Wow!

And that was a 43?

Yes it’s a 43.

Supposedly the hull heritage is a popped 9’ wide midnight express hull with 2 steps and pad added at some point. The parveys have worked on their bottom as well. The 43s seems a bit rare compared to the 46s.

Great Thread. With all the talk of a Further-aft CG being best, what is the reasoning for staggered setups? My best friend owns a 39 Outerlimits quattro, staggered 525s and XRs on ITS transoms. Boat runs in the 90s and handles very well. Would it run faster rigged side by side but handle worse? Im sure each setup has its ideal CG location and what works on a straight bottom v may not work with 4 steps and a notch. Honestly curious. I'm putting together a 272 Formula, 468 BBC and bravos, and contemplated moving the batteries and trim pumps up under the rear seat to move the CG forward any little bit as it handles ass-heavy at anything below 55-60mph. Wants lots of tab not to porpus.

Dvr4hire,

It has always been my understanding that the purpose of a staggered setup had everything to do with the relative depth of the drives while planing vs on plane. With side-by-side, the props are set really deep at idle and planing, so that they can be at the proper depth while on plane, forcing a reduction in prop pitch to get on plane. The prop depth doesn't change nearly as much with staggered twins, which allows for more pitch in the props. I would guess staggered handles better at speed, but is less agile while docking.

Thanks. Brad.
(937)545-8991

Staggered installs also let’s them mount the drives closer together which keeps the props in the water longer, as the hull lifts.
(As stated above)

On my OB’s they are mounted on a 24” center to center (the min for twin OMC loopers) for this same reason.

You can get your hand between the cowlings but not your arm.

I noticed on the BT when it was docked at Captain Ron's, that there looks to be some sort of extension on the back of the hull from the outer chines inward and back. Would like to see that boat on a trailer to look at the bottom. Those things rode and handled the Lake right out of the box.

I noticed on the BT when it was docked at Captain Ron's, that there looks to be some sort of extension on the back of the hull from the outer chines inward and back. Would like to see that boat on a trailer to look at the bottom. Those things rode and handled the Lake right out of the box.

Thanks for the info, I honestly didn't know the full reasoning for staggered twins. Part of me thought mainly CG related, getting CG forward and the center of the mass of the driveline /motors closer to the center of the boat. I never considered that moving the drives towards the centerline on a v-bottom boat effectively raises the X dimension while at speed, due to how the water comes off the hull.

For my experiences in the bilge, the best reason for staggered setup is the relative ease of serviceability!!

brings the rotational mass closer to the centerline of the boat and lower, the propulsion closer to the center, and as you know my drive prop shaft is 1.5” above the bottom. (1” with the spacers installed) If we did nothing but move the drives out 4” on the same horizontal plane, they would be at least 1” below the bottom in that relative line.

Makes great sense and thought that must be part of it.

All the steps are doing at that point are packing air! LOL

That thing is singin!

Drv4hire,

That can't be an unwelcome bonus. I can't imagine changing the plugs in a side-by-side twin set-up.

Thanks. Brad.
(937)545-8991

Keith,

The steps did their job at a much lower speed, allowing for higher pitch props when the hull was seeing a lot more wetted surface.

Thanks. Brad.
(937)545-8991

Look up "ben perfected" i think cg is approx 35% forward of the transom. They had the boat fully fueled, both drivers and picked it up on 1 sling at lake x to determine that.
ben perfected is a 30 panther B class boat that holds a world record of 104, haven't seen sprague on here in a long while.

alot of info on how it was set up with the how and why's.

I think it makes the boats rotational inertia along the length greater. This should prevent the boat from making big attitude changes when hitting waves (it will stay flatter)

i was thinking you could put hard plastic sliders on your trailer bunks, then take one set of wheels off your trailer, load the boat back on the trailer. On flat ground slowly winch it forward until it “breaks over” and is balanced on one axle.

https://www.offshoreonly.com/forums/...b-panther.html

https://www.offshoreonly.com/forums/...t-panther.html

you'll have to dig but there is a thread on the set up and why

PERFECT!

Finally the info icee been looking for.

Thank you sir!

Now I have some reading to do :-)

Found this:
”On modern Deep V hulls, this is done for better balance, front to rear, but mainly to get the two engines closer together than you could if they were literally side by side. This closer placement allows the outdrives to be closer together as well, and closer means they can mount the drives deeper in the V of the transom. This helps get more of the hull out of the water when on plane.”

and this thread:

https://seriousoffshore.com/forums/s...ad.php?t=15663

All above prob not absolutes, but good info/ideas/etc

Thanks again.

Much appreciated.

And a 104 mph Panther???
Holy hell Batman!

So they did their kilo run and race conditions with that same C of G?

35% of 25’ hull is 8’9”.

Sooooooooooooo………., if a build a small cradle to fit the keel of my boat, in that general area, buy a stronger floor jack and just start lifting it until it starts lifting evenly, as in not bow first etc, I think I’d find what I’m after.

More great reading!

Thx!

same set up, kilo and race. Last time i talked to sprague (9 years ago) it was 108 with the upgraded engines.
i would search the threads about his set up, an awful lot of work was done to achieve that 30/35%, alot of bottom work to get it's running angle and alot of lake x time.
someone was joking about it as the million dollar scarab with the work, could've been him.
good reading for sure

You could probably slide a cradle back and forth and jack it off the trailer to find that cg, but that cradle should go out to the chines if possible
bottle jack

Talked to Kenny from Velocity and they recommend staggered if your running 110 or more in the 39. It keeps you from getting airborne. I removed some weight from my engine compartment and moved my toolbox and supplies from the cabin to the engine compartment and I run more trim than I used to in big water, so removing the weight moved the CG forward. In rough water you want the CG a lot more forward to keep the boat level. I run a lot in 3'+ in everything from a 16' Senza to my Velocity 280 and they both liked a full tank of gas otherwise you are pounding your brains out. The Senza had the fuel tank up front, may not have been the fastest but I could run in anything.


https://cimg2.ibsrv.net/gimg/www.off...c18994a083.jpg

This reminds me of the wide F-14 fuselage that provided a full 25% of the total lift.

Found some good Int.

Anything traveling in 2 different fluids (air/water) is going to be more complicated. Increased speed and choppy water ads to the complexity.

While knowing the working to the static CG helps, the dynamic CG is where it all comes together, and it always moves with speed.

https://cimg0.ibsrv.net/gimg/www.off...86d5ac95ed.jpg
https://cimg1.ibsrv.net/gimg/www.off...3355782b92.jpg

https://www.aeromarineresearch.com/d...stability.html

Interesting that you posted this as I am a friend of the author and was just thinking of reading up on it one of his books that I have.

THANKS!

And yeah, when the hull is light enough and has enough bow lift, it is a moving target.

The boat in that picture is an Allison (had one) and the guys w/the fast ones move sand bags (small, 2-5 lbs) around to balance the boat at speed!

Some of the prettiest vee bottoms at speed!

At an event I used to host, we had GPS runs.

Throw a handheld GPS in the boat and give drivers 15 mins to post a number.

Was held on the Ohio River and one yr in less than optimal conditions, for 500 lb hulls w/300 + HP.

Fastest boat was a Fla buddy in his STV tunnel boat at 128!
(Had been 144 in perfect conditions!)

He told me to give the award to the 2nd place boat which was an Allison at 126!

Was a magical moment as everyone else had run and were standing on the river banks waiting for this boats pass.

As he was rounding the bend in the river (@ WFO!) a barge was passing in front of us so we all knew he’d have to abort his run.

The barges knew our event was taking place and passed at an idle to reduce wake but it was still there.

So this guys bad ass Merc is echoing off the trees at 10,500, he catches the barge, then his wake and did not lift!!
Could have heard a pin drop on the shore line.

He passed us and that barge at 126, idles into shore and hands me that GPS.

I read the # to the gang and they thought they had just seen God walk on water!

That boat was balanced!

Then the drivers crew arrived w/a wheel barrel for his balls!

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.
​​​​
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.
​​​​
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.