CG on tunnel boats

[Superrod1969]

Got a hull on the way to use for testing the outboards I am working on and have a general question on CG. I have been doing a lot or reading on full size tunnel boats and they run them with the CG fairly far forward to control the lift ftom the hull. Do you do the same type of thing on the scale tunels.

Thanks

Jimmy

 

[Jerry Wyss]

Nope, generally back at the begining of the last 1/3rd

 

[topfuel443]

Like Jerry said, usually around the 30-33% mark from the back of the sponsons...

~James

 

[GRoth265]

Yes: the renolds numberas are different when dealing with models vtry 30 to 35% Greg

 

[Superrod1969]

My only concern with the 30 to 35% for static CG is that the gas engines and legs are much heavier than the nitro motors. The hulls for the gas motors should be wider I think to get the lift needed to carry a boat that will end up in the 14 pound range. I run my cat boats at 33 to 37% depending onthe hull but I am not sure how they compare to a tunnel. I think I will start with the cg at 30% and put the fuel tank on a slider to easily move weight forward. The boat will have trim on the third channel so I can pick the nose up some if needed.

Thanks

Jimmy

 

[topfuel443]

Good ideas...

I think you may be suprised with how little center section lift a tunnel boat will actaully need, especially at speed, regardless of the size/weight. Its a very thin line, but who knows? Let us know what you find out...

My 1/4 Tunnel is 44 inches in length.

~James

 

[Superrod1969]

I think the pi I have on the way is 52" with a 10" wide tunnel. It was designed as a gas boat from the start. Should be fun learning how to get this thing to run.

Jimmy

 

[topfuel443]

52"!! Geez... that's a big one.

Got any pics of one?

~James

 

[Superrod1969]

Here is a link to Blackhawk hobbies. That is the hull I have on the way. http://www.blackhawkhobbies.com/ Scroll down and click on the pic.

Jimmy

 

[racejunkie538]

Looks like a HPI design to me.

Nice boat.

Gr Marc

 

[kilr95ss]

HPI or DPI?

 

[F1Rodman]

Hi Jimmy, love the F1 Tunnels fullsize and model!

Do you have any pic's of your motor that you are working on at all? I have only seen a couple of different setups, mostly similar to lawless drives.

How will the trim work on 3rd channel?

Cheers.

F1Rodman

 

[racejunkie538]

Its DPI of course

Thanks !!

Marc