Presenting the new KEP's T3-21 Freebie!
NOTE! I'm currently in the process of updating the T3-21 so there will be an updated version later this fall or early winter 2017. (it's mainly the turn fin and the turn fin mount that is improved)
Main KEP's T3-21 News (compared to the earlier KEP's T2-21):
- Flat sided sponsons. It really does not matter if the sponson top-view is elliptical, as the earlier T2, or flat sides as the new T3 - there are no performance benefits with elliptical so I changed it to flat sided instead. The new flat sided sponsons are much easier to build also!
- Longer sponson ride-pads. Improves rough race water handling.
- Improved side profile of the sponsons. Creates less lift and less water drag (from the spray behind the ride pads).
- Improved turn fin bracket. More rigid (thicker 3 mm material used) and positioned at a more optimal place - further up and away from the water also.
- Lower AoA of the sponson ride pads. Improved handling in heat-racing conditions.
- Longer after-plane. It makes it a tiny bit better in rough sea (other improved items makes more of a difference though).
- New turn-fin design - deeper, more hook and a different swoop design. Improved cornering and even easier to drive.
- The tub is leaning forward (lower in the front then in the back). Improved ride that overall creates a better stance of the complete boat on the water.
- Slightly different nose shape of the tub.
- Wider spacing on the sponson tubes (front & rear). Improved rigidity. As the tub now leans forward the tube centers are also adjusted so they are parallel to the water.
- Channel 2 & 3 servos sit on either side of the flex and the receiver on the tub floor. Much easier to fit the mini servos.
- Wider ski with improved AoA. Better in rough water and it's easier to maintain the overall boat AoA everywhere on the course.
- Optional ski design with rakes on the running surface. Improved side stability in the corners and on the straights.
- After plane length: 550 mm (21.65")
- Overall length from transom to the tip of the sponsons: 765 mm (30.12")
- Outside-Outside sponson spacing: 500 mm (19.69")
- Tub length: 682 mm (26.85")
- Tub inside width: 62 mm (2.44")
- Tub outside width (with 4 mm thick sides): 70 mm (2.76")
- Tub height: 47 mm (1.85")
- Sponson width: 23 mm (.91")
- Sponson ride pads (removable): 2 x 30 x 165 mm (.079" x 1.18" x 6.5")
- Ride pads AoA: 3.4°
- Ski width: 35-40 mm (1.38-1.57")
- Ski AoA: 1.4°
- RTR Weight (without fuel): around 1650 g (58.2 oz)
- Futaba 4PLS radio
- 2x Futaba S3172SV mini servos for channel 2 & 3
- Futaba BLS571SV low profile steering servo
- Vapex 1000 mAh 2S LiFe receiver battery
- V.S. Third channel fuel metering base with O.S. needle
- V.S. Speed 2101M motor
- Note: the T3-21 works equally well with an in-line engine. It will run a tad bit lighter in the front though but that is NO problem.
- Hipex 180° Exhaust Manifolder
- Hipex MP1-21 Hydro Muffled Parabolic Pipe
- Walter Barney @ Tanks 2U made SS tank T2/T3 (same size)
- 8 x 10 mm pultruded carbon sponson tubes (475 mm long)
- 10 x 12 mm aluminum tubes for the tub and sponsons
- 2 mm carbon rod for securing the sponson tubes (much better then any other securing system we've tried by far).
- Propeller: The T3-21 is not that critical regarding props I think and it depends on how you race and drive. For me personally I like an "easy" prop with not that much cup but with a a bit more COB pitch so you get good acceleration. I also like to be able to throttle at all times so that means I don't like props that are heavy on the engine and I don't use that short pipe lengths either. All props I've used are done by Mark Sholund and the ones Ive used the most are ABC 50x69 with 45.25 mm dia, 2.81 COB pitch and 3.33 cup. The ABC H6 with 45.9 dia, 2.9 COB pitch and 3.33 cup works fine also and they let you rev the engine quite easily.
Extra T3-21 info:
- The current KEP's T3 design is based on "3-point flat-plane technology" that means they run very light on the water. This type of outrigger design rely on a good balance between aerodynamics, hydrodynamics, center of weight, how much weight you have on each of the 3-points, rudder and the turn-fin. If you build the T3-21 according to the plans and don't make any of your own design or geometric changes - then there is plenty of adjustment in the changeable/removable ride-pads, the changeable/removable ski and the strut height/angle.
- As the T3's run so light you will most likely be disappointed if you expect the boat to be able to run "WOT" (wide open throttle) everywhere and in all water conditions. It's simply not possible unless you build it really heavy.
- A. Ease off if you need to make a left turn.
- B. Accelerate through the turns and ease off halfway down the straightaway or at least before going into the turns. After a short "off" it will settle down and then you can turn as hard/fast as you are able to (depending on race conditions, weather, wakes etc).
- Please make the turn fin according to the plan and bend it to the specs. DON'T use any other turn fin shape and/or hook. (Make sure its sharpened properly also.)
- Don't place the turn fin too far forward. The boat will "dart" (wanting to continue to turn coming out of the corners) and it will be difficult to keep straight.
- If your T3 is pulling to the right at speed on the straights: Double check that you have mounted the sponsons straight vs the tub and the turn fin bracket has a 1.5 mm toe-in. If not - correct that. If it still pulls to the right, check that the turn-fin is sharpened correctly and not dull on the leading edge. A turn fin that is not sharp will make the T3 to pull to the right even at slower speeds.
- The current T3 design is not really suitable with any boat size bigger then a .45 (7.5) if you plan to race them together with other boats. The bigger riggers (.90's and Gas etc) are a completely other set of beasts so to speak and they need to be designed accordingly to their needs. So, if you do your own scaled-up T3 for a .90 or Gas size - you will be disappointed I think.
- If you want some building tips etc - look to the right in the menus for the earlier T2-21 Build Series I did. The T2 and T3 is not exactly the same but you will get a feel for how to build one. If scratch building is not your thing though - go to Zipp Kits and buy a JAE 21G2 Kit instead and start learn to build on that. :)
HERE for download (works best on a stationary normal PC/Mac).
HERE for download (works best on a stationary normal PC/Mac).
If you want to cut-out the tub sides, ski sides and sponson side views on a CNC etc - Click HERE for download of a zip file that includes dxf & dwg drawings of these three T3-21 template side profiles. Note, you need to specify the hole dias yourself (in a CAD program).
If you have the earlier KEP's T2-21 - Click HERE for a download of an updated "T3-21" fin that is adapted for the T2.