Can a Stinger be too long?

[Travis]

Is there an ideal stinger length for a mono and can it be too long?

In this specific case, a 22.5" Arowana.

Cheers,

Travis

[siberianhusky]

Good question, I've wondered this as well, within reason of course.
Once I read 10% of the hull length but I've never seen or heard this anywhere else.

[steveo]

i read the 10% as well, also have read that to long will cause more prop walk

[Travis]

Thanks for the feedback guys, I'm relatively new to the boat thing despite having played with brushless planes and helis for sometime.

What physical syptoms would you see to describe prop walk?

Cheers,

Travis

[tiqueman]

The transom of the boat will want to "walk" to the side because of the rotation of the prop. So physically, you would see the boat wanting to ride like it needs an alignment.

[Jeff Wohlt]

Longer keeps the prop in the water under rougher conditions or during porpoising...makes a big difference in handling

[martin]

What are the down sides to a longer stinger. Martin.

[CornelP]

I only tested stingers in the 11-13% length, but as I heard shorter keeps the transom in the water lifting the nose a bit, longer is the opposite.

[sailr]

I remember reading in the forums a while back about people that shortened the stingers! I would think that a long stinger would cause all sorts of prop walk but not sure.

[siberianhusky]

My brain says longer would cause more handling problems than shorter unless set up perfectly. I just think longer would magnify any setup mistakes.

[m4a1usr]

What are the down sides to a longer stinger. Martin.

Depends on how long of a hull you put it on. I've heard of the 10% rule myself. Probably not a bad rule of thumb. However look at the SV27. It has a longer then 10% of hull length stinger, yet handles fairly well. I do know some racers have shortened their SV27 stinger by one inch. That makes the hull more responsive and gets it down under the 10%.

Lets look at what a stinger is. To understand it is to know it. A stinger is nothing more then a "Moment Arm". Its main purpose, other then to get the prop away from the hulls wake, is to get the prop into consistent water. Since all of the propulsion energy into the water is driven thru the stinger, and its doing this in some dynamic media, it behaves like a forcing arm. With the transom the fulcrum. The longer and the heavier a hull is, logic would indicate, the longer a stinger should be. Since our RC boats dont scale very well compared with real boats I dont know of a decent rule to use.


John

[Fluid]

There isn't a single "rule" as much as some folks seem to want one - there cannot be one. An example is the Hurricane mono, a gas hull often used for FE. Some guys get by with the stock SpeedMaster stinger, others have to shorten it - on hulls from the same mold. Why?

A lot depends on the speed, design and weight of the hull, and the depth of the stinger. The prop lifts the transon (yes, even a "low lift" X-series prop) as it delivers thrust, and as you move the prop back it is running in 'deeper' water coming up from the transom bottom. The further back the prop the more lifting force, which either drives the bow down or helps to lift the entire hull. Since most stingers are installed with little to no possible height adjustment, shortening the stinger is the only way to affect the prop's inate lifting effect on the hull. Some guys cut off 1/2 to 2/3" to get the boat's handling right.



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[Travis]

Thanks for the feedback guys, the boat tends to chine walk when it gets up and going and it almost seems like there's not enough boat in the water.

I've taken off the 70mm stinger and put on a strut assembly which brings it back to 50mm. Puts it back around that10% rule you've mentioned. Let you know if it makes any difference.

Cheers!