Odd Shaped Fins

[mccoy300]

My wife wanted to build a rocket with a star theme. I simmed this design in Rocksim, and it shows to be stable, but there was a note that said fins with cutouts may not sim correctly. Anyone with experience know what to expect?

 

[RocketFeller]

I would predict a stellar performance!

 

[neil_w]

I would predict a stellar performance!

You just won this thread.

Anyway, it looks stable from here. Those fins are not that crazy, surprised Rocksim is even complaining.

Neat looking rocket. I hope those aft points are reinforced for landing somehow.

 

[mccoy300]

You just won this thread.

Anyway, it looks stable from here. Those fins are not that crazy, surprised Rocksim is even complaining.

Neat looking rocket. I hope those aft points are reinforced for landing somehow.

That was the dad joke of the century. you just wont the internet... Fins are 1/8th ply, i should think it is sturdy enough. going to put this one up on the apogee medalist motors and see what happens.

 

[milehigh]

Cool looking rocket!

 

[dr wogz]

yes, stellar indeed!!

you stand a good chance of 'sticking' your landings!

 

[afadeev]

Fins are 1/8th ply, i should think it is sturdy enough. going to put this one up on the apogee medalist motors and see what happens.

FYI - over time, I broke all pointy-ended 1/8th ply fins I ever glued to my rockets.
A few during landings, most during transportation.

YMMV,
a

P.S.: If it has a pointy end, it better be made of, or reinforced with, fiberglass.

 

[mccoy300]

Appreciate the input. As they break I suppose best coa would be to sand to bare wood, fiberglass then refinish?

 

[LW Bercini]

The fins on my Starlight upscale are 1/4 balsa. To reinforce the points, I replaced the bottom 4" of leading edge with 1/4" dowel. Then I laminated 1/16" onto the trailing edges of the fins (which were left square). Those bad boys cut into the dirt like a machete, but they haven't broken.

 

[K'Tesh]

The popularity of this thread is going to be meteoric.

 

[qquake2k]

Very cool design! But I'd be surprised if you didn't break a tip here and there.

 

[Eric]

I think that looks amazing... Those fins will do fine. Pointy fins are awesome...

Sent from my VS988 using Tapatalk

 

[adrian]

The popularity of this thread is going to be meteoric.

Which direction do meteors generally travel? (Hint: not up. )

As for the rocket, pointy fins have been done before. As an example, the Fliskits Adfecta. So there's nothing inherently wrong with the design. Using plywood for the fins is a good idea - a wood with a single grain direction, such as balsa, would make the side points very weak. Maybe use a parachute one size up from what you'd normally use for a rocket that size and weight.

There's usually a rule about not trying to catch a rocket while it's on the way down. Definitely follow that rule with this one!

 

[OverTheTop]

Nice looking rocket! Don't forget to use some extra chute area to be gentle on the pointy bits

 

[mccoy300]

I did go with a 24 inch chute just in case. And yea I only really ever try to catch a rocket if it is headed for the drink. I think we have all had that moment. Rocket recovery via pool skimmer sucks.

 

[K'Tesh]

Which direction do meteors generally travel? (Hint: not up. )

You've never heard of a meteoric rise in popularity?

 

[neil_w]

You've never heard of a meteoric rise in popularity?

Now that you mention it, that is a weird, almost oxymoronic expression.

 

[Bat-mite]

Now that you mention it, that is a weird, almost oxymoronic expression.

Well, what comes down must have gone up ... at some point.

 

[K'Tesh]

Sorry to the OP for the tangent this has undergone...

 

[dr wogz]

Sorry to the OP for the tangent this has undergone...

Wouldn't 'irregular orbit' be more apropos?

 

[mccoy300]

Sorry to the OP for the tangent this has undergone...

Some people pay for entertainment like this.

 

[Daddyisabar]

Better to have oddly shaped fins than no fins at all. Your star fins will be just fine!

 

[afadeev]

Appreciate the input. As they break I suppose best coa would be to sand to bare wood, fiberglass then refinish?

The only successful path to repairing broken ply fins is fiber-glassing over them.

I did try sanding and re-epoxying the break line, but it becomes a permanent week point and breaks at the spot of the repair.
I also tried cutting the fin off completely, making a new fin slot, and epoxying another fin right next to the broken one (I inner-fillet my HP rockets, so the root of the fin wont come out). That worked better, but produced an unbalanced booster, which was also not great.

Good luck with yours!

a

 

[mccoy300]

The only successful path to repairing broken ply fins is fiber-glassing over them.

I did try sanding and re-epoxying the break line, but it becomes a permanent week point and breaks at the spot of the repair.
I also tried cutting the fin off completely, making a new fin slot, and epoxying another fin right next to the broken one (I inner-fillet my HP rockets, so the root of the fin wont come out). That worked better, but produced an unbalanced booster, which was also not great.

Good luck with yours!

a

Heaven help an unbalanced booster. I can definitely relate to that.