IMPBA 6 scale gas rule change proposal

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Joined
Nov 18, 2005
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I have submitted to IMPBA a possible rule change that would make it more closely resemble the 8 scale rules as it relates to the exposed exhaust. I have been asked to explain my rationale so here it goes...

I have been building 6 scales for quite some time. My first was a blazer lauterbach that I converted to a 71 miss madison. It was a challenge to make a fake allison to work over the side exhaust but it looked awsome once completed. Unfortunately there was some of the carb and header showing. Enough to make it technically illegal. I have built several 1980s style boats and incorporated a rear exhaust in most cases which made it easy to conceal both motor and exhaust. 2 recent issues have surfaced with this class. First, in the last few years there are fewer rear exhaust options which makes it increasingly more difficult to conceal the carb and header. I have personally raised the height on the deck of wooden hulls to conceal the carb and header with good results. It hides the motor and still "appears " scale. Unfortunately this may not be an easy option for a newbie with a glass hull. I know of 1 modeler rotating the motor about 15 degrees to hide the header but still has issues with the carb. The second issue is that more modelers are building more recent designs of unlimiteds. These boats have really short exhaust stacks and shallow decks in the back making it nearly impossible to run the pipe out the transom with out burning the hull. Running the exhaust out the fake turbin exhaust works great. It allows the pipe to stay cool but makes the boat illegal as too much pipe shows. I personally know of 1 boater who was forced to cut off the muffler of his CMB pipe to try to be legal. We shouldn't have to sacrifice dangerously high decibel levels just to hide the pipe. I had to extend the fake exhaust on my miss boeing at the internats to be legal. (It looked stupid).
For the future of the class, we need to relax the rules just a little, similar to the 8 scale rules in the interest of safety and increased popularity. No one, including me, wants to see a bunch of gas sport hydros in the 6 scale class but we need some safe and easy options so that the class can continue to grow.
 
How about posting some pictures of the pipe with measurements of the pipe and the afterplane?
 
Wish I had gotten into gas scale a long time ago. I love the boats and the class. Huge bummer that rear exhaust motors are no longer available.

I was just curious as to why 1/6 scale was selected. Not that I am advocating for larger hulls, but would a 1/5 scale size have the dimensions to allow side exhaust motors to fit into more hull designs? Is that a direction to go to grow or save the class also?

Late to the party - Doug
 
Doug, IIRC, it was due to several things. Back in 1991, Roger Newton tried to start a true 1/6 scale club with the boats all powered by the BH Hanson G-230 "Indy" mod engine. There were several issues with the boats, as was later discovered:
  • They were too large to be easily handled with the average boat being between 57 and 64" long
  • Boats modeled from boats over 30 feet long required splicing the longer frames and deck since the longest ply available was 60"
  • The G-230 was unable to get the boats up to the speeds the guys building them wanted. While the boats were able to exceed scale speeds, they were considerably slower than a nitro scale of the same boat
  • The costs associated with these large boats made them cost prohibitive and drive shafts long enough hard to find.
By going smaller, to 1/6.7, the boats are easier to handle, can reach speeds comparable to nitro scales, cost less to build and, depending on the boat and engine , can be run in both gas scale and T-boat class without any major changes.
I was working on the 1973 Pak which was, ironically, one of the smaller boats. It was 57" long and 26" wide and would end up being too large to put in my car. I still have it though, like all but four boats that were started by various people, it was never finished
 
Wish I had gotten into gas scale a long time ago. I love the boats and the class. Huge bummer that rear exhaust motors are no longer available.

I was just curious as to why 1/6 scale was selected. Not that I am advocating for larger hulls, but would a 1/5 scale size have the dimensions to allow side exhaust motors to fit into more hull designs? Is that a direction to go to grow or save the class also?

Late to the party - Doug
Yes, you are correct in that 5th scale would allow easier concealment and hydro junkie is correct about 5th scale being too big for logistics like transport and launching etc. These boats are really big and heavy and can be a bear to retrieve when they die. That said, they are a BLAST to drive. It is much easier to react to one of these than a nitro snorting 20 rigger going 70.
 

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You explained a rationale, Wes, but you didn’t say what the proposal is!???
The wording is basically identical to the 8 scale rules.

Wesley Ellet IMPBA #9911S would like to propose to amend or change a rule for VI - GAS SCALE UNLIMITED

I would like to remove rule C-3-c which says:
c. Gasoline engine and complete exhaust system excluding up to 1" of exhaust outlet must be concealed with fake engine or cowling as per prototype boat

I would like to replace it with:

c. Effort must be made to conceal glow engine with fake engine or cowling as per prototype
boats.

At least 50% of engine and at least 50% of header/pipe/silencer combination must be concealed as per prototype boat."


This would be similar to the long standing 8 scale rules with considerations for gas boat challenges. I believe this rule change will allow more styles of boats to be legal including most of the more modern boats which have a shallow rear deck and exposed turbine making it very difficult to conceal the pipe and muffler without having heat issues inside the boat. The pipe could then be run out of the fake turbin without heat issues and still be legal. An older boat with an exposed Allison or Griffith motor could be built as long as 50% of the gas motor was hidden with a fake motor. The 50% rule would keep someone from running the entire exhaust out the boat similar to some Gas sport hydro configurations. In the interest of growing the sport I believe this rule change will make it easier for scale enthusiasts to build their favorite boat without fear of not being able to conceal all but 1 inch of the pipe.



Wesley Ellet

--
Wesley's Custom Graphics
208 W. DeYoung
Marion, IL 62959
61
 
As more and more Nitro 1/8th Scale enthusiast make the jump to Gas, the Gas Scale unlimited class has grown steadily and I’ve not heard of the current rules being an issue. If the new wording is accepted, it would open a whole can of worms. Guys could and many would be building their Gas Scales exposing 50% of the engine and 50% of their exhaust just to produce better cooling in hopes of gaining an advantage.
 
As more and more Nitro 1/8th Scale enthusiast make the jump to Gas, the Gas Scale unlimited class has grown steadily and I’ve not heard of the current rules being an issue. If the new wording is accepted, it would open a whole can of worms. Guys could and many would be building their Gas Scales exposing 50% of the engine and 50% of their exhaust just to produce better cooling in hopes of gaining an advantage.
This right here.............
 
While I agree the wording needs changed more gas scale boats run at local races here Than most areas of IMPBA I can count 20 built and race ready if these images dont depict the issues at hand your not listening received_659240501890037.jpegreceived_678614316512395.jpegreceived_659240501890037.jpegreceived_1573664216335910.jpegreceived_678614316512395.jpeg
 
Just playing devils advocate here…

Would a Zenoah with a drop down header work in that hull or one with both a drop down and 90 or 100 degree bend?
I only ask because by putting a muffled pipe on that particular set up, a rear exhaust engine, kind of makes me say well that’s BS. I would have a tuff time with that particular pipe in my boat with a Zenoah, So then I have to ask, is it the hull, the motor or the exhaust that’s the problem and what other choices can I come up with to make something work in this hull?

I’m not against a rule change, I only worry about the wording and people taking advantage of the new rule. Like I explained to Wesley already, the Scale class isn’t easy and I don’t believe that it should be. In your example above, did the builder make every attempt to make something work or in his mind did he say this is what I want to do and call it a day. I’m building two hulls and I struggled a little bit with how I wanted to run the exhaust. I came up with two solutions, one was to make a header, the other was to make a new exhaust flange spacer. I ended up getting two headers made to make it all work.
Again, not against a rule change just have some concerns over the wording with it and guys acting in good faith. With that said I personally think that was a poor example, but it’s only my opinion, right?
 

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Chris what do you mean poor example? It's a cmb rear exhaust with the recommended cmb pipe. We are talking about rear exhaust motors,any rear exhaust has all the same issues with modern hull after plane lengths
 
Chris what do you mean poor example? It's a cmb rear exhaust with the recommended cmb pipe. We are talking about rear exhaust motors,any rear exhaust has all the same issues with modern hull after plane lengths
I guess that’s it then, the problem is what motor/exhaust combo you want to run in that hull. Again Devil’s Advocate here. What if we were talking 1/8 Scale and I wanted to run a side exhaust motor for whatever reason and I couldn’t get most of the pipe and header under the deck of the hull that I was building. What would you/they say to me then?

Don’t get mad I’m only asking questions! Like I said my only issue is wording.
 
I think all they want is a little wiggle room on Exhaust exiting rear of boat. And a small bump in cowl for carb or Exhaust clearance. Had these rules mirrored scale rules we would not be having this conversation imho
 
I think all they want is a little wiggle room on Exhaust exiting rear of boat. And a small bump in cowl for carb or Exhaust clearance. Had these rules mirrored scale rules we would not be having this conversation imho
Yep, I scratch my head all the time wondering why there are some of these differences in the rule book.
I don’t mind a change but only worry about guys taking advantage and not wanting to do things in good faith, that’s all.
 
Where the problem is, as I see it, isn't the pipe. It's what the designers and crews have done to improve aerodynamics with the newer full-sized hulls. Had the boat Mike posted the pictures of above been an early Bud T-2/3, Winston Eagle, Miller American/Circus or 1991 Madison, this would be a moot point. The pipe could have run through the turbine exhaust tube, making it a non-issue. With the lower deck lines, short to non-existent turbine exhausts, further aft cockpit and such, the newer boats are just not really suited to the gas engines and pipes now on the market. Either the header has to run under the deck, along with part of the pipe to shorten the length, the deck raised to allow the header and pipe to fit under it, allowing cosmetic changes to the boats to compensate for the length of the pipe or being willing to accept the pipe being visible. All four options aren't really that good but, unless you want to eliminate the newer boats from being made legal due to this issue, a rule change is inevitable. I know Wes was looking at the IMPBA rules, but this isn't going to be just an IMPBA issue. Eventually, NAMBA will need to be looking at the same thing since the rules are very similar in both organizations.
I do have to agree, however. Whatever is decided, someone will try to take advantage of it
 
Took a while to find it but here is another example of a "illegal" boat under the current rules. Both the carburetor, header and pipe are partially exposed. In order to grow the class we need at least as much flexibility as the 8 scale class whose rules have worked for many years. To limit the style of boat in the class is to limit the class as a whole. 100_1294.JPG
 
Build a proper cowl that hides the engine and exhaust like I did here on my 1/8th Scale. Problem solved. (Sorry. Not the best picture). 6B31F2E3-78C1-49B2-B75B-9D20E6E925E0.jpeg

Gas Scale Unlimited is what I like to call a builders class. I say build the boat to the rules instead of changing the rules to make it easier to build.
 
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