msu68stang

My Feedback: (7)

I have a set of parts that I'm using from a GP 60 float set. They include this extra fin to put on the bottom of the plane. I'm planning on putting the floats on a GP 60 size cub. DO I really need this extra fin thing? I've never seen a pic with one on there.

vupilot

Yes, put the fin on. The added surface area of the extra fin helps the airplane track straight in the air other wise the nose will wander left and right in yaw due to the added area of the floats ahead of the C.G. Most full scale aircraft use them when floats are added. If you really cant stand the extra fin people have had good luck in disreguarding the extra fin. It's necessity varies with different aircraft designs and types.
I am currently building the GP .60 floats for a friends .60 Cub and I will be adding the fin to it. What .60 Cub do you have? Great Planes?

msu68stang

My Feedback: (7)

yep the GP cub.

Turbobeaver

The part that you are referring to is commonly known as a "ventral fin".It is designed to give the aircraft more directional stability due to the increased frontal area of the floats forward of the C.G as stated previously.On models like real aircraft,the effect of adding floats to an aircraft will vary greatly.Some will need a fin and some won't.However,adding it WILL increase the stability of the model and it doesn't hurt it any to use it.It's a personal decision from an aesthetics and practicality point of view.Me personally,I use it on all my float planes because it does improve stability and when turning,the model will look much more co-ordinated in flight.It will keep the tail of the aircraft tracking much straighter.Ever seen a float plane spin out of control with no chance of recovery?I've actually witnessed this first hand.Two models exactly the same,one had a ventral fin,one didn't.At this float fly,both models were performing the same flight manoeuvers and the model with the ventral fin recovered immediately after neutralizing the sticks.The other one that didn't have a fin,it just kept on spinning out of control after he let go of the sticks all the way down to the water.SPLOOSH!!!!When I was talking with him later,he claimed that no matter what he did to neutralize the spin,it just wouldn't react to any rudder input.It DOES make a difference.Good flying guy's.

TexasAirBoss

My Feedback: (22)

What Turbobeaver said !!!

Friends and I got into float planes in late 1980's. We found out in a hurry that extra fin is very important on some planes. Some of the models were actually unflyable without it. I had a fairly large ventral (or is it dorsal) fin and my plane would still spin like crazy.