It would be great to have that level of tuned hull/weight.

I'm surprised at the 2.5 - 5 lb sand bags that make thar much difference.

Jim Russel has contributed a lot of great info over the years. I should snag one of his books.

I have a Cobalt 300 (Carrera SS9M) that had Arnsons put on. I haven't ean it yet, but it's supposed to have poor manners at higher speeds. No details on numbers per say. Pre GPS as being common.

The Blown BBCs got pushed right up to the front firewall. That's a lot of weight forward. Lower weight of Arnesons on the transom vs TRS. Cobalt added a lot of weight in the cabin. Fridge etc.

Orig owner said he never needed to use tabs to plane out..with the heavy 26° vee. Seems like the CG is too far forward. That would make sense, if it was bow steering and chine walking.
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I'm putting the cabin on a diet, and getting it setup to run this season. I'm thinking the best option is to push the engines back and put boxes on the transom. Also extend the 280s to 380s.

Damn Carrera often ran with SBCs...425hp if the race announcers were correct. They would have had 72Cs, and placing them a little forward compared to Bravos.

Cool stuff!

Im a Cobalt fan.

That sounds like wayyyy too far forward too me.
Plus w/the surface drive you lose some of the props bite for bow lift.

I rigged this boat and it ran over a 100.

In the beginning I had all the weight in the ass end.
At about 90, it would try to blow over!

Moved the battery to under the dash and totally cured it!
Became one of the best balanced fast OBs I ever owned!


https://cimg0.ibsrv.net/gimg/www.off...270926349.jpeg
https://cimg2.ibsrv.net/gimg/www.off...e1ca8a4bd.jpeg

on the 46' skater open class boat and the 40' skater super cat we would add or subtract between 5 and 20 pounds up in the nose depending on water conditions. even 5 pounds per sponson made a big difference on a 10,000 pound boat.

That is wild.

But I guess 5-20lbs with a 37ft level is a lot of force.
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There was some formulas on the CG location. It calculated from the wetted surface vs the entire length of hull.

we used a CG calculator for small aircraft to see how much the center would move based on the weight up front. we did a lot of testing and kept notes of what effected what so we could set it up at the start. those boats had ballast tanks but in rough races we would put the weight in so you only used the ballast tank for the really rough parts of the course.

I put a 15 gl drinking water supply bladder in the anchor locker of my Checkmate that I use as a ballast tank.