Tuesday, 22 March 2016

FT Mini Arrow - hotwire version

This is a ripping little wing, perfect for combat and proximity FPV.

Wingspan - 775mm
Flying weight - 400g

The Flite Test version is made from cheap US foamboard, which is not available in Aus.

My arch enemy combat pilot Chris made one from 6mm depron covered with packing tape, and I made a hotwire version from XPS foam.

Initial streamer combat flights have been fantastic, very addictive. Chris is narrowly leading the scoreboard....for now.

I suspect our numbers will be growing rapidly judging by the comments from the audience on the day. Combat video coming soon.

We decided to standardise motors, ESCs and battery for matched performance.

Motor - Turnigy 2822/14 1450kV
ESC - 20 to 25A
Battery - 1300mAH
Prop - 7 to 8"


Hotwire templates (Right click and download)

Hotwire foam blank plan
(Same template with 2 different views)


Aileron and winglet templates
(6mm depron or 4mm coreplast)




Build overview

Maiden, repair and re-maiden


Mini Arrow streamer combat

34 comments:

  1. Hey, Andrew, great build. One question: I've located an L-shaped aluminium piece from kitchen's cupboards, used to keep the side panels from delaminating when exposed to steam. It is 2mm thick, would that be thick enough to be used as motor mount or do I have to look for a thicker one?

    I've also tought on using a couple of git cards glued together as motor mount, how about that?

    Cheers and thanks for the fun.

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    1. Hello, yes 2mm should be perfect, mine are 1.6mm. I have one full gift card folded around the rear foam edge and glued with hot glue, then the aluminium is stuck on with strong double sided tape. Sounds like you're on the right track.

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  2. Very cool. I am starting to really love hot wire cutting. Thank you for sharing the templates!

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  3. Thanks for the template. Gonna build a mini arrow.

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    Replies
    1. Excellent, let me know how it goes.

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  4. Thanks for the template.. I'm about to build this..
    How did you find the Center of gravity?
    Can this plane bring a gopro or is it to heavy?

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    1. No problem. CG was same as Flight Test design. Worked out right with the 2822 motor and 1300mAH battery. I dont have one just now but I'll find out for you. GoPro? Might be too big just have to try it.

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  5. Thanks for the airfoil templates.
    I liked my depron version of the Arrow.
    Builds are in progress (already cut).
    1 will be with motor, other one for slope soaring attempt at a rocky location (needs something tough & crash resistant).

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    1. Excellent, it will survive anything.

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  6. Hey, I am building mini arrow atm, and noticed that smaller airfoil template is 14 cm length. On the foam board plans its 11 cm. So 3 centimeters of airfoil is sticking out. Is it normal?

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    1. Yes that's right, it helps to have the template sticking out a bit so you can rest the hotwire before starting the cut.

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  7. Hi Andrew Great Plan. I have been playing around with hotwire cutting of it. I'm not sucessful at it yet. I found a place near me that would gladly CNC hot wire cut the plans for me. I have a couple of questions, I hope you can answer it.

    Airfoil: Clark Z
    Root Chord: 284mm
    Tip Chord: 109mm
    Wingspan: 390mm each side
    Setback: 303mm

    Do I have this correct?

    ReplyDelete
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    1. Hi Mark,

      Yes the measurements are correct.
      But the airfoil started as Clark Z then I stretched it out a bit and thickened the trailing edge of the wingtip so it didn't end up too thin.
      It is very tricky to cut with the taper and I always have to smooth out the cutting defects.
      Good luck

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    2. thank you for the very quick reply. A machinist friend of mine made me some metal templates from your plans for the root and tip cords. I have been practicing on blue insulation foam, already went through a 4 feet by 8 feet section. Getting better, but just not there yet. I have a nice big block of epp foam sitting aside till I get it perfect. So for the meantime I was going to have someone just cnc it for me.

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  8. is this the sam clark z template you are using for you trainer ?

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    1. Greetings,

      Not quite, this one has been stretched and thickened at the trailing edge or the wing tip.

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  9. the small template has 14cm of length and the small part of my wing has about 11,5 cm, is that correct?

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    Replies
    1. Yes that's right, templates are longer than the final wing size. Just trim off the trailing edge after cutting

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    2. Actually that's misleading sorry, the template is longer so you can rest the wire on the overhang before starting the cut.

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    3. ok , thanks for the fast answer

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  10. this would be my first airplane to build , and my first airplane to fly, do you think its easy enough? i am 16 and i am want to enter to this hobby

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    1. I wouldn't recommend this as a plane to learn with. It's too fast and agile, but give it a go. You will learn quickly. It is tough and can handle crashes well.

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  11. I start in this hobby three years ago, and I try to build same planes and final drown plans myself and made a blog: http://www planesplans.blogspot.com. To help people to build wings I hab share your video that is wery helpfuly. Thunks

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    1. Excellent work on your blog, I'll follow you.

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  12. Can you help me I do not know where I made my mistake I also built a wing Also the airfoil with wire cut But took other forms Naca 2412 The wing accurses directly Or makes a looping I'll send you an example video https://youtu.be/ZNhrqjgy03c
    sorry for my bad English

    ReplyDelete
    Replies
    1. Hello. Your wing looks nicely built.
      My first thought is that the ailerons are reversed.
      Or it may be tail heavy - move the battery forward or add weight to the nose.
      Let me know how you go and good luck.

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  13. Hello Andrew
    I made a hot wire cut Mini Arrow as per your plans & recommendations, used your recommended Bunnings Foam, hot wire frame & $70 variable Power supply from China. I got an excellent result, although I am not overly keen on the Bunnings Foam as it very hard to get a smooth hot wire finish (I had 3 attempts)& the foam is very brittle.
    The Mini Arrow flew perfectly from the 1st hand launch, I have upgraded the motor to a Turnigy 2826 - 2200 kv & it performs very very well although I an not impressed with the low speed handling (ClarkZ Airfoil) which is when I do damage on landing. I am making another using an MH70,12% Airfoil and using a much lighter foam.
    Finally, I have all the Mini Arrow drawings in CAD & PDF format. If you want them please let me know.
    Regards
    Neil M
    Canberra

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    1. Brilliant Neil, it would be a wild little beast with that motor. Let me know if your new airfoil works better. Would love the PDF drawings to have a look at thanks. apnewton@gmail.com

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    2. Hello Neil would i be able to grab those drawing off you as well i would like to laser the airfoils out of ply so having your cad drawings would be awesome you can send them through at dursunmax@gmail.com please reply thanks!!

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  14. Excellent work! I will build one this weekend. Have you tried David windestål hot wire technique? https://youtu.be/R0ZCnR_g6ZU
    Do you think it could work with this design?

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  15. Yes I have tried that method but it is not suitable because you have no control over the other end of the cut, it is just a scaled down version of the template. I wanted a different airfoil on the narrow end.

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  16. Please can you tell me if it carries the mini arrow some degrees of deflection in depth?

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  17. Hello Andrew.I Like your jobs.where is the Centre of Gravity in the mini arrow please.I build one coming soon.Thanks.Best regards.

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