Estes Saturn V #2157 buld thread

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bobbyg23

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I found a 6' launch rod today. That will help also.
20200623_221018.jpg
 

dtidmore

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True. I will put the stock fins over the boyce ones and get some different engines. Probably E30-4
A few years ago I started a very ambitious modded Estes #2001 SV. Health issues put it on the shelf and I am only now getting back to finishing that build. I am also planning on building the #1969 SV which is still in the box and will likely get its share of mods as well.

I used the Sirius Rocket's Moldin' Oldie fairing/fins on the #2001 and they are oversized (same as the #1969 fins). I have the Boyce version on hand for the #1969 and was considering how to use the excellent injection molded fins from the #1969 kit as flight fin extensions, but had not really tackled the mechanics of an adequate mechanical attachment.

MANY years ago I build the Estes K36 SV (the original Estes SV) which had clear plastic flight fins that were basically just 2 pieces of plastic material glued together at the edges and then friction-held to the balsa wood show scale show fins for flight. (FYI, those flight fins are WAY larger than even the current oversized #1969 fins). Attached is a drawing from the K36 kit showing the relative sizes. I know part of the reason for the much larger flight fins was the facts that the K36 was only marginally powered and off the rail speeds were a bit on the low side, so the larger fins provided both better longitudinal control, they moved the CP rearwards even more which helped with the fact that the K3 could fly with a 3, C6-3 engines in a cluster (ie pulling the CG rearwards).

What was your plan of attack on securing the larger fins to the show fins.
Screen Shot 2020-06-25 at 7.44.13 AM.png

david
 

jrap330

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I wish I would have known that before. Here is the size difference. I will add the stock ones over the boyce ones.
Big difference almost 150%...I wonder if my 30th anniversary edition kit fins are that big. What made you decide and try Boyce?
 

bobbyg23

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Big difference almost 150%...I wonder if my 30th anniversary edition kit fins are that big. What made you decide and try Boyce?
The detail on them and the ease of installation.
 

bobbyg23

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A few years ago I started a very ambitious modded Estes #2001 SV. Health issues put it on the shelf and I am only now getting back to finishing that build. I am also planning on building the #1969 SV which is still in the box and will likely get its share of mods as well.

I used the Sirius Rocket's Moldin' Oldie fairing/fins on the #2001 and they are oversized (same as the #1969 fins). I have the Boyce version on hand for the #1969 and was considering how to use the excellent injection molded fins from the #1969 kit as flight fin extensions, but had not really tackled the mechanics of an adequate mechanical attachment.

MANY years ago I build the Estes K36 SV (the original Estes SV) which had clear plastic flight fins that were basically just 2 pieces of plastic material glued together at the edges and then friction-held to the balsa wood show scale show fins for flight. (FYI, those flight fins are WAY larger than even the current oversized #1969 fins). Attached is a drawing from the K36 kit showing the relative sizes. I know part of the reason for the much larger flight fins was the facts that the K36 was only marginally powered and off the rail speeds were a bit on the low side, so the larger fins provided both better longitudinal control, they moved the CP rearwards even more which helped with the fact that the K3 could fly with a 3, C6-3 engines in a cluster (ie pulling the CG rearwards).

What was your plan of attack on securing the larger fins to the show fins.
View attachment 421823
david
I assembled them and they slip right over the boyce ones so I just used welders to hold them on. Here they are installed.
20200620_205507.jpg
 

mbeels

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Looking really good, where did you find a rod that long?
 

Spitfire222

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Good luck on the next flights, I hope they turn out better than the first. This thread has been invaluable as I am currently struggling with motor selection for a slightly overweight Big Daddy. It was very helpful to see how an E12 actually performs on a 17oz rocket. With mine being in the 9-10oz range, I'm cautiously optimistic that the E12 will work ok, though I might just go straight to an E30. Back to OR for more simulations....
 

dtidmore

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I assembled them and they slip right over the boyce ones so I just used welders to hold them on. Here they are installed.
Ah, so you decided to loose the ability to have the detailed, scale sized fins for show. I really want to maintain the scaled fins for show. I had already determined that the #1969 fins would slip over the Boyce fins very nicely and I suspect that with paint on the boyce fins, the fit might be sufficiently fiction tight for flight, however, in looking at the #1969 fins over the Boyce, I realized that there is just enough room at the bottom interior to epoxy a very small all-thread section that would slot into a small hole drilled right at the base of the boyce fin (ie inconspicuous otherwise) allowing me to use a nut on the inside of the fairing to better secure the fin and it would also actually improve the fit of the extension.

I am curious, what did simulations indicate as the stability and off the rail speed on your original build. While I did build in an internal launch tube, I will likely never use it opting for a rail. I shoot for off the rail speeds of at least 40KPH. Without going into all the mods, the smallest single engine that I plan to use is an AeroTech F25.

david
 

bobbyg23

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Ah, so you decided to loose the ability to have the detailed, scale sized fins for show. I really want to maintain the scaled fins for show. I had already determined that the #1969 fins would slip over the Boyce fins very nicely and I suspect that with paint on the boyce fins, the fit might be sufficiently fiction tight for flight, however, in looking at the #1969 fins over the Boyce, I realized that there is just enough room at the bottom interior to epoxy a very small all-thread section that would slot into a small hole drilled right at the base of the boyce fin (ie inconspicuous otherwise) allowing me to use a nut on the inside of the fairing to better secure the fin and it would also actually improve the fit of the extension.

I am curious, what did simulations indicate as the stability and off the rail speed on your original build. While I did build in an internal launch tube, I will likely never use it opting for a rail. I shoot for off the rail speeds of at least 40KPH. Without going into all the mods, the smallest single engine that I plan to use is an AeroTech F25.

david
I have some aerotech e30's on the way. I believe with the boyce fins off the rod speed with a 3ft rod was some where in the 35mph range.
 

bobbyg23

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Good luck on the next flights, I hope they turn out better than the first. This thread has been invaluable as I am currently struggling with motor selection for a slightly overweight Big Daddy. It was very helpful to see how an E12 actually performs on a 17oz rocket. With mine being in the 9-10oz range, I'm cautiously optimistic that the E12 will work ok, though I might just go straight to an E30. Back to OR for more simulations....
E12 will be just fine on a big daddy. I had many factors that added up to my failure. Fin size, rid length, weight and motor selection. I have to say that I have learned a lot from this rocket.
 

Spitfire222

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E12 will be just fine on a big daddy. I had many factors that added up to my failure. Fin size, rid length, weight and motor selection. I have to say that I have learned a lot from this rocket.
I hope you're right, and I'm learning more and more about the intricacies of motor selection beyond the basic letters and numbers. I just hope that I can learn from your misfortune here instead of learning from my own when I launch my BD. It's really disheartening to lose/damage a rocket that one puts a lot of time and effort into. Again, good luck, and please be sure to post your future results!
 

dtidmore

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I had many factors that added up to my failure. Fin size, rid length, weight and motor selection. I have to say that I have learned a lot from this rocket.
As the CP is independent of weight/engine/rail length, I thought it would be interesting to compare things.

My build, in basic flight config, has a CG at 23.15" from the tip of the apollo escape tower. As the externals of my build measure identical to the Estes, the CP will be the same as your build.

I ran simulations using the stock Boyce fairing/fins vs the #1969 fins over the Boyce fins.

Using the Boyce fairing/fins plugged into a simulation, the CP moved forward almost 4 inches, dropping the stability to .831 caliber. A .831 caliber stability might work under ideal wind conditions. Put in a bit of wind and such a flight would likely behave exactly as you experienced. A more powerful engine MIGHT have given you a bit more altitude in which to recover, but then it might not.

I then simulated the extended fin on the Boyce fairing/fin
IMG_5240.JPG

Stability is now 1.74 caliber (CP moved aft almost 4 inches compared to stock Boyce) and such a flight would have a much better chance of success.

Assuming you did achieve a 35MPH (56.3KPH) which is plenty fast off the rail, I would say that the smaller Boyce fins were most likely the major contributor of the lawn dart experienced due to the below minimum stability (ie at least 1 caliber). Your previous successful flights had teetered on the edge without exposing the danger.

The fins on the versions post the K36 Estes SV, ditched the scale show fins with extended flight fins and simply made the fins larger than scale to simplify the build and flying the rocket. I had not really consider the fins since I was building using the newer fin size all along. FYI, Sirius Rocket's Moldin' Oldie fairing/fins have extended fins.

david
 

bobbyg23

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As the CP is independent of weight/engine/rail length, I thought it would be interesting to compare things.

My build, in basic flight config, has a CG at 23.15" from the tip of the apollo escape tower. As the externals of my build measure identical to the Estes, the CP will be the same as your build.

I ran simulations using the stock Boyce fairing/fins vs the #1969 fins over the Boyce fins.

Using the Boyce fairing/fins plugged into a simulation, the CP moved forward almost 4 inches, dropping the stability to .831 caliber. A .831 caliber stability might work under ideal wind conditions. Put in a bit of wind and such a flight would likely behave exactly as you experienced. A more powerful engine MIGHT have given you a bit more altitude in which to recover, but then it might not.

I then simulated the extended fin on the Boyce fairing/finView attachment 421854
Stability is now 1.74 caliber (CP moved aft almost 4 inches compared to stock Boyce) and such a flight would have a much better chance of success.

Assuming you did achieve a 35MPH (56.3KPH) which is plenty fast off the rail, I would say that the smaller Boyce fins were most likely the major contributor of the lawn dart experienced due to the below minimum stability (ie at least 1 caliber). Your previous successful flights had teetered on the edge without exposing the danger.

The fins on the versions post the K36 Estes SV, ditched the scale show fins with extended flight fins and simply made the fins larger than scale to simplify the build and flying the rocket. I had not really consider the fins since I was building using the newer fin size all along. FYI, Sirius Rocket's Moldin' Oldie fairing/fins have extended fins.

david
I agree that the instability of the smaller fins was a major factor in my outcome. I really want to try it with the same engine to see what happens with the larger fins, but don't think I have the courage to do it.
 

Kevin O'Dell

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I've about decided the vacu-formed plastic wraps.....SUCK! I miss the paper ones from the original and Version 2.....
 

jrap330

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You have a farm..... good but at your other launch site...consider taking both pieces down on one parachute....maybe a 30"?
 
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