September Fury - a new Q-40 design
 

A few years ago Lee LaValley got started on a Q-40 version of the 2007 version of the Reno SeaFury racer "September Fury". Time and life got in the way and the design never progressed beyond a preliminary sketch. Here is the thread that he started: http://www.rcuniverse.com/forum/m_70...tm.htm#7014440

Since Lee is almost finished with the AR-6 Q-40 that I drew for him, I wouldn't want him to run out of things to do, ;) so I thought I'd pick up on the September Fury idea and document the way that I go about designing a Q-40 version of a full-size racer. Unfortunately, the CAD file of that sketch that he had is no longer available, so I'll have to start from scratch

This will be a fairly long, drawn out (no pun intended) process, and postings will be on a "when I get around to it" basis.

Since we don't have the real factory drawings of the SeaFury or the mods made to it to turn it into a racer, the best we can do is to start with a 3-view from an artist. There is a Japanese artist/draftsman that has made some beautiful drawings of several different airplanes, so we will use those as our reference material. http://www.taichiunlimiteddrawings.c...Built%20Racers

RE: September Fury - a new Q-40 design
 

Let's start with the side view:

I import the image into my CAD program, rotate and center the drawing so that it is aligned with the axis system and then using the various line and curve tools, trace over the main lines that define the outline of the airplane. I like to use a "center point line" for my initial tracing. I zoom in tight on the drawing somewhere on the straight line that I am interested in and then click to start the line and drag it out over the image until it aligns the way that I want it to.

The first image is the initial work, and the second is after things are trimmed and cleaned up a little.

RE: September Fury - a new Q-40 design
 

Really cool design... Lee sent me a drawing of it a while back and I did some sketch work with it but was never real happy with the motor and muffler placements. Will be interesting to see what you come up with. I like the wing and tail planform though.

DE

RE: September Fury - a new Q-40 design
 

Hi Gary,

I can offer you a CAD file of the Sea Fury with all the sections already lofted if you would like it. I started to design a Sea Fury for myself but got side tracked and have not yet progressed beyond what you see below. It's yours for the asking if you think it will speed things along.

http://i23.photobucket.com/albums/b376/CVEICH/FURY.jpg

RE: September Fury - a new Q-40 design
 

Hi Chad: Yes, that would be great. I'll send you a PM. Of course a Q-40 airplane is so distorted from the real thing by the time the thing is done, that it is almost unrecognizable. I'm just starting with the outlines of the September Fury racer to get a general idea of the thing. Soon I'll be "massaging" it to meet the Q-40 dimensional rules.

RE: September Fury - a new Q-40 design
 

Yes, I have some BIG concerns about trying to do a Q-40 version of a radial engined airplane. The largest cross section of a typical radial airplane is the engine cowling, which of course is right up front. Honestly, I don't know if the result of this little exercise will be satisfactory or not, but at least it will be interesting to see what happens.

RE: September Fury - a new Q-40 design
 

After I clean up the side view and turn off the background image it looks something like this: Things to remember, the September Fury is not a stock SeaFury. It has a different engine and cowling (off of a DC-6, I think) a minimal canopy and the forward fuselage contour have been extensively modified to blend it all together. Also, radial engine airplanes are not "continuous" from spinner to tailcone, the cowling is a completely separate piece on a real airplane, but on a Q-40 model, it has to flow smoothly from spinner base to tail cone. Also, artistic images, especially when scanned, converted put on the internet are distorted and may not be symmetrical. Obviously, an airplane of this type is symmetrical and the cowling is round, so we take that into account when making the tracings. At this point in the process, we don't really care about the "scale", we are just getting some basic lines to start with. I will scale the drawings at a later step.

RE: September Fury - a new Q-40 design
 

Now let's do the same thing with the top view. These images are of the roughed out tracing and then with cleaned up and with the background image removed for clarity. It turns out that the trailing edge of the wing, excluding the raked wingtip is a circular arc, which makes things a bit easier to draw. The ONLY things that we are interested in at this point are the primary control lines, which include the upper and lower fuselage profiles, the max half-breadth line (top view profile) and the outlines of the wing and tail surfaces. Unfortunately, we don't have any information about the cross section shapes EXCEPT that we KNOW that the cowling is a circle.

RE: September Fury - a new Q-40 design
 

From here on out, things get more interesting. I like to work in 3D since I think better that way. I will work in 3D from here on out until it's time to make the 3-view drawing of the proposed model for submission to the approval board.

I copied the sketches of the side profile and the top view and combined them into a new 3D drawing. I aligned the drawings at the base of the spinner and then rotated the side view until it was oriented correctly in space. The aerospace coordinate system is different from the mechanical engineering coordinate system. I will use the aerospace system because I am more familiar with it. The positive X axis goes from nose to tail along the fuselage, the positive Y axis is out along the RIGHT hand wing, and the positive Z axis is vertically UP. I like to place the origin at the base of the spinner.

The cowling diameter of my tracings doesn't quite match from the two sketches, it would have been a miracle if it did, but I will deal with that later. I know that it has to be a true circle. Lee told me that he wants to use a 2" spinner so that will provide the information that I need as things progress.

The next thing is to scale the sketches to the correct size for a Q-40. In my opinion the most important dimension on a Q-40 is the wingspan. It is limited to 54 inches, and the higher the aspect ratio, the less the induced drag. So, I scaled the span of the wing planform to 54" and everything else scales proportionally. I will keep the same fuselage length and moments to insure that the model retains a resemblance to the real thing, but will scale the other lines and areas to meet the Q-40 rules.

RE: September Fury - a new Q-40 design
 

OOPS! The maximum span dimension for a Q-40 wing is 56" not 54". See what happens when you rely on a failing memory as opposed to actually reading the rule book...

Here it is sized to 56" span.

RE: September Fury - a new Q-40 design
 

Now I just start working on the individual parts. First the wing. I measured the area of the actual scaled planform and found that it was 690.223 sq in. I scaled the wing in chord ONLY so as to keep the span at 56" but also keep the planform such that it resembles the actual SeaFury wing. The scaled wing has 401.227 sq in. ( a little slop for building and measuring inaccuracies)

RE: September Fury - a new Q-40 design
 

Looking good Gary.. Hopefully I'll have the AR-6 done so I can start on this one..

RE: September Fury - a new Q-40 design
 

Gary, Here were my thoughts on how to get around the round cowl. Yes on the two inch spinner, the cowl outside diameter should be a circle around the motor centerline to allow the 3/4 inch cylinder exposure. I was going to make the cylinder stick out pointed down on a 45 and that would put the muffler down on a 45 on the other side. It also would lower the venturi / spraybar which would help on tank placement (would not be so critical). The cowl would have a inside piece and an outside piece so when they were glued together it would give an airfoil shape with the idea to make the airflow smooth inside the cowl around the motor and out the exit.

Back in 92 or 93 I raced T6 class at Madera and a friend named Gary Hoover had a T6 that was 10 mph faster than anything there. He had some college students design a cowl / engine cover that smoothed out airflow to help it get out.... That was the difference between 118 mph and 130 mph. Just some thoughts. Keep us posted

DE

RE: September Fury - a new Q-40 design
 

If I add an airfoil (arbitrary at this point) and skin the wing, it might look something like this:

RE: September Fury - a new Q-40 design
 

D.E., you are correct, the round cowl for the radial engine is going to be tough. It might be a "show stopper". Cracking out the rule book shows that there are 4 big hurdles that have to be jumped for the fuselage design to make a legal Q-40. The rules state that the fuselage must have a minimum 5" at its deepest point, a minimum width of 3" at its widest point, a minimum cross section of 12.5 sq. in. at "some point", and the cylinder head must protrude 3/4" out of the cowling Yipes! My first thought was to try to kill two birds with one stone. A 4" diameter circle has just over 12.5 sq.in. of area (pi x 4= 12.566 sq.in.) so that seemed like a natural thing to try first as a cowl radius. it would exceed the minimum 3" width and take care of the 12.5 sq.in. rule all at once. I imported a 3D model of a Nelson Q-40 engine courtesy of Scorpion Racing (thanks Scott!) and created a 3D cowl of 4" diameter. Here is what happens. As you can see, there is a lot of interference and this just isn't going to work. I'll try several other cowl diameters and see if there is any possibility of making this work.

RE: September Fury - a new Q-40 design
 

That doesnt look too bad, The cowl will require some creative mold making but it is doable and would definately be unique.

Your 12.5 inch area rule might not work in cowl area as I dont think it can be in the "cheek cowl" area but just behind where cowl meets fuse area should be fine. It would also probably be covered at the 5" deep area as well. (cockpit area) that area will probably be around 3" wide as it is a smooth taper from cowl to tip of tail. My AR6 is 4" wide in front and goes okay. I think that airplane will work as good as any with some work on air around the cowl. It is the wing and horsepower that are most important. If Lee doesnt want to do it I might after I finish my F5D project. I am going to do some kind of Q40 just dont know what yet..... Press on!

DE

RE: September Fury - a new Q-40 design
 

I reduced the diameter of the cowl ring to 3.6" Diameter. That will give the 3/4" head exposure and also meet the 3" width rule so I can still kill two birds with one stone. Also I can see "light" between the muffler and the cowl, so this might work. I think that what I'm going to have to do in order to meet the rules is to continue to increase the diameter of the fuselage aft of the original base of the cowl until I get to 4" diameter so as to make the 12.5 sq. in. rule, then I'll meet the 5" height rule in the canopy area. Decisions, decisions.

RE: September Fury - a new Q-40 design
 

The wing was easy, the fuselage for a radial engined airplane is HARD! For the last several days I have been making various test drawings trying to meet the 3/4" cylinder head exposure rule without interference between the muffler and the cowl and then still be able continue the body aft in order to meet the 12.5 sq in and 5" height rule. So far, I haven't been able to do it and keep a scale outline that I personally think to be acceptable. One possibility might be to make the cowling elliptical in cross section instead of circular, it wouldn't be correct, but at least it would meet the rules and keep the same theme. Then the rest of the fuselage contours would be able to match the scale outlines. Another possibility would be to make "troughs" in the cowl to meet the 3/4" head exposure requirement and to clear the muffler. Troughs are allowed by the rules.


It just occurred to me that if I were able to add a 1/4" muffler stand-off extension that the problem would be solved. Not being very familiar with Q-40 engines, I don't know if such a part exists and if it would screw up the engine timing. Either Henry, Mike or Dub would probably know. Has this ever been done? Would it work. Is it legal, or would it screw up the timing? Inquiring minds want to know...

RE: September Fury - a new Q-40 design
 

Dub has a 1/4" and a 1/2" stand-off.

I have used them on a 428 engine. The 1/2" seems to very slightly affect the performance on a 428 engine. I did not see any difference with the 1/4". But that was on a SS Q-500 engine. And that was on a test stand.

I have actually used a 1/4" and a 1/2" together on a fun plane and the engine still comes on the pipe. Still get great performance.

RE: September Fury - a new Q-40 design
 

Gary,
While you can use a trough to provide clearance for the muffler, you cannot use one for the cylinder.

RE: September Fury - a new Q-40 design
 

Mike Langlois emailed me and as I had feared, a standoff will screw up the timing on a Q-40 engine. Oh well, I guess that would have been too much to hope for. Now you know why radial engined Q-40's are so hard.

It looks like a trough for the muffler will be the only way to meet the cylinder head exposure requirement and still be able to meet the 12.5 sq in requirement farther down the fuselage. Since this design (modeled from an Unlimited) does not have "cheek cowl's" like a Q-40 modeled from a Formula One would have, the width and cross sectional area requirements can be met anywhere along the length. I plan to meet the cross sectional area requirement just aft of the end of the cowling.

RE: September Fury - a new Q-40 design
 

It's starting to look like a Q-40... This layout meets all the dimensional requirements but will require a muffler trough. The scaled tracings are in blue, as you can see, I tried hard to keep the scale profile on the Q-40 while still meeting the dimensional specs.

RE: September Fury - a new Q-40 design
 

Looking good Gary..

RE: September Fury - a new Q-40 design
 

I think it looks great, and I'm not sure why a trough / dimple wouldn't work just fine...

From the pictures it looks like the motor is mounted upright? Is that how you are intending to do it...?

RE: September Fury - a new Q-40 design
 

I think he just did that to get it in there.. The trough isn't an issue as long as the entire trough is on one side of the parting line and doesn't create a negative draft..