Fins - Katana 4

Discussions on mid/high powered model rockets using F powered motors and above.

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joeman
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Fins - Katana 4

Postby joeman » Wed Jun 21, 2017 3:04 pm

Hi,
I've been putting a lot of thought into Fin Profiles and the shape they should be.

In terms of priorities:-
* Getting to MACH speed is not a priority.
* Height/altitude is greater priority.

So reduced speed leads to reduced drag. [Sure if I put a motor in it and it gets to Mach 1 nearer to the end of the powered flight. Ok. But I get the impression the drag will go up at that part of the flight resulting in poor performance there. (Can't have it both ways)]

So based on this, I'm going :-
- Round the Leading edge
- Make a 'v' edge on Trailing edge.

Now the rocket I am building is a Katana 4. And is actually comprised of 3 x 2 = 6 fins...2 for every 120degrees.

I'm curious as to what the is for. Is it for looks ? Or does it actually lead to less drag? Perhaps? I assume it has no bearing on my decision to round leading and 'V' the Trailing.
Actually, I should do a simulation of one 'equivalent' fin perhaps instead of two...though I'm not sure if OpenRocket would be able to work at that 'level'.

mmm another thought is, perhaps I should get rocksim instead...apparently this is better for simulating flights..

Thoughts?

Cheers!

Joe
L1 - Callisto (H133) - 11-Jan-2016

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OverTheTop
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Re: Fins - Katana 4

Postby OverTheTop » Wed Jun 21, 2017 4:22 pm

Split-fin designs are usually just for good looks. They do take a bit more work when making the fincan, and aerodynamically they are a little more drag.

Open Rocket or RockSim should both do a reasonable job of simulating the flight. I use RS and it is usually quite close for my Velociraptor which has split fins, without having to do much fine-tuning of the sim file.

Looks like it will take a good selection of motors. You can even adapt down to 54mm motors if you want.

Have fun :)
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SpaceManMat
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Re: Fins - Katana 4

Postby SpaceManMat » Wed Jun 21, 2017 9:36 pm

If you are interested in the effects of fin profiles the take a look at RasAreo II. It's free and has quite a bit more options such as angles.

Normally I stick with OpenRocket. RockSim has some additional options for building some of the more complex designs that you might see in low / mid rockets - think pods and the like although OR is catching up in this regard. RasAero II as mentioned before has better estimates on drag prediction, I use this for faster/higher flights along with OR.
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joeman
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Re: Fins - Katana 4

Postby joeman » Thu Jun 29, 2017 6:16 pm

G'day Guys,
RasAero II does sound very interesting.

Thanks for the info and suggestions!

Cheers

Joe
L1 - Callisto (H133) - 11-Jan-2016

joeman
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Re: Fins - Katana 4

Postby joeman » Sun Jul 30, 2017 8:11 pm

Only just started gluing fins...taking it slowly and carefully.

Just realised the split fins just make the internal Filleting just a little more difficult. Think I'm going to have to 'bog' up gap between them with 105/206/403 before doing internal fillets.
L1 - Callisto (H133) - 11-Jan-2016

joeman
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Re: Fins - Katana 4

Postby joeman » Sat Sep 02, 2017 7:49 am

Hi All,
Started doing the external fillets. Going to lay down all the Epoxy first and then I'll sand it with my doweling/sandpaper rod.

Reasonably happy with it. Not perfect and so will need to to work on the transition and some points. But pretty confident I can get it looking nice.

Here is a picture.

IMG_3594_sml.jpg
IMG_3594_sml.jpg (120.66 KiB) Viewed 471 times



Was going to use fibreglass repair kit paste to finish transition. Sound like a good material to use? Figured if it works in car body repair, I can probably use it to "remove" any blemishes.

Cheers

Joe
L1 - Callisto (H133) - 11-Jan-2016

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Re: Fins - Katana 4

Postby kopius » Sat Sep 02, 2017 9:32 am

Looks good so far Joe ;-)


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SpaceManMat
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Re: Fins - Katana 4

Postby SpaceManMat » Sun Sep 03, 2017 9:10 am

Looks, good. What material are the white fins made of?
QRS: 124
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joeman
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Re: Fins - Katana 4

Postby joeman » Sun Sep 03, 2017 5:14 pm

:)

The white material is called G10 - 4.8mm thick Composite laminate (Fibreglass sheeting) - Very strong. I think it is similar to FR4 which is used in PCB (Electronics) - the difference is that FR4 has fire retardant properties.

Got a spare piece from Blake to practice working with.
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Re: Fins - Katana 4

Postby SpaceManMat » Mon Sep 04, 2017 9:02 am

Ok, didn't realize it would be so white
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


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