# 3 estes bt-80 tubes on a 24mm tri cluster

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#### neil_w

##### Good at some things
TRF Supporter
Other than Belleville, the pure cheapest sources for Estes stuff are (a) Hobby Lobby with 40% coupon, or (b) ACSupply. ACSupply has 40% off all Estes motors all the time; D12's are $7.19 a pack; their shipping is less than Belleville and free if your order exceeds$100.

Just FYI.

#### dippind27

##### Active Member
Thank you! That might have to be my route next time.

#### cavecentral

##### Well-Known Member
I feel old remembering D12 3-packs for $5 each. Now it is$5 a motor!

#### dippind27

##### Active Member
I always say i was born in the wrong era. We need to go back! I like the sound of those prices much much better

#### dippind27

##### Active Member
Pictures of the main body tube and engine mount. Just waiting for a good day to paint.

#### dippind27

##### Active Member
Been flying D12 clustered BT-80 models for decades. I've found it is best to build the Cluster motor mount onto a mixing chamber. This chamber is nothing more then a BT-80 coupler lined with Stainless steel screen, 1/8" plywood bulkheads and epoxied to the BT-60 Upper stuffer tube.
One more thing 4- D12's fit very nicely in a BT-80 in standard BT-50(24mm) motor tubes.

This arrangement has worked perfectly on a number of Up-Scale Models, Ram-Jet, Ultra Orbital Transport, 3X Laser-X, Aerobee-Hi Test, 5-D12 Clustered Brighthawk (3D cluster core & 2- boosters) 3X Bomarc.

Contrary to DaddyisaBar D12-5 or 7 suggestion: D12-3's are usually the motor of choice because of the increased Frontal Area, Mass & Drag of these rockets. 3 Seconds genearlly has them deploy right at apogee. I have used D12-5's in a 4-D12 cluster augmented Optima (Single D12-5 Core and 3 strap-on D12-5's).
I had a feeling i should of went with the 3 second timer but i have never used a motor larger than 18mm until now so i had no idea what to expect out of it. I hope the extra 2 seconds doesnt toast my rocket. When i fly something that needs a 3 second timer and use a 5 second instead, my parachute gets a little burnt nothing too major and the tubing gets exceedingly hot compared to all my other rockets. Im assuming its because the heat from the engine is being trapped inside the rocket until it pops, during this time its traveling at low speeds if not moving at all so its not getting wind cooling it off?

#### tmacklin

##### Well-Known Member
Here's what 3 Estes E9-6 engines will do in a scratch built BT-70 rocket with an internal baffle. Love me some BP clusters!

#### dippind27

##### Active Member
Here's what 3 Estes E9-6 engines will do in a scratch built BT-70 rocket with an internal baffle. Love me some BP clusters!

How do internal baffles work? I saw them online while researching recovery alternatives but was nervous about their performance so i decided i would just stick with some good old wadding.

#### tmacklin

##### Well-Known Member
Visualize a longer than usual tube coupler that has a perforated disk at each end where the holes are not directly inline. This allows the gas pressure generated by the ejection charge to pass on through the body tube and eject the laundry but blocks much of the debris and hot particulates from damaging the parachute. I still use a few sheets of wadding just in case.

I bought my baffle from Sunward Aerospace but other vendors also make/sell them.

https://www.apogeerockets.com/Build...affles/BT-80_size_66mm_Ejection_Charge_Baffle

#### dippind27

##### Active Member
Visualize a longer than usual tube coupler that has a perforated disk at each end where the holes are not directly inline. This allows the gas pressure generated by the ejection charge to pass on through the body tube and eject the laundry but blocks much of the debris and hot particulates from damaging the parachute. I still use a few sheets of wadding just in case.

I bought my baffle from Sunward Aerospace but other vendors also make/sell them.

https://www.apogeerockets.com/Build...affles/BT-80_size_66mm_Ejection_Charge_Baffle
Good to know that they do work. I was just worried that with using a smaller size engine and the amount of tube volume it has to cover the baffle would cause alot of pressure loss and i knew i would need all the pressure i could get.

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
Hey Micromeister, please re read my post of the 25th! I have not seen his built rocket but it doesn't look like he is building a heavy drag queen like a BOMARC that would automatically need D12-3's. Looks like a single BT 80 Nose cone on a three 24mm mount. I also launch at a mile high or higher in dry conditions. If he is launching down at Sea Level in high humidity D12 3's could work. What is the worst that could happen? A little early or late on the ejection is usually no problem. Use a nice long shock cord and there are many additional anti-zippering techniques if one desires to use them.
No need to re-read your post: D12-5 and D12-7 motor are Always too long a delay for BT-80 and larger models regardless of where you are flying! Increased frontal area DRAG effects flight performance of BT-80 Estes .021" wall model rockets. Coast time is GREATLY deminished in Larger body models, Hell even the big daddy has problems on single D12-5's.
I know you don't use Sim's or long-hand calculations so I won't mention it beyond..Choosing the proper motor and delay for our models is our job.
Why Yes! Too long a delay and either D12-5 or 7's does in fact cause high speed deployment zippering and/or Chute Failures. Sticking a motor in a model and seeing what happens may be your method of flying but it is not a good or proper way to fly model rockets. Doing the math saves lots on headaches & unnecessary model repairs.
nuf said.

#### tmacklin

##### Well-Known Member
Would not 3 D12-whatevers provide three times as much thrust as a single D12-whatever and thus greater velocity at burnout?

#### dippind27

##### Active Member
Well its a good thing i spent too much money on the card before my order went through. Had to cancel it. i will re order with D12-3s instead

#### dippind27

##### Active Member
I built an Estes Shadow many years back with a 24mm 4 engine cluster mount. No stuffer tube used. Flew great. Some photos are shown here:

How tall does it stand? Mines about 42" without fins on it. I have got bertha style fins so they will add an inch or so

#### grog

##### Well-Known Member
How tall does it stand? Mines about 42" without fins on it. I have got bertha style fins so they will add an inch or so
Without the nose cone the length is 39.5". With the nose cone, it is a little over 47.5" (close to 47.75").

#### gna

##### average joe-overbuild member
Well, I threw together a quick OR design based on:
• 3 Estes BT-80 3090 Tubes
• Estes PNC-80BB Nose Cone
• Estes 30" Nylon Parachute
• Guestimate of fin design, used balsa 3/16"
• 2 3/16 Launch Lugs
• Long motor mount/stuffer tubes
• Elastic Shock Cord

View attachment dippind27 cluster.ork

This may be wildly inaccurate, most probably the weight, especially if you used heavy duty materials. My experience is that OR weights are always much lighter than built, too.

#### dippind27

##### Active Member
Well, I threw together a quick OR design based on:
• 3 Estes BT-80 3090 Tubes
• Estes PNC-80BB Nose Cone
• Estes 30" Nylon Parachute
• Guestimate of fin design, used balsa 3/16"
• 2 3/16 Launch Lugs
• Long motor mount/stuffer tubes
• Elastic Shock Cord

View attachment 321426

View attachment 321428

This may be wildly inaccurate, most probably the weight, especially if you used heavy duty materials. My experience is that OR weights are always much lighter than built, too.
Thats actually pretty spot on looking. When it is completed i can give you the exact weight. Ive been having trouble finding time to work on it between graduation and work. I have got 2 fins on it. just needs the other 2 fins and some paint and itll be ready to go. Im having trouble reading the fine print on the picture though. Does it say apogee at 610 or 810?

#### neil_w

##### Good at some things
TRF Supporter
It says 810 (when I loaded it on my machine it gave 818). Note that the model has weirdly thick balsa fins (.281", not sure where that number came from). Thinning them down buys you some more altitude, and stability. What are your fins exactly?

#### dippind27

##### Active Member
It says 810 (when I loaded it on my machine it gave 818). Note that the model has weirdly thick balsa fins (.281", not sure where that number came from). Thinning them down buys you some more altitude, and stability. What are your fins exactly?
Im pretty sure you had it right with 3/16 but its basswood not balsa. Wanted that bit of extra durability without having to use filler on balsa.
Route edge is 6 1/2"

#### gna

##### average joe-overbuild member
It says 810 (when I loaded it on my machine it gave 818). Note that the model has weirdly thick balsa fins (.281", not sure where that number came from). Thinning them down buys you some more altitude, and stability. What are your fins exactly?
Oops my bad. Tried to enter .18. must have missed.

Im pretty sure you had it right with 3/16 but its basswood not balsa. Wanted that bit of extra durability without having to use filler on balsa.
Route edge is 6 1/2"
Root edge is 6 1/2"? I guessed 5, but I'll try again...I don't think I have the shape quite right; I'm guessing height is 4 1/2. Yours are more graceful than the ones I drew.

View attachment dippind27 cluster.ork

And the projection:

I didn't post that because I didn't want to be argumentative. Depending on lots of other factors, the weight will no doubt be more. Engine hooks, parachute swivels, kevlar cord--they do add up. Glue and paint do, too. When you have a better idea of the weight we can run it again.

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##### Oddrocs Rule!
TRF Supporter
BT 80 - 2.6" clustered rockets fly fine on D12-5s as they are the recommended motor for a number of kits, including a number of Launch Pad kits that use light parts. Build light and strong and you will be fine. The Perseus uses only two D12-5 as dose the Scimitar with even more drag. TLP Nike Ajax on 3 D12-5's. The weighty Roachwroks Nike Hercules uses 4 D12-5's. The ASRAM uses two D-12 5s, but will fly fine with two D12-7s! How do I know this? I have flown these rockets many, many times and look - no zippers or massive damage!

Looks like you are flying an extended Perseus, like the one on the left. With 3 D12 motors, like an F 36, and basswood fins you will be fine on a 3 or 5 delay in good conditions.

Label papered balsa is lighter and just as durable and easy as basswood.

#### bill_s

##### Well-Known Member
I messed around with that last sim and sure enough, you have to add a lot of weight (1/2 pound) to get the optimum delay to drop below 5 seconds, and the optimum delay also starts dropping if you reduce the weight more than 2 oz. as well.

It seems to me cluster like this is closer to a minimum diameter rocket (with only D power, though) than a "fat" rocket.

#### dippind27

##### Active Member
Well now i dont know who to trust xD first im told 5 seconds then 3 seconds now 5 seconds again. Lets just hold the debate till im finished with the rocket and i will give you guys pictures and exact dimensions of the rocket. Im hoping to have it finished by the end of the week. Im using testors paint so lots of drying time before i can mask it up for stripes and such

#### gna

##### average joe-overbuild member
BT 80 - 2.6" clustered rockets fly fine on D12-5s as they are the recommended motor for a number of kits, including a number of Launch Pad kits that use light parts. Build light and strong and you will be fine. The Perseus uses only two D12-5 as dose the Scimitar with even more drag. TLP Nike Ajax on 3 D12-5's. The weighty Roachwroks Nike Hercules uses 4 D12-5's. The ASRAM uses two D-12 5s, but will fly fine with two D12-7s! How do I know this? I have flown these rockets many, many times and look - no zippers or massive damage!

View attachment 321584

Looks like you are flying an extended Perseus, like the one on the left. With 3 D12 motors, like an F 36, and basswood fins you will be fine on a 3 or 5 delay in good conditions.

Label papered balsa is lighter and just as durable and easy as basswood.
Nice looking stable. Agree on the papered fins--I built a larger BT-80 rocket to fly on single Ds and Es, and I papered the 1/8" balsa fins:

They seem plenty strong, though I have no idea how to sim that in OR. If I were to build his design, and I may just do that, I would paper 3/16" balsa fins, or even try 1/8", and maybe try a 29mm motor mount and fly Estes black powder motors like the E16-6.

His design seems to sim fine on 3 D12-5s--it has more coast time.

#### dippind27

##### Active Member
My next rocket is going to run on the larger E engines. Its 14" bt-80 transition to 20" bt-60 so she will be 36". Im excited for it already and i havent even finished this one.

#### dippind27

##### Active Member
Was starting to get nervous that my rocket wouldnt comply with regulations. I thought it had to weigh less than a pound but its not its 1500 grams. Thats a big relief!! put the fins on and put the chute and chord in just to weigh it. With it all put together BEFORE PAINT (Most of it anyway) it weighs 405 grams. Never weighed a rocket before and after paint until now so i have no idea how much paint really makes a difference. It stands exactly 47" from ground level to the nose.

#### dippind27

##### Active Member
Progress pictures. Nose cone is complete. Body needs a few more stripes. My crap camera on my phone doesnt do any justice to the true beauty of that purple. The purple bled pretty bad on the fins. Im assuming from the minimal prep work i did to them. Like you guys said im sure papered balsa fins would mask and paint much better.

#### tmacklin

##### Well-Known Member
Progress pictures. Nose cone is complete. Body needs a few more stripes. My crap camera on my phone doesnt do any justice to the true beauty of that purple. The purple bled pretty bad on the fins. Im assuming from the minimal prep work i did to them. Like you guys said im sure papered balsa fins would mask and paint much better.
Nice paint job even with the bleed thru on the fins.

I just looked at my 2015 paper catalog of Estes products and according to them, one D12-5 is good for a maximum of 10 ounces total lift off weight so three of them should be good for thirty ounces...right? You said your rocket weighs 405 grams and I assume without engines? Three D12's will weigh about 135 grams so your total lift off weight will be about 540 grams, or 19 ounces. Looks to me like you've got 11 ounces of spare power although you'll probably need some nose ballast to obtain one caliber of CG/CP margin. Just make sure all engines ignite and that your recovery harness is long and robust.

#### dippind27

##### Active Member
you'll probably need some nose ballast to obtain one caliber of CG/CP margin. Just make sure all engines ignite and that your recovery harness is long and robust.
Care to explain? Im still not completely sure what exactly it all means. Im assuming its center of gravity. Nose cone is sealed off so i cant add any weight to it, but for a bulkhead a used a big round block of balsa that weighed like 50 grams instead of just capping a coupler so i hope that added plenty of weight. For shock cord ive got 1/2" x 92" estes pro series. Ive never used a chord this big, is it suppost to be that long or should i shorten it up?