# Duncan's got a Flea

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by rtfm, Aug 3, 2017.

1. Oct 2, 2017

### rotax618

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I flew my flea very carefully, as I said I was never really comfortable with the inability to quickly pick up a wing displace by a gust. I did not enjoy the experience and only flew early in the morning when it was still. At that time I built a Drifter type of aircraft and flew it regularly. I had several ground loops landing the Flea, never damaged anything but my pride.
Once airborne and well away from the ground the Flea was stable but I never was confident in exploring the limits.

2. Oct 18, 2017

### rtfm

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Hi guys,
I'm busy putting together a Builder's Manual for my Rangi-Pou, which seems a better way to document the actual build of the plane than posting it here on HBA. Id=f anyone is interested, you can find the (evolving) document here:
https://www.dropbox.com/s/b7kz04ctcpiooq5/Build notes.docx?dl=0

Regards,
Duncan

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3. Oct 19, 2017

### nestofdragons

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I love this type of build-up guide. But ...be sure to let see from time to time the overal view. Only details gets you lost. You have no idea which corner you see of the build up.

4. Oct 19, 2017

### Victor Bravo

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Does this opinion/experience/wisdom match the general consensus of the Pou community in Europe ? Do the majority of the established Pou pilots in Europe only fly in calm conditions? Or does this only become an issue in Australia because of more turbulent conditions, gusts, etc.?

Koen... Matthew... can either of you address whether the Europeans would agree with Rotax618's observations ???

5. Oct 19, 2017

### rotax618

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I doubt that geography has anything to do with the ability to feel comfortable flying a flea. Loosing an axis gives a very different flying experience. The Wright brothers realised the necessity for roll control, sure you can fly an aircraft using 2 axes, but why would you? For the addition of a couple of pedals, a couple of hinges and a few extra cables you can have full 3D control in 3D airspace. It is only the dogmatic Pou fundamentalist who would stifle progress.
I am not advocating changing the basic formula, the front wing pitch control and overall simple and compact construction, these features make the Flea a great candidate for amateur construction, but it could have greater appeal.

6. Oct 19, 2017

### cluttonfred

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I certainly respect rotax618's opinion and I have only flown a Mignet type once, briefly. That said, after talking to pilots about the Pou-du-Ciel over many years including many people who have built and/or flown them, I can put the comments into four categories: 1) Hate them (never flew one); 2) Love them (never flew one); 3) Don't like them (flew one or more); 4) Like them (flew one or more). Disregarding 1 and 2 as not very informative, I can say that I have met dozens in category 4 and just a handful in category 3. Those in category 3 were almost always very experienced pilots of conventional aircraft, while those in category 4 were often, but not always, beginners. That suggests to me that, as Mignet intended, the Flea is great for novice pilots but can be disconcerting to more experienced pilots with thousands of hours of reflexes to unlearn.

7. Oct 20, 2017

### rtfm

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Hi. Thanks for the feedback. And I agree - I will try to incorporate your suggestion.

One feature of the build manual I find particularly useful though is the breaking down of the entire build into 40 tasks. It breaks the build up into manageable steps. I am currently working on Task # 9: The Main Gear (4 hrs, Total time: 25 hrs)

Duncan

8. Oct 26, 2017

### rtfm

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Hi,
Well, I've been doing a lot of work on the Build Manual - a huge amount, in fact. It is a little time consuming to have to constantly pause while building to take photos, and I've missed a few.

One thing I have come to realise, however, is that there is simply no substitute for T-88 epoxy. The stuff sticks like sh#t to a blanket. And I quite like working with it. Something about its thick syrupy consistency appeals to me.

I think I forgot to mention - I am building a second airframe - and using the initial one (now hanging from the "museum" ceiling) for reference and nostalgia. The reason is quite simple. I rushed in without thinking through the proper sequence of building the thing, and painted myself into a corner, as it were. The second airframe is far more accurate, has all the holes drilled in the correct places, and all the firewall cutouts already completed before I bonded everything together. And it is lighter by almost 1.5kg (up to the same build stage). And 1.5 kg difference is huge when you consider that the total airframe at this stage is only 5kg vs 6.5kg

And lest you think this has been an expensive re-working, not so. A total of $135. I'm currently on Task #12 (of 40) having spent 33 hours on Build #2 so far. But I've run out of epoxy so I went looking for some more. Locally:$102.25 for 473ml (!!?)
From ACSpruce: $86.67 (including air freight) for a LITRE of the bloody stuff. Sheesh... It should be here in a week. Duncan Last edited: Oct 26, 2017 9. Oct 26, 2017 ### rotax618 ### rotax618 #### Well-Known Member Joined: Nov 1, 2005 Messages: 672 Likes Received: 249 Location: Evans Head Australia FGI have a very good epoxy wood glue. 10. Oct 26, 2017 ### Aesquire ### Aesquire #### Well-Known Member Joined: Jul 29, 2014 Messages: 2,326 Likes Received: 939 Location: Rochester, NY, USA Don't feel bad. I built a garden trellis out of botched hang glider tubing. Did I just make 2 right leading edges? yes... yes I did. :ermm: 11. Oct 26, 2017 ### rtfm ### rtfm #### Well-Known Member Joined: Jan 3, 2008 Messages: 3,192 Likes Received: 571 Location: Brisbane, Australia NICE TO KNOW I'M NOT ALONE... 12. Oct 26, 2017 ### Victor Bravo ### Victor Bravo #### Well-Known Member Joined: Jul 30, 2014 Messages: 6,106 Likes Received: 4,883 Location: KWHP, Los Angeles CA, USA Many of us have built two left fuselage sides back in the model airplane days Duncan, THANK YOU for working on a build manual! Even if I never build a Flea personally, I can guarantee you that you will be doing a valuable service for many people in the worldwide Flea community for years to come. Le Saint Patron is smiling down on you ! 13. Oct 26, 2017 ### pictsidhe ### pictsidhe #### Well-Known Member Joined: Jul 15, 2014 Messages: 6,873 Likes Received: 1,853 Location: North Carolina Have you looked at Amazon for stuff like T-88? They often have an international shipping option that isn't too horrendous. I used it a few times from the UK. A quart of T-88 is ~$40 in Amazon.

14. Oct 26, 2017

### rtfm

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Hi,
Interestingly, although I bought the T-88 from Aircraft Spruce, the receipt I received was from Amazon. My quart cost me $34; So good deal. (Although the air freight cost more than the epoxy). Oh well, still saved HEAPS over buying the stuff locally. Duncan Last edited: Oct 26, 2017 MadRocketScientist likes this. 15. Nov 2, 2017 ### rtfm ### rtfm #### Well-Known Member Joined: Jan 3, 2008 Messages: 3,192 Likes Received: 571 Location: Brisbane, Australia The T-88 arrived today. Weirdly, although the bottles were sealed, one of them leaked a bit. But a quick bath in some white vinegar soon cleared that up. I'm off to the supplier tomorrow for some more wood to enable me to finish the keel, sand the longerons, fit the sides, fit the tailstock, make the fin and make the rudder. You can get quite a lot done with$100. As soon as I start building again, I'll update the Build Manual and let you know.

Duncan

16. Nov 4, 2017

### rtfm

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I've been thinking about how to make my wings.
From the Build Manual:
Following the tradition of forward-swept wing outer panels, here is my take on the planform:

I've tried to indicate with colours where the panels join, and what the double-folding wings will look like folded. (I hope you can make sense of my colour-coded diagrams). The main wing is just under 8ft wide. The central section is horisontal (ie no dihedral). Panel 2 angles upwards when fixed into position, panel 3 angles up again, and the wingtips (fixed) are angled upwards again. Like so:

Overall, this give a multi=panelled wing with an overall dihedral of about 6 degrees. At this stage I'm usure if 6 degrees dihedral is sufficient or if it is too much. I'll need to check.

As for the construction method:
1. Hotwire a panel (I have a CNC hotwire)
2. Line it with stretchalon (stretchy plastic film
3. Vacuum this (low vac) onto the bottom of the female mold. This bypasses any additional preparation as far as finishing, coating the foam, applying release agent etc)
4. Lay 1x layer of triax glass
5. Lay in graphlite spar caps
6. Lay in the second layer of triax cloth
7. Vacuum infuse
This will give me a wing panel with the spar cap completely embedded in the skin itself.

Repeat for the upper skin

The shear web will be a strip of 19mm x 19mm Hoop Pine bonded onto the top of the embedded spar caps, with a strip of 1.5mm Hoop Pine ply bonded to this.

Calculating the weight of the wing:
• Skins (whole wing) Using Triax cloth (189g/m^2): approx 4kg finished weight vac infused
• Hoop Pine base for shear web (5kg)
• Shear web (4.25kg)

Total weight: 13.25kg

This is without the hinges, and other hardware.

The rear wing will weigh approx 10kg

Duncan

Last edited: Nov 4, 2017
17. Nov 4, 2017

### pictsidhe

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Why a double fold?

18. Nov 4, 2017

### rtfm

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Much shorter when folded.

19. Nov 5, 2017

### pictsidhe

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looks similar to that achievable with a single fold.

HM380:

Balerit:

20. Nov 6, 2017

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