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Jul 10, 2017, 12:37 PM
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"Kollmann 2Buck Racer-X, Racer-T and Racer-V" Series

Hi All,

There has been some early interest in the specifics of the little racers we've been test-flying.

I'll put up the guidelines pretty soon...I've been formulating the concept and testing the planes for about a month now and I think I've come up with another good formula for a cheap,
easy pylon racing series.

"Kollmann 2Buck Racer-X, Racer-T and Racer-V"

Formula Limitations so far are :

Stock Class:

1.Must use emax MT1806-2280 KV motor with BLheli 12A esc. These are $16.00 for a motor /esc/carbon prop if bought in sets of four and are bulletproof, efficient motors on 3S with a 5" prop.
2. 3s battery must be used. We are having luck with turnigy 800 MAH, graphene 800 and pulse 800 3S batts. These all fit well and give a six-10 minute flight staying cool. The Turnigy 800mAh 3S 30C is $8 each and is more than adequate.
3. Must use FT "tiny Trainer" fuselage and power pod at stock length made of FT waterproof foamboard or DTFB.
4.Any wing or tail profile or configuration is allowed. Any Prop is allowed, any covering is allowed. Developments of aerodynamic efficiency, exploring limits of "clipping" and different aerodynamic "cheats" are encouraged within these limits.

Unlimited class:
1. Forward Power pod and motor mount from "FT Tiny Trainer" must be used. Any length, materials or configuration is allowed
2. Any entrant may be "claimed" for $150 cash by any entrant or spectator "as flown" in the race.
This should discourage "throwing money" or insanely complex or expensive building techniques at the quest for speed
during competition without discouraging experimentation and development outside the competition events.
3. no other restrictions exist

I have been using "HTRC 4 x EMAX Original ES08A II 8.5g Mini Plastic Gear Analog Servo for RC Model" These are $4 each bought in sets of four from Amazon and are good reliable servos that fit well and center well. ..but any servo is allowed.

I will cut a set of templates so the design can be traced on a DTFB sheet in a few minutes without needing to print the plans. This way there is no printing cost. with a 1 piece wing, the plane fits on 1.25 sheets of DTFB, with a two -piece wing it fits on a single sheet of foamboard.

The idea is to have a cheap, relatively quick, fun, nice flying airplane to race and fly together with a $2 materials cost for an airframe. So far, I've seldom had as much fun for $40 total and everyone who has flown the two prototypes agrees they are a blast to fly. I'm building an AF in about three-four hours including paint and I'm sure it could be done in far less, cause I'm sort of slow and am figuring out the T-tail, and Vee tail configurations as I go. They look pretty cool and there is a LOT of unexplored potential for speed in there. It would fly well as a three-channel airplane with a single aileron servo and no rudder bringing the cost down to about $30 total. It flies and launched very well, with no bad habits, slow landing speeds despite the significant "clip" from the trainer wing and on high rates it does a great snap/spin (to the right) and rolls like a drillbit. The ailerons are zero chord at the tips allowing significant in-flight "cambering" without adverse stall tendencies. This should allow camber change in turns and creative mixing for straight line flight and elevator -flappervator. The Decalage is minimal and could be reduced for more speed. And this airframe is TOUGH. I've cartwheeled after a 60deg knife edge impact with zero damage. Even a straight-in dive would likely only require a power pod as it comprises the front six inches of the plane and is held on by teriaki skewers. The rubber band wing absorbs most of the shock loads of a crash

This can be built from the FT "Tiny Trainer" speedbuild kit, $25 (if you can't get your lazy self behind cutting foam with a box-cutter and don't want to make your motor mount and horns from plywood) with different wing profiles that could be trimmed from the trainer wing (and some added fairings and techniques). The speed build kit comes with horns, firewall, control wires and rubber bands and a spare glider/trainer wing and a glider nose which could be used as a spare power-pod. I'd encourage watching the "tiny Trainer" build video as almost all of the build is covered there, short of the hot knife-edging of the trailing edges and build of the T-tail and Vee-tail, fairings and canopy.

I'll continue posting developments, flight test data and series rules as they are completed. Greg and I ran about 50 laps Sunday and the #3 (conventional tail) and #4 ("T" tail) airplanes are very closely matched. I'll test the V-tail next week, but I suspect it will have no great advantage. Speed advantages will likely be more due to battery health, finesse in the build/tuning and pilot proficiency. We flew once in a 14KT wind and while it was interesting, we made it down in one piece...well one piece each.

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Jul 10, 2017, 06:00 PM
So many planes, So little time
Xflyfun's Avatar


I've ordered the parts needed, had to use; AMain Hobbies, Get FPV, Amazon, Flite test and RC Dude.
I'm all warmed up for Prime Day tomorrow!
Jul 12, 2017, 07:29 PM
Registered User
Thread OP
Hmmm, I just ordered the motors/rx's/batts from hobbyking. All in the uS warehouse.

And the servos from amazon.

I have 5 or six of the motor/esc/prop combos in hand for anyone who wants to do one. $16 each
Jul 13, 2017, 08:36 AM
So many planes, So little time
Xflyfun's Avatar


I was locked out of HobbyKing, I'll come to you for future motor and esc needs.
Flite test sent me the quick kit for the Tiny trainer, so I have all the stuff here now.
I have done some work on the Super Bee, enough to burn the side of my index finger off.
Working on another project that's due for Saturday, I don't think my plane will be ready this weekend.
The foam board planes are fun, Flite test guys do a great job with the build videos too.
Jul 13, 2017, 10:15 AM
Registered User
Thread OP
Heh! I keep a glass of water near the build so when I get a bunch of hot glue on me and think "ooh crap that's gonna burn" I can dip it in the water before it blisters...makes the glue easier to get off your fingers too! I also use a damp sponge to "snap dry" the hot glue in some places (in the build...not on me).
Jul 13, 2017, 10:33 AM
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Thread OP
BTW, and this is important!

The credit for the "Tiny Trainer" is obviously and completely Josh Bixler's.
I can't stress enough how much I admire the efforts, humour and candor that the Flite Test crew has brought to the hobby. I spoke with most of them at length down at Flight Fest in Sonoma and liked them all. This may seem obvious, but As I age I genuinely like fewer and fewer people, but this crew is energetic, passionate and fun-loving in a way that enriches the experiences of building and flying model aircraft. Not only do they "Do the work" instead of just talking about it, but share all the knowledge and manage to bust each others chops pretty well without really hurting anyone's feelings. The average manufacturing/engineering environment could learn a lot from these guys. It's like the Lockheed Skunk works with a smaller budget and a bigger smile.

So, If the Tiny Trainer is a stock '64 mustang, Maybe the TwoBuck is the Shelby...same basic stuff, just a few fairings and doodles from the basic, but a way to learn about some design principles of drag, load, balance and optimizing an airframe for a desired purpose. And of course, to look a little cooler while doing it.
Jul 16, 2017, 07:54 PM
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Joe - I'd love to build and help test a Racer-T. Have you posted plans on the FT forums yet? If not, how can I get access to them? I'm ordering parts and materials now - looking forward to some racing with you out at FAW.

Jul 17, 2017, 10:30 AM
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mondofresh's Avatar

One other question...

Joe - what sized spinners are you using? From your photo, looks like about a 1", that right? Thanks!
Jul 18, 2017, 04:10 PM
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Thread OP
Print as Poster in the default PDF viewer and the scale should come out right. For the T-tail, I used a mini sullivan rod for the elevator but it really wasn't necessary. I also doubled the vertical fin on either side, but that was also probably overkill, just some gussets at the top inner joints would be fine. These wings are just a bit smaller than the prototypes, but they were the profile I'd be trying next. The Proto has WAAAYYY too much aileron for smooth pylon-style flying. With about 27% aileron differential to counteract the adverse yaw, none of these really benefit much from the rudder, but it does allow a nice hammerhead and a violent snap-roll quality. I've been laying the wings out as a single piece, no joint, no dihedral with a popsicle stick ahead and behind the servo lead trough flat on the upper skin before folding the wing up. Also I added skewers to the leading and trailing edges of the inner wing where the rubber bands tend to cut into the foam. ANd skewers on the leading edges of the vertical fin and horizontal stabilizer just for durability and to keep them from warping under the heat of transport.

That Spinner is a 1.5" electrifly, but I was intending on printing some of the Spitfire spinners from thingverse as a standard, I also want to try and print some power-pods and horns this week. It should make the nose a bit stronger and faster to build. The plywood parts take as long as the rest of the airframe to cut out!!

Jul 18, 2017, 06:09 PM
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Thread OP

pdf plans packed

Here are two sheets printable on 10ea 8.5 x 11 tiles (use "poster print" in adobe viewer to tile ). These fit better on the DTFB sheet once you paper doll them and layout for best economy. Overlap is set at .005" so they should make decent templates and save some printer paper.

Jul 19, 2017, 09:48 AM
So many planes, So little time
Xflyfun's Avatar


Thanks Joe,
Printed out the plans, no problem.
I'll print out a couple of spinners as well.
Jul 19, 2017, 10:55 AM
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Thread OP
I maidened the last of the three variants last night, the racer-V and it flies as well as the others. I doubt there is really much speed or handling difference between the three, but it gives some visual variety and the vee is theoretically, at least, the fastest platform.It does keep the surfaces out of the grass a bit better on landing, but it's not quite as stable on the table upside down as the t-tail while loading batteries. At least the elevator is pull for "up" unlike the -T. So there are minor advantages/disadvantages.

I did design it with a couple degrees of decalage (the incidence negative on the ruddervators with respect to the wing chord line) and it proved excessive and unnecessary. I'd build future v-tails with zero angle, basically aligned with the upper surface of the pre-fairing fuselage top, chamfered to allow for the 90 deg vee to nest in the upper rear fuselage. It seems plenty strong, but I did put skewers in the leading edges of the ruddervator stabs.

I tried a two blade 5 x 4.5 two blade prop on this one and it's nice and fast but broke easily on the first soft landing, unlike the thin three bladed bull nose green ones which seem indestructable...well... Except for Dave.

So! All three have been flown and tested. I count three in hand and flown, three in progress and about three in the "I should really do that too" stage. SO I think we have a good chance of putting together a field of six-10 racers for a first shot at a trial race within the next couple of weeks
Last edited by Joe Kollmann; Jul 19, 2017 at 11:02 AM.
Jul 19, 2017, 11:22 AM
So many planes, So little time
Xflyfun's Avatar

Sounds Good

I've got three spinners printing up now, white PLA
Jul 19, 2017, 12:27 PM
Registered User
mondofresh's Avatar

My first FT build - question about firewalls

Any advice on firewalls? I don't want to buy speedbuild kits, I'd prefer to just use DTFB.

Is it best to cut firewalls from ply using a bandsaw? I've been thinking of buying a 9" bandsaw for my garage. This might nudge me towards finally getting one.

Joe - did I hear you correctly talking about 3D printed firewalls?

Rick P - did I hear correctly that you have a CNC router that you're using to cut firewalls?

Thanks in advance for the advice!

Jul 19, 2017, 09:11 PM
Registered User
Thread OP
I've just been sawing the firewalls out with a razor saw...then dremeling the little cutouts and holes. But I have a file for a 3D printed version of the firewall and motor mount as a single plastic piece. Should have some of these printed by Sat or Sunday if you want to wait.

Also, I have a bandsaw here if you'd like to saw away. I also Have a nice little jigsaw for your shop if you are interested.


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