Purple Parrot - MD 38mm

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SpaceManMat
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Purple Parrot - MD 38mm

Postby SpaceManMat » Thu Nov 26, 2015 6:28 pm

Currently I'm trying to kickoff my next build, the kit is a Purple Parrot from Animal Works
http://cart.amwprox.com/index.php?optio ... gory_id=60" onclick="window.open(this.href);return false;

This is a 38mm thin wall fibre glass rocket with a 29mm motor mount. However the plan is to build it minimum diameter for a CTI 5g 38mm case. I won't have room for a standard minimum diameter retainer so will manufacture my own. Nose cone will contain EggFinder and a Raven and recovery is just a 18 inch chute.

Image

There are a few details I still need to nail down:
1. Fins - the above sim has 1.5mm carbon fibre in a clipped delta form. These give about 50 feet more than the standard fins trimmed down for my purposes. I've not worked with carbon fibre before, I want to bevel the fins at a very shallow angle about 2 degrees or so. Are the layers in CF as fine as those in FG? Will the CF be weakened by this or is it pretty much the same as FG just a bit lighter?
2. Fillet Glue - Still need to research this.
3. Fillet Size - need to sort 2 first.
4. Nose Cone - need to figure out if I want to pursue an alternative one. I've played around with the sims and the stability takes a bit of a hit adding other types of nose cones so would need to compensate for that.
5. OR and RasAreo give me differing optimum altitudes and weights. OR says 934g to 12922 feet, RA 1028g to 13721 feet. Thinking I'll just average the two. Mostly I suspect this is a difference in CD so I've graphed the two

Image

6. Should I ignore the results from FinSim? It says the fins will fold up at only Mach 1 on the standard fins, which I believe is not the case. I've tried to obtain details about the materials from the vendor but not heard back. I do know that the density of the fins is greater than what FinSim is using.
Last edited by SpaceManMat on Wed Sep 27, 2017 5:06 pm, edited 1 time in total.
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

Lister
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Re: Purple Parrot - MD 38mm

Postby Lister » Thu Nov 26, 2015 7:17 pm

This is an awesome project. Good luck.

1. As far as I know there is no diffence in bevelling CF compared with FG.. out of curiosity where are you getting the CF sheet and is it woven CF?

2. For minimum diameters my way of thinking is to use a high temp epoxy (I use jbweld) for the root joint as you will have alot more heat radiating to the joint as oppose to TTW fins. For fillets I would do a small jbwelb fillet and the a bigger regular epoxy fillet ( west systems, nuplex R-180, z-poxy 30min etc)

3. Fillet size depends on thickness of fins, strength if fillet material and other things im sure.. for this rocket I would use a tounge depressor for the fillets which is probably a bit smaller than a 1" conduit fillet.

4. Nosecone I would go for a 5:1 or an ogive shape.. for high speed rockets I dont like the conical ones..I have a 5:1 mould.. once I get the silicone to redo PK's 38mm mould I can send you one of them if you like.

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Purple Parrot - MD 38mm

Postby SpaceManMat » Fri Nov 27, 2015 10:19 pm

Don't think areo heating will be much of an issue, heat from the motor perhaps. Primary basis for choosing the epoxy will be strength.

Do you have a sim file with that NC? Interested to see what it would do.

One thing that is holding me up. I have a 5G CTI 38mm case on order with Austalia Rocketry, but pretty sure this will not show up for months yet. If there is someone at QRS who can lend me one for the build it would really help.
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

Lister
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Re: Purple Parrot - MD 38mm

Postby Lister » Sat Nov 28, 2015 7:38 am

Wasnt meaning aero heating.. more the motor heating the root joint and messing with the epoxy.. its probably over kill on a smaller MD but I have seen alot of people use it for larger MD's.

I dont have an accurate sim for it. I just input length and base diameter and select the shape and over ride the weight.

From tip to the base its 180mm..
Base diamter of 41mm
Shape is ogive
weight is 65g from memory.

Have you spoken to blake about the case? Why do you need the case to progress with the build?

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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Sat Nov 28, 2015 7:52 am

Thanks Lister I'll play around with those details.

I need the case so I can accurately set the position of the retainer, but no have not discussed with Blake, it was ordered with the last motor order so I suspect will be shipped with that.
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

Lister
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Re: Purple Parrot - MD 38mm

Postby Lister » Sat Nov 28, 2015 8:29 am

Ahh ok im with you now, you can still build the rest of it and just put the retainer in when you get the case? Im making a 38mm MD much the same so it will be interesting to compare them.

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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Sat Nov 28, 2015 9:51 pm

Lister wrote:Wasnt meaning aero heating.. more the motor heating the root joint and messing with the epoxy.. its probably over kill on a smaller MD but I have seen alot of people use it for larger MD's.

I dont have an accurate sim for it. I just input length and base diameter and select the shape and over ride the weight.

From tip to the base its 180mm..
Base diamter of 41mm
Shape is ogive
weight is 65g from memory.

Have you spoken to blake about the case? Why do you need the case to progress with the build?


There are some downsides to a ogive, the NC I have weighs only 35g, so a heavier NC reduces the weight available for electronics. Not sure if that puts it over weight or not at this stage. Also there is more side profile so it drags the CP forward a bit. To maintain the same stability I need to increase the fin size a couple of mm. Still it looks to come out about 800 feet better so really weight is the main concern. Can you please confirm the weight Luke?
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

Lister
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Posts: 967
Joined: Fri Jun 05, 2015 5:36 pm
Location: Bendigo, Victoria

Re: Purple Parrot - MD 38mm

Postby Lister » Sun Nov 29, 2015 10:38 am

the nosecone weighs 58 grams with the bulk plate.. without it its 56g. yeah the ogive and Von Karmen nose cones tend to make a fair bit of difference in the sims.. dont know if it makes as much difference in the real world.

Could you please upload the vertical motion vs time and Stability + CP location vs time plotted data screenshots. just want to see what speed it will be going for the majority of the flight and how much the CP location deviates.

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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Sun Nov 29, 2015 7:42 pm

Been doing the sums on my av bay weight. I believe I will be able to use the Ogive NC and remain within my weight budget, I'll PM you.

I'm aiming for a minimum of 1.2 caliber of stability, don't really want to cut it any finer. I find that only 2 mm of fin span makes the difference between marginal and 1.2 ish, so the slightest error in measurement / estimate could be an issue if I try to go any lower. This is a typical plot of the stability I am aiming for

Image
Last edited by SpaceManMat on Wed Sep 27, 2017 5:08 pm, edited 1 time in total.
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

Lister
Engineer
Engineer
Posts: 967
Joined: Fri Jun 05, 2015 5:36 pm
Location: Bendigo, Victoria

Re: Purple Parrot - MD 38mm

Postby Lister » Sun Nov 29, 2015 9:32 pm

How much weight are you aiming for? Im heading to the local mens shed on tuesday and one of the things on the list is a slightly thicker plug for the 38mm nosecone which will again bring weight down.. could try maj
king a fibreglass one but I wont be able to make them until my silicone and urethane from Barnes arrives which will be the end of the week-monday week.

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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Sun Nov 29, 2015 10:59 pm

Had a few PC issues, but here is the velocity and altitude graph you asked for. Target weight for the nosecone is a bit hard to tell at this stage as I need to know the mass of all the other components.
Image
Last edited by SpaceManMat on Wed Sep 27, 2017 5:09 pm, edited 1 time in total.
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

Lister
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Engineer
Posts: 967
Joined: Fri Jun 05, 2015 5:36 pm
Location: Bendigo, Victoria

Re: Purple Parrot - MD 38mm

Postby Lister » Mon Nov 30, 2015 8:39 am

As far as i know that speed range an ogive or Von Karmen would perform the best. What parts do you need the weight of?

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SpaceManMat
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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Mon Nov 30, 2015 5:21 pm

Sled, screws, wiring, epoxy, Kevlar, switch etc
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

Lister
Engineer
Engineer
Posts: 967
Joined: Fri Jun 05, 2015 5:36 pm
Location: Bendigo, Victoria

Re: Purple Parrot - MD 38mm

Postby Lister » Mon Nov 30, 2015 5:44 pm

I would just guestimate it but make the weight you input into OR/RovkSim 35% less than guesstimated, that way if it doesnt weigh as much as you guessed it will still be stable.. if it weighs more it will make it more stable.. i would think an av bay in a 38mm airframe would weigh 30-40 grams at the most.. 2cents worth.. do you want the dimensions of the cavity in my 38mm nosecone? If you need more space I can always add more shoulder too it for you.

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Re: Purple Parrot - MD 38mm

Postby SpaceManMat » Mon Nov 30, 2015 9:56 pm

Increasing weight to bring it up to my target weight is easy, it's reducing the weight that's difficult. Anyway I think there is enough wiggle room in there to get reasonably close to optimum weight.
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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