Two x Estes Epic II, My First Kitbash.

[scadaman29325]

So, I got two Epic IIs for my b-day. I pondered my options and thought "an XL Epic II with two boosters" a not Extra Large, but Extra Long.

Doing a dry fit, I had to lay it on the floor, my rocket table is small.

Length, 2 x12" (bodytubes) + 2x2.75 (sustainer & nosecone) + 2x3.5" (boosters) = 36.5"

Minimum diameter.

Fins, 3 sets of 3 on the aft sections. The slice and dice the remaining set for forward and mid-section sets (?).

I've been reading about techniques from the masters. I want try to document for a RocketReview, but all I can think about is whooping out the CWF, sandpaper and Elmer's and getting started.

(Taking a deep breath, trying to slow down my anxious mind and rapid heartbeat.)

First, take pictures (attached) and assess (go for it). Ask for opinons and help.

What do y'all think? How should I proceed? (I may wait for replies, maybe not.)

Thanks, Phil.

 

[BABAR]

So you are going to have three stages: Booster 1, Booster 2, Sustainer?

Should work, especially with extra length, although you may want to sim it.

What is your strategy for coupling between the first and second booster?

Your full stack mass (all three stages, motors, wadding, chute) should be less than 113 grams.

For first flight (assuming you want a second one!)

Go with B or C on first booster.

Go with B6-0 or A8-0 (if you can find one ) on middle stage

Go with A8-5 (or A8-3 if you can’t get the A8-5) on sustainer

Consider changing color scheme with bright fluorescents at least on the boosters, will make them easier to find.

Hope you get three straight trails and a short walk!

 

[neil_w]

Hope you get three straight trails and a short walk three short walks!

Fixed.

Sounds like a fun project!

 

[BABAR]

Fixed.

Sounds like a fun project!

I still remember the time my Apogee II staged on the rod. Dad’s and my eyes followed the rocket up, not realizing it had staged on the rod. We SAW the sustainer come down. Wondered where the booster fell. Felt pretty silly after looking all around end then finding it ON the pad when we went to load up the launch equipment for the ride home.

 

[scadaman29325]

So you are going to have three stages: Booster 1, Booster 2, Sustainer?

Should work, especially with extra length, although you may want to sim it.

What is your strategy for coupling between the first and second booster?

Your full stack mass (all three stages, motors, wadding, chute) should be less than 113 grams.

For first flight (assuming you want a second one!)

Go with B or C on first booster.

Go with B6-0 or A8-0 (if you can find one ) on middle stage

Go with A8-5 (or A8-3 if you can’t get the A8-5) on sustainer

Consider changing color scheme with bright fluorescents at least on the boosters, will make them easier to find.

Hope you get three straight trails and a short walk!

I'm not into SIM yet.
Strategy? Same as boost to sustainer, just tape them together and shove the MM/Fin Can on.

(Did that pic insert work? We'll see...)
Less than 113 gram. Nice, I haven't got that far yet.
For first flight (assuming you want a second one!) That's a good one right there. Had a belly laugh.
A8-0 and A8-5. I just happen to have those handy for just that reason. I like seeing the entire flight, I got tired of chasing and/or losing rockets.
fluorescent. Oh yes, like red-orange or a flaming pink for my granddaughters/rocket recovery team.

Thanks, Phil.

 

[Nytrunner]

3 stage doesn't usually equal "short walk" but good luck on this project!

 

[K'Tesh]

If I'm not mistaken, that Yellow Tube Coupler is only 1" long. That's not good... Especially if it's the same material as the tube spacers. It's too short. Presuming I'm right, I'd recommend that you replace it with a scrap tube spacer, and cut it to at least 2" long.

From the scan of the facecard you provided, it looks to me that the image is of an actual built kit, and not a computer generated image. Where the short engine mount tube meets the long body tube that makes up the rest of the sustainter, it looks like there's an imperfection in the joint. Also, I noticed that the blue looks to extend to the top of the booster.

 

[BABAR]

I don’t have the kit, but I suspect the kit built stock has a an engine block at the REAR end of the booster, probably a very short one. If you put this in your mid stage booster you will not be able to get the first/lowest booster to fit into the mid booster. I also don’t know if you leave that piece out if it gives you enough overlap to “nest” the lowest booster securely enough into the mid stage booster.

Tell you what, show me a pic like your first one, except use motors instead of couplers, maybe you will see the problem then.

For comparison, here are plans for Estes Farside
https://www.spacemodeling.org/jimz/estes/k-12.pdf
It is NOT a minimum diameter kit, so you could use couplers.

I think the Epic is a minimum diameter kit, so you HAVE to use the motors AS couplers. To do this, your middle stage length must be the same length as the motor (the sustainer motor sticking out the back of the sustainer “nests” in the mid stage booster, the mid stage BOOSTER sticks out the BACK of the mid stage to nest in the first/bottom BOOSTER.

I THINK this is how the MPC Microsonde III did it.
https://www.spacemodeling.org/jimz/mpcr209.htm

I don’t understand the “short” segment of tubing with the EpicII kit, I THINK it is used with a coupler to make the sustainer LONGER and also simultaneously serve as an engine block (I LOVE using one part for two things.). If I am right, it is probably EXACTLY the length you need for the middle stage, I am NOT sure how the fins will fit on it.

Anyway, try repeating into your first pic with three taped motor cases (or I think the yellow tubes are exactly the size of motors, just tape them butt to end to butt to end, as you are trying to do non gap staging, which is the most reliable.) I believe you will find this WON’T work with the regular booster length tube as mid stage, but it WILL work if you use the short tube from one of your kits.

You could then use the extra coupler and booster tube to make a REEEEEEAAAALLLY long sustainer. This will help out your stability as it will move CG further forward, if you can afford the extra weight.

Be warned.....multistage low power rocs tend to weathercock badly due to so much fin area at the base. This, combine with the extra altitude they reach, means it is a really bad idea to launch them when winds are over say 5 mph.

 

[K'Tesh]

@BABAR the kit is minimum diameter. It's a repackaged Estes Sterling Silver (7275), the only changes are the decals and the instructions (the EPIC II's only have English instructions). The body tubes are 12", 2.75", and 3.75". The 3.75" part is the booster, the other two form the sustainer. There is an engine block at the rear of the booster. The "Yellow Tube Coupler" is from my photographic analysis (copying the image, cropping the enclosed ruler, and using it to measure the yellow coupler), I've got a figure of 1". From the scans Phil sent me, the booster's fins are 2.5" at the root, and the sustainer's are 1.75" at the root.

From my sim in progress, that has the coupler protruding inside the short 2.75" portion ~3/4 inch. That leaves only 1/4" for it to form the joint with the main body tube (the sustainer's motor protrudes ~3/4" from the end). That's really pushing things. Personally, building this kit, I'd like at least 3/4" protruding inside each section for strength and alignment reasons.

 

[BABAR]

@BABAR the kit is minimum diameter. The body tubes are 12", 2.75", and 3.75". The 3.75" part is the booster, the other two form the sustainer. There is an engine block at the rear of the booster. The "Yellow Tube Coupler" is from my photographic analysis (copying the image, cropping the enclosed ruler, and using it to measure the yellow coupler), I've got a figure of 1". From the scans Phil sent me, the booster's fins are 2.5" at the root, and the sustainer's are 1.75" at the root.

From my sim in progress, that has the coupler protruding inside the short 2.75" portion ~3/4 inch. That leaves only 1/4" for it to form the joint with the main body tube (the sustainer's motor protrudes ~3/4" from the end). That's really pushing things. Personally, building this kit, I'd like at least 3/4" protruding inside each section for strength and alignment reasons.

Okay. That helps.
My 2 cents.
Options.
Are the two yellow tubes motor mount pushers? They can be used as couplers
Use one to couple the two long tubes for the forward end of your XL sustainer. As a plus, attach your shock cord to this coupler, gives you plenty of room for streamer, a strong fixation point, and with the XL length keeps it way above the ejection charge
Use the second yellow tube as a coupler between a 3.75 inch BOOSTER section and the aft end of the sustainer tubes above, you will need to place it so the AFT end of the coupler leaves the same distance between the butt of the coupler and the butt of the 3.75 section as you WOULD have had with the short coupler and short tube, if I follow your measurements, should be 2.25 inches (so 1/2 inch of motor sticks out the back.)

Use the 2.75 inch white tube for your middle stage booster. With a 2.5 inch root base on the booster fins, that will fit on this just fine. With the engines taped, 1/2 inch of sustainer motor nests in the forward end of this mid stage, and 1/2 inch of this stage’s motor sticks out the back to go into the first/bottom stage.

The first/bottom stage is built stock.

Put lugs on the sustainer and the first/bottom stage booster, no lug on the mid stage.

You can fly this as single stage, two stage, and three stage with this setup.

Will using the longer couplers be a weight problem? Like to keep it under 113 grams including paint, motors, wadding, and streamer.

 

[K'Tesh]

From the info that Phil just gave me, the coupler is not made from the same material as the spacing tube... And it's 1" long.

I would then recommend using a normal CR... Along the lines of the 520 Adapter as the engine block, and the coupler would be half in the upper and half in the lower body tubes.

 

[BEC]

OK - I just found my Sterling Silver kit in the stash (I came home from NARAM-60 with it) and opened it.
There is a standard EB-20B at the aft end of the booster (1/4 inch wide). The yellow coupler is 1 inch long and has a wall thickness greater than the EB-20 - it is NOT the same material as a regular yellow dummy motor tube(s). So it is well suited for the dual purpose of joining the tubes and serving as the sustainer's motor block.

Dry fitting the parts per the instructions (EB-20B in the bottom of the booster tube, two stacked yellow motor spacers, base of sustainer, then the coupler) yields the 1 inch coupler projecting exactly half way out of the bottom of the lower sustainer body tube (1/2 inch). It also fits firmly enough in the tubes that I'd not be concerned that it's "only" half an inch into each tube it's trying to join. This is only BT-20, after all....

If the Epic II is really just a Sterling Silver in different livery then the result should be the same. This arrangement also has the sustainer motor projecting 1/2 an inch from the bottom of the stage. To turn this into a three-stager the new second stage would have to be shortened 3/4 of an inch (and of course the EB-20B left out), making it the same length as a motor, in order to have the second stage motor project similarly into the first stage as it would otherwise do from the second (now third) stage/sustainer and so to do the stage coupler function.

The kit's booster fins would fit on this shorter middle stage, just barely. I would be a little concerned about the actual stability of this in three-stage configuration - something that should be checked with a loaded swing test if not done in OpenRocket or RockSim.

Oh, and Jim, the fins are 1/16, not 3/32 - at least in the Sterling Silver I have to hand. I guess I could go get an Epic II at Hobby Lobby and confirm they are the same (or not).

 

[BABAR]

I would be a little concerned about the actual stability of this in three-stage configuration - something that should be checked with a loaded swing test if not done in OpenRocket or RockSim.

Always a good idea. I think using the second long tube to extend the sustainer length will definitely help stability, but may not be sufficient, so may need a little nose weight. Again, with the longer sustainer, a little nose weight will go a long way due to the longer moment arm.

 

[BEC]

True....that would make a big difference.

 

[scadaman29325]

Hmmm, just got back to this thread. It's going to me minute or maybe a week to decipher what y'all just said, and doing a lot of dry fitting. This may be more work (I mean fun) than I thought.

I've been photoing and weighing and calculating and documenting and making corrections to documentation...

If I was the kind of guy that would string y'all along for this ride, I'd ask about the total weight of the final assembly versus the ability for the motor to make it fly. Like, adding all the parts up that will be used, comes to about 118.4g plus glue, primer and paint... And a c6 is estimated to lift 113g. I'm sure YMMV.

How much does glue, primer and paint weigh on something like this, given that I'll be doing what I've been reading about the various techniques, CWF, sand, repeat, repeat, repeat, prime... paint... and really trying to keep the weight down by not leaving a lot of build up behind?

Here's my confusing notes:
The Epic II consist of:
1 12" bodytube 5.2g
1 2.75" bodytube for sustainer 1.9g
1 3.5" bodytube for booster 2.3g
1 smaller set of 3 fins for sustainer 1/16" 1.9g post sanding
1 larger set of fins 3 for booster 1/16" 3.8g post sanding
1 2.75" nosecone (visible length) 3.7g
1 coupler 1.8g
1 engine block, bluetube, 0.1g really 0.0g but that's not possible
1 30x1-1/8" streamer 1.5g
1 36"x1/8" rubber shock cord 2.5g
1 launch lug 0.1g
Instructions and waterslide decals
24.8g before glue, prime and paint
Built as instucted

Motor, wgt, lift capacity
A8-0 13.3 85
B6-0 16.4 113
C6-0 22.7 113
C6-7 26.9
24.8 plus 49.6
74.4 plus prime and paint

Three stage,
24.8 plus 11.3 in more parts,
46.1 plus 72.3 in more motors,
take off weight 118.4 plus glue, primer and paint...

TTYL

 

[BEC]

If you do this, I hope you have a BIG field and several sets of young eyes to help you track the sustainer. Assuming it's stable it's going to go a long long way. While Estes' altitude estimates are generally optimistic, they are projecting 2600 feet for this guy....so on three stages loaded with Cs it might realistically touch 3000 if it goes straight up. That's going to be a real challenge for recovery. Have fun!

 

[BABAR]

Stack from bottom to top
B6-0. 16.4
A8-0. 13.3
A8-5. 17.6

47.3 grams of motor.

The B6 will probably barely get off the rod before it stages. The A8-0 will come off quick. The XL length on the A8-5 shouldn’t be too high. IF, and it is an IF, you can get it stable AND winds don’t exceed 5 MPH, it is doable, still need a decent field and multiple sets of eyes. Consider getting some marker tape and making a really long streamer, the length won’t slow it down much (streamer length over 10 to 1 doesn’t buy any significant additional drag) but it WILL make it easier to spot.

You load all three with Cs
C6-0 22.7
C6-0 22.7
C6-7 26.9

72.3 grams of motor

and it will probably be unstable (two issues, mainly too much weight in the tail, and the increase in weight means it will be slower getting off the rod.)

if it IS STABLE you will probably recover the first stage, doubtful you will find the mid stage, and the sustainer will probably never be found.

Not sure what the 13mm/18mm plastic motor adapters weigh. They would allow you to fly the mid stage on an A10-0T and the sustainer on an A3-4T. For the MOTORS saves you probably about 15 grams, but the adapters might eat much of that up.

 

[scadaman29325]

NICE! Sounds like I'll be doing this at the ROSCO launch at the sod farm.

 

[BEC]

A couple of considerations in using the 13-18mm adapters. First, using them turns direct staging (motors taped directly together) to gap staging with a 1 inch gap between one motor and the next. I'm not sure where/how one would do the necessary venting to keep the stages from separating prematurely. Which leads to: the external shape of the upper ends of the adapters will make taping the stages together "interesting".



I think this small model, flown B to A to A is going to stage the first time rather higher than just off the rod. A heavier and larger/draggier model (Muli-Roc) stages 70 up or so flown B to A or B to B (per FlightSketch Mini data - look at the little kink in the velocity curve here: https://flightsketch.com/flights/248/) The Multi-Roc is BT-50-based and mine weighs ~65g with no motors.

 

[BABAR]

A couple of considerations in using the 13-18mm adapters. First, using them turns direct staging (motors taped directly together) to gap staging with a 1 inch gap between one motor and the next. I'm not sure where/how one would do the necessary venting to keep the stages from separating prematurely. Which leads to: the external shape of the upper ends of the adapters will make taping the stages together "interesting".

View attachment 397611

I think this small model, flown B to A to A is going to stage the first time rather higher than just off the rod. A heavier and larger/draggier model (Muli-Roc) stages 70 up or so flown B to A or B to B (per FlightSketch Mini data - look at the little kink in the velocity curve here: https://flightsketch.com/flights/248/) The Multi-Roc is BT-50-based and mine weighs ~65g with no motors.

Experience always beats MindSim as well as computer sims. I was surprised at the estimated weight of the Epic XL II + I threes stage version Phil described, hence I figured the B motor’s main thrust would be just overcoming inertia. As said, my Apogee II stages ON the rod, but it was a pay loader with big draggy fins, especially the booster, and I probably overpainted it adding a lot of weight, I think I was 12 or 13.

Sounds like a sod farm launch would be a great place for this rocket, and sounds like B-A-A would give a nice entertaining flight, with decent altitude to see both staging events and good chance of recovery of all parts.

Interesting terminology note as to whether with adapters taped staging is still gap staging since the actual motors don’t touch. I say, “No, but....”. The adapters are going to act like extensions of the body tube, and given the motors are taped, they shouldn’t separate until the next stage lights and forces the stages to separate. So I don’t know if you NEED a vent. I’d say no, the, “but....” part is that I suspect either the forward blow of the mounted motor in the adapter or more likely the jet from the next motor up is gonna melt the plastic adapter. Maybe not, I guess they are designed to handle the ejection flame from regular motors (which I HAVE seen burn through Kevlar shock cords, despite their purported flame resistance.

With black powder gap staging, there is NO tape, in fact you WANT the fit to be snug in yaw and pitch (sustainer shouldn’t wobbly but should be held in perfect axial alignment) but really loose in axial tension, if you have the rocket on the rail and you briskly lift the sustainer it should separate easily. This is WHY you need a vent on gaps, so when the cold air in the space of the gap blown forward by the forward burn through of the zero delay motor propellant doesn’t prematurely separate the sustainer before the flaming hot bright gas gets to the nozzle of the sustainer.

Has anybody tried the adapters on boosters with staged rockets? Do they get barbecued?

The weight/mass savings is not all that great.

From @kuririn

https[URL]https://www.rocketreviews.com/compare-estes-a10t-to-estes-a8.html://www.rocketryforum.com/threads/estes-motor-adapter-weight.155755/#post-1932163[/URL]
“You asked, Estes delivers!
https://estesrockets.com/product/009753-24-mm-to-29-mm-engine-adapter/

Per my digital scale, weights are as follows:
13-18mm: .158 oz./4.48 g.
18-24mm: .230 oz./6.50 g.
24-29mm: .461 oz./13.10 g.“


13 mm A10-3T with adapter comes out at 12.4 grams, compared to 18mm A8-3 at 16.2 grams
(Incidentally, the A10 and the A8 have almost identical thrust profiles, so once you buy the adapter, the A10 is both cheaper and lighter than the A8, so it is a win-win swap)

https://www.rocketreviews.com/compare-estes-a10t-to-estes-a8.html

18 mm C6-3 with adapter comes out to 31.4 grams, compared to D12-3 at 43.1 grams

C6 is a much weaker motor than the D (as opposed to the A10 to A8 comparison above)

https://www.rocketreviews.com/compare-estes-a10t-to-estes-a8.html


Hope you have light winds!

 

[BEC]

I don’t think I’ve used them in multi-stage models....I will have to give it a try. The adapter in the middle of the picture is multiply flown and there is quite a bit of ejection charge residue in the “funnel”—that’s why it looks darker in my quick picture there.

I’ve been flying the the Checkmate (a recent two-stage 13mm motor model:https://estesrockets.com/product/007276-checkmate/) and have used close to two dozen A10-0s now. Recent ones (2018 or 2019 date codes) seem terribly wimpy for no reason that I can currently explain. I need to do some instrumented test flying of old vs. new A10-0Ts before I can say more.

For this Epic II (now Epic III?) I’d be more comfortable with A8-0 if it were me . That its sustaining thrust after the initial spike is about four times as high is a bonus. Graphs screen-shot from nar.org.



For what it’s worth.....

 

[BABAR]

I don’t think I’ve used them in multi-stage models....I will have to give it a try. The adapter in the middle of the picture is multiply flown and there is quite a bit of ejection charge residue in the “funnel”—that’s why it looks darker in my quick picture there.

I’ve been flying the the Checkmate (a recent two-stage 13mm motor model:https://estesrockets.com/product/007276-checkmate/) and have used close to two dozen A10-0s now. Recent ones (2018 or 2019 date codes) seem terribly wimpy for no reason that I can currently explain. I need to do some instrumented test flying of old vs. new A10-0Ts before I can say more.

For this Epic II (now Epic III?) I’d be more comfortable with A8-0 if it were me . That its sustaining thrust after the initial spike is about four times as high is a bonus. Graphs screen-shot from nar.org.

View attachment 397616 View attachment 397617

For what it’s worth.....

Curves look more similar on RocketReviews site. I haven’t a clue which is more accurate.

https://www.rocketreviews.com/compare-estes-a10t-to-estes-a8.html

If yours is correct, I would think the longer burn, (even without thrust) would give the altitude advantage to the A10. But I am not am not competent in OpenRocket or RockSim, and frequently what seems intuitive is incorrect.

 

[BEC]

The curves I posted are from the NAR certification data. The weak thrust of the tail on the A10's burn is great for a small light model, but even on the Checkmate (which is smaller than a stock Epic II/Sterling Silver) you can see it sort of struggle once the initial thrust spike is done. I really wish there was an A3-0T (and that the A3-6T was back).

 

[scadaman29325]

I gotta say, I enjoy watching y'all jaw back and forth about this...

And my paralysis of analysis is getting in the way, I need to start painting CWF and sanding, but I'm trying my best NOT to screw this up by rushing into this, especially since it is a kitbash.

Anyways, here's my latest:
========================
Dry fitting everything.

The Epic II eXtra Long will consist of:

2.75" Nosecone
I may glue the nosecone to BT below
12" Upper bodytube w/launch lug
I may glue the coupler* to upper BT only and slip fit into the lower BT
12" Lower Bodytube
I will glue a coupler* to lower BT and sustainer BT/MM
3.5" Sustainer Bodytube/Motormount (3rd stage)
with engine block* glued at 2.5" from rear
and launch lug
2.75" 2nd stage booster bodytube/motormount not glued,
motors will be taped to 1st stage booster and 3rd stage sustainer
2.75" 1st stage booster bodytube/motormount not glued

Note, Motor length of 2.75" will make it hang out the back of the sustainer by 1/4", Booster motors will go into BT/MM by that same 1/4" and hang out back of BT/MM boosters by 1/4". (Maybe this should be 1/2")

*I'm thinking I may hollow out a spent engines (for thinner walls) to make two couplers and saw a spent engine for a 1/4" engine block for the sustainer to be mounted 2.5" (2.25"?) from bottom of 3.5" BT/MM.

I may use an extra long(48"?)/extra wide (3"?) metallic streamer stuffed into yhe upper BT attached to the 36"x1/8" rubber shockcord and 135# twisted kevlar double looped from engine block and attached to shockcord 1" below top of upper 12" BT.

Smaller set of 3 fins for sustainer (3rd stage)
Larger set of 3 fins for 2nd stage booster
Larger set of 3 fins for 1st stage booster


EXTRA PARTS
1 2.75" nosecone (to be used for shortened version of this rocket when leaving of XL upper BT)
1 smaller set of 3 fins
2 1" couplers
2 engine blocks, bluetube
2 30"x1-1/8" streamers
1 36"x1/8" rubber shock cord

(In the picture below I had setup Qualman's alignment tool with the extra set of small fins, and for 5sec I thought, 4 stages!!! He he he...)

If you would, PLEASE correct language for better terminology and less confusing statements.

Thanks!

BTW, my son is a fireman in the Una community of Spartanburg, SC, a dad could not be prouder knowing he raised a hero!

 

[scadaman29325]

Learning to airfoil and paper fins on this model. Wierd shaped airfoils and lumpy papered fins.

I have a shallow spot in the middle of a fin. How could I manage that? I think that fin slid it's way over the edge of the table while I was sanding...

Will try a glue stick on my next set of papering.

Frustrated.

 

[K'Tesh]

Learning to airfoil and paper fins on this model. Wierd shaped airfoils and lumpy papered fins.

I have a shallow spot in the middle of a fin. How could I manage that? I think that fin slid it's way over the edge of the table while I was sanding...

Will try a glue stick on my next set of papering.

Frustrated.

Another suggestion... Use scrap bits of balsa to practice on... It's a lot less frustrating. The shallow spot was likely caused by finger pressure pushing the material into the grit, where it was abraded away. When the pressure was off, the wood returns to its original position, and you've got a depression.

 

[Mugs914]

When the pressure was off, the wood returns to its original position, and you've got a depression.

...you've got, well, depression.

 

[scadaman29325]

...you've got, well, depression.

I was depressed until I tried glue sticks and top/bottom sanding, which made the process much easier!

 

[Bruiser]

If the balsa is soft you can dent it trying to hold it while sanding. If that's the case, then it's too soft for a rocket fin...

-Bob

 

[Ablative]

I’ve had luck papering fins by putting down a drop of wood glue then spreading it really thin with a plastic razor blade and wiping away the excess glue. Once I lay the paper I smooth out the paper on the fin with another clean plastic razor blade.