New Design for Slope Racer

[jvaliensi]

Hi,
I've been think of features I want in a sailplane for racing and fun.
Five piece wing:
100mm long removable tips without ailerons.
1.5m long Center section bolts to the top of the fuselage.
650mm long Aileron sections with optional carbon and steel joiners to adjust the ballast.
Load wing ballast from the outer ends because center section is one-piece.

Round, tapered boom that attaches to the front part of the fuselage with a machined aluminum interface and three screws.

Vee-tail with X08 (8mm) servos in each section.

Empty wait around 1800-2000g

The idea is a center mounted one-piece wing can be held on with three breakaway bolts. All the parts are modular so they can be replaced. The airplane can be broken down to a small size for travel.
The servos in the tail have a slight weight penalty, but make it easy to take apart and have very positive control. The modular front fuselage can be made for electric, so you can practice flying from the flat land and swap to pure glider for the slope.

I think having heavy joiners will make the airplane easier to control at hight speeds. Also the ballast box would be the lenght of the center section so different loading schemes can be tried.

 

[Konrad]

What racing class are you thinking of? In FAI F3F racing the wing joiners are a problem. That is why you read so much about how large brand "X"'s joiner is compared to the competition's joiner.

If looking at a DS ship again joiners and gaps are to be avoided.

If you want to go racing one needs to get a truck. Not only for transporting the ship. But also for the high ground clearance and 4 wheel drive needed to get to some of the best racing sites.

 

[Wayne]

I like the thought you have put into this. I will ask why removable tips?

Is your primary goal a plane that will be compact for storage and transport? That is totally valid, but it will come with some compromises.

The complexity of your wing will make this an expensive plane to produce. It will cost less and weigh less if you do not have so many joints. The modular fuselage is a good idea, but again I think you are adding expense and adding weight and taking away strength. Probably better to have a seperate fuselage for the electrics. Fuselages tend to be the cheapest part of the plane to produce.

 

[jvaliensi]

The modular approach I want is for crash repairs, comp[act portability is a side benefit to me.
I figured it is best to leave the last 100mm of wing without aileron, so having a joint here is easy to do, but you are correct about cost increase. There may be benefits to having tips with different shapes or airfoils.
I think the one-piece center section would be stronger for a given weight that the traditional two piece wing. I think span-loading ballast decreases the stress at the center as well.
I've seen a few glider fuselages snap behind the wing from a rough landing, due to imposed torque from the tail. So, I think a simple tapered and replaceable tail boom has value.

The tail servos will make the airplane a little heavier. But I like the idea of easy disassemble of the Vee-Tail. I leave them on and the airplanes get bounced around quite a bit on the off-road trip to the hill.

Now, I want Doc to design the airfoils and fuselage shape so we can get started. I'm wishing here.

 

[Wayne]

LOL I think he may be a bit busy right now.

Yeah, the fuselages do tend to take damage on the boom if the plane rotates on landing.

I personally like the servos inside the Vtail method. The mini Terminator does this pretty well.

Some of the F3F guys are very worried about span weights. They are using X08 out at the aileron to reduce mass so they can bank a bit faster. Making the wing with more joints will pick up more weight, and complexity. You will see that sort of wing on a large thermal ship, but not very often on a fast slope ship.

Onto the V-tail setup - I was just thinking about the ability to put the 8mm (or thinner) servo into the tail, and use a rather conventional linkage and horn setup to the elevators, but design it so the linkage and the top of the servo is inside the fuselage. Basically have a small cover on the bottom side of the fuselage that covers the linkage.. That could be interesting. It is still not ideal as you will have an V-tail that is at least 9mm thick where the servo is. . Everything is a tradeoff, especially when you are talking about a racer.

 

[Konrad]

LOL I think he may be a bit busy right now.

Yeah, the fuselages do tend to take damage on the boom if the plane rotates on landing.

I personally like the servos inside the Vtail method. The mini Terminator does this pretty well.

Some of the F3F guys are very worried about span weights. They are using X08 out at the aileron to reduce mass so they can bank a bit faster. Making the wing with more joints will pick up more weight, and complexity. You will see that sort of wing on a large thermal ship, but not very often on a fast slope ship.

Onto the V-tail setup - I was just thinking about the ability to put the 8mm (or thinner) servo into the tail, and use a rather conventional linkage and horn setup to the elevators, but design it so the linkage and the top of the servo is inside the fuselage. Basically have a small cover on the bottom side of the fuselage that covers the linkage.. That could be interesting. It is still not ideal as you will have an V-tail that is at least 9mm thick where the servo is. . Everything is a tradeoff, especially when you are talking about a racer.

Has the XO-8+ worked out? I have full size aileron servos in my 3 meter F3F ships. I may need to drop down to a DS135MG for my 6 volt ships and the mini X10 for my 7.4 volt ships. I don't have the guts (yet) to try a XO-8 in an F3F aileron.

 

[jvaliensi]

I think the KST X08 will have enough power. The amount of force needed is based partly on the amount of deflection of the surface and the size of the surface, F3F Vee-tails don't have much of either.
Doesn't Aer-o-tec have a racer with servos in the tail, the Impulse?

My design ideas are not meant to be a super competitive racer. More of a beginner's racer and a great sport plane that will not cost a fortune to fix. I think the greater moment of inertia from the three/five piece wing will make it more forgiving to fly.

 

[Konrad]

Maybe for the tail, I'm still concerned with the durability of the gear train. But the ailerons are much larger and see a lot of load as I dive into the coarse.

Doc. has mentioned that his tail airfoils are a bit on the thick side. This might be an advantage hiding the XO-8+ in the tail feathers.

I'm pulling out the large servos and moving to the mini X10 (same servo tray).

As a general rule I find inertia counter productive to controllability. I know for DS ships they are set up with mass out at the tips for a host of reasons we often don't see on the front side of the hill.