CG question

[AVENGER 44s]

Just woundering if anybody would know the CG on a 44" Cal-craft? I'm going to install a modified 260 Zenoha. Installing a surface drive gas stinger from speedmaster. going to put in a 500 IV gas bag for fuel. 3" wide x 1 3/4" deep trim tabs. a speedmaster rudder with a 4" extention so as to be correct with the length of the prop. If anybody has any input, please feel free. Iv'e set up several hulls but never a 44" Cal-craft..

 

[shadow]

I have a 44 inch Cal-Craft Nitro with a CMB1.01in it. I'm not sure if the CG would be the same for a gas boat, But I'll check it and get back to ya.

Cliff

 

[AVENGER 44s]

Cliff, Thanks for the reply! I talked to lenny over at rum racing and he has his engine out of the boat for the year. I wounder if the cg would be somewhat the same? Iv'e been a guest on this sight for awhile and got some great information. I'm hoping someone has a hull that is st up with gas and could tell me the proper setting... What hardware are you running in the rear? How does the boat run in race water! Thanks.... James..

 

[Rigged]

id try 32-33%....

 

[John Finch]

All mono hulls should be balanced with a benchmark of 30 percent. If you move the cg forward the boat tends to drop the bow when the boat becomes airborne. I have run as much as 36 percent cg but every once in a while the boats tend to make like submarines and (find a hole) because the forward cg lets the bow drop. I would suggest 30 to 31 percent on all mono hulls if you want the boat to FLY level.

 

[Rigged]

All mono hulls should be balanced with a benchmark of 30 percent. If you move the cg forward the boat tends to drop the bow when the boat becomes airborne. I have run as much as 36 percent cg but every once in a while the boats tend to make like submarines and (find a hole) because the forward cg lets the bow drop. I would suggest 30 to 31 percent on all mono hulls if you want the boat to FLY level.

My gen1 insane mono at 34% would still pop the bow up a bit when catching air....?

 

[Ken Retallick]

John, It depends on the design of the hull! 30% might be ok for some, but not others.

 

[John Finch]

30 percent is the benchmark (starting point) As you move it forward the boat will go faster with less trim tab, but there comes a point when you go too far. Yes, every boat has a best cg somewhere between 30 and 36 percent. The thing to keep in mind is that the boat becomes airborne and at that point how does the boat fall back to the water. It is sometimes better to keep a 30 percent cg and add weight to the cg so that the boat does not lift, but still flys level when airborne. If your boat goes bow up every once in a while it might be one of many things that have nothing to do with the cg.

 

[Peter Zicha]

This is my 57" Apache and I am at 26% . worked good all summer , because of the small pond I ran the Lehner in star config and not delta or at about 60% power

http://ca.youtube.com/watch?v=T6jkqS-csxE

 

[John Finch]

This is my 57" Apache and I am at 26% . worked good all summer , because of the small pond I ran the Lehner in star config and not delta or at about 60% power
<a href="http://ca.youtube.com/watch?v=T6jkqS-csxE" target="_blank">http://ca.youtube.com/watch?v=T6jkqS-csxE</a>

Coooooool electric setup! I notice the electric boats are pretty heavy but they have the power to be faster than their gas and nitro cousins with all those electric horses. It's a good combination for more speed and good control. Awesome! you don't have to worry about CG on that boat because it is always touching the water at the transom. If the transom doesn't leave the water the boat can't submarine. Awesome power!

 

[Chris Wood]

john,

would you say that the same cg senerio apply's for a boat that doesn't use trim tabs like a seaducer?

chris

 

[Peter Zicha]

Thank you for the kind words john..........

 

[John Finch]

john,
would you say that the same cg senerio apply's for a boat that doesn't use trim tabs like a seaducer?

chris

Yes I would, because when I talk CG I am talking about how the boat aerodynamicaly flys over the water when it becomes airborne. So long as you have a heavy boat where the boat transom stays planted, a forward cg is fine. The gas boats are more successfull with the forward cg because the boats are heavier and they don't leave the water as easily as the nitro boats.

I am always hearing people say that trim tabs make the boat think it is longer. If they are always in the water I can agree, but when the boat become airborne I think not.

 

[El Zorro]

My 30" Twincraft that I raced for about 8 years had a problem of popping out of the water and spinning around at times when it hit a rough piece of water while in the corners ( like a ground loop with an airplane ). This cost me a US-1 one year at the Internats. After some thought and throwing some questions at the mono guru I made new hardware to extend everything 1" further behind the boat ( longer brackets for the strut, rudder, turn fin and extended the trim tabs ). This kept the CG at 29% and the boat never did loop around in the corners anymore. As John was saying, this made the boat " think " it was longer. The boat would fly level to the water when you were running in rough conditions. Having the fuel tank mounted at the CG also was a BIG help in letting the boat come out of the water like this and keep going at speed. Not many times the boat didn't finish a race unless the driver screwed up..............

Dick Tyndall

 

[AVENGER 44s]

Thanks to everybody that replyed, Really appreciate it! Great help. I'm going to start with 31% and go from there. I was also woundering if you could tell me where the trim tabs should be located. 1/2" start from the ends or should they be closer to the keel? I just got done with a 46" Twin Craft. Dick Tyndall totally set me up with his set up sheets. I set the rudder on a 10 degree angle. I was woundering if this same set up could be beneficial with a Cal-craft on gas? Also, how far should the rudder run beneath the hull? I will put up some pictures of the Twin Craft when i figure it out... Thanks again for all the help guy's.... James...

 

[El Zorro]

Thanks to everybody that replyed, Really appreciate it! Great help. I'm going to start with 31% and go from there. I was also woundering if you could tell me where the trim tabs should be located. 1/2" start from the ends or should they be closer to the keel? I just got done with a 46" Twin Craft. Dick Tyndall totally set me up with his set up sheets. I set the rudder on a 10 degree angle. I was woundering if this same set up could be beneficial with a Cal-craft on gas? Also, how far should the rudder run beneath the hull? I will put up some pictures of the Twin Craft when i figure it out... Thanks again for all the help guy's.... James...

James, If you will notice on my set-up sheets, some of them will have a line drawn horizonally through the center of the diameter of the strut ( looking at the rear view of the boat ). This is where the inside edges of the trim tabs should be. Position and mount the strut first, then locate and mount the trim tabs. All of the dimentions from these set-up sheets came from boats that were running in heat racing trim.

Dick

 

[John Finch]

Thanks to everybody that replyed, Really appreciate it! Great help. I'm going to start with 31% and go from there. I was also woundering if you could tell me where the trim tabs should be located. 1/2" start from the ends or should they be closer to the keel? I just got done with a 46" Twin Craft. Dick Tyndall totally set me up with his set up sheets. I set the rudder on a 10 degree angle. I was woundering if this same set up could be beneficial with a Cal-craft on gas? Also, how far should the rudder run beneath the hull? I will put up some pictures of the Twin Craft when i figure it out... Thanks again for all the help guy's.... James...

James, If you will notice on my set-up sheets, some of them will have a line drawn horizonally through the center of the diameter of the strut ( looking at the rear view of the boat ). This is where the inside edges of the trim tabs should be. Position and mount the strut first, then locate and mount the trim tabs. All of the dimentions from these set-up sheets came from boats that were running in heat racing trim.

Dick

El Zorro, the masked man on the black stallion. You got it going on!

 

[AVENGER 44s]

Thanks to everybody that replyed, Really appreciate it! Great help. I'm going to start with 31% and go from there. I was also woundering if you could tell me where the trim tabs should be located. 1/2" start from the ends or should they be closer to the keel? I just got done with a 46" Twin Craft. Dick Tyndall totally set me up with his set up sheets. I set the rudder on a 10 degree angle. I was woundering if this same set up could be beneficial with a Cal-craft on gas? Also, how far should the rudder run beneath the hull? I will put up some pictures of the Twin Craft when i figure it out... Thanks again for all the help guy's.... James...

James, If you will notice on my set-up sheets, some of them will have a line drawn horizonally through the center of the diameter of the strut ( looking at the rear view of the boat ). This is where the inside edges of the trim tabs should be. Position and mount the strut first, then locate and mount the trim tabs. All of the dimentions from these set-up sheets came from boats that were running in heat racing trim.

Dick

Dick, set up the Twin Craft just as you said, everything is perfect to your lay out! I was woundering if this would also apply to the 44" Cal-craft i started? Running a modified 260 motor in this. I talked to lenny from Rum Racing, got the layout from him on the trim tabs ( 1 1/2" start from the bottom of the keel). I'm thinking that a 3" wide x 1 3/4" length trim tab would be allright with useing a speedmaster stinger drive. The stinger length is 3 1/4" long. Iv'e seen Cal-Craft's running 3" long trim tabs. Do you think 1 3/4" long will be fine? Also, I want to set up the rudder like i did with the Twin Craft ( Rudder on the right side of the strut set at 10 degrees to the right. Rudder not straight up and down!! I would really appreciate some more info on this theory.. Thanks for all the help!! James..

 

[El Zorro]

James, I would assume that the set-up for the Twincraft would work on the Cal Craft or at least get you in the ballpark. I set up a Cal Craft B mono long ago for my Dad with this set-up and the boat ran well. Try the short trim tabs ( 1 3/4" X 3" ) first, but make a longer set just to see if the boat likes them better..............ALWAYS try something different! The more you KNOW that DOESN'T work, the better your boat will be running and the LESS time you will be spending at the lake testing! Something I learned from the mono guru LONG ago.............

Dick