Classic Thunderboat Rule Change - IMPBA

As many of you know by now, the IMPBA has voted in some new rules for the Classic Thunderboat class to follow. Unfortunately for me, my cowl will need to be rebuilt as my opening behind the sponson transom exceeds the 4-3/4" rule.

Currently, my entire engine and exhaust flange are hidden and tuned pipe is within the hull. Tuned pipe is visible from top view for a few inches past the new dimension. I disagree with new rule passing for my boat, but I will rebuild the cowl eventually and move on. Very frustrating, as the custom cowl is a one of a kind built after my Blazer Cowl was destroyed in 2018 crash.

After studying the new rule some more, I do agree with new rule how it affects the class overall. The yes vote that narrowly beat out the no votes, has not only created a little work for me, but has also created work for many (if not all) all of the Insane Thunderboats and other builders from being an accepted cowl. The new rule allows the spark plug hole in cowling to exist for the spark plug, but does not allow the cooling cap to be seen beyond the hole for the spark plug.

The diagram in the December Roostertail rule change proposal shows the outside edge of the cap as being hidden from view. That dashed line means a hidden object line is shown and that the outer edge of cooling cap must not be seen.

As it is for me, it is also unfortunate many other boaters will have to purchase or build a new cowl to comply with the new rules.

Other things I see in the rule affecting a few boats is that the cockpit area can remain open for ventilation if needed. The deck area is what is defined on the opening size and vent cover / louvre. I know there are a few boaters with opening under the drivers cockpit that concerned them.

Also, on the carburetor side of the hull, the diagram appears that this area must be covered as well. Aft of the sponson transom, the opening / louvre rule applies. The drawing could be interpreted as being open in front of the sponson transom if someone wanted to "argue". Looks covered to me.

The 50% rule still exists for the engine and as rule states, that does not include the header. The new rule allows for the tuned pipe to be exposed to 4-3/4" aft of sponson transom, but the cowl over/around the header will be needed to help cover at least 50% of the engine from view. Should make cowl building challenging.

The decking behind the sponson transom on the exhaust side will also need to follow the opening / louvre rule. Not sure how this will be done to comply with the new rule, but many creative people will take on the challenge I'm sure. Pipe can be seen to 4-3/4", but openings behind sponson transom must meet new size requirements.

The good news with the rule change is I am glad to see the cooling cap concealed and ventilation "holes" moderated in size. These new rules will help maintain the Classic Thunderboat look. Just not as good as my 2011 Blazer Lauterbach (w/custom cowl), that really helped this class become what it is today.

Hopefully all you boaters can help keep this class somewhat of a scale looking class built to look like boats from the 1950 to 1970's.

See you at the races.

we can live with the rule, not so sure about the the size limits on vents, but it could not be left open spaces either. Are there some hull that would not meet the 4 3/4 open cowl rule?

The diagram in the December Roostertail rule change proposal shows the outside edge of the cap as being hidden from view. That dashed line means a hidden object line is shown and that the outer edge of cooling cap must not be seen.

Duke,
I think your reading more into this than there is. The new rules wording highlighted in the roostertail does not say anything about the exposure of the engine. That portion of the rules has stayed the same. The diagram was provided specifically for the exhaust rule change. Contact the gas director with concerns like this before you start a rebuild project.

The whole intent of the rule change was to legalize a lot of boats that have been running and accepted for years. The boats that started showing up recently with the big slots cut in the decks made people start scrutinizing the rules and that's when it came apparent that boats like the insane that have been racing for 10 years without any protests would now be illegal. Since these boats have been racing for 10 years with no protests, they basically have been accepted as legal. The rule change to the exhaust exposure now officially makes them legal. My thought on it as a board member is that I did not want boats that nobody seemed to have issues with for years taken off the water.

The venting rules are there to stop the huge wholes that the guys were putting in the decks. Brian Blazer had some issues that he posted on Facebook, but they should be resolved. Venting in the cockpit is still allowed. NACA duct venting will be allowed. These type of things do not take away from the intent of having the boat look like a classic hull from the 50-70's era and maintaining the vintage look as what the rule change is intended for.

Also, if your pipe was exposed from the top, it was illegal before the rule change anyway as the old rules state that none of the exhaust system was to be visible. The new rule just means you have less to cover up now.

Thanks Mike, Always there need a bit of clarification of a new rule, i have seen some pictures of guys cowls that may have slots longer than new rule but probably no one would protest small difference. New rule is to guide new builds to stay with the intent of the rule.

This will for sure be a point of contention for the CD’s. If a protest is made you go look at rule book. According to new rule you have to have solid deck aft of sponson transom. Only exception is the 4 3/4” to allow TUNED PIPE to be exposed. New rule should say exhaust system. Now this makes the header being seen still illegal.

Dan Pralle said:

This will for sure be a point of contention for the CD’s. If a protest is made you go look at rule book. According to new rule you have to have solid deck aft of sponson transom. Only exception is the 4 3/4” to allow TUNED PIPE to be exposed. New rule should say exhaust system. Now this makes the header being seen still illegal.

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No, Dan, it does not...read the 50 percent coverage part of the existing rule. There's some key words in there ...cmon guys, read the entire class rule, lol. The header shiwing has NEVER, been illegal. This stuff gotten comical. It's actually a very concise, easy to ubderstand rule now. In the old rule, it was open to interpretation, all this does is set actual numbers. Relax everybody, lets go play !!!

nickhartdegen said:

No, Dan, it does not...read the 50 percent coverage part of the existing rule. There's some key words in there ...cmon guys, read the entire class rule, lol. The header shiwing has NEVER, been illegal. This stuff gotten comical. It's actually a very concise, easy to ubderstand rule now. In the old rule, it was open to interpretation, all this does is set actual numbers. Relax everybody, lets go play !!!

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Nick,

I would agree with Dan that aft of sponson transom deck must be a solid deck with venting holes that follows the new rules (Except for tuned pipe exposure). Its pretty clear.

Copied from Dec 2018 Roostertail:



Mike,

Just reading the new rules as written and plan on complying with it and helping racers in D4 meet the new rule. I do have a minor fix for my cowl-not a big deal. The new rule does clear up some of the issue with recent boat builds with large open decks.

If the old rules were administered better by all, a new rule would not have been needed. I did not see the "intent" written into the rules to grandfather in all existing boats or any specific hull. Favoritism is definitely shown if rule was written to specifically include one style hull that may exclude others running legally for years.

The actual rule in black and white is now what matters and does not grandfather old boats. If a newbie comes into the hobby, they would pick up the rule book and follow it. Diagrams are part of the rule and are provided to clarify what is required. The majority of the cooling can is concealed as shown in the drawing, by the use of a dashed line. Maybe that was not the intent, but that is the meaning and is what passed as the new rule.

It is disappointing that many Insane Hulls and other boats that have been running will also need a new cowl to meet the new rules.


Duke

Duke Mordja said:

Nick,

I would agree with Dan that aft of sponson transom deck must be a solid deck with venting holes that follows the new rules (Except for tuned pipe exposure). Its pretty clear.

Copied from Dec 2018 Roostertail:

View attachment 277119

Mike,

Just reading the new rules as written and plan on complying with it and helping racers in D4 meet the new rule. I do have a minor fix for my cowl-not a big deal. The new rule does clear up some of the issue with recent boat builds with large open decks.

If the old rules were administered better by all, a new rule would not have been needed. I did not see the "intent" written into the rules to grandfather in all existing boats or any specific hull. Favoritism is definitely shown if rule was written to specifically include one style hull that may exclude others running legally for years.

The actual rule in black and white is now what matters and does not grandfather old boats. If a newbie comes into the hobby, they would pick up the rule book and follow it. Diagrams are part of the rule and are provided to clarify what is required. The majority of the cooling can is concealed as shown in the drawing, by the use of a dashed line. Maybe that was not the intent, but that is the meaning and is what passed as the new rule.

It is disappointing that many Insane Hulls and other boats that have been running will also need a new cowl to meet the new rules.


Duke

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Duke, you are way off base brother.....lol.

nickhartdegen said:

No, Dan, it does not...read the 50 percent coverage part of the existing rule. There's some key words in there ...cmon guys, read the entire class rule, lol. The header shiwing has NEVER, been illegal. This stuff gotten comical. It's actually a very concise, easy to ubderstand rule now. In the old rule, it was open to interpretation, all this does is set actual numbers. Relax everybody, lets go play !!!

Click to expand...

i. A minimum 50% of the gasoline engine must be covered with either a cowling or period correct fake engine. This does not include header and/or tuned pipe.

this rule has nothing to do with aft of sponson transom. Unless your engine is mounted aft of sponson transom I guess. This now has to be covered.

It also states that header and tuned pipe are 2 different things which they are.

It’s not comical. It is the written rule which now every tboat has to adhere to.

Dan Pralle said:

i. A minimum 50% of the gasoline engine must be covered with either a cowling or period correct fake engine. This does not include header and/or tuned pipe.

this rule has nothing to do with aft of sponson transom. Unless your engine is mounted aft of sponson transom I guess. This now has to be covered.
View attachment 277121
It also states that header and tuned pipe are 2 different things which they are.

It’s not comical. It is the written rule which now every tboat has to adhere to.

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Dan, all I was referring to was your statement about the header not being able to show. I'm out...this horse is waaaay dead, lol !

Nick these rules are what we all have to go by now. The writer took out exhaust system and replaced with tuned pipe and the rule passed. Please explain why my statement is incorrect.

Is the header not part of a tune pipe ??

ButchLaPorte said:

Is the header not part of a tune pipe ??

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Butch,

A tuned pipe is purchased separately from a header. So my opinion is no. The header and tuned together make the exhaust system.

Duke Mordja said:

Butch,

A tuned pipe is purchased separately from a header. So my opinion is no. The header and tuned together make the exhaust system.

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Well if you talk to a 2 stroke engine builder the part of the pipe that goes to the cyl is called the head pipe . so are we using the proper names ? To solve this problem i think the rules need to be written clearly so everyone is clear . just my 2 cents .

Are the side vents in the Zipp Kit missle illegal under the new rules? Trying to figure out if we need to fill them in?

Joe Petro at zip-kits will advise

advise what.

Samuel Hagan JR said:

Are the side vents in the Zipp Kit missle illegal under the new rules? Trying to figure out if we need to fill them in?

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I think they ok now per the open slot rule they are smaller than the max

I didn't care for the fact that the proposal changed two things in one vote, 1) the deck openings and 2) removed the requirement for "period appropriate" decorations. I would have voted for one and not the other had they been separate proposals.