Fat n Slow

[Art Upton]

Food for thought-

The Big Daddy’s pretty much a blank canvas, but Aerotech kits aren’t great ones to wrap. The fins are molded with external fillets and tabs that snap into an internal locking mechanism. Any change of airframe diameter would prevent that system from working, and it works well.

On a hard hit, the fins will pop out of the lock for easy repair, if you’ve used CA for assembly as directed. Epoxy construction or additional external fillets can make repair more problematic. I’m betting you’ll like the thought put into that kit.

Correct, if your going to play those upgrade games, it destroys every thing from the motor tube and fin-locks to the body tube design. Also for bigger motors you would need to replace the fiber rings with plywood and shock cord mount to plywood rings, elimination the motor clip and use another method to align the Fin-Locks as the clip serves that purpose. Likely also making it a Head End Deploy [HED] ejection instead of a mid-point separation for ejection recovery for engines with smaller BP charges in them. Folks that did HED ejection have commented that smaller mid-power motors don't have the "oomph" to get every thing out the top.

Lots of engineering was put into the G-Force Kit to make it look good, perform well with Mid-Power Engines and keeping the weight under the required 1500g in a 4" rocket. The box on mine says "Mid-Power Kit" , it was not designed to be a HPR kit. The Mega Initiator is on the other hand with plywood fins.

As you say the AT kits are great as used as they were designed. I'd leave them alone, and I have built several and still have a few new in the box I saved more than a decade ago, including a G-Force.

LOC kits are better suited for such HPR and upgrades.

 

[bill_s]

The Estes E12 and F15 motors combine an unusually good initial thrust spike and about 3 second burn solid right to the end, and can be flown low and slow with their shortest delay versions.

I built a sort of 6" funnel-stabilized rocket that would only make it about 400' on an E12, bigger than a saucer but needed good recovery. Coast was only 2 seconds so it would be pointed straight down at ejection, needing a streamer since it impaled parachutes.

 

[os_tempore]

Food for thought-

The Big Daddy’s pretty much a blank canvas, but Aerotech kits aren’t great ones to wrap. The fins are molded with external fillets and tabs that snap into an internal locking mechanism. Any change of airframe diameter would prevent that system from working, and it works well.

On a hard hit, the fins will pop out of the lock for easy repair, if you’ve used CA for assembly as directed. Epoxy construction or additional external fillets can make repair more problematic. I’m betting you’ll like the thought put into that kit.

That's cool. I wasn't aware of that feature. I'm looking forward to seeing how it all goes together. I do love a well built item! Just like most of my model trains are brass or rivet counters.

I think I'll do a build thread with questions to see what the consensus is.


And I do love me some CF.

 

[os_tempore]

Looks like I messed up while editing the message. Try deleting "If you make a few".

Generally, a fabric weight is for just the fabric, not after adding the epoxy.

Now I'm doubting myself. I honestly don't remember and you may be right. Most of my layups are structural, so not as critical when looking at individual ounces - I usually build for the strength and simply enjoy the weight benifits.

My edit: you're correct, it is the dry wgt per yard. Idk why I was thinking it wasn't, other than distractions in 1,000 ways.

 

[Art Upton]

Now I'm doubting myself. I honestly don't remember and you may be right. Most of my layups are structural, so not as critical when looking at individual ounces - I usually build for the strength and simply enjoy the weight benifits.

I edited my post, please re-read it. The pics of screws into the rocket are coming in a few mins.

 

[Art Upton]

Here is the payload bay of my LOC Caliber ISP. This is an Electronics Bay but for your situation think of it just as the coupler. You can see the small screw in the coupler and the nose cone shoulder. Make sure nothing will get damages and send/drill a pilot hole into the body tube with the Coupler and Nose Cone already pushed into it.

Then tap the screw into it. This 3" rocket only has one screw for each on one side. My larger rockets have two. I did three on my 7.5" diameter L3 Cert rocket. Later 7" rockets I only used 2, but as the rocket size goes up , I use a larger sized screw.

As you can see, it is pretty simple, not rocket science. That big screw in the white band is a Switch for the Altimeter. They call that White band a "Switch Band". This rocket last flew on a 54mm I motor to ~4900 feet. [I don't want to mess with down loading the altimeter again today, already worn out from getting some rockets out of my storage building as I am still recovering]

 

[os_tempore]

The Estes E12 and F15 motors combine an unusually good initial thrust spike and about 3 second burn solid right to the end, and can be flown low and slow with their shortest delay versions.

I built a sort of 6" funnel-stabilized rocket that would only make it about 400' on an E12, bigger than a saucer but needed good recovery. Coast was only 2 seconds so it would be pointed straight down at ejection, needing a streamer since it impaled parachutes.

Speaking of which, I just got a super big Bertha, a bunch of D12-3 motors for it and a pair of F15-6's.

 

[T-Rex]

You might also want to consider something from Art Applewhite.

https://www.artapplewhite.com/free/index.html

Lots of saucers, pyramids, etc. Motors from Micro Maxx to 54mm. Big, slow, and smoky.

 

[os_tempore]

You might also want to consider something from Art Applewhite.

https://www.artapplewhite.com/free/index.html

Lots of saucers, pyramids, etc. Motors from Micro Maxx to 54mm. Big, slow, and smoky.

This is pretty neat. Very atypical looking stuff on there.

 

[BABAR]

Saucers are an excellent suggestion, and can easily be made from throw away pie tins to cheap dollar store items.

https://www.rocketryforum.com/threads/halloween-flying-saucer-model-for-little-over-a-dollar.70788/

https://www.rocketryforum.com/threa...bomb-and-late-st-patrick’s-day-saucer.167674/

https://www.rocketryforum.com/threads/eses-birdie-build.43130/
This is a kit but can easily be cloned

Apogee also makes the Slo Mo, a bit pricey at $32 plus shipping for my taste but then it does have precut angled fin slots so maybe justified. @jqavins reported it was a nice show rocket.

 

[jqavins]

Indeed it is. There is one deficiency in the kit which led to many repairs of detached fins. Since it's long and skinny I won't burden this fat-n-slow thread, but PM me if you'd like to know.

 

[BABAR]

Indeed it is. There is one deficiency in the kit which led to many repairs of detached fins. Since it's long and skinny I won't burden this fat-n-slow thread, but PM me if you'd like to know.

Reversing the fins would probably help. May need a touch of nose weight.

Outside the box (it at least tube) solution would be……chopsticks.

One each side, pointed down. These would hit first, may break (easily replaced or repaired) and save the fins. Wood dowels would work, but don’t sound as cool and you can’t get them free with chow mein.

 

[lakeroadster]

Reversing the fins would probably help. May need a touch of nose weight.

Outside the box (it at least tube) solution would be……chopsticks.

One each side, pointed down. These would hit first, may break (easily replaced or repaired) and save the fins. Wood dowels would work, but don’t sound as cool and you can’t get them free with chow mein.

Rear Eject solves fin breakage issues.​

​

 

[jqavins]

Reversing the fins would probably help. May need a touch of nose weight.

Outside the box (it at least tube) solution would be……chopsticks.

One each side, pointed down. These would hit first, may break (easily replaced or repaired) and save the fins. Wood dowels would work, but don’t sound as cool and you can’t get them free with chow mein.

My problem with the kit is not a problem with the design. The fins hit first, but they're plywood and use TTW attachment, so they can take it. Or, they would be able to take it if they were implemented right.

The problem (here I go, after stating that I wouldn't) is that the root edge of the tab is straight. Imagine the fin goes all the way through the tube, and consider the shape of it's intersection with the tube, i.e. the actual root edge when things are made real. For normal fins, the intersection is a straight line. But when when the fin is canted, that intersection is concave, specifically a little bit of an ellipse. But the laser cut part in the kit is straight. When you insert the fin through the body tube and the tab reaches the MMT, it rocks rather than seating firmly. You glue it down the best you can, then it's difficult to apply good fillets, and fillets are not as effective as one would hope when there's a sizable gap in the surface attachment. The contact with the body tube along the rest of the root has the same problem. So, lots of detached fins. In that rocket's final, fatal lawn dart, all three fins popped off at once even though they didn't hit the ground. OK, they hit the ground, but only after detaching.

If you plan to build a Slo-Mo, I recommend wrapping some sand paper around around a coupler (so the business surface of the paper is at about the OD of the MMT) then, holding the root edge of the tab as close as you can manage to the cant angle, and sanding in that elliptical concavity. It may not be practical to shape the remainder of the root edge, so I hope doing it for the tab is sufficient.

 

[Azamiryou]

The problem (here I go, after stating that I wouldn't) is that the root edge of the tab is straight.

A secondary problem is that the body tube in the fin area is weakened by big cutouts between the fins. A cleanly popped off fin is easy to fix. But if it takes pieces of tube with it, it gets a lot trickier — especially where the tube has lots of cutouts and there's a centering ring blocking you from sliding in a coupler for extra support.

Mine has flown many times and I've reattached the fins many times. Making a new, bigger chute helped a lot. But on its last flight the chute didn't open and all three fins popped. This time, I think the tube area may be beyond repair.

When I replace it, I think I'll reinforce this area during construction (and use a bigger chute).

 

[jqavins]

Yes, that certainly makes the repairs tricky. Yet I think those tricky repairs wouldn't be needed if the tab root edge were properly curved. After a while, I decided that refinishing wasn't worthwhile, so I gave the whole rocket an ugly paint job to compliment the ugly repairs.

 

[BABAR]

Rear Eject solves fin breakage issues.​

View attachment 640170​

Rear eject is great for fat rockets, it is a PITB to load a chute or streamer in long narrow rockets like BT5 in BT20 or BT20 in BT50. At least in my experience.

 

[BABAR]

My problem with the kit is not a problem with the design. The fins hit first, but they're plywood and use TTW attachment, so they can take it. Or, they would be able to take it if they were implemented right.

The problem (here I go, after stating that I wouldn't) is that the root edge of the tab is straight. Imagine the fin goes all the way through the tube, and consider the shape of it's intersection with the tube, i.e. the actual root edge when things are made real. For normal fins, the intersection is a straight line. But when when the fin is canted, that intersection is concave, specifically a little bit of an ellipse. But the laser cut part in the kit is straight. When you insert the fin through the body tube and the tab reaches the MMT, it rocks rather than seating firmly. You glue it down the best you can, then it's difficult to apply good fillets, and fillets are not as effective as one would hope when there's a sizable gap in the surface attachment. The contact with the body tube along the rest of the root has the same problem. So, lots of detached fins. In that rocket's final, fatal lawn dart, all three fins popped off at once even though they didn't hit the ground. OK, they hit the ground, but only after detaching.

If you plan to build a Slo-Mo, I recommend wrapping some sand paper around around a coupler (so the business surface of the paper is at about the OD of the MMT) then, holding the root edge of the tab as close as you can manage to the cant angle, and sanding in that elliptical concavity. It may not be practical to shape the remainder of the root edge, so I hope doing it for the tab is sufficient.

Some @Dotini magic might be the ticket.

I call them cheaters* or balsa fillets.




*cheaters: term I use when one is placed BEFORE the fin is attached (using non-thru-the-wall technique .) It is placed along the fin marker line with double glue technique. Because it is so light it attaches easily, and a couple rubber bands keep it from warping. Assuming you line THIS up right, it guarantees the fins will be straight (thus it “cheats) and usually makes for a faster and stronger bond.

 

[jqavins]

Good solution. Placing cheaters on the MMT for the tabs would be, um, interesting. But they might not be important with balsa fillets applied externally. One should still sand the curve into the tab root edge, just to get it positioned right.

 

[lakeroadster]

Rear eject is great for fat rockets, it is a PITB to load a chute or streamer in long narrow rockets like BT5 in BT20 or BT20 in BT50. At least in my experience.

But... this is the "Fat n Slow" thread. ​

 

[BABAR]

Good solution. Placing cheaters on the MMT for the tabs would be, um, interesting. But they might not be important with balsa fillets applied externally. One should still sand the curve into the tab root edge, just to get it positioned right.

I’ve only done one thru the wall rocket, my Interceptor E. The only “easy” way this would work would be for pre-built motor mount/fin attachment with slots that extend all the way to the rear end of the body tube. Never done that, I understand that significantly weakens the construction, plus you’d have to get the fins on the motor tube EXACTLY right to fit into precut body tube slots.

 

[Art Upton]

I’ve only done one thru the wall rocket, my Interceptor E. The only “easy” way this would work would be for pre-built motor mount/fin attachment with slots that extend all the way to the rear end of the body tube. Never done that, I understand that significantly weakens the construction, plus you’d have to get the fins on the motor tube EXACTLY right to fit into precut body tube slots.

I build most all my rockets that way, even a BT60 Estes. LOC now recommends it on many of their kits also.

 

[BABAR]

I build most all my rockets that way, even a BT60 Estes. LOC now recommends it on many of their kits also.

If you made balsa fillets/planks, that width-wise ran from outer wall of motor mount to inner wall of body tube, you would add surface area on the outer edge to glue the body tube.

A mild challenge would be to cut the long strips transverse to the grain. Makes it very fragile to work with initially but far stronger when glued in place.

I would think this would be solid as a rock.

 

[lakeroadster]

Rear eject is great for fat rockets, it is a PITB to load a chute or streamer in long narrow rockets like BT5 in BT20 or BT20 in BT50. At least in my experience.

The Estes "Skydart" was/is a BT-20 glider that utilizes a "rear ejection Power Pod". Eazy Peazy.​

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