most powerful engine flown on a rocket w/o thru the wall fins?

[smokenfire]

I was wondering what is the most powerful Motor flown on a rocket with out thru the wall fins I was debating flying a 3" 1.5lb rocket on an f67
ideas?

thanks! toby

 

[Steve Shannon]

The most powerful certified motor flown on a rocket without through the wall fins was an O.
Through the wall construction is strong but surface mount fins can be also.

 

[jsdemar]

A 'P' staged to an 'N' with surface mount fins on both airframes. Mach 3.5, 85Kft. Robert DeHate, 2011. P motor was made by me.
https://photos.app.goo.gl/d41LVaZNcJvFw0Aa2

 

[Andrew_ASC]

What about the CSXT team research S motor? I believe those fins bolted on but I could be wrong.

 

[Theory]

Through the wall construction is strong but surface mount fins can be also.

^^^ this ^^^

Rocketry, like many other things in life is 95% execution

 

[Bat-mite]

The key is to have the fins securely mounted. They can be bolted on, or you can apply a layer of fiberglass or carbon fiber to the entire fin can.

TTW fins are great when you just want to use epoxy with fillets.

 

[Andrew_ASC]

Also if your using epoxies and are not going through the wall make sure the surface prep sanding is adequate on the body tube and fin area that touches body tube. Recently saw an large diameter subsonic L3 rocket disintegrate on a M motor due to improper build tactics. Usually 60-220 grit the fins a quarter inch up from root then do the edge that touches the body tube. And sand BT where fin and epoxy touches. Nice fillets help. That’ll handle Mach plus flights on most motors in hobby with correct thermally rated epoxy. Though my experience is limited to I class motors. I’ve never had a fin fall off yet without through the wall construction using anything from rocketpoxy to cotronics for HPR fiberglass and carbon fiber builds.

Jim Jarvis has some excellent build tutorials for pushing the limits and Tip to tip wraps. I personally haven’t found a need to tip to tip wrap with flights under Mach 2.

 

[jsdemar]

What about the CSXT team research S motor? I believe those fins bolted on but I could be wrong.

There was no airframe over the motor. Bolted to the motor is not surface mount on an airframe.

 

[kyle]

Dude just do good surface prep and good fillets. You'll be fine on an F67 as long as you take time to do it right.

What's the phrase? Oh yeah, "If you don't have time to do it right, you must have time to do it twice."

 

[blackjack2564]

Largest one I worked on was the Mega Darkstar 12in airframe with a 10in P-motor. Surface mounted fins Motor was bell shaped preventing using a MM tube.
Fins were foam core with 3layers of 5oz carbon over them and entire fincan.


It will fly again 2-staged at LDRS this Sept.

 

[JimJarvis50]

For rockets that aren't "S" motors, like what the OP is asking about, I would say that a factor to consider is the strength of the tube the fins are being connected to. The tube staying round is what allows surface mounted fins to work.

For carbon, surface-mounted fins in non MD rockets are fine up to 6" or so. In my opinion, it is counterproductive to cut up a nice carbon tube, and lose that strength, just to install TTW fins.

For fiberglass, the threshold might be lower, and for cardboard, lower still. Doubling up the air frame is something that can be done to help keep the tube round, and there might still be a net weight savings.

Jim

 

[Nytrunner]

Although the blanket "most powerful motor without ttw fins" question has been answered....... I think the answers have been far outside the range of relevance for the OP.

3" rocket with an F67?

Sand the surface, (maybe remove the thin outer layer of paper first), make sure your fins are lined up straight (guides from payloadbay.com help), neat healthy fillets of epoxy or yellow (wood) glue for cardbard and wood

 

[RainierWolfcastle]

I’ve flown a 3” LOC Onyx several times on F-H motors. Only time it’s ever had anything break was when it accidentally got sat on, oh and the nose cone shock cord mount of course. Epoxied the fin back on and it’s back in action. Just used decent epoxy with microspheres for some light weight fillets. Just make sure you have a good surface for the glue you use to stick to, it will be fine.

 

[Rob702Martinez]

A 'P' staged to an 'N' with surface mount fins on both airframes. Mach 3.5, 85Kft. Robert DeHate, 2011. P motor was made by me.
https://photos.app.goo.gl/d41LVaZNcJvFw0Aa2

Your rocket has been my office computer background. Amazing!

 

[smokenfire]

thanks for all your help!

 

[PhlAsh]

I fly "Twice as Mean Machine" on I motors without TTW Fins

 

[beeblebrox]

Two stage K Rocket flown at Black Rock II. Minimum Diameter K300 Blue Thunder 1800ns Booster, Upper stage K250 White Lightning 2560ns. The Hawaiian Punch. Booster was Fiberglass fins and body tube, upper stage was stock Laser LOC paper tube, plywood fins. Mach 1.6 at burnout of second stage. tracked at 17,500' Theoretical burnout altitude was 17,250' Apogee was missed by one tracker but theoretical peak altitude was 42,000' Seven miles with a paper rocket! Staging was accomplished with a pressure switch that was mounted in the booster head end. At ignition, upper stage igniter was shorted to a 1000µf Capacitor. Pressure switch was designed to close at 50-60psi. connected to combustion chamber with a piston in it. This charged the cap from a 9v battery. At booster burnout the switched closed shorting the charged cap to the e-match in the upper stage.

 

[TonyL]

So you didn't specify 'successfully'...Stephen Forbes' Pike flew at BALLS in 2017 on a 6" Q, I believe it had surface mount fins [G10 on G10]. One can debate whether it was airframe buckling or fin loss that was the ultimate issue shortly after burn out [my motor worked fine].

I would think there is no particular inherent limit, one just has to design for the flight loads.

br/

Tony

 

[gldknght]

I have a Mariah 54 minimum diameter rocket ready to fly on an I 150, but the rocket can take much bigger motors. Pin holes were drilled in the body tube where the fins mount to allow the epoxy to penetrate and fiberglass strips were used in the fin root fillets. The body tube and about 3/4 inch of the fins were thoroughly roughed up so the epoxy had a good grip.

 

[Binder Design]

Most thrust or most total impulse?