Here are some ideas that Mike Crawford and I put together, the ideas basically come directly out of some of the other gas and nitro class rules. We have compiled the ones that we believe fit the intent and spirit of the Large Scale Gas Tunnel Class.
Large Scale Gasoline Outboard Tunnel Class
Purpose
The intent of the “LS” Gasoline Outboard Tunnel Racing class is to provide a gasoline racing class for the outboard tunnel class with the emphasis on scale appearance rather than ultimate speed. The engine restrictions are intended to equalize performance
Hull Specifications
1. The large scale gasoline outboard tunnel class shall use tunnel boats only and maintain the basic hull lines of quarter scale tunnels 36” to 50”.
2. The large scale gasoline outboard tunnel class shall not lock down the engine or use any auxiliary steering system.
Engine Specifications
1. The intent of this class is to utilize commercially manufactured gasoline powered 2 and 4 cycle engines
2. Engines must be standard factory production with a minimum of 100 units available for sale to the general public. To be eligible for the International Regatta the engines must have been offered for sale to the general public not less than ninety (90) days prior to that year’s International Regatta
3. These engines may be started with a recoil, pull or electric starter. Clutches are not mandatory, but those engines not equipped with a clutch must be stopped completely with transmitter controls.
4. The engine must use a spark plug type ignition. No glow plug or compression induced combustion allowed. All engines must have a positive off-on switch, or in lieu of this switch, the primary ignition lead must be removed from the spark plug except when in the pits, out of the spectator area, or in preparation for racing.
5. Any size or brand name of carburetor may be used. All engines must be normally aspirated and have a piston ported or reed valve fuel induction system.
6. All engines must have a canister muffler, custom exhaust system or tuned pipes.
7. The engine external parts shall remain as originally manufactured within series except as shown in Part 3. Clarification: No water-cooled engine parts shall be used with air-cooled engine parts. Common engine parts that are used on both engines models may be interchanged. Slide valve exhaust adapters may not be used with carburetor equipped engines.
8. The following exceptions will be allowed in the Large Scale Gasoline Outboard Tunnel specifications.
• Adhesives (loctite), set screws and jam nuts
• Any carb linkage arms
• Any motor mount
• Any spark plug
• Any type of steering arm
• Any flywheel nut
• The lower unit below the cavitation plate may be trimmed, sharpened or polished. No material shall be added to the lower unit.
• Adjustable mixture controls will be allowed, however the original needle valve must remain in its original position.
Engine Classes
Classes Cubic Inch Displacement Cubic Centimeter Displacement
LS27 up to 1.647cid maximum 27.0cc maximum
LS36 1.648 thru 2.196cid maximum 36.0cc maximum
Formulas CC x .61 = CID CID divided by .061 = CC
Fuel
1. Pump gasoline and your choice of oil mix shall be used. No nitro additives allowed in all gas engine classes
Racing Rules
1. Racing rules will conform to the IMPBA, Contest and Racing Rules, Classes and Courses (1/4 & 1/3 mile).
2. At the IMPBA International Regatta all classes will run for 6 laps.
3. IMPBA clubs hosting outboard races may change the number of laps for the above classes upon notification to the contestants 14 days prior to the date of the published event.
Optional Noise Ordinance
This option sets the standards by which noise levels will be measured and recorded. In the event that clubs or districts decide to exercise this option, it shall be posted on their flyer, time trial notice, or other Sanctioned Event.
1. Decibel limits will be determined by a Sound Measuring Device (Radio Shack or similar device).
2. Measuring will be performed with the boat running at idle, at the shoreline, facing sideways. The measuring device at a distance of fifty feet (50 feet) and at a vertical height of not more than four (4 ft) feet above the ground. The check will be confirmed when the driver runs the boat at full throttle.
3. The maximum decibel reading shall be 92 decibels or less on the “C” scale.
Special Note:
Sites requiring such noise limiting requirements at sanctioned events (local or national), shall post the following statement clearly on each race flyer, or media use for publications and/or distribution. Noise restrictions are in affect at this event.
Safety Precautions
1. Sand containers shall be present and used as a depository of racers contaminated fuel. This shall be the responsibility of the host club who will also provide disposal of such fuel
2. An area shall be roped off from spectators and other racers to use as an engine test area
3. Fire extinguishers must be located in the pit area and engine test areas as well.
Bill Van Kirk
His and Hers Hobbies
Mike Crawford
Wood Stuff Outboards
very nice boat!!
