Now hear me out.....

[StreuB1]

Finishing up the fin fillets on an upscale 4" FG Big Daddy and Fat Boy (both with 54mm MMT's)

And it hit me.....





BTW....ignore the CF plate fins, it's a long story.

 

[Sparkyflyer14]

Yes.

 

[Hobie1dog]

More fins

 

[Sandy H.]

StreuB1 : The upper fins have 4, not just 3 like the lower.

Marty DiBergi : Oh, I see. And most rockets only use 3 fins?

StreuB1 : Exactly.

Marty DiBergi : Does that mean it is any more stable?

StreuB1 : Well, it's one more, isn't it? It's not 3. You see, most blokes, you know, will be flying with 3. You're on 3 here, all the way up, all the way up, all the way up, you're on 3 on your fins. Where can you go from there? Where?

Marty DiBergi : I don't know.

StreuB1 : Nowhere. Exactly. What we do is, if we need that extra stability, you know what we do?

Marty DiBergi : Add a 4th fin?

StreuB1 : 4. Exactly. One more.

Marty DiBergi : Why don't you just make 3 fins a little bigger and optimize both the both the bottom and the top stage?

StreuB1 : [pause] But this one has 4.
___

For youngsters, search for 'it goes to 11' on youtube or similar if you have no clue what that's from (Movie: This is Spinal Tap, not other music stuff that might pop up).

I like the idea. Do it!!!

 

[watheyak]

If you don't do it I'm gonna.

I still might even if you do.



We are talking two stage, right?

 

[smstachwick]

StreuB1 : The upper fins have 4, not just 3 like the lower.

Marty DiBergi : Oh, I see. And most rockets only use 3 fins?

StreuB1 : Exactly.

Marty DiBergi : Does that mean it is any more stable?

StreuB1 : Well, it's one more, isn't it? It's not 3. You see, most blokes, you know, will be flying with 3. You're on 3 here, all the way up, all the way up, all the way up, you're on 3 on your fins. Where can you go from there? Where?

Marty DiBergi : I don't know.

StreuB1 : Nowhere. Exactly. What we do is, if we need that extra stability, you know what we do?

Marty DiBergi : Add a 4th fin?

StreuB1 : 4. Exactly. One more.

Marty DiBergi : Why don't you just make 3 fins a little bigger and optimize both the both the bottom and the top stage?

StreuB1 : [pause] But this one has 4.
___

For youngsters, search for 'it goes to 11' on youtube or similar if you have no clue what that's from (Movie: This is Spinal Tap, not other music stuff that might pop up).

I like the idea. Do it!!!

A smart engineer would say “give me $100 and I can design you one with 5”

 

[tsmith1315]

And this would be a Fat Daddy?

 

[techrat]

And this would be a Fat Daddy?

That's exactly what I was thinking!!

 

[techrat]

Stupid question though: Doesn't the lower stage require MORE fin area to be stable, or does it not matter?

 

[cls]

Stupid question though: Doesn't the lower stage require MORE fin area to be stable, or does it not matter?

Not a dumb question. Intuitively, yeah. Actually, not always.

Think of the Talon rocket, with the large fins forward and little fins in back. The Cp of the large fins are at the Cg of the entire model, so they really have no effect. the aft fins do the steering because they have a long lever arm.

In reality, Talons of all scales benefit from some nose weight. Because I don't like flying nose weight I usually made the aft fins a little bigger...