Adding Weight

[Propjockey]

Just wondering...I keep hearing builders say to "set the balance point at......."

Then, after construction "add...........weight to the sponson tips"

Why not move the balance point forward during the building process?

 

[MarkScott]

PJ... Believe the CG needs to be set at the 27 % to 30 % as this is the best place for a boat to run. Then when all the cool and light weight radio equipement goes in, the CG is more like 20%.. Hence, need to add weight to the front. Jim Iwrin posted a point in another thread, which I never thought of doing. For moving weight around, use what ya have.. He takes the battery (5 cell no less) and places it OUTSIDE the radio box.. 8) 8) At the end of the day, shot of WD40.. Let it dry... I'd only do this on a tunnel... ;D

Cool!!!!

Mark..

OB Nut Racing.. Learn something new everyday!!!

 

[topfuel443]

I once won a district race with two old 13mm crankshafts taped to the nose of the cowling for added weight.......then again it WAS white capping 8)

Not that this has anything to do with your question......just gettin' my post count up ;D

 

[MarkScott]

TF - ROFLMAO.. ;D

Mary's boat uses bb's and epoxy mix to the tip of the cowl.

Mark

OB Nut Racing: Need more post to catch TF ;D

 

[topfuel443]

Ive seen guys use pill bottles that is epoxied in the nose of the cowl. you can easily add weight by adding more or less BB's by taking off the cap. its filled with foam to keep everything from moving around. looked like a good idea

T/F racing ~ one more post ahead of OB Nut ;D

 

[Propjockey]

Thanks guys. That's kinda what I was thinkin...just not sure if I was missing something.

I've always done that on planes, where the balance point is critical. Build it with the balance point in mind, then move radio gear around to fine tune it.

 

[snowdog-2112]

To question Mr. Irwin's and OB Nut's

"batteries outside of the radio box" statement.

HOW? Doesn't that present yet another hurdle to our continuing struggle to keep water out of the radio box?

OB Nut, so nicely described...you have a way with words!...when you want!

Team Snowdog - Continually adding $*&) to the mix!

 

[GTR]

Hi Guy's

Everybody talks about adding weight to the nose when the real answer is to remove weight from the rear. This may be a benefit of a lawless lower as it moves the weight forward, add this and TimD carbon tuned pipe and it's getting there.

Just a thought.

GT ;D

 

[lohring]

If it's possible, keeping the weight forward to eliminate lead is the best system. Weight concentrated in the center of the hull helps stop pitching. Weight at the ends will cause a boat to pitch in waves. Observe how an inboard catamaran rides in really rough water compared to an outboard. Also notice that adding weight in the center of a boat helps rough water performance.

Lohring Miller

 

[Ron Olson]

Back to his question initially, it's hard for any boat designer to figure out what equipment you are going to run. placement and size of the fuel tank that you put in, a 4 or 5 cell battery pack and how big that is. Are you using a stock or modded motor on it. A lot of variables had to be considered, even which motor mount you are using, some are longer than others. By making it tail heavy, it gives you easier adjustability also for water conditions. It's easier to add weight to the front or center than take it off the back.

Wet Paint Racing, I'm almost there!

 

[Jimboat]

When ever "adding weight" is the needed fix, there should be the other (and more effective) alternative of correcting the balance problem by shifting the weight. Alternatively, a change in the lift characteristics of the tunnel, deck or sponsons will change the dynamic stability of the hull - and this is usually much easier than it sounds.

 

[snowdog-2112]

I feel the need to comment again here...

Perhaps my equipment is so new that I don't know of other systems. The way my hulls are setup, there is no way to move stuff around inside the radio box enough to make enough of a difference to eliminate the need for lead. The batteries (5-cell) are all the way forward. I've been tossing around the idea of moving my servos forward to the middle of the box but I don't think doing so will make enough difference. Also, could somebody describe how you move your batteries outside of the radio box without having to worry about getting water inside the box? I see doing so as another hurdle in our efforts to keep the radio equipment dry.

Snowdog

 

[lohring]

I only have extensive experience with Leecraft hulls, but I believe most hulls can be setup with a good starting CG by putting the batteries at the front of the radio box, the 1/4 scale steering servo next, and then everything else after that. I often have a lot of empty radio box toward the stern. The Leecraft XT-460 will still need a little sponson tip weight but the XTR-21 will run fine if setup this way.

Aerotech had a system for installing the batteries in the cockpit area in front of the radio box. We (B&M Leecraft) once built boats with a front battery compartment. Our design leaked and had other problems, but it almost eliminated the need for weight on the XT-460. You can still setup the Leecraft using the Aerotech battery system, but few people bother.

Every hull has its design quirks. I am amazed that the XT-460, designed when tunnels ran in the 40 mph range, can still race at 60 mph with the best modified tunnels by adding a little lead.

Lohring Miller

 

[lohring]

I only have extensive experience with Leecraft hulls, but I believe most hulls can be setup with a good starting CG by putting the batteries at the front of the radio box, the 1/4 scale steering servo next, and then everything else after that. I often have a lot of empty radio box toward the stern. The Leecraft XT-460 will still need a little sponson tip weight but the XTR-21 will run fine if setup this way.

Aerotech had a system for installing the batteries in the cockpit area in front of the radio box. We (B&M Leecraft) once built boats with a front battery compartment. Our design leaked and had other problems, but it almost eliminated the need for weight on the XT-460. You can still setup the Leecraft using the Aerotech battery system, but few people bother.

Every hull has its design quirks. I am amazed that the XT-460, designed when tunnels ran in the 40 mph range, can still race at 60 mph with the best modified tunnels by adding a little lead.

Lohring Miller

 

[Gattorno]

Hi Boys.

Which it is the average of weight that is added to balance?

and which is the average of weight or better weight for a tunnel 3.5 mod already balanced?

in my tunnel 3.5 add almost 11onzas in the front to balance.

There is weight I specify in regulation for tunnels 3.5 mod?

I expect comments.

Thanks

Gatt.

 

[Jerry Dunlap]

Gatt,

Wow, 11oz in a 3.5 tunnel?? What hull and motor are you running?

For my 30" WOF tunnel with modified 3.5 I'm probably only adding 5 oz to the sponson tips. The front edge of the radio box is located at the leading edge of the center section.

Jerry D.

 

[GTR]

Hola Gatt

With all that weight you have to add to get the boat to balance it must be that low friction solid gold plating on the K&B making it hard to balance. Maybe K&B unobtanium is really heavy not light.

Just pulling you leg. LOL

GT ;D

 

[[email protected]]

Jerry right remember this guy?? I was at a race on day and it was so windy that no B-OPC could stay on the water. Jim was about to race and I was in the pits. I was gonna open a soda and Jim yells "Rod, let me borrow that before you open it", he then opened his cowl and slide it in the nose. He went full speed in the rough water and won w/no problem. Funniest thing I ever saw.

 

[snowdog-2112]

RCBoats2,

I sure hope you didn't open that soda when the boat came back in.



Snowdog

 

[Gattorno]

Re:maximum Weight in tunnel 3.5

Hi JD.

Therefore add 8oz so that the center of gravity this as to 9 inches and with that was sufficient then I take it a photo so that checks that am doing .

Now I believe that I need it to add the sponson tips, so that do not sink the nose.

The tunnel is an own design and the motor (air cooler PICCO, carb O.S. 40B remote needle, K&B mofle pipe ;D ) this modified and I believe that it weighs a little but of the normal thing, therefore wanted to know which is the weight most maximum or adequate total for a tunnel 3.5cc.

Thanks by thinking, all by obtaining greater velocity.

Gatt.