Parachute concern

[Trenman]

I told wildman I needed a chute for my 38mm mongoose and he sent me a 24" x-type chute which seems VERY small. The overlapping area is really only a square foot or so which has me concerned. I DID tell him I wanted a chute thatll bring my rocket down fairly fast but I am going for my L1 and am concerned that itll damage the rocket. What do you think?

 

[bobkrech]

Go here to get a rough idea of the descent rate.

https://aeroconsystems.com/chutes/index.htm or

https://www.rocketreviews.com/tools.shtml

https://www.rocketreviews.com/tool_descent_rate.shtml

From Aerocon calculator. Ideal descent velocity is 15 fps so circular chute.

1 pound = 28" diameter
2 pound = 40" diameter
3 pound = 48" diameter
4 pound = 56" diameter
5 pound = 63" diameter

From rocketreviews calculator. Descent rate of 24" x-form chute.

1 pound ===> 22 fps
2 pound ===> 31 fps
3 pound ===> 38 fps

Unless your rocket recovery weight is 1 pound or less, your chute is too small. From experience Wildman is usually too small with his chute recommendations.

Bob

 

[blackjack2564]

This is a very high performance rocket achieving much more altitude for any given motor., than most other paper, phenolic or fiberglass tubes.

It also is made of extremely strong and light carbon fiber. This allows it to handle a much higher than normal descent rate and not sustain damage.

Unless you are flying on a very hard surface, you will be fine. One of the design features is the fins are forward of the rear ed by an 1 to 1 1/2 depending on how you build. The fin shape also is not prone to getting whacked first upon landing. If anything in most cases your motor will take the hit.

For this rocket the recommended chute is the 24 X most I have seen fly with this. You can go bigger and go for a loooong walk. Or stay with the X and not hike so far. Especially if you are doing a L-1 motor eject.

If you are going DD then a little larger chute may be in order when using the largest motors available due to increased weight of needed components for DD and the case.

I fly the 29mm with a little 12in chute . It drops like a stone,but no damage after a dozen plus flights including 2 lawn darts and a tangled chute where it hit a gravel runway. These mongooses can take alot of abuse.

You will be fine. What motor are you using? Motor eject? And good luck on your cert flight.

You are definitely doing it in style!

 

[Trenman]

I am using motor eject but I will have an avionics bay. Although I wont be using it or DD I did build one to 1) Get comfortable building an av bay 2) To learn how to use an RRC2 to determine FPS and altitude

My eBay will make it a tad heavier but not by much. I dont know exactly how much itll weigh but I am hoping that it wont come hurdling back to earth.... ugh im so 50/50 on getting a bigger chute....

 

[blackjack2564]

You still have not mentioned what motor you are flying. Make sure you set the delay time correct for your rocket.

 

[Trenman]

38/240 with a 3 second delay. Just want a successful flight for my L1. THEN i will put in big motors for more fun.

 

[nh4clo4]

38/240 with a 3 second delay. Just want a successful flight for my L1. THEN i will put in big motors for more fun.

13 seconds maybe?

 

[GaryT]

Still No Motor listed though?? Not the case size, I recommend doing your research 1st, Know what it is you want out of the flight, Know what said motor is going to do before just calling a vendor and asking for a chute? Have more than just one chute on hand to compensate for weather conditions and wind, Watch other flights of similar kits to your kits weight and size, Watch what the upper winds are doing, These things can help you decide which chute to use once your on the field.

 

[Trenman]

Still No Motor listed though?? Not the case size, I recommend doing your research 1st, Know what it is you want out of the flight, Know what said motor is going to do before just calling a vendor and asking for a chute? Have more than just one chute on hand to compensate for weather conditions and wind, Watch other flights of similar kits to your kits weight and size, Watch what the upper winds are doing, These things can help you decide which chute to use once your on the field.

That's great advice. The reason I didn't list a particular motor is because I don't have the cert to buy one yet. The president of the club is bringing me a reload and is letting me use his case. That's all I know. I know I sound completely ignorant but don't think I am. I am just new to hpr and am learning alot at a rapid pace.

Thanks for all the help guys.

 

[Trenman]

A question: Will I need wadding or anything between the engine eject and the parachute?

 

[kandsrockets]

Okay maybe it is just me but shouldn't you know how to size a chute if you are planning to move to HPR...:confused2:

 

[tbzep]

A question: Will I need wadding or anything between the engine eject and the parachute?

If you have a kevlar shock cord and a nomex chute protector, or if the model has a baffle, you won't need wadding. If it's of regular construction, you will need wadding. The cheap and easy way is to use cellulose insulation. Often there will be folks at the launch that will offer to give some away to whoever will take it, especially people new to HPR. One bale of the stuff will last what seems a lifetime.

The person who is supplying your hardware and making the reload purchase for you will be able to help you with all these things, but it is good that you are asking beforehand to get good background knowledge and know what to expect.

 

[tbzep]

Okay maybe it is just me but shouldn't you know how to size a chute if you are planning to move to HPR...:confused2:

X-forms are quite a bit different from flat circular chutes he's probably used to, so he has nothing to compare with. I think he's doing right in asking now instead of going in blind. That lets us refer him to information sources like Bob did with the rocketreviews calculator.

 

[Trenman]

X-forms are quite a bit different from flat circular chutes he's probably used to, so he has nothing to compare with. I think he's doing right in asking now instead of going in blind. That lets us refer him to information sources like Bob did with the rocketreviews calculator.

That is correct, and thank you. I prefer to do research and ask questions as opposed to going in blindly.

 

[cjl]

I have no idea what a 38mm mongoose weighs, but if it's about the same as a PML Cirrus Dart (or even a bit more), that chute will be fine. I flew my Cirrus with a 24" round chute, and if anything, it was too big. It was in large part by luck that we found the rocket at all.

 

[sylvie369]

Okay maybe it is just me but shouldn't you know how to size a chute if you are planning to move to HPR...:confused2:

To be fair to him, the whole idea of these little 29mm carbon fiber rockets is to have something that will survive a really hard recovery (they are flown on occasion with just streamers...). I don't think that the "right way" to size a chute applies very well to that idea.

I'm not wild about that concept, myself, at least for L1 certs. It seems to me that successfully recovering a rocket that doesn't need to have the right size chute isn't the best way to demonstrate that you know how to successfully recover a rocket. I understand the need for a fast recovery in a small and overpowered rocket, but I hope the folks who are learning on little glass and fiber rockets also understand the need for a reasonable descent rate in normal situations (yes, I know that opens a whole 'nother line of argument).

I think that fact that the young man raised concerns here shows that he DOES understand something about how to size a chute properly. He just put himself in a situation in which the normal advice is typically ignored. (not to disagree with those who have actually flown the thing and found smaller chutes to work fine: that's the real test, of course).

P.S. - I'm more concerned about that "3 second delay" comment. I sure hope he means 13 seconds. If he ejects after a 3 second delay, it won't matter much what size parachute he watches drift away from his plummeting rocket.

 

[kramer714]

he has learned the biggest lesson...

ask a question, and then be able to sort the (all well intended) contradictory responses to find the one that your judgment, and/or the judgment of the one or two sources that understand your situation (field - rocket- construction-budget...) give you.

If someone going for their level 1 shows me the understanding to sort out all the information and make good judgments, I'm good with that, seldom is it a single right answer. If they try to find the be-all end all one source answer to all questions then I'm concerned that they don't understand.

BTW, what does the kit manufacturer recommend is usually a good starting point.

 

[Trenman]

So many helpful and supportive comments. Thank you. I took advice and purchased another larger chute so that on launch day, I may assess wind conditions and determine the responsible and safe way to recover my rocket. I bought a nomex parachute Protector and swivel so that I may easily switch parachutes. Thank you to all for the valuable information that has helped me to come to an educated decision. L