good comments from High Plains. I recommended staying with the original root section because it will fit the wing saddle on the fuselage w/o modifications. I don't remember any bad flying characteristics from the under cambered tip racers other than the later planes with real airfoils and less washout were quite a bit faster and turned much better. These early planes were all flown with a fairly forward CG where later designs tolerated a much more aft CG and flew like they were on rails.

Spruce, that airfoil should work fine at the tip and I wouldn't go thicker if it was mine.

I woke up a few memory cells and remembered cutting new cores for several QM 15 planes back in the same time period. Like F-1, they also had the undercambered tips on quite a few designs including the Stafford P-51 and these were changed to symmetrical sections. If I had to guess, in those days it was probably what we called a "zip" airfoil meaning we probably drew the airfoil with a french curve and if it looked right we used it. That was pretty common at the time. I've even heard of people accusing others of drawing their airfoil around their show sole. If we didn't use a zip section, we copied something that was known to work well. Things weren't always very scientific back then.

Though people like to thumb their noses at wings with under camber or flat bottom tips, I remember one extremely competitive QM-15 design that had a flat bottom airfoil at the tip with minimal washout. The design was still popular and setting records right up until the 15 class went away. It was fast and turned extremely well.

TFF

Build both wings. My old QMs flew great. You just have to slow them down before you want to land. I think you will be surprised how good it flys.

Sprucedeuce

Ok! I have the templates cut and im getting ready to block out the foam chunks in preparation for cutting the new wings. In order to get the washout in the tip how much should I angle it up in relation to the root foil? Should I get scientific about it, or will it be ok to just bring it up like 1/8th of an inch or so?

Truckracer

My Feedback: (19)

That can be a tough call with many answers! I'm thinking the 1/8" will be safe without causing any adverse effects. You've got me really curious now and I may take my old plane down from the wall to make some measurements. I also have an old Prather wing in storage that I could measure. I should have some info for you later today if you're interested.

Truckracer

My Feedback: (19)

Wing update:

Due to construction blocking my door, I couldn't get into my storage unit to retrieve the Prather wing. I did take the old F-1 plane down from the wall and measured that wing. The wing has NO washout at the tip and is a 7.5% symmetrical section at the tip. I have attached a photo of the tip section. That old plane was certainly not the fastest one I every owned but it was a very stable, easy to fly race platform. My race partner and I both shared the same color scheme and backup airplanes and that plane was his F-1 trainer. It won its share of heat races against much faster planes mostly due to consistency. As stated earlier, the plane was just flown for sport after it was retired from racing and the wing had no bad habits at any speed. Landings were slow and predictable and I can't ever remember it dropping a wingtip. Hard to believe that old plane is 38 or so years old now! Dang, I'm getting old!

Your old Minnow kit probably has 3/32" strip aileron hardware. Most of the later planes changed to 1/8" wire to reduce the chances of flutter and I would recommend
this change.

All Day Dan

My Feedback: (5)

I do believe that the chord of the wing tip is pointing down at the leading edge in relation to the chord at the root if washout is used. I never use it myself. I just land faster to avoid avoid any kind of a stall. Dan.

Sprucedeuce

Well, just now getting back to the project. That wing in the picture is just a little thinner than the wing for a sig plane called a midget 450 that I have a kit of. I am going to kick the root template up about 1/16th at the back edge. What kind of finishing materials did you use on that plane? Glass and resin under Superpoxy paint?

Truckracer

My Feedback: (19)

That old wing was fiberglassed with polyester resin (common in the 70's) then painted with Superpoxy primer and colors. Panel lines were drawn on with a Rapidograph drafting pen and India ink. The clear topcoat was DuPont Imron. That was pretty much the standard finishing method at that time. I could pretty much finish a whole wing from bare wood to finished product in just over a week.

Regarding the SIG Midget Mustang designed by Hank Pohlman, the one I had used a wing very similar to the Stafford wing, undercamber tip and all. They had an earlier kit called the Midget 450 but I never built that plane and don't know what kind of wing it had.

Sprucedeuce

Here are some pics of my progress.

Truckracer

My Feedback: (19)

Wow, you're jumping right into the project! Its good to see some of the old stuff come to life once again. Should make for a nice flying plane.

Did you increase the span or wing area any?

Sprucedeuce

Joined the wing halves about an hour ago, I made it an even 50 inches from 49 and 1/4. I also moved the firewall forward about half an inch since I'm not using a rear induction motor.

OldScaleGuy

My Feedback: (2)

Interesting project. Will be following along.

Sprucedeuce

I should have more to show later this wkend.

Sprucedeuce

I should have more to show this weekend.

Truckracer

My Feedback: (19)

The only problem I see with the project is finding a place to hide that FOX muffler. Was that the silent muffler or the tuned muffler?