Larger Main Chute Recommendation for Smallest Packing?

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jmmome

jmmome

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36 pound rocket/ 3" dia. Blue Tube/ about 18" of body tube for the chute/ Jolly Logic Chute Release/ piston ejection. Looking for a main chute that packs small enough to fit into the 3" body tube with the Chute Release attached. I have a 84" Iris Ultra Standard but the fit is very tight. 78" Topflight Crossfire fits, but may not slow the descent sufficiently (having some trouble finding the Cd of that chute). Would appreciate any suggestions.

Mike Momenee
TRA#12430 L3
 
I could be wrong but you are going to have a tough time matching the CD of an Iris Ultra. I have gone by the rule that I can downsize by one when looking at the Iris Ultra compared to other chutes, so a 48 Iris compares to a 54 other style, which are 2.2CD. Looking at Rocksim default chutes they range, but most of the ones I looked at are .75CD. Have you tried or considered a longer D-Bag, with a small pilot wrapped around it and the CR holding it together?
 
If you need tight packing space there is no competition for a Fruity Iris.

Maybe drop a size?
 
My packing limitation is actually 13" of body tube depth. I guess I'll look at the Iris Ultra Compact, as compared with my Iris Ultra Standard.

Mike Momenee
TRA#12430 L3
 
Are you going Dual Deploy? If so can you plug the motor and gain anything by switching main and drogue locations?
 
I think Top Flight's flat chutes are 1.34. I would think the Crossfire would be around that. Someone, maybe Gary, posted the Cds for his chutes not that long ago, but don't remember seeing the Crossfire. I think flat chutes were 1.34 though I could be mistaken.
A quick email to Gary at Topflight or pm to Crossfire (also Gary) would probably get ya the Cd for a Crossfire.

Top Flight website says the max weight for that size Crossfire is 20 lbs, btw.

Mikey D
 
Last edited:
Gary's response to this question back in Aug...

Hi
The CD Par9-Par24 1.09
Par-30-58" 1.34
Par70-120" 1.40
The XT chutes are .98
Have a good Day
Gary
 
jmmome said:
36 pound rocket/ 3" dia. Blue Tube/ about 18" of body tube for the chute/ Jolly Logic Chute Release/ piston ejection. Looking for a main chute that packs small enough to fit into the 3" body tube with the Chute Release attached. I have a 84" Iris Ultra Standard but the fit is very tight. 78" Topflight Crossfire fits, but may not slow the descent sufficiently (having some trouble finding the Cd of that chute). Would appreciate any suggestions.

Mike Momenee
TRA#12430 L3
Click to expand...

36 pounds and 3" diameter? Please elaborate in that a bit.
 
mpitfield said:
I have gone by the rule that I can downsize by one when looking at the Iris Ultra compared to other chutes, so a 48 Iris compares to a 54 other style, which are 2.2CD.
Click to expand...
watermelonman said:
If you need tight packing space there is no competition for a Fruity Iris.
Click to expand...

The quoted size is only half the story because the "size" is measured differently by different manufacturers. Using Spherachute as an example:

An 84" Iris Ultra weights 19oz and packs into a tube 4" in diameter by 9" long.
A 120" Sphereachute has the same weight and packing volume.

Fruity chutes quotes 39lb @ 20ft/s
Spherachute quotes 37lb @ 20ft/s

In other words - they within the error bars on performance with the same weight and packing volume...


Also - I echo the others here - 36lb in a 3in rocket? Is that the burnout weight or the launch weight?
 
DCX-Main.jpg

This is my Delta Clipper project mentioned in another thread- attached is a photo of a small kit I found online, but mine should look quite similar. 4 1/2 feet tall and 18" square at the base. Just laying on the very last of the fiberglass skin. Ample forward weight so that the CG is well forward of the estimated CP- that's why the weight creeped up to 36 pounds. The 3" dia. center Blue Tube is the spine of the rocket, and I'll use Jolly Logic Chute Release for the main chute deploy. Perfectflite Altimeter for apogee ejection charge deploy, with a Perfectflite timer as back-up. With a 75/3840 motor, piston ejection, small drogue chute and the Iris 84" chute, everything JUST fits, but the Iris is SOO tight. I'll ground test in the spring of course, but I'm most likely going to buy the 84" Iris Compact to allay my worries.

And 36 pounds is just the rocket weight- the motor hardware/reload adds 8 pounds. Nicely stable per Rocksim- I added four clear polycarbonate fins.

Mike Momenee
TRA#12430 L3
 
Last edited:
Best bet might be a pilot chute and a deployment bag, whichever chute you go with...

Later!

--Coop
 
jmmome said:
View attachment 308636

This is my Delta Clipper project mentioned in another thread- attached is a photo of a small kit I found online, but mine should look quite similar. 4 1/2 feet tall and 18" square at the base. Just laying on the very last of the fiberglass skin. Ample forward weight so that the CG is well forward of the estimated CP- that's why the weight creeped up to 36 pounds. The 3" dia. center Blue Tube is the spine of the rocket, and I'll use Jolly Logic Chute Release for the main chute deploy. Perfectflite Altimeter for apogee ejection charge deploy, with a Perfectflite timer as back-up. With a 75/3840 motor, piston ejection, small drogue chute and the Iris 84" chute, everything JUST fits, but the Iris is SOO tight. I'll ground test in the spring of course, but I'm most likely going to buy the 84" Iris Compact to allay my worries.

And 36 pounds is just the rocket weight- the motor hardware/reload adds 8 pounds. Nicely stable per Rocksim- I added four clear polycarbonate fins.

Mike Momenee
TRA#12430 L3
Click to expand...

That's very cool. Do you have room to enlarge the tube to hold a larger chute?

Also, with pistons, I have placed the piston bulkhead closer to the ejection end of the prison before in order to get more room for a chute.


Steve Shannon
 
jmmome said:
View attachment 308636

This is my Delta Clipper project mentioned in another thread- attached is a photo of a small kit I found online, but mine should look quite similar. 4 1/2 feet tall and 18" square at the base. Just laying on the very last of the fiberglass skin. Ample forward weight so that the CG is well forward of the estimated CP- that's why the weight creeped up to 36 pounds. The 3" dia. center Blue Tube is the spine of the rocket, and I'll use Jolly Logic Chute Release for the main chute deploy. Perfectflite Altimeter for apogee ejection charge deploy, with a Perfectflite timer as back-up. With a 75/3840 motor, piston ejection, small drogue chute and the Iris 84" chute, everything JUST fits, but the Iris is SOO tight. I'll ground test in the spring of course, but I'm most likely going to buy the 84" Iris Compact to allay my worries.

And 36 pounds is just the rocket weight- the motor hardware/reload adds 8 pounds. Nicely stable per Rocksim- I added four clear polycarbonate fins.

Mike Momenee
TRA#12430 L3
Click to expand...

Okay, that explains the weight vs diameter disconnect, nice build project from what you have posted in the build thread so far.
 
Have you considered using two chutes ? One sized for the body and a smaller one for the cone with ballast? I'm assuming the nose section could survive a harder impact ?

Eric
 
Thanks for the reminder about turning the piston around. I think I read somewhere that it is actually the correct way to orient the piston. If i had it to do over again, I'd use a 4" tube for the spine- live and learn. The turned wood nosecone (thanks Gord from Roachwerks) only weighs 1 pound 9 ounces- all the forward ballast is in the top 12" of the rocket body.

Spring launch at Three Oaks, MI

Mike Momenee
TRA#12430 L3
 
Gord does some fantastic lathe work. I've got a number of nosecones from him, and have always been pleased with the product once I get it!

Jettisoning the nose, then, probably won't help much as far as recovery weight, but I'd still consider it, and using the nose and pilot to pull your main out of a bag. I really think that's going to be your best bet for packing that size chute in the given space...


Later!

--Coop
 

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