IMPBA Gas Tunnel class

I have been asked to poke around and see what interest there is in a gas tunnel boat class nationally/internationally.

Is there enough to make it an official IMPBA class?

Is it already an IMPBA class, I don't really know.

It's a tunnel, so (I assume) it must follow the tunnel rules, and it's gas, so it must follow the same gas rules I suppose...

Can someone shed some light onto this boat/motor combo and where it fits in the organization for me?

Regards,

Garrett

Oh, if it's not a class, I have been asked to look for 'volunteers' to write a proposal for one...

Kevin S, and Brian N, feel free to chime in here as I know you've both spoken with the same person as I have..

and fill in the gaps that I might have missed.

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

I take it from your "rules" that you intend for the engines to be available as a complete package (ie powerhead,lower unit and exhaust) in order to be legal. Does this mean no "home-built" outboards allowed?

I am in a NAMBA stronghold but would like to see a gas tunnel class as I am also an IMPBA member. The rules above are pretty straight forward but it's kind of the cart before the horse or catch 22. Most of us could build a hull much easier than fabricate the outboard lower unit. I see a few around but nothing standard or produced in numbers yet. Engines are out there but no legs. If the lower becomes availible without having to know someone or the secret handshake or the list, I'm in. The fun part would be the evolution of all the new hull ideas. Take a look at the growth of gas boats and if the tunnel faithful don't respond we will become nitro dinosoars.

krpnova said:

I take it from your "rules" that you intend for the engines to be available as a complete package (ie powerhead,lower unit and exhaust) in order to be legal. Does this mean no "home-built" outboards allowed?

Click to expand...

My bad I glossed over this in the rules. Just my opinion but we need to be open any lowers that come into production. Regulating engine specs can be done. If history tells us anything K&B put nitro tunnels on the map and there haven't been too many complete outboards to follow. Now there are several engine choices and some lower unit options, but it took time. Gas needs numbers first to survive before over regulation

Bob, I dont see where that conclucion is drawn from, but it does not say specifically either way.

I say any lower unit should be allowed. Geared, flex shaft whatever...

I agree, we need to get these things going first, before we put a ton of rules limiting things. I can count on one and half hands how many people actually have a gas powered tunnel, just dont want to shoot our selves in the foot.

I can tell you guys have put some thought into this, and I like the general direction youre heading, especially the scale appearance part.

I dont understand what you mean in part 3 of the engine specs. Clutch is not mandatory, but you must be able to come to a complete stop with the tranmitter functions??? Do you mean you must be able to shut off the engine by going full reverse on the throttle? If so I agree, but its worded kinda funny. Almost sounds like we should be able to pop it in neutral with the transmitter.

I also think the minimum hull length should be 38 inches, not 36. This rule would force the hulls to be more scale sized than if you put gas motor on, say an HTB 360.

For instance, at our National Tunnel Race coming up, in our GAS class we have 30cc as the only limit on the engine/class and that it must be an outboard motor, on a tunnel. In the OPEN 1/4 scale class, we have a minimum of 38 inches. We went with open to try and draw enough interest to run the class, regardless of power, nitro, gas or electric ( there are apparently a few 1/4 scale electric tunnels around?)

~James

Actually we did not intend for them to come together as there is no one making them as a single unity.... In the proposal, we mentioned that the engine had to be made in quantity, but made no mention of the lower units..... simply because there are no lower units made in quantity.....

The area that mentions the clutch unit comes directly from the IMPBA rule book for the LS gas class.... I read that to mean that if you are not clutched, you must be able to kill the motor from the transmitter..... IE Ignition kill switch.... I did not make any wording changes simply because it is exactly how it was already written in the rule book.

Of course we agree that the class really needs to grow prior to choking it off with a package of rules, however there also needs to be guidelines to help keep all of the potential 1/4 scale tunnel racers, builders, etc going in somewhat the same direction..... otherwise we may end up with a group of people that went in different directions and not enough to run a single class because of the differences....

We are not trying to make the rules, just simply trying to get the conversation and ideas flowing so that when it comes time to make the class rules, we have all had our say and input into its creation.

Thanks everyone

HI there

Nice set of rules, but how about this:

- outboard engines only, or inboard engines too, since they will give also different steering options.

-steering, only through the outboard lower unit?

- Allowing or not of recovery pads? inside the sponsons the trimming line is allowed?

-any weight suggestions??

The gearing: is gearing change allowed during water time, or only on shore?

Well lets give it all a good thought.

Ronald.

If I may add to this ,I know of 3 proto combinations available,we should let it grow in to a full regulated class,Scale type appearence is less important than speed,Are we going to heat race them,and set saw and oval records or ride around like restricter plate racing Had some hands on this weekend at the Orlando Winter Nats,The Ossi boat is a nice peice,well designed, 53.5" long.Aeromarine is 50",Brand X was well built but was probably out of the Scale apearing deal due to large cowling. Heard alot about the Woodstuff Boat would like to see more on all of them,since ther already being produced let try to accomadate all the hulls and lower units,exhaust systems,shoot if your going to scale guess we could have adjustable expansion chambers, and water injection alsoI know theres going to be alot of rules and regs to follow ,(Standard heat racing safety rules of course)but if we keep it as simple as possible in the beginng we will be able to modify as the class grows.

Just my opinion, Food for Thought

Steve H.

Guys,

Much interesting debate and I would agree let things develop before getting hung up on too many rules. However, there is one thing I will stress - what is the intent behind building large scale tunnels? If it is to represent attractive, realistic looking race craft I think you need some kind of scale appearance clause. Otherwise you will go down the function over form path that has afflicted almost every other class (1/8th scale being the exception) where they are barely recognisible as boats. Having previously raced 1/5th scale cars I would support a 'stand off scale' approach where it is clearly a representation of a racing boat without having to be true dimensionally to scale.

Anyway its good to see more tunnel interest and I think gas is the eventual way of the future for a lot of people. (sorry electric guys - eventually your way maybe )

GT

Many folks looked at the scale tunnel I had at the winter nats. The boat we are working with is 56" and needs to be close to this size to make the engine look scale and have the bouyancy needed to support the weight of the gas engine. I am with the scale guys on this class if it becomes one. My feelings are that we should require an engine cover with scale appearance and the exhaust must be contained by the cover. This can be done with cans easily and pipes with a little more work. Heat will be a problem and will have to be addressed in the design of the cover and the exhaust. I would like to thank all those who dropped by and looked at the boat and engine and gave input on what we have done so far and what they would like to see as we proceed with development.

Jimmy