Any use for fins toward the front?

[Senior Space Cadet]

I notice that some missiles have small fixed fins near the nose.
I also know that weathervaning can be an issue, with model rockets.
I was wondering if fins, toward the front of the rocket, could be employed in windy conditions? Not that shooting rockets in windy conditions is a good idea.
Do any of you put them on your rockets, other than scale models of rockets and missiles that have them?

 

[dhbarr]

Fins near the front are always going to move the center of pressure forward. Not necessarily a huge issue, but generally needs to be counterbalanced with more weight up front and/or more fin in the back.

If you're going for altitude or speed there's not much reason to do it, so that leaves appearances as you point out.

 

[RocketflierVB]

Those are called canards. On actual missiles and rockets they are used to control the flight because they are steerable through the navigation system. Be careful if you have a design that has them. They must be attached as straight as possible. If they are cocked they will steer the rocket on their way up.

 

[rocketman4h]

if you put fins foreward it will indeed move the CP (Center of Pressure) foreward remember the relationship between the CP and CG (center of Gravity) is what makes the rocket stay pointing forward. The rule is the CG needs to be at least 1.5x the Guage (diameter of the rocket) in front of the CP. If it is less than that like .5 to 1.4 than there is a large probability the rocket will not fly with the nose forward. if the relationship is less than zero the rocket will unsafely spin. the only way arround it is to add a gimble control on the rocket. and that is an entire can of worms to open

 

[o1d_dude]

Those are called canards. On actual missiles and rockets they are used to control the flight because they are steerable through the navigation system. Be careful if you have a design that has them. They must be attached as straight as possible. If they are cocked they will steer the rocket on their way up.

Rheintochter missile with guidance canards.
Circa 1944.
Photo courtesy Smithsonian

 

[Bat-mite]

Keep in mind when studying real missiles that they are not hollow shells like our models. If there is a heavy warhead or payload in the nose, then forward fins actually help stabilize the rocket. But in our models, where all the weight (the motor) is in the back, they are not helpful.

 

[jrap330]

I notice that some missiles have small fixed fins near the nose.
I also know that weathervaning can be an issue, with model rockets.
I was wondering if fins, toward the front of the rocket, could be employed in windy conditions? Not that shooting rockets in windy conditions is a good idea.
Do any of you put them on your rockets, other than scale models of rockets and missiles that have them?

Bad idea....which is why you will always get clay weights with those models...so for someone worrying about which clay weight is best..answer is NO, do not consider unless you are building a scale military missile.

 

[neil_w]

99% of the time in model rockets they're for looks. Certainly do pull CP forward, must be accounted for. I like 'em, most of my designs have them in some form or other.

 

[lakeroadster]

Do any of you put them on your rockets, other than scale models of rockets and missiles that have them?

Yes... but the ballast in the nose is quite heavy.

 

[mbeels]

In windy conditions the stability margin will largely determine how much the rocket weather cocks. If two rockets have the same stability margin, and one has canards, they'll weather cock to a similar degree.

However, the addition of canards, accompanied with larger rearward fins, can increase the damping ratio of the rocket, so it does have an effect on the dynamic characteristics of the rocket.