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Jan 26, 2014, 05:39 PM
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Build Log

30mm EDF Hawker Hunter F.Mk6 Ė Composite Scratch Build

Hi all,

Iíve had so much inspiration for you all on this forum and I love following your projects. Over the Christmas break I managed to make a start on a project I had been rolling around in my head for ages.

Iíve never been one for micros of any sort, until I got an Eflite UMX Mig 15 DF for Christmas over a year ago. I had never flown an EDF and loved it from day one, itís sooo much fun ..Ö you could say that the worm had turned.

Iím shooting for as close to scale as I can get it and bought a Revellís 1:32 Mk6 to use as reference. Around the same time we got a 3D scanner and printer for work. Its tech I been keen to learn and my Hunter project was another reason to bite the bullet. The Nextengine scanner and Replicator 2X could be classed as for the high end hobbyist / entry level designers. Although the learning curve has been steep, Iím starting to make some good progress with both technologies. Itís certainly not as easy as the media makes out.

So the goal is to use the tech to design and build a Hunter as much to scale as I can. Nothing is rule out from a material perspective and hope to mould a lot of it. The CAD model will be parametric to allow me to scale it to what every size I like. So far this approach has worked great and any changes I make to the master model propagate down nicely to the child parts.

Even though the project covers a wide spectrum of disciplines, Iíve decided to post the design & build here as Iím sure you guys will have much advice etc. to offer.

This is where Iím at and hope to do more in-depth posts on these points when I get the time.

3D Scanning & translation to CAD
I have a master scan of the Revell model. The translation to CAD has been a lot more difficult than original thought. There is a huge amount of clean up etc. to get the mesh to a usable state. As with all things, there is room for improvement. But I had to draw the line to get the project moving.
Creating an efficient workflow to getting the scanned data into SolidWorks has been the big challenge. RapidWorks, my 3D scanning software is capable of developing parametric solids from the scanned mesh and exporting them directly into SolidWorks. It sound great on paper, but in reality the translation can be more effort than itís worth, as well as creating bigger problems down the line. Also, I didnít want to copy the Revellís model manufacturing errors and you could say that I been using the scanned data as a very accurate 3D tape measure - only been using it for reference.
I have never designed a model so there has been a whole lot of reading and learning. I have established the CG position and scale to suite a 40mm EDF unit. An in-depth post will follow.
3D Printing
Another HUGE learning curve! I spent large amount of time getting the printer to work & print correctly. At the moment Iím doing more printing then fixing, which is good, but that could all change tomorrow.
Learning to design for 3D printing is a whole new ball game. I have to keep reminding myself that just because you can print it doesnít mean you should. The trick is to see it as just another tool in the toolbox.
Six months ago, I had never laid up a strip of fiberglass. I did a lot of reading, bought a bunch of supplies and just started playing. I mocked up a simple nose cone half in SolidWorks, printed it, designed & printed moulds etc. I think I have come up with a system that should work and look forward to seeing what you guys make of it. Huge thanks to the guys who put videos up, especially hornetpilot, invertmast and Danís F4 build.
EDF System & Ducting
The only experience I have is with the Eflite UMX Mig 15, so Iím learning as I go along. I have learnt loads from NitroChargedís posts and the inspirational Electrolyte micro sport jet build.
Looking forward to your comments.

Cheers, Steve
Last edited by meerkat13; Jul 15, 2014 at 05:23 AM. Reason: Started 40mm EDF, now 30mm EDF
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Jan 27, 2014, 11:15 AM
Dont forget the velcro straps
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Man...thats some impressive cad work!
Jan 31, 2014, 02:14 PM
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Great looking CAD work man! It i can be of any help when you get to the molding stage or CNC cutting of some internals, let me know! I love hunters and wouldnt mind getting my hands on a small one :

Feb 02, 2014, 10:30 AM
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Cheers Corsair.

Thanks for the offer Thomas, will definitely be asking plenty of questions when it comes to moulding and layups.

Cheers, Steve
Feb 02, 2014, 10:58 AM
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3D Scanning & CAD Translation

A little info on the scanning of the model.

In my naivety, my original plan was simple.
  • Scan the Revell plastic model in HD.
  • Convert the scanned mesh into surfaces.
  • Import the surfaces into SolidWorks and scale to suit.
  • Ö. Easy as pie (NOT)

As good as the scanner is, after the first couple of scans, I realised that I didn't have a chance in hell of making this work.

Even scanning in micro mode the scanner had huge problems in capturing the very thin edges of the wings and tail.

When sectioning the mesh I soon realise the model wasn't symmetrical. Manufacturing errors in the plastic injection moulding were obviously copied.

These errors aren't noticeable to the naked eye. However, if I were to create an exact copy of the plastic model, and say scale it up say 10x, these errors would be huge.

Using the softwareís auto surface feature worked great, but created huge files that were impossible to work with in SolidWorks. For example the majority of the fuselage could be created with a couple of surfaces in SolidWorks. Auto surfacing using scanning software would create hundreds of surfaces and basically grind my workstation to a halt.

I upgraded the scanning software to RapidWorks (a simplified version of Geomagic) in order to speed up the translation of usable CAD data. RapidWorks is a fully parametric mesh to CAD solution that allows you to easily create solids and surfaces that are very accurate. The solid forms and surfaces are then exported straight into SolidWorks and remain parametric.

This workflow works to some extent, but I had to spend a lot of time fixing errors to get to work etc.

In the end I made the decision to use the scanned data for reference only and used a variety of methods to getting that information into SolidWorks. Once in SoldWorks, I then modelled the parts in a traditional manner.

Although I have only modelled the bare essentials, the SolidWorks model is very accurate. The wing outlines are to scale, but I have modelled a different aerofoil plus a 1.5 degree incidence at the root, washing out to about -0.5 degrees at the tip. This isn't set and is very easy to change Ė I just needed to drop something in there to keep this moving.

Itís taken a while but on the whole I'm pleased with the accuracy Iím achieving.
Feb 02, 2014, 12:36 PM
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Hi Steve

Thanks for your comments on my build. It could hardly be lower-tech whereas yours is just the opposite. I am dealing with gross distortions and inaccuracies; you are dealing in tiny fractions.

I look forward to seeing you translate the 3D models into solid structures. One question at this stage: Do you have a target weight for the plane in relation to the expected thrust to come from your ducted fan? In simple terms, what is needed to make it fly?


Feb 03, 2014, 03:36 AM
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I would love to get near to 1:1 thrust / weight ratio but don't know how feasible that is. I would expect that it would fly fine as low as 0.75:1, but I'm NO expert.

The plan is to work from the ducting outwards. I'm almost ready to test the first duct design with the motor and rota. Just need to finish the the thrust test stand.

Why don't you run yours up now to test your ducting and you could also measure now much thrust you have to play with?
Feb 03, 2014, 04:23 AM
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As the ducting is not fully enclosed, I will have to wait until the fuselage is covered to do any meaningful test of the fan.

Even if the thrust reaches the quoted maximum of 130gms, I will at best have a thrust to weight ratio of 0.5 to 1. The kit was originally designed to be free flight with the battery and fan having a combined weight of 140gms (before adding the weight of the airframs!) and a thrust of 60gms. My fan and battery weigh a combined 80gms. The additional weight of servos, wiring, receiver and speed controller should be no more than say 40gms. The original model was reputed to be underpowered but it could still fly.

There is little I can do to reduce the weight, particularly as I will need to strengthen the tail fin and tail plane, so I will just have to plod on and hope.

I will watch your progress with interest.
Feb 22, 2014, 10:02 AM
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Just a quick update on the project

Most of my time has been spent on the duct design as well as developing a 3D printing solution. The biggest win is that I can now print reliable single walled parts with a layer height of 100 microns and a thickness of 0.35mm.

Components printed in ABS result in extremely strong and light parts that are glass smooth after finishing. For comparison as similar part printed commercially by Shipways would be over twice the weigh. Their Strong & Flexible plastic has a minimum wall thickness of 0.7mm and the plastic is also slightly heavier than the ABS filament Iím currently using.

40mm EDF or 28mm EDF ?

After printing the ducting to suit a 40mm EDF I realised that it would be a better idea to drop to a smaller scale on this first one. Any print time etc. would be greatly reduced as well I could use a lot of the parts out of the Eflite Mig 15.

Test Rig

I designed / built the test rig based on Brettís setup (hope you donít mind). You can see Brettís in action here.

Itís fully adjustable as I wanted to be able to test the EDFs complete with ducting etc. If anyone has access to a 3d printer and would like to print the parts, please let me know and I will upload the files etc.

Fan Balancing

I also designed a little fan balancing rig using a couple of M8 bolts and rear earth magnets. I got the idea from here, but there are a lot of similar setups. Again give me shout if anyone would like the 3D printing files.

Fan Shrouds

I tested my printed 40mm shroud against the original and it performed exactly the same. My version ended up being a tad lighter.

Printed Rotors ??

Just for the hell of it I thought I would try printing a 40mm Rotor. I didn't bother refining the design for 3D printing as I just wanted to see what would come out the other side. The results were encouraging and defiantly worth pursuing. Iím just in the process of trying a 28mm rotor with custom dissoluble supports. If feasible would open up all sortsí opportunities.

28mm EDF Hunter

The hunter scaled really well for the 28mm and feels right. The proof of concept ducting has been designed, printed and is ready for testing with the stock 28mm Eflite rotor and motor from the Mig. I will also print a 12mm Inrunner shroud that I can just swap in.

Iím itching to get started on the airframe but need to do some more testing / learning first.
Feb 22, 2014, 04:08 PM
Lee Liddle
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Wow! Awesome work. Amazing printed ducting! Any chance of doing a video of a fan test on your rig, and maybe some close up video or pics of the ducting with some size reference, like someone holding it or next to a soda can, or even a ruler?
Feb 22, 2014, 05:48 PM
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Looking really good Steve!

Once you get this micro one done, you should do a big one
Feb 23, 2014, 03:18 AM
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Cheers lee. I'm just about ready to test the 28mm ducting so will take some video. With the 40mm tests I just made notes of the results and wasn't all that systematic.... having too much fun

I have got a Eagle tree logger now so can hopefully do a better job. Hoping to record motor & ESC temps + rpms.

The plan was to have started testing yesterday but got side tracked. I designed a printable version of the 28mm rotor using a technique I hadn't tried before. The 1st prints have come out fantastical well and there is loads I can do to improve them.

I will take some photos once the I have finished dissolving the support material. It's still early days as they still need to be balanced and hopefully run up. Hopefully the first tests will be a comparison between the 28mm stock Eflite unit and the printed version ... no ducting, but with a printed inlet ring.
Feb 23, 2014, 04:16 AM
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LOL... something the size of your Tomcat. Maybe one day, but that takes some serious commitment.

The idea is that anything I design in CAD should be completely scalable. I know that you use SolidWorks so understand that a lot of the work is done upfront and if done right can save a huge amount of time further down the line.

A good example was my resent decision to drop the EDF and airframe scale from 40mm to 28mm. The new scale propagated to any dependant parts and assemblies i.e. the ducting automatically scaled. The whole process took no more that an hour and saved weeks of rework

So scaling up, to suit a 90mm EDF, would be just as easy. I'm even going to the extent of using external data sheets to drive parameters like print extrusion thickness. This way I only need to change the parameter in one place and it automatically updates any parts and assemblies that use that variable. Again its more work up, by saves hours down the line. It also allows me to try experiment without the hangup of CAD rework.

I'm confident that I will be able to include the panel lines etc. in the 3D model but at the moment just want to work on a proof of concept, otherwise it would take forever to get to a flying model.
Feb 23, 2014, 08:11 AM
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Nearly there with a printed 28mm rotor. Just need to redesign the hub internals and we should a rotor good enough to test

The white rotor is the printed one.
Feb 23, 2014, 03:32 PM
Lee Liddle
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Those kind of pics really put it in perspective. Very cool. How about a shot of you holding that pink ducting. Those are some cool parts.

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