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SB 09-20-2022 09:38 AM


Originally Posted by dvr4hire (Post 4845498)
For my experiences in the bilge, the best reason for staggered setup is the relative ease of serviceability!!

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

Twin O/B Sonic 09-20-2022 09:42 AM

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?


Originally Posted by outonsafari (Post 4845546)


Twin O/B Sonic 09-20-2022 09:50 AM

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.

Twin O/B Sonic 09-20-2022 10:12 AM

More great reading!

Thx!


Originally Posted by SB (Post 4845561)
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


outonsafari 09-20-2022 07:52 PM


Originally Posted by Twin O/B Sonic (Post 4845562)
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?

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

outonsafari 09-20-2022 07:58 PM


Originally Posted by Twin O/B Sonic (Post 4845565)
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.

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

ThisIsLivin 09-21-2022 04:51 PM

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

Tartilla 03-01-2024 11:53 PM


Originally Posted by Twin O/B Sonic (Post 4845131)
I’ve done quite a bit w/rebalancing trailers to get proper tongue weight which is a great example of how much I have shifted weight in the hull.


Although I never checked tongue weight as purchased it did tow perfect at 80 mph on its way home.

Once the power conversion was complete it was scary to tow and swayed terrible!

I weighed the tongue at that point and was only 135 lbs!
Far from the targeted 10% of gross, loaded weight which is 4500 lbs.

Had to move hull as far forward as I could which was almost 2’ and got tongue weight to 450 and now tows great.

As to weight shift in small boats, I designed/built and raced outboard hydroplanes for 9 yrs so I totally get that.
I firmly believe I am as good as I am on trim buttons because I spent 9 yrs w/my ass being the trim buttons 😂

Also spent many yrs playing w/fast single OB hulls.


https://cimg2.ibsrv.net/gimg/www.off...4c60fad8e.jpeg
https://cimg3.ibsrv.net/gimg/www.off...467647c74.jpeg
https://cimg4.ibsrv.net/gimg/www.off...13484fa3d.jpeg

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

Tartilla 03-02-2024 12:14 AM

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

Twin O/B Sonic 03-02-2024 06:14 AM

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!



Originally Posted by Tartilla (Post 4892138)
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



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