Was the aluminum 2024, or 6061? I have some sheet identified with Aircraft S&S. Meeting with my buddy on Monday to talk rib cutting. We are embarking on another project for our local club that should yield some fun stuff with our guys. The Shyfox project is the next build I would like to get them engaged with. There are plenty of stock .25's around that would make this project exciting!I also downloaded your Mk II mods and like them. I was going to build a Mk i to get my feet wet, but I like that version a little better!

K&S says that their 1/8 aluminum sheet is 6061-T6. Their SKU is 83072. The 2024 would work even better (it is stronger), if you have some. It has added copper, which increases the strength and fatigue resistance, but is more susceptible to corrosion in full-sized planes. But that's not really an issue with models....

I will note that the gear will handle some abuse, but if your pilot is in the habit of slamming the plane down right in front of the pitman, you CAN bend the gear leg. If that is the case, a single wire strut might be a better choice. If you are considering that, then I would suggest using 5/32" music wire for a single-strut setup.

Thanks for the alloy clarification, Dave! I will follow the plans for the first built. I always follow a recipe for the first meal and tweek things later for my taste. I like the look of the bird. I am meeting with my dear friend on Monday to discuss the build. I think I will make the Mk II version out of the chute to gain some experience with SSR. I flew fast rat MANY years ago, so I need to learn how this works, and then promote to others in my club to join in the build. We may start with virtually any airplane with 300 squares or more to "get in the game"! We are starting with the Flying Clown event as a club racing event, and there are 7 or 8 builds going on. I have gotten a lot of help from Bill with providing our guys with tanks and shut-off's to get started.

SSR and to a lesser extent Clown are both "floaty" design forms due to the size of the wing that is required by rule and the normal weight that these come out. That means that the landing approach and landing gear have to take that into account. That makes these fly much different than the more traditional "rat" classes. For example, in shakedowns. But, the SSR rules also prohibit the use of shutoffs which means you need the glide lap anyway. The rules for Clown apparently changed to allow the use of shutoffs which makes things easier on the pilot at the speeds the things were going.

True, with no shutoff in SSR, you need to be prepared to hit the pits no matter where the engine quits. But, with the wheel in the right place, you can put it on the ground faster without bouncing if you practice a bit. A half lap of gliding is better for your race time than a lap and a half of gliding, as long as you know you can do it. I have a selection of SSR gear legs with different sweep angles and wheel locations so I can find the "sweet spot" for the wheel.

Bill,

I guess I was trying to discuss durability issues, not wheel trim issues. The caution was that an SSR was going to float, and if the pilot's inclination was to slam it on the pavement and feed it to a pitman too fast, both the aluminum gear and the wing (if that's what the mechanic decided to grab) were going to take a beating. That said, a really good pitman with a soft touch is invaluable. Especially when the pilot gets excited (ie. wants to win!) and really stuffs it into the pit.

As to the correct wheel placement, I can say that on both my Mk I and Mk II prototypes the balance and wheel location were good without adding tail or nose weight. The plane balances on the wheel in the normal range of 15 degrees or so ahead of the CG. (I would have to measure again to verify.) Those dimensions are shown on the plans for the Mk I. I think the Mk II nose is slightly shorter, measured from the LE. And, as I previously noted, the tail on the actual Mk I prototype was a bit oversize from the plans, so a bit heavier. I use firm wood for the fuselage, and the tail and fuse are glassed with 1/2 oz. cloth. So there is pretty good info on where the balance comes out, where the plane handles well in the air, and why the wheel location isn't a random guess. If anyone needs measurements or weights, I can do that.

Your point is a good one that if the plane flew well, but wouldn't set down and stay stuck, I would have had to make another engine mount/gear leg piece. The wire gear is more forgiving of swapping those out or even bending to suit.

I have a quick question, Dave. I was discussing with my rib cutter last night this build. He had a question about the Mk. II build. The new ribs are longer than the Mk. I version. Is the placement of the bell crank and lead out position still relative to the Mk. I version? And if the wing placement of the Mk.II version is a half inch forward of the Mk. I version, the spar location is still in the same relative position in the fuse? Are those good assumptions?

The lead out position should be calculated as a percentage of the root chord to be the same on both planes. Same with the spars, belcrank and balance point.

MM

The location of the bellcrank mount is immaterial to how the airplane will fly. The position of the leadout guide relative to the CG is what matters. The bellcrank can be anywhere as long as the leadouts don't bind in the guide. Trust Mr. Hull's measurements. He knows what he's doing.

Thanks. I know the bell crank does not matter, as long as it is structurally sound. Lead out position is most important. I made some assumptions that lead outs stayed in the same relative place?

Charles,

Let me get the plane down off the wall tomorrow and take some measurements for you. I might have to make a sketch to make sure I am giving you the correct interpretation of the changes.

Dave

That would be awesome, Dave! We are like to get a best understanding of the changes to the Shyfox! I think it is going to be an awesome bird! I have started getting supplies for the build and wrapping up some late winter builds for the upcoming contest season. 

A few measurements on the ShyFox I and II for comparison:

The fuselage overall length of both versions is the same. Including the rudder, they are 24" long. Note that by rule, the fuse must be at least 22" from the drive hub to the hinge line of the elevator.

The nose on the Mk II is 1/2" shorter, as measured from the wing LE. The original is 6" and the Mk II is 5-1/2".

The aft edges of the wing spars are in the same place on both the original and the Mk II. Both are 8-3/4" back from the nose.

You can see where I mounted the bellcrank on the plans for the original. I'm pretty sure I used the same mounting system for the Mk II, relative to the spars.

Essentially, the redesign was a change to the wing and some minor shaping changes to the nose for improved streamlining. The design approach was to locate the new wing on the same fuselage so that no other changes (ripple effects) would be needed. So the wing grew forward from the spar, and grew aft from the spar, until I got to the new root chord/area/span that I wanted. The rib grew more behind the spar to maintain proportions.

I assume you have the sketches of the root and tip ribs of the Mk II. Sorry they are not cleanly drafted. I might look for my "kit" box and see if I can get a cleaner tracing from the templates. I think I used aluminum templates as I normally do.

I also assume you have the planform sketch of the Mk II wing. I generated that for someone a few years back that was building one.

I hope this helps. If you have more questions, ask away.

Dave

Awesome! I think that is great info! Let the building begin! I will try to figure out how to put pictures on SH to show my work. I will share with T.J. So he can post on NCLRA newsletter! I am looking forward to it! I already have a tank I got from Bill. I have a few more things I need to reach out to Bill for the Clown build we are working on.