HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 23, 2009, 05:15 AM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
Question
where to place ballast

i am about to re-ballast my 47" spruance destroyer. right now i have the lead spread 1/4 each fore and aft, and 1/2 amidships. would it be better to place it all amidships? was wondering before i start pouring lead.
seadog985 is offline Find More Posts by seadog985
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 23, 2009, 06:30 AM
Veni, Vidi, Feci
patmat2350's Avatar
Motor City
Joined Dec 2004
12,748 Posts
Spreading fore and aft is rumored to help fight a lively pitch (higher polar moment of inertia, same thing like an ice skater slowing her spin by extending her arms).

Won't do a thing for roll though...
patmat2350 is offline Find More Posts by patmat2350
Reply With Quote
Old Oct 23, 2009, 09:29 AM
Big Boats Rule!
boater_dave's Avatar
Wisconsin
Joined Jun 2007
2,051 Posts
Polar inertia works against rudder effort, too. Spreading the ballast out fore and aft will also reduce the steering to some degree.
Is it possible to place the ballast in bags and perform some sea trials? Then you can move it if you're not satisfied.

Dave
boater_dave is offline Find More Posts by boater_dave
Reply With Quote
Old Oct 23, 2009, 09:35 AM
no wings any more, just dust!
Ghost 2501's Avatar
stoke on trent
Joined Oct 2004
8,052 Posts
rather than putting it in 3 lumps, perhaps divide it up and spread it all even around the hull. I found that moving the ballast around in my cargo ship so that it was lower but longer improved handling, made it more stable in the water, with less pitch and a reduced roll because the cg of the ballast is lower down
Ghost 2501 is offline Find More Posts by Ghost 2501
Reply With Quote
Old Oct 23, 2009, 02:37 PM
Registered User
Blackpool, Lancs
Joined Feb 2006
3,006 Posts
If the weight distribution is similar to the real thing, handling will be as well. If it requirement that the destroyer handles like a launch, ballast central, otherwise, spread it.
mfr02 is offline Find More Posts by mfr02
Reply With Quote
Old Oct 23, 2009, 04:07 PM
Registered User
United States, MA, Lowell
Joined Dec 2008
536 Posts
We at Homeport will say this .
KEEP YOUR WEIGHT AS CLOSE TO THE BOTTOM OF THE HULL.
We had a not so good scare with one of our Tico`s.(same hull as the Spruance)
Use some stick on tire weights, work out ward from the center of the boat.
What kind of battery`s are you useing?
Make sure you secure your Battery in place then start adding weight .
Paul
Homeport is offline Find More Posts by Homeport
Reply With Quote
Old Oct 23, 2009, 07:13 PM
Registered User
time4420's Avatar
S.E. Mass.
Joined Oct 2007
268 Posts
Place the ballast as close to the center line and amidships as much as possible while keeping as low as possible.
Stay away from the turn of the bilge and the ends.
time4420 is offline Find More Posts by time4420
Reply With Quote
Old Oct 23, 2009, 09:02 PM
Registered User
United States, NJ, Frenchtown
Joined Mar 2003
9,272 Posts
Real ships put as much weight in the center & as low as possible.

Copy them.
cyclops2 is online now Find More Posts by cyclops2
Reply With Quote
Old Oct 24, 2009, 09:18 AM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
thanks all. i am using one NIMH 6 cell packthat is at the bottom of the hull in the center. right now i have loose shot in bags, 2 in the center and one fore and one aft. as some of you may have noted on the montgomery model boat club thread my boat has a tendency to lean. when it starts this i bring her in and give her a shake side to side until she sits correctly. i have blamed this on the lead shot moving in the bags and as the hull is only 5" wide and the brass mast being so heavy it doesn't take much to sway her though she has never tried to roll all the way over. my thought was to put some solid weights in her to stop the shifting. once i get the molded weight in then i will fine tune with some 1/4 ounce stick-on wheel weights.
seadog985 is offline Find More Posts by seadog985
Reply With Quote
Old Oct 24, 2009, 01:52 PM
Registered User
United States, MA, Lowell
Joined Dec 2008
536 Posts
That Tico problem we had was due to the weight being left loose.
It was scary cool to watch the railings go under water.
Someone call 911
Try one of these it will bring you close to the water line. http://www.batterymart.com/p-6v-12ah...d-battery.html
That will reduse your ballast and give you a great run time.
They have these in 12v to.
Homeport is offline Find More Posts by Homeport
Last edited by Homeport; Oct 24, 2009 at 01:58 PM.
Reply With Quote
Old Oct 24, 2009, 04:50 PM
Registered User
United States, NJ, Frenchtown
Joined Mar 2003
9,272 Posts
Top heavy " Leaners ".

On the blue devil destroyer, I RTRVed a lead weight on the OUTSIDE bottom.

Sweet little lean at full speed. Long skinny weight. Just like the real DD 519 I was on.
cyclops2 is online now Find More Posts by cyclops2
Reply With Quote
Old Oct 27, 2009, 03:01 PM
GILL
GILL RC's Avatar
United States, NJ, Hopatcong
Joined Aug 2005
2,666 Posts
On my "DEVIL" USS STEVENS, I lightened the super structure as much as possible. I use a 7 cell NiCad for power and it sits on center at the bottom of the hull, motors and radio gear are as low as possible. I get very little lean in turns at speed. My Calypso is one that is known for it's lean and I get almost 0 lean. again every thing is low as possible and from the deck up it is as light as possible.
GILL RC is offline Find More Posts by GILL RC
Reply With Quote
Old Oct 28, 2009, 02:39 PM
r/c ships and workboats
bellingham, wa
Joined May 2006
4,672 Posts
Agree with the others on ballast as low as you can go and a mid ships. If possible, rebuild your mast out of alluminum tube or plastitruct tubuing as it will save a lot of weight top sides!
keith S is offline Find More Posts by keith S
Reply With Quote
Old Oct 29, 2009, 08:54 PM
Registered User
United States, MA, Lowell
Joined Dec 2008
536 Posts
I new it was out there.
Here is a link that will give you scale weights for all military war ships.
U.S. ones that is.
http://www.wmunderway.8m.com/cgi/yab...num=1227383978
Homeport is offline Find More Posts by Homeport
Reply With Quote
Old Oct 30, 2009, 01:35 AM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
homeport, helpful info. according to that formula my spruance should come out to be about 7 pounds. as far as changing out the masts i don't want to even think about that at this time. took me over 36 hours to build both of them. i'm going to take all the ballast and place it in the center of the hull. i'll melt it down and form it to fill the area under the battery. i can then fine tune with the wheel weights. this will be on hold for now until i get my new motors and mounts in. the motors will weigh more and thus less lead will be needed.
seadog985 is offline Find More Posts by seadog985
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Where to place servo's in Moth ? Purple Baron Slope 7 Jul 22, 2004 01:41 AM
where to place fuel tank xoon The Builders Workshop 6 Jun 07, 2004 11:30 AM
where to place the wing xoon The Builders Workshop 1 May 26, 2004 09:05 PM
Where to place motor diode mtbrider Power Systems 8 Apr 25, 2004 04:22 PM
Where to place the bungee hook? Appie Electric Ducted Fan Jet Talk 1 Jan 26, 2003 09:36 AM