|Apr 04, 2007, 02:34 AM|
Sukhoi Su-37 Super Flanker Park Jet
Here’s my next project to share with the forum, the Sukhoi Su-37 Super Flanker park jet. Some of the development details of this model were previously discussed in another thread located here.
This is my new #1 favorite park jet! It is smooth and graceful in the air, yet when pushed hard demonstrates incredible agility—just like the real Su-37 in the many videos posted on YouTube. This model was designed for twin Littlescreamers Park Jet (LSPJ) motors and features a working 3-axis thrust vectoring system (pitch, roll, and yaw) just like the real thing. With the TV system off, this model handles as well as any other park jet I've built and is very predictable, easy to fly, and has no bad habits. But with the TV system on, it can do wingtip flips, incredibly tight turns, and wild tumbling maneuvers. The TV system also provides excellent controllability at ultra low airspeeds and high alpha. With the twin LSPJs, top speed is in the neighborhood of 80 mph ( ) and thrust-to-weight ratio is between 1.4 and 1.7 for unlimited vertical. AMAZING performance! And with counter-rotating propellers there is no prop torque, resulting in very smooth launches and more jet-like handling qualities.
Here are the technical specs:
Wing area: 290 sq in
Weight RTF: 22 to 28 oz
Wing loading: 11 to 14 oz/sq ft
Motor: Two Littlescreamers Park Jet (LSPJ)
Battery: Thunder Power 2100 mAh 11.1V Prolite
Prop: APC 6x4 regular and pusher (counter-rotating props)
Current: 36 amps total
Watts: 350 watts total
Power loading: 220 watts/lb
Speed control: Two Castle Creations Thunderbird 18 or Phoenix 25 ESCs
Receiver: Berg 7P
Flight controls: Stabilators (tailerons), rudder (optional), thrust vectoring (optional)
This model was designed specifically for twin LSPJ motors so it’s sized slightly larger than my other standard park jets, with 290 sq in wing area instead of 250 sq in. This was done to account for the higher weight of the propulsion system (two motors, two ESCs, larger battery) and thrust vectoring system, yet still provide parkflyer-type wing loading. Other motors could work OK (such as Axi 2212/20's), but they need to be lightweight (both for balance and to reduce the load on the TV servos) and spin a small diameter prop (to reduce gyroscopic effects when using the TV). However, it will be very difficult to beat the performance of the LSPJs—they are ideally suited for this application since they are so light and provide so much power with just 6" diameter props!
I haven't shot any flight videos yet since the model is still unpainted, but look for one in the near future. My next priority is to paint this ship. I'm planning to go with the stock tan/brown/white Su-37 paint scheme shown below, partly because I've got too many "air superiority grey" park jets already and partly because this will allow me to leave the bottom half of the plane unpainted (saves weight and time).
Plans for this ship are posted in a following post below.
EDIT (7-26-07): Here's a flight video of this model:
|Apr 04, 2007, 02:39 AM|
Here are some photos showing the build of this model. Construction methods are very similar to the rest of my park jet designs. Although it's a bit more complicated than the F-15 and F-18 park jets, it's a lot less complicated than the F-14 and F-22 park jets. But overall the build is pretty simple and straightforward and goes quickly. The hardest part about building this model is that it requires a LOT of sanding due to all the complex curves and fillets. This design features extra large corner doublers in the fuselage and nacelles to allow sanding those parts to a scale round shape, but all that extra sanding is definitely a lot of work. But then again it wouldn't be a real Sukhoi without those beautiful curves… ;D Just be sure to wear a dust mask when sanding so you don't inhale all that foam dust and make yourself sick (don't ask me how I know… )
Note there are wide variety of options for how this model can be built, including:
* Canard or no canard – The plans show all the modifications required to convert this Su-37 to one of the original non-canard Su-27 or Su-30 variants. All that's required is to delete the canard, install a modified strake and modify the vertical tail. The changes required to do this are shown in red on the plans.
* Twin motors or single motor – This design can be easily adapted for a single centerline motor, which could be done with or without thrust vectoring (in this case it would be single-axis or pitch only). Note the upcoming Littlescreamers Super Park Jet Special motor would be an excellent motor for a single-motor version. The changes required to do this are also shown on the plans.
* With or without thrust vectoring – The TV system provides amazing maneuverability on this model but also adds quite a bit of weight, cost and complexity. For those that want a simpler version, this model can be built without the TV system and will still be a great-flying park jet. Another option would be to simplify the TV system by slaving the TV and stabilators together mechanically to eliminate the need for one pair of servos and a lot of complex transmitter programming. I'll describe the TV system in more detail in the next post.
* Flight controls – There are a wide range of flight control options on this model. To actuate everything (stabilators, flaperons, rudders, canard, thrust vectoring, throttles) would require 9 channels and up to 8 servos! But on the other hand, this model could be flown just fine using tailerons only—3 channels and 2 servos. The setup on my model is in the middle, with tailerons, rudder, thrust vectoring, and twin throttles, for 7 channels and 5 servos. I'll describe the flight controls and mixes required in more detail in a subsequent post.
|Apr 04, 2007, 02:43 AM|
Thrust Vectoring System
This model uses the same thrust vectoring system as my F/A-22 Raptor park jet, just with two of them instead of one. The design is based on 3/8" square hardwood sticks with 1/8" plywood brackets that swing around a small bolt, driven by Hitec HS-85MG servos. A strong metal-geared servo is required for this application, and the HS-85MGs have worked flawlessly in my model.
The F/A-22 has single-axis (pitch) TV, but using two motors together allows full 3-axis TV (pitch, roll, and yaw). Both motors gimbal up/down together for pitch, opposite for roll, and differential throttle provides yaw. The TV servos are electronically slaved to the stabilators to match their pitch/roll inputs, and the two ESCs are plugged into separate channels in the receiver to allow differential throttles (which are mixed to the rudder channel).
For those that haven't already seen it, here's a quick video showing a demo of the 3-axis TV system on my work bench:
Thrust Vectoring Demo
My model uses separate servos for the tailerons (Futaba S3110s) and the thrust vectoring, for 4 servos total. This allows me to turn the TV system on and off at will (via a switch on the Tx) and also allows adjusting the trims and rates of the TV system separately from the stabilators. To me, this setup provides the maximum fun factor. However, this model was also designed so that you could eliminate the two stabilator servos and just slave the stabilators and TV together mechanically. That eliminates the cost and weight of the extra pair of servos and also greatly simplifies the transmitter programming. To do this, just use the HS-85MGs, run a pushrod from the servo to the stabilator control horn (note the control must be installed pointing down instead of up as shown on the plans), and then run a second pushrod from the control horn to the TV mechanism. There are already two holes shown in the control horn template to allow this. Note this setup will require a lot of adjustments in the linkages to ensure the stabs and TV are properly aligned, especially once the airplane is trimmed. With the setup I used, all adjusting can be done easily just using the transmitter, which is very convenient.
In my experience with this model so far, 90% of the value of the thrust vectoring system comes from pitch. That's what allows the tight turns, flips, and low speed/high alpha control. Roll and yaw are also fun to play with, but I've found them to be useful only for post-stall maneuvering and tumbling maneuvers. Part of the reason for this is that the pitch TV responds instantly due to it's long control arm, but roll and yaw respond rather sluggishly due to their short control arms. This opinion could change though as I get more experience flying this ship and learn to use the TV better. I'm also eager to hear what some of you fellow modelers learn once you build this ship!
|Apr 04, 2007, 02:46 AM|
There are many ways the flight controls of this model could be set up. To actuate everything (stabilators, flaperons, rudders, canard, thrust vectoring, throttles) would require 9 channels and up to 8 servos! But on the other hand, this model could be flown just fine using tailerons only, with 3 channels and 2 servos. There are many pros and cons for all the different setups, but I chose to go with a middle ground setup on my model. It uses tailerons, rudder, thrust vectoring, and twin throttles, for 7 channels and 5 servos. It does not have flaperons or a moving canard. My rationale for this is:
* Flaperons aren't needed because this model already rolls well at high speed with the tailerons and well at low speed with the thrust vectoring.
* After giving it a lot of thought, I decided that a fixed non-movable canard would be the best way to go on this model. Although the real Su-37 has a moving canard, it isn't linked directly to the stabilators. It's actively controlled by a computer to provide high alpha stability and can move either with or against the stabilators, whichever is required. On an RC model we don't have that luxury and must slave it directly to the stabilators one way or the other. And I decided that simply leaving the canard fixed would cause it to stall early and reduce or eliminate the pitch-up that is common to highly swept wings with strakes. Flight testing has verified that this setup works as intended—this model has no high alpha pitch-up (like on the F/A-18 park jet).
As usual, rudder is optional on this park jet. It's nice to have but not required. I originally built this model without rudders thinking the yaw TV would be enough, but flight tests showed that the yaw TV response was so slow that it really wasn't effective for normal maneuvering. So I ended up retrofitting rudders into the model.
Attached is a chart below that summarizes all the channel assignments and mixes I used for my model. Note that I used all 7 channels of my Berg 7P receiver and used all 7 programmable mixes on my Futaba 9CA transmitter! This is not a simple model to set up, but once done it's easy to fly since everything is controlled automatically. All I have to do is flick a switch to turn the TV on or off! If you want to build this model but don't have a fancy transmitter, you can just build the mechanically slaved TV version. That eliminates the need for all the programmable mixes and 2 additional channels.
|Apr 04, 2007, 02:56 AM|
Plans, Construction Guide, and Kits
The plans for this model are posted below in the usual tiled and untiled formats. For those that prefer a kit, laser-cut kits are now available from www.6mmflyrc.com. Custom molded clear canopies are available from 6mmflyrc as well. Lucien Miller will also offer his usual plans printing service for this model, including custom enlargements. Contact Lucien by PM if you're interested in that (his Ezone username is LBMiller5).
An illustrated construction guide is attached below. This guide is based on the one I developed for the 6mmflyrc kit, but has been customized to show the slightly different build procedures for the scratch build version relative to the kit version.
For those that would like to show their appreciation for all the work that went into these plans, contributions to my "Depron fund" can be sent via Paypal to firstname.lastname@example.org ($5 to $10 suggested). While contributions are appreciated, please don’t feel obligated to do so. I don’t want or expect everyone that builds one to send a contribution, just those who are really inclined to and for whom it's convenient.
Enjoy, and of course the #1 rule is--post pictures if you build one!
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|Apr 04, 2007, 05:15 AM|
Wow Steve, great work as always! The plane looks beautiful, thanks so much for sharing the plans with us. Looking forward to building one of these sometime.
|Apr 04, 2007, 05:50 AM|
Great to see the Flanker go public at last. I'll have to work on decals for it when I get back from my upcoming trip. If anyone has some high res photos of some sexy Flanker schemes that are decal-worthy then please post them here.
|Apr 04, 2007, 06:37 AM|
|Apr 04, 2007, 08:56 AM|
Ahhh...finally the plans are out. Great work, Steve, getting everything together in double quick time.
I still haven't maidened mine, hoping to get her in the air this weekend.
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