RHTmarine sport 21 Gen 2A

Andy Brown · Feb 9, 2014

namba276 said:
Good to know Andy...to be honest, I built the boat to run in namba originally. I have sold boats in the past to guys in IMPBA and they all had a belly pan. I looked at the namba rule book, and found nothing pertaining to a belly pan on sport hulls. I could swear it was noted at some point, but nothing currently.

Thanks, Bob

The belly pan is fine in IMPBA as long as it does not go rearward of the 50% mark.

namba276 · Feb 9, 2014

Andy, I will check that...good info from the KING!!

namba276 · Feb 9, 2014

Andy, I have dug through both NAMBA and IMPBA rules on-line and see no notations regarding belly pan length or depth in either rule book. If you know if these rules are indeed in there...please share with me. I want my boat to be deemed legal in both associations. I only have the Internet version of either rule book.

Thanks, Bob

Dasboatman · Feb 9, 2014

NAMBA Rule Book is up to date.

Here is what the IMPBA Rules will supposedly be when available on their web site. CHEERS !!! Bob

namba276 · Feb 9, 2014

Wow...thats more than I saw on line. Looks like the only question is how the pan terminates. Smoothly? Does that mean that it blends in? Mine ends blunt so that water breaks off it cleanly. Its also open to drain the bilge after launch.

Dasboatman · Feb 10, 2014

Hey Bob,

To the best of my knowledge, the above I posted is what has been approved and will be the new IMPBA Sportsman Rules. The last page 5 of 5 was nothing more than a voting ballot - not of concern to those of us trying to build boats that will be IMPBA and NAMBA legal for 2014. Most people build this time of the year so the 2014 rules would be great to have before the racing season starts.

I read that the belly pan has to fair (blend) into the hull bottom smoothly - not terminate as yours presently does.

NAMBA did eliminate a rule about the belly pan depth a number of years ago now. The hull most effected was Phil Thomas's SS45. He provided a quick fix to make his SS45 NAMBA legal under those rules, using some 1/4"square stock spacers and a new epoxy glass sheet bottom to reduce the depth of the belly pan. He subsequently changed the bottom mold to incorporate this temp fix, and actually improved the performance of the SS45. The rule was voted out shortly after. I don't have access to my pics on this PC, but will post some FYI when I get to my computer. CHEERS !!! Bob

Dasboatman · Feb 10, 2014

Hey Bob,

Here are the pics described above that Phil Thomas made to his SS45 years ago to comply with now eliminated NAMBA Belly Pan rule. 100_1883.jpg appears to be a good example of IMPBA current rules:

"Belly pans are allowed but MUST terminate aft smoothly and extend no further than 50% of the aft plane. Belly pans MUSTbe at least 3/8" above the bottom planing surface of the boat measured with the boat resting on it's 3 points on a static table."

Phil's SS45 has been in production for years, and are of the only or few epoxy glass hulls available to Sportsman 20/40 boaters these days - which includes Phil's newer Round nose Sport 40 hull. I don't have any pics of the bottom of Phil's Sport 20 hulls. Whiplash Sport 20 and 40 wood kits, and some from ML Boatworks and that's about it .

CHEERS !!! Bob

Old mods to SS45 hulls:

Phil's newer round nose hull:

namba276 · Feb 11, 2014

I quess I can build two versions...I feel like if it's tapered back to the tunnel top, it will draw the transom down...thats the whole idea of moving the radio forward...You guys in IMPBA want the belly pan? I could delete it on your boats...Input please

Mark Leyde · Feb 11, 2014

Oh hell more IMPBA rules that are not well defined. Smoothly???? Just put a 45 degree angle back up to the bottom on the aft of the belly pan. Is it smoothly enough??? For me it is, it is not a sharp 90 degree angle. I would say put the pan in on my brothers hull. We will make it "smoothly" as we can.

P THOMAS · Feb 11, 2014

HA thats what i was thinking of that belly pan rule we can make it smooth enough to not provide a ride surface. If thats what the rule is all about? I wanted to just leave out all that about belly pans. Looks like those guys tring to use the Vegas hull for sport20 will have to do some mods as the pan on that boat is square at the back. If you build a sport boat you will need a lawyer to defend your design if thay come up with anmore restrictions. LOL

Grimracer · Feb 11, 2014

the Vegas is also past the 50% point.. When i did my Sport 20 Vegas years ago I faired mine in..

Grim

namba276 · Feb 11, 2014

I'm going to add triangle stock at the trailing edge of pan. Mine is only about 4" into after plane which is 18-1/2" and about 3/4" above planing surface. If it rides on that...you have a serious set up issue. Thanks everyone for the input, Bob