New girl on the block needs help

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Rocket Girl 66
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Re: New girl on the block needs help

Postby Rocket Girl 66 » Sat Jul 02, 2016 7:53 am

Hi Mat,

Thanks for that!!.
If I run into any problem, I will send you a message, thanks for your help.

Sari

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SpaceManMat
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Re: New girl on the block needs help

Postby SpaceManMat » Sat Jul 02, 2016 9:29 am

Just read through the 2 reviews I posted earlier and a few things come to mind:
1. One of the builds he said he did not bevel (shape) the fin edges. This is a mistake for 2 reasons. First it will reduce the altitude by about 30%. Secondly it makes the fins less effective due to the square ends creating turbulence. At the very least you should round the trailing and leading edges as well as the tip.
2. Both of the reviews reinforce the fins. For this kit it sounds like a very good idea. If I was to create this rocket myself from I would not use balsa for the fins. One of the reviews adds fiberglass the other adds a layer of epoxy. If you read the flight logs you will notice that on a few occasions they did actually lost fins.
3. Stability is something you will need to look very closely at with this kit. Any weight added aft (say by reinforcing the fins) will reduce stability. As will your exact placement of fins (forward fins reduce stability). One of the issues scale models of rockets is that the real rockets use active stabilization meaning the control surfaces are constantly correcting the course of the rocket preventing any stability issues. On the other hand our models do not have control surfaces they are statically stabilized, relying completely on the flow of air over the fins to correct the flight. To ensure that the rocket as you build it is stable you will need to accurately simulate it in Open Rocket or one of the other rocket simulators. By accurate, the important points are to measure size, weight and placement of parts when entering them in your simulation model as you have built it. Suspect we will need to go through the finer points on this later.
4. The kit uses a motor hook. I've only used these for 18mm motors. You may want to consider using a retainer instead as this will give you access to a much wider range of motors, perhaps someone with more experience then me with 24mm motors can chime in on this point. This is something you should consider before you build the motor mount tube as it will affect placement.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
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Re: New girl on the block needs help

Postby OverTheTop » Sat Jul 02, 2016 10:51 am

you should round the trailing and leading edges as well as the tip.

Watch out for this one. Rounding or beveling the "tip" (edge parallel with the airflow) actually allows the airflow from both sides of the fin (at non-zero angle of attack) to combine easier. This is a reduction in "lift" which is effectively a reduction in fin efficiency. The force generated by the fin to restore straight flight is reduced, so response to perturbations is slower.

Rounding or beveling the leading and trailing edges is a good idea to increase performance. Careful if you make the edges too fine, as then they damage more easily.

I have kits where I have chosen to not bevel or round, and just taken the performance hit. Likewise I have chosen to bevel the outside edge on occasion, for aesthetics. These are the choices you make as a builder.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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SpaceManMat
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Re: New girl on the block needs help

Postby SpaceManMat » Sat Jul 02, 2016 2:59 pm

Looks like there is a rocksim model here

http://www.rocketreviews.com/the-launch ... -3099.html

RockSim is not free, most people use Open Rocket which is. It can also read rocksim files, you should save the file as an open rocket file once opened. As previously mentioned it is important to update the sim file to be accurate to how you build the rocket.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

MaxQUSA
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Re: New girl on the block needs help

Postby MaxQUSA » Wed Jul 06, 2016 10:20 am

Lister wrote:Seeing as everyone is saying to start simple, have a look at the apogee website. They have kits in skill level categories which might be of help in finding a basic kit.

+1 n Apogee - I've enjoyed cruising their website, they have some nice introductory links for beginners and their technical newsletters are pretty good for beginners and experienced as well.

https://www.apogeerockets.com/

I built their Aspire - nice looking and it flys on a range of motors, including a long burn 8 second they used to offer...this kit has a dedicated following.
It will fly well on smaller motors but given it is apogee deploy, it will go for a ride if the winds upstairs get strong...lost mine on an E 9, but I'm getting another - it is too much fun not to.
https://www.apogeerockets.com/Rocket_Ki ... Rocket_Kit

Agreed on point on the TLP kits....I've built the Nike Ajax and Pershing...they look terrific, however, many of them will require a delicate hand with turning paper shrouds and transitions, and while they are lightweight, rely on thin balsa and paper materials, so they don't take much abuse on rough landings.

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Re: New girl on the block needs help

Postby Lamp » Sat Jul 09, 2016 7:32 pm

G'day Rocket Girl 66, we are having a club meeting on Wednesday (send me a PM for the details if you are interested). If you can come along you will be able to get some advice and tips on rocket construction which will make things a bit easier for anything you want to build, especially if you are going to go straight to building MPR.

Don't discount low power...it is a lot of fun. I am in the middle of building a rocket that currently sims to reach 20,000' and have a maximum velocity touching Mach 2 on the right motor, but I still enjoy flying little rockets on A and B motors in the local park :wink:

Also, we are currently looking at having a launch at serpentine on either the 16th or 17th of this month if the weather cooperates. This would be another place you could get some advice and if you make it up you would also see everything in the power spectrum from low power to Level 3 high power being launched.
‘It takes sixty-five thousand errors before you are qualified to make a rocket.’ — Werhner von Braun
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SpaceManMat
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Re: New girl on the block needs help

Postby SpaceManMat » Sat Jul 16, 2016 9:23 pm

Had a quick look at the standard simulation file, on a E30 it hits nearly 500Km/h with acceleration of just under 24G

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tlp_rapier.zip
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QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

Rocket Girl 66
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Re: New girl on the block needs help

Postby Rocket Girl 66 » Fri Jul 22, 2016 12:37 pm

Thanks for that Mat, and everyone else.


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