Lets do some comparisons

[Grimracer]

Hey gang.

So that those of us who surf this site can better understand the differences between NAMBAs OPC class and IMPBAs Sport tunnel class lets talk about a few key points and differences between the two. Let keep this to 3.5cc motors for now..

Seems to me that for those that do not race this class and might like to try it could be confused but the two.

Also: If you had your chance, what changes would you like to see happen (if any) to either of these classes.

ROCK ON

Grim

 

[mark poole]

Hey Grim. I recently rejoined the IMPBA and I don't have a NAMBA rule book. Could you post a couple lines on the NAMBA rules for us?

I like the idea of this type of class. Some people feel better about starting in a class where they know that they are not overwhelmed by an unlimited amount of extreme engine mods. Also, if the sanctioning bodies keep these type of classes then it could encourage more manufacturer participation....such as what Jim Irwin is doing. We need somemore tunnel boaters here in the Southeast and I think these classes would keep some new people coming in. Also, the 3.5 class won't empty your wallet!

 

[user 115]

Hi guys,

My take on the two classes.. Please correct me if I am wrong as I haven't read a NAMBA rulebook but have read IMPBA's rules for Sport 21.

NAMBA - Pull 3.5 engine from the box.. Must be all same mfg, ie k&B O.S...., don't touch a thing and go run it..I think you can loctite screws but not sure about that.. Nothing can be done to the motor.

IMBPA - Pull 3.5 engine from box.. Again, all same company for engine, lower unit, etc.... Send engine to favorite engine builder or experiment on your own but make sure engine's carb and exhuast must not be larger than .320.. No tuned pipes either.

Obviously people have and will manipulate the rules in NAMBA.. But their interpretation is more pure than IMBPA's. IMPBPA's is basically 3.5 mod tunnel without tune pipes and aftermarket carbs.

I dont' think changes are needed, but as mike said people just need to be informed. The fastest boat does not always win in 3.5 tunnel.. This is especially true in 3.5 tunnel. In fact, a slower more stable boat will do great at any race.

Charley

 

[Jerry Dunlap]

In NAMBA, the lower unit can be reworked from the cavitation plate down. The would include such changes as sharpening and reshaping the skeg.

An interesting situation in NAMBA is the ability to transfer parts off one series of engines to a later series. Two examples of this are replacing the large bore carb that came on the K&B 7.5 Pro with a smaller bore carb that came on the K&B 7.5 w/c motor and replacing the flywheel with a smaller diameter flywheel that came on the K&B 7.5 many, many years ago. I don't have a problem with replacing the carb since it is possible to purchase the smaller carb. I do have some issues with replacing the flywheel since it is not available.

It has been my experience that "out of the box," some engines are better than others. I probably have three or four K&B 3.5 engines I can run in NAMBA A(3.5) Stock Class. Before the start of a racing season, I'll try to run each one to see if one seems "stronger" than the rest.

In my opinion, in stock class the set up, prop, and how the hull is working is just as important as how well the engine is running.

JD

 

[Geraghty]

A great set-up and a patient driver will let a less than perfect motor shine.

A junk set-up with the best driver in the world will make the "perfect" motor perform like a sprint car tied to a UPS truck.

Now put a "hand fitted" 3.5 limited performance outboard together with a great, set-up,and that is when you learn how to drive a model boat with finesse and patience.

 

[Grimracer]

Can you drive the spike any further then that Rod? You are 100% right on..

Setup is everything with a low power motor.. Not that you can not or should not have it anyway its just necessary with a non piped motor.

What I like about the IMPBAs sport class rule is no tear down time after racing is over. I use to race Slot Cars and tear down was a real pain in the butt. You could watch them tear the thing down in front of you so as not to damage anything but have them drop just one set-up..(motor can and magnets..$100 bucks) and hours of honing the mags…and well…you can see the problems.. The time it took to do it was a pain too..

The go-no-go system that the IMPBA uses is the best I know of for inspections.. Only so much air and fuel in and only so much exhaust out.. Shove in all the air you can under these rules and that is all you get.

Because the Sport class was not intended for the new racer, guys like us that like to tune our boats can make good with the little power we can make..

Lots of fun to me..

Grim

 

[Kevin_R_Clark]

I have to ask this. What was the original intent of these classes when they were first set-up? As the Secretary of are club here in Spokane I can tell you we put considerable effort on the club level to encourage new members to start out in this class. Why, because boats are readily available and cheap. They are fairly user freindly and slow enough most people can handle them. Honestly though no matter how much we try to convince them to start in this class they always show up with something that they get frustrated with and after a few times we don`t see them anymore. I would like to see this class split up into 2 separate deals. One for those of us with experience say 2 years plus and the other as a mandatory entrance class for beginners. The beginners running box stock right down to the props, a certain % of fuel. I just think the word STOCK infers beginners. I know in car racing you don`t see the shoes racing in the stock class. Anyhow that`s my view of it.

 

[Scott Schneider]

:unsure: You guys pretty much have to rules down between the two santioning bodys.

For years when the original owners of K&B were in Downey Ca and then Lake Havisu, AZ there was a "small in crowd" of suported racers that got access to the prepacked parts bins and would fit together a best of the best engine from parts and gather their back up inventories. We had to race these guys under NAMBA rules and while you could not modify any parts the ones who had access to those "best of" parts had an unfair advantage that was a crap shoot for everyone else who purchased an assembled engine built from "as is" parts. Those hand picked engines had performance that showed up as being superior at all events. So even with solid spelled out rules you will find and get the rule benders looking for every possable advantage. Thats Racing I know but it still sucked !

Scott

 

[Jack Garcia]

Scott, don't know where you got your information about guys going to K&B and cherry picking for good parts. :huh: But I can tell you that the parts bins were not accessable to everyone. Speaking for my self, ( and there are many people who will vouch for my honesty), I got all my parts out of the junk box at Bobby Tom's customer service. Worn but round pistons and sleeves well fitted make the best engines.

My two bits

 

[Grimracer]

Kevin

IMPBA addition of the class had nothing to do with brining new boaters to the hobby.

IMPBA used this class as a bragging rights class and thats what it remains to be today..

As it is Tunnel Hulls and box motors do make the most since as far as brining new modelers to the hobby. I like to think this anyway..

It sounds like NAMBA may have had different intentions then IMPBA.. this is good info if im right..

Grim

 

[osracer]

My two cents is once you get a good needle and a good set up you are set to start practicing. If a driver practices getting on the clock and knowing where he and his competetors are and practices running on the bouy's instead of fifty feet off of them, or ten feet off them for that matter, the time honing these skills will pay off much greater rewards than trying to get another few miles per hour from his engine. A driver that doesn't get good starts and doesn't run on the bouy's can have an extra five miles an hour of speed and still won't win the race.

This is one reason the stock class is so popular as an entry level guy with good driving skills can be just as copetetive as anybody. Then you throw in some older guys with some good skills and Annie bar the door your going to have some good racing.

 

[Mark Anderson]

Jerry

What are you talking about those flywheels are available. I have several brand new ones in the shop. Now the pricing you may not like, but they are available.

I don't believe the them and us stories of the old days. I raced through those days and for part of them did get some help from K&B. The fast guys were the fast guys no matter what they were racing.

Boat and propellor set up are where the speed is in limited power classes. The IMPBA rules allow for more power than the NAMBA rules but both are power limited. Getting good starts and driving lane one will make up for alot in the horse power dept.

Mark

 

[[email protected]]

Charly is right in NAMBA, pull motor out of box and that's it, go run it. JD said you could mod the skeg and sharpen it. Hummm, I didn't know you could do that, cool!

Bottom line comes down to we need more producers of a complete motor that is affordable. Let's admit it, K&B put out a good motor for the price compared to today's prices. It cetainly ain't a $300 power head that needs all kind of reworking and special lower ends to play in the Mod class. But, I have my old engines and now my boys are using them that I'm gratful for.

 

[Tunnelbill]

Grim,

I have been racing IMPBA for several years. The Sport Class sould be a Stock Class. As O/B Director, you are the man to get this done or should I say started because I will be retired before you can get anything changed in IMPBA. I think it would better the sport. Thanks TB

 

[not2bright]

the other question is when are we going to get the two organizations to combined into one so we have one set of rules? just a thought

 

[user 115]

The organizations will NEVER merge..Ever..

Charley

 

[not2bright]

why not

 

[user 115]

Start a new topic and ask the boating organizations to merge and see what you get.. It has been discussed many many times.. A petition was formed to discuss a merge at one time. Nothing has ever happened.

Charley

 

[not2bright]

it has its ups and downs

 

[GTR]

Hi Guy's

It's a shame you couldn't merge the organisations as it would have distinct advantages - not the least is increased lobbying power with manufacturers and Governments. Nothing get's the attention of the powers that be like a 'National Organisation'. As it is at the moment you have divided strength this is often what kills of institutions - in the end all the individual ones struggle to attract new blodd or get effective representation. I feel sorry for you guy's in the US because it can't be helping the hobby (sport?) overall.

It's strange that the US seems to be the only country having this problem.

Just $0.02 from someone on the outside looking in.

GT :blink: