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Leo Ho

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About Leo Ho

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    http://www.btorcboat.com/

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    Male
  • Location
    Hong Kong
  1. Leo Ho

    JetChopper30 mono deep v hull FRP

    JetChopper30, GO .21 3P: http://v.youku.com/v_show/id_XNDkyNzQ0ODI4.html?from=s1.8-1-1.2
  2. Leo Ho

    JetChopper30 mono deep v hull FRP

    jacodewit https://www.youtube.com/watch?v=-l085bbxH3M Joel Mertz https://www.youtube.com/watch?v=z8WzN4D8eUs https://www.youtube.com/watch?v=z8WzN4D8eUs
  3. Leo Ho

    JetChopper30 mono deep v hull FRP

    JetChopper30 setup instructions(view from deck, view from transom, view from port): Drive shaft offset to right by 5mm. Drive shaft tilt left, form 1.54 degree with the centre line.(adjustment required) Drive shaft angle slightly negative. Set hull angle of attack to a small positive angle, for stability. Drive shaft length(Transom to prop. hub) 81mm. Rudder blade offset to right by 57mm. Rudder blade length 54mm exceed right bottom plane. Right turn rudder blade turn angle 11 degree, 8m turn radius. Left turn rudder blade turn angle 20 degree. Transom to rudder blade distance 65mm. Turn fin tip 19mm above the keel. Weight bias on left side to produce 0.54Nm moment to balance the torque roll(adjustment required). Upon triming done, uninstall the trim tab. CG 29% from transom. The hook near the transom shall be grinded off to make a nearly perfect straight line. If the above instructions were followed. JetChopper30 shall have following features, desired for oval racing: Stable full throttle right turn. Effective left turn. Perfectly neutral rudder for straight course. Unnoticeable prop. walk. Torque roll perfectly balanced. Chine walk rarely happen. Jumping rarely happen, if happened, are balanced. No porpoising.
  4. Leo Ho

    JetChopper30 mono deep v hull FRP

    Hello Jose, JetChopper30 nitro NOVAROSSI PLUS 21-5KT: https://www.youtube.com/watch?v=oqjLXX7h2WA JC30 is IMPBA, NAMBA, NAVIGA legal MONO and OFFSHORE class. But illegal in deep V class, because of the RIDE PAD, freeboard height less than an inch. Ride pad can be grinded to smooth arc cross section. Then it is deep V legal. Rgds, Leo
  5. Leo Ho

    Long stroke / Short Stroke

    Agree with Andy. The cylinder of current product NR KEEP-OFF.21-4: Displacement: 3,49 cc R.P.M. (max power): 36.000 RPM Practical range: 6.000-38.000 R.P.M. Bore x stroke: 16,26x16,80 mm Sleeve: 4 ports Regarding to the vertical distance. The exhaust port of buggy/low exhaust angle engine are very close. So MES is almost no advantage and impossible to make, in many case. While I believe that. The ex. port of on road engine is high. Gas no need to travel a long distance to refresh. So I believe, extra long stroke design give more advantage to on road engine, wide ex. port but little contamination, but less advantage to off road engine. While ex. long stroke in buggy engine is a matter of can use common engine parts, on/off road engine use same or very similar crankshaft.
  6. Leo Ho

    Long stroke / Short Stroke

    NR P5XLT CYLINDER, SINGLE EX. PORT, PART # 08536: MES-MULTI EXHAUST SYSTEM CYLINDER: T-PLUS 21-9 3.5cc ON ROAD ENGINE CYLINDER PART # 08564/13 T-PLUS 7C 3.5cc OFF ROAD ENGINE CYLINDER PART # 08573 Numbers in the picture are distance in number of pixel. Picture source: http://www.novarossi.it/ pictures edited by me.
  7. Leo Ho

    Long stroke / Short Stroke

    I don't remember exactly. As what I know. From 199X to 2010, O.S. .21 engine use 16.6mm/16mm bore stroke ratio. While NR REX was square engine. Then MES was invented. NR use 16.26mm/16.8mm bore stroke ratio. The O.S. way make MES is almost no advantage in buggy engine. The O.S. VZ(16.6mm/16mm bore stroke) did not use MES, but a rib in the centre of the exhaust port. Until recent years, 201X. O.S. launch the XZ, 16.27mm/16.8mm bore stroke ratio, the first smaller than 1 design. XZ has MES. Longer stroke make MES in buggy engine possible/efficient. The NR bore stroke ratio continue to decrease. The latest NR .21 engine use 15.88mm/17.6mm bore stroke ratio. We can see the bore stroke ratio is decreasing. I believe the designer want to maximise exhaust and scavenging efficiency. They are Contradictions, cannot gain both. http://www.rcuniverse.com/magazine/article_display.cfm?article_id=770 Model Name: O.S. 21VZ-B V-Spec Displacement: 0.211ci (3.46cc) Bore: 0.654" (16.6mm) Stroke: 0.630" (16.0mm) Practical RPM: 3000-40,000rpm Output: 2.48hp @ 33,000rpm Weight: 12.7 oz. (360g) Carburetor: 21C Slide-Valve Glow Plug: O.S. P3 Turbo http://www.osengines.com/engines-boat/osmg1621/index.html O.S. 21XZ-M Inboard Marine Engine Stock Number: OSMG1621 Displacement: 0.21 cu in (3.5 cc) Bore: 0.640 in (16.27 mm) Stroke: 0.661 in (16.8 mm) Practical rpm: 4,000-45,000 Output: 2.71 hp @ 33,000 rpm http://www.osengines.com/engines-car/osmg2043/index.html O.S. Speed R2101 Engine Stock Number: OSMG2043 Displacement: 0.213 cu in (3.49 cc) Bore: 0.633 in (16.08 mm) Stroke: 0.677 in (17.2 mm) Practical RPM range: 4,000-45,000 Output: 2.7 hp @ 33,000 rpm http://www.novarossi.it/2012/index.php/en/products/off-road-engine-nova/3-5-cc/keep-off-21-4.html NR KEEP-OFF.21-4 Displacement: 3,49 cc R.P.M. (max power): 36.000 RPM Practical range: 6.000-38.000 R.P.M. Bore x stroke: 16,26x16,80 mm Sleeve: 4 ports Rear ball bearings: ceramic Front ball bearings: steel Crankshaft: 14 mm - turbo - tuned Carburetor: plastic - 9 mm - reverse Glowplug: Turbo (C6TGC) Exhaust position: rear Starting: - Weight: 360 g Fuel type: 25% nitro http://www.novarossi.it/2012/index.php/en/products/off-road-engine-nova/3-5-cc/keep-off-21-7xl.html NR KEEP-OFF.21-7XL Displacement: 3,49 cc R.P.M. (max power): 36.800 RPM Practical range: 6.000-40.000 R.P.M. Bore x stroke: 15,88x17,60 mm Sleeve: 7 ports Rear ball bearings: ceramic Front ball bearings: steel Crankshaft: 14,5 mm - turbo Carburetor: plastic - 9 mm - slide Glowplug: Turbo (C6TGC) Exhaust position: rear Starting: - Weight: 370 g Fuel type: 25% nitro Best regards, Leo
  8. Leo Ho

    Long stroke / Short Stroke

    I believe this is a tricky question. My opinion. Short stroke engine has larger piston top area, can get more down force from expanding flame, but shorter moment arm. While long stroke, things reversed. I believe this not related to torque but the efficiency of scavenging process. In about late 198X's. .21 engines branched to on road and off road lines. They differ mainly by height of exhaust port. On road engine has higher exhaust port, this make MES possible, while there is little charge and burnt gas mix. But MES in off road engine is almost no advantage, NR P5XLT use single exhaust. Because low exhaust angle make exhaust port very close to the transfer port, that gas max is more likely, means lost of fresh charge. To reduce gas mix in off road engine and make MES possible. Extra long stroke engines are made, NR bore 15.88mm, stroke 17.6mm. Cylinder diameter is smaller, height is greater, so the distance between exhaust port and transfer port is greater. Even with MES, gas mix in off road engine is less. It seems longer stroke has more advantage, interms of gas mix. No. A small bore big height cylinder make scavenging process less efficient. Gas need to travel a higher distance to refresh. Less gas mix and efficient refresh, cannot gain both. New NR KEEP-OFF.21-7XL and O.S. R2101 are extra long stroke. I believe they are approaching the limit. Best regards, Leo
  9. Leo Ho

    NovaRossi Keep.21M information

    Hello, KEEP.21M sleeve part # 08069. Same as KEEP-ON.21 on road car engine sleeve part #. So it is on road exhaust timing, 92 degree or higher, total 185 or higher. Low torque high rpm feature. But I believe KEEP.21M DD, sleeve part # 08075, is low to medium exhaust angle, total 175 or lower. A moderate to high torque engine. Can turn larger prop., larger blade area, less chance to cavitate. This feature is important for heavy but low speed boat, mono. Best regards, Leo
  10. http://www.modelgasboats.com/resources/tips-and-tricks/tuning/ Refer to Glenn Cupit's article on rudder set up, RUDDER "CASTER", A LITTLE CAR TALK, BACK TO BOATS. Articles talk about rudder length and rudder lift. With many testing, I got the following conclusion on JetChopper30 set up: Offset the rudder 55mm to the right. Pretty stable turn at full throttle. Rudder too close to the centre line has too much prop., keel lift, lower turn stability. In perfect situation, rudder lift just balance the prop., keel lift. Happy rc boating, Leo
  11. Leo Ho

    JetChopper30 mono deep v hull FRP

    http://www.modelgasboats.com/resources/tips-and-tricks/tuning/ Refer to Glenn Cupit's article on rudder set up, RUDDER "CASTER", A LITTLE CAR TALK, BACK TO BOATS. Articles talk about rudder length and rudder lift. With many testing, I got the following conclusion on JetChopper30 set up: Offset the rudder 55mm to the right. Pretty stable turn at full throttle. Rudder too close to the centre line has too much prop., keel lift, lower turn stability. In perfect situation, rudder lift just balance the prop., keel lift. Happy rc boating, Leo
  12. Leo Ho

    Wild thing mono kit build

    Hello Guys, I am interested in Wild Thing .12 & .21. Could not found any drawing so far. Hope one can give me a .dxf download link. Best regards, Leo
  13. We tested with different RUDDER SETUP. Found that this setup has pretty good stability to turn at full thottle:
  14. Leo Ho

    JetChopper30 mono deep v hull FRP

    We tested with different RUDDER SETUP. Found that this setup has pretty good stability to turn at full thottle:
  15. Hello All, JetChopper30 hull is now NAMBA FE P-LIMITED MONO STRAIGHTWAY RECORD HOLDING. NAMBA web site record: http://www.namba.com/content/records.asp?EventType=11 Happy rc boating, Leo
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