Cracker Box Question

[john22469]

Question on a stock cracker box can the left side chine be rounded or does it have to be a 90 degree per Impba or Namba

 

[Mike Hughes]

NAMBA RULE
C6. Crackerbox
a. All boats will be models of full sized crackerboxes.
b. The letter “P” must precede or follow the NAMBA number on each side of the hull.
c. The minimum length will be 43.5 inches and maximum length will be 49 inches.
d. Minimum beam width will be 16.5 inches.
e. The bottom must be generally flat with a maximum of a three-degree V across the full width of the transom and refer to rule C.6.a. There may not be any pads or lap strakes.
f. The deck and hatch must resemble that of a full sized crackerbox.
g. Two drivers of ¼ scale size and appearance, wearing helmets and life preservers must be used. A steering wheel, instrument panel, and other detailing is encouraged.
h. No parts (rudder, prop, plates, etc.) may be more than four inches behind the transom.
i. The exhaust system must be enclosed by the hull. No part of the exhaust system may extend beyond the transom with the exception of a small pipe muffler or transom exhaust flange.
j. No servo adjusted trim tabs are permitted.

 

[Mike Hughes]

I dont see anything that points exactly adgainst what you want to do. But C6a will be a judgement call if you are protested.
Mike

 

[Randy Rapedius]

In IMPBA rules it must be at a 90 degree. Rounded is not legal.

 

[john22469]

Good Evening Randy
Iam not doubting but could you please let me know where you read this I have looked at the impba rule book revised October 2022section large scale gas under Crackerbox I-8 and cant seem to find anything would you please let me know where i could find it. iam in the process of building and dont want to screw it up

 

[Randy Rapedius]

Good Evening Randy
Iam not doubting but could you please let me know where you read this I have looked at the impba rule book revised October 2022section large scale gas under Crackerbox I-8 and cant seem to find anything would you please let me know where i could find it. iam in the process of building and dont want to screw it up

Rule 2a covers it. A cracker with a rounded bottom at the rear does not follow the lines of a real full-size hull. I had one of Ivan’s Crackerboxes with a rounded rear and it was deemed illegal by the IMPBA Tech guys.

 

[Michael Lewis]

John, keep your chines sharp. With a rounded chine your just going to increase drag on the port side of the boat. My zipp kit crackerbox hauls down the straights but it takes throttle management in the turns. Even scale boats have to back off in the turns. Play with the skid fin under the boat also... different sizes and shapes and good luck!!!
Mike

 

[Grimracer]

Some day I have to build one of these.. I would run a straight shaft out the bottom of the boat.. I have deigned both and the straight shaft was superior to out the transom. Set the trailing edge of the prop at 15% boat length. Amazing In the corners! I offset shaft needs to be tested per design... Just do not remember the percentage on that!

Anywho..

Grim

 

[John Finch]

The fastest way around the course during heat racing is to chop the throttle 10 feet before you make the turn. Got to go slower to have a good lap in traffic. Bert told me that in Charleston this year at the fall nats and he was right. At home I could run wide open through the turns but in chopped up water Chopping the throttle was the way to go. Thanks Bert. It is a boat you need to learn to drive as Bert would say.

 

[Grimracer]

tunnel boat driving!!!! O YEA!