eengelgau
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Hi Everyone - as promised in another thread post last weekend I tested a prototype for a new design that some would call a Rocket Rage clone. The common industry term for this type of chute is a pull down apex. This simply means that the top crown of the chute is via extra shroud lines pulled down inside the canopy via an additional tether. It forms a shape called a toroid that is cut in half - think doughnuts 
.
After reading the thread about the Rocket Rage chutes and how much folks missed these, I decided now was the time to put this to the test and really find out how well this design performs. It's also been on my back burner for some time to make, plus there a really cool design. This first prototype is based closely on our elliptical design with some small tweaking in the crown area to allow it to flair and be pulled down. My wife was kind enough to sew in in a few days and by Wednesday I have the "first draft". This has the same 20% spill hole opening (4% area). But due to fudging the patter a bit too much the pull-down part was too deep. So I chopped off some (7.5") making the opening more like 25% (6% area) and reattached the top shroud line and everything was looking good, the shape was nice and tight with no wrinkled areas. The spill hole is a bit large, but otherwise it looked great.
Now for the test.
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For my test rocket I have my ultimate short fat rocket called Mag Max. It is only 4' tall but 7.5" in diameter. It's based in a chopped off Pole Cat Patriot, and I mean really chopped down! To make it stable it needs 3lbs of lead in the nose. Loaded this rocket is over 17lbs on the pad - perfect for chute testing because it weighs a boat load and stays low so I can see the whole flight. I have a MAWD in it and use a Tender Descender tether for dual deployment (why not!).
Friday I pre-prepped the rocket and loaded up the chute into a 5.5"D x 7"L deployment bag (fits very easy). When using tethered dual deploy you must use a bag for your main. Saturday I complete me assembly and built a J540R motor. I weighed the beast - 17.2lbs - perfect! I made out a flight card, checked it in and lugged it our to the HP pads.
Here are the pics of the flight and chute in action:
Here is Mag Max taking off the pad (all photos courtesy Martin Hall). It was a gorgeous day, very little wind. The rocket went about 2K feet. The nose cone popped off at apogee as expected and a small 18" drogue came out tethered to the main d-bag and the airframe. The rocket descended at about 60fps to 500' where the tether released.
This shows the main still in the bag extending the shroud lines. Moments later the main popped open and the rocket abruptly slowed down.
Here is a great shot of the prototype showing details of the chute and the inner shroud lines, and pull down tether. The canopy looks really nice considering the pattern was a bit of a WAG.
Here is a side view showing the low profile characteristic of these chutes. It's this abrupt shape on top that increases the chutes efficiency.
The rocket landed a short ways away.
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So the big question is - what is the Cd of the chute? All I need is two variables - the exact descent weight of the rocket and the projected area of the chute. Before cleaning I weighed the rocket again and it weighed 15.53lbs - so that is the descent weight. The projected area after factoring out the spill hole is 27.14 sq'. The altitude at launch is about 300' or so, I'll consider that the same as sea level.
Results - the Cd is an astounding 2.13 - :surprised:
I ran a similar test last year using my 84" stars and stripes chute and the 72" toroidal design outperformed the 84" chute.
---------
Next steps:
I have a new pattern generator ready that generates the sections mathematically creating an ideal shape. This design will be similar overall but have a more refined canopy shape that uses about 9% less fabric than our current ellipsoid design. The spill hole is 2% of the area increasing the efficiency even more.
I expect to test a new design next month. I'll test a 60" chute in my Talon 4 on a K700 should go 6500'. I have a HCX and MAWD to get two data sets to compare. If it performs as expected I should have a Cd that is just a bit higher. This will be considered V1 of the production design. After verification we'll sort out pricing of the chutes (they take more time to make). However the performance is higher and you can pack higher performance into a smaller space.
I expect we'll start to offer these around April / June time frame. They will only be available from 60" - 198" sizes.
Anyone interested in purchasing our new chute please use the Contact Us form on Fruity Chutes - https://fruitychutes.com/buyachute/index.php?main_page=contact_us.
Be sure to mention you are interested in the up-coming toroidal chute (official product name announcement coming at later time). I'll notify you directly once the product is ready for release... We will take pre-orders about a month in advance for a discount TBA.
Feel free to let your friends know as well it's coming.
Feed back welcome!
.After reading the thread about the Rocket Rage chutes and how much folks missed these, I decided now was the time to put this to the test and really find out how well this design performs. It's also been on my back burner for some time to make, plus there a really cool design. This first prototype is based closely on our elliptical design with some small tweaking in the crown area to allow it to flair and be pulled down. My wife was kind enough to sew in in a few days and by Wednesday I have the "first draft". This has the same 20% spill hole opening (4% area). But due to fudging the patter a bit too much the pull-down part was too deep. So I chopped off some (7.5") making the opening more like 25% (6% area) and reattached the top shroud line and everything was looking good, the shape was nice and tight with no wrinkled areas. The spill hole is a bit large, but otherwise it looked great.
Now for the test.
-----
For my test rocket I have my ultimate short fat rocket called Mag Max. It is only 4' tall but 7.5" in diameter. It's based in a chopped off Pole Cat Patriot, and I mean really chopped down! To make it stable it needs 3lbs of lead in the nose. Loaded this rocket is over 17lbs on the pad - perfect for chute testing because it weighs a boat load and stays low so I can see the whole flight. I have a MAWD in it and use a Tender Descender tether for dual deployment (why not!).
Friday I pre-prepped the rocket and loaded up the chute into a 5.5"D x 7"L deployment bag (fits very easy). When using tethered dual deploy you must use a bag for your main. Saturday I complete me assembly and built a J540R motor. I weighed the beast - 17.2lbs - perfect! I made out a flight card, checked it in and lugged it our to the HP pads.
Here are the pics of the flight and chute in action:
Here is Mag Max taking off the pad (all photos courtesy Martin Hall). It was a gorgeous day, very little wind. The rocket went about 2K feet. The nose cone popped off at apogee as expected and a small 18" drogue came out tethered to the main d-bag and the airframe. The rocket descended at about 60fps to 500' where the tether released.
This shows the main still in the bag extending the shroud lines. Moments later the main popped open and the rocket abruptly slowed down.
Here is a great shot of the prototype showing details of the chute and the inner shroud lines, and pull down tether. The canopy looks really nice considering the pattern was a bit of a WAG.
Here is a side view showing the low profile characteristic of these chutes. It's this abrupt shape on top that increases the chutes efficiency.
The rocket landed a short ways away.
---------
So the big question is - what is the Cd of the chute? All I need is two variables - the exact descent weight of the rocket and the projected area of the chute. Before cleaning I weighed the rocket again and it weighed 15.53lbs - so that is the descent weight. The projected area after factoring out the spill hole is 27.14 sq'. The altitude at launch is about 300' or so, I'll consider that the same as sea level.
Results - the Cd is an astounding 2.13 - :surprised:
I ran a similar test last year using my 84" stars and stripes chute and the 72" toroidal design outperformed the 84" chute.
---------
Next steps:
I have a new pattern generator ready that generates the sections mathematically creating an ideal shape. This design will be similar overall but have a more refined canopy shape that uses about 9% less fabric than our current ellipsoid design. The spill hole is 2% of the area increasing the efficiency even more.
I expect to test a new design next month. I'll test a 60" chute in my Talon 4 on a K700 should go 6500'. I have a HCX and MAWD to get two data sets to compare. If it performs as expected I should have a Cd that is just a bit higher. This will be considered V1 of the production design. After verification we'll sort out pricing of the chutes (they take more time to make). However the performance is higher and you can pack higher performance into a smaller space.
I expect we'll start to offer these around April / June time frame. They will only be available from 60" - 198" sizes.
Anyone interested in purchasing our new chute please use the Contact Us form on Fruity Chutes - https://fruitychutes.com/buyachute/index.php?main_page=contact_us.
Be sure to mention you are interested in the up-coming toroidal chute (official product name announcement coming at later time). I'll notify you directly once the product is ready for release... We will take pre-orders about a month in advance for a discount TBA.
Feel free to let your friends know as well it's coming.
Feed back welcome!
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