Forward swept fins, any experience?

[Voyhager3]

So I’m new to the forum (so that’s why this may be out of place) but not so new to rocketry. And I am getting ready to put some parts on order, but I have a question.
Does anyone know if forward swept fins will work?
I know I’m aviation it’s not very stable and I can’t find anything on it that anyone else has tired to put forward swept fins to the test. OpenRocket says it will be stable with some nose weight. Any opinions and or comments welcome,
Thanks!

 

[Theory]

Yup, can work, there are (have been) low power kits on the market that used forward swept fins and WM’s shredder is a HP kit that uses a mix of forward and standard swept fins.

 

[neil_w]

There have been many kits with forward swept fins. Works fine, not an issue at all.

 

[H. Craig Miller]

The icon says it all.. flown several times.

 

[Worsaer]

For those not familiar, this is what Wildman’s Shredder looks like.

 

[Voyhager3]

Ok, thank you everyone, I really just wanted a second or third, or fifth opinion.
So let’s just hope this thing go up, and not sideways!

 

[techrat]

https://www.rocketryforum.com/media/ahpla.347974/

 

[rharshberger]

Swept fins work fine, but they do have a desire to want to twist/oscillate starting at the tip twisting rearward, stiffer is better. Its the same phenomenom the Grumann X-29 experienced. Disclaimer: I am not an engineer....

 

[GrouchoDuke]

Swept fins work fine, but they do have a desire to want to twist/oscillate starting at the tip twisting rearward, stiffer is better. Its the same phenomenom the Grumann X-29 experienced. Disclaimer: I am not an engineer....

I am an engineer. Yup. I wouldn't plan any forward swept Mach 3 flights.

 

[JackC]

They work fine, at least with mid-power and H and I motors. Google “EMRR”, “rebel” and “wolf 2.1” to see a review on a rocket with swept forward fins.

 

[icyclops]

Built many LP kits with forward swept fins. In the 80s Estes had kits as it was a new design back then….FireHawk, zipper, yellow jacket, etc. to name a few.

 

[OverTheTop]

As others have said, they need to be quite stiff so as to not suffer from flutter at higher velocities.

You don't see them often in real aircraft as the stiffness requires additional mass and also makes it more difficult to put things like fuel or landing gear on the wings. It is an efficiency trade that is mostly not worth taking.

 

[lakeroadster]

So I’m new to the forum (so that’s why this may be out of place) but not so new to rocketry. And I am getting ready to put some parts on order, but I have a question.
Does anyone know if forward swept fins will work?
I know I’m aviation it’s not very stable and I can’t find anything on it that anyone else has tired to put forward swept fins to the test. OpenRocket says it will be stable with some nose weight. Any opinions and or comments welcome,
Thanks!

My Ahpla is basically an upscaled Alpha with the fins mounted backward. It flew great. It did have considerable nose weight.

 

[Scrapmaster87]

One of my early mid-power scratch builds had a set of 4 forward-swept fins made out of .080"? G-10. It always had beautiful straight flights until it caught bigger-motor disease.

I think it was a G-104 that it got the death wiggle on. 2 adjacent fins blew off spectacularly. They broke off at the body (TTW built) but no other damage. We rebuilt the thing with conventional fins and later converted the body transition to an e-bay for HPR flights. I still have it, it just needs some major surgery on the motor mount, motor retention, e-bay...

 

[Back_at_it]

They work great. I decided I wanted to do something different with some old Alpha III kit parts I had laying around and this is the result. Flies great on B6-4 and C6-7 motors.

 

[gldknght]

Ok, thank you everyone, I really just wanted a second or third, or fifth opinion.
So let’s just hope this thing go up, and not sideways!

Your rocket will fly fine, if, as with any rocket, you make sure your CP/CG relationship is correct. Stiff fins are your friends!

 

[Grog6]

I had an Estes Sentinel model, that I put the fins on backwards, that flew many times, until It was taken hostage by a large rattlesnake; I decided he could keep it, lol.

 

[lakeroadster]

Swing test the rocket... put your mind at ease...

 

[Hobie1dog]

Hyper-X has great reviews with FS fins, helicopter recovery too.

 

[BABAR]

Vast majority of my scratch built rockets use forward swept wings. I am a proud L-0 low power enthusiast, and I am not looking to break Mach and since I am usually in a relatively small field (when I can find one at all), I don’t have any particular high altitude aspirations. So I respect the opinions above, I suspect you are more likely a sport Flyer and those concerns aren’t applicable to the realm in which you probably fly.

forward swept fins are a bad choice if high speed and/or high altitude are your goals. On the other hand, many people (including me) like the look of a forward swept fins, and for sport flying they work nearly as well as rear swept fins, meaning that unless the rocket is borderline stable with rear swept fins, flipping them isn’t going to be a problem. Swing tests and/or open rocket can be helpful if you are concerned, but I think most kits have enough overstability built in that reversing the fins isn’t a problem.

the OTHER more practical reason for forward swept fins is survivability. the venerable Alpha is a great rocket, but most Parachute and streamer recovery rockets are going to come down and impact on the fins, increasing chance of broken fin or popped fin. Forward swept fin rockets tend to impact motor casing first, so the fins are spared the shock of the initial impact.

one other reason for me was that my original four sided helicopter rockets integrated the fins into the rotors. Worked great, but when deployed had A slight resemblance to a WWII symbol of dastardly repute, so I added the forward sweep to quash any comparison.

a DISADVANTAGE is display, you will need some sort of stand, as forward swept models can’t “stand” on their own three (or four) feet!