Baby Flea

[Geoff S]

Apparently Ian Redshaw's half scale flea is tricky to fly and has to take off and land exactly into wind, so be careful, Max, so as not to spoil your lovely little example. Full size fleas were prone to dive when the pilot tried to climb as I'm sure you know.

Geoff

[J D 8]

 

With it's lower wing moved back the Carden-Baynes flea eliminated the wing airflow interference problem of the HM 16 and may be more sutable as a pull out plan.

Nice looking model,Good luck with first flight.

Edited By J D 8 on 08/09/2018 15:02:24

[Max Z]

Thanks Geoff/JD8.

The Flying Flea that had the unrecoverable dive problem was the HM 14, on which the Carden-Baynes was based without any changes to the basic layout according to my reference (the book by Ken Ellis / Geoff Jones). The HM 16 was of later date, but never flown by anyone else but Henri Mignet himself. No plans were published, and only one example was ever built. The HM 14's wings are indeed further apart, but that did not prevent the (fatal) incidents from happening. The problem apparently occurred when more experienced pilots put the plane into a dive deliberately, which caused the stick force required to recover to increase by such an extent that the pilot could no longer regain normal flying attitude. If you just tottered around, the flaw never exposed itself.

I designed and built the HM 16 model earlier at a smaller scale, and it flew great, so fingers crossed...

Max.

[Max Z]

I re-read the chapter on the fatal flaw of the HM 14, and it was not so much the stick force as the travel on the pivot of the front wing, which in even a shallow dive was not enough to recover from it. Experienced pilots would realise they had lost control, and increased the dive angle to recover, only to increase the problem.

I shall not dive......

Max.

[J D 8]

Hi Max,I also looked up the changes made from the HM14 on later models, and the main one seems to be a change of pivot point and travel limit on the wing using rods not wires.

Can't be a bad design as there are microlite versions flying today. John.

[Max Z]

I am also using rods, but I deliberately made them from mild steel rather than piano wire, I'd rather see them bend on "funny arrivals" than pushing through the wing or destroy the servo gears........

[Stephen Jones]

Looking Good MAX .

Look forward to the flight report.

I have made a few flying Flea`s all flew ok.

I designed my own take on the Flying Flea and that one i am able too fly fast or slow or very slow and it can also pull loops for fun.

Steve

[DeeBee1]

Nicely done, that's a good looking Flea.

[Max Z]

Thanks guys. I am still waiting for some decent flying weather, in particular for the wind to lessen. It is not so much the wind persé, but more the turbulence close to the ground. A nature park is growing up around our field, and the shrubs that have been planted close by are causing such turbulence. I am afraid that the Flea will not have much roll control to counter sideways gusts, no ailerons and little dihedral (albeit on both wings). And the rudder is short coupled to the wings, so that is not helping either.

Max.

[Max Z]

Well.....the first flight is history, and let me first say the baby and me are fine . But it needs "finetuning". For one thing I needed not worrying about rolling, it was what it did best. Keeping a straight line on takeoff is something else, it only wanted to turn left. Side thrust may be a solution here. And as soon as I had taken off it wanted to climb sharply, indicating a tail heavy plane on a normal configured plane, but a lot of down would bring it into a sort of level flight, and that "normal" plane would have gone into a steep dive by then. So is it the CofG? I don't know, but I am going to move it forward to test that, probably by moving the motor forward (The battery is already in its most forward position). Maybe a bit of down thrust too.

I managed to make two flights, each one ending with a decent landing. The thing seems to float reasonably well, but I kept a bit of throttle until just before touchdown. The thing I don't quite understand is how it flew reasonably level with the front wing pivoted all the way forward, resulting in a negative incidence angle relative to the rear wing, but it seemed stable enough, at least at low throttle settings.

Max.

Edited By Max Z on 13/09/2018 16:43:45

[Stephen Jones]

Hi Max,

If you have a negative fore plane then you're CoG is wrong.

The Cog point on These fleas is more rearward than normal in my experience. And the angles on the wings and thrust line all need to be right. But as you have already discovered slow them down and it will still fly so long as you have enough control throw to correct.

You could make up a small chuck glider version so that you can play around with the CoG and angles of the Fore plane. In my experience the tailplane is level in level flight and use that as you're datum line and set 3 degrees down thrust from that.

If you like i can check the CoG on my models although i do not have the same design as you .

Mine are the HM14 and my own designs.

Steve

[Max Z]

You know Steve, I did design this one earlier on a smaller scale, THIS one, with the same airfoils, angles and distances. In fact, I just scaled everything up, only modifying some construction details. I looked at the original drawing and noted the CofG was at 55% of the chord from the L/E of the front wing. I balanced the large one at the same %, and since the little one flew great I expected no less from it. Today, my friend Rob (RBCkits) assisted me and when I showed him how it was balanced in the usual way, balancing it on my fingertips and judging the hang angle (which is quite difficult when you are alone) he pointed out that it was still leaning backwards, and probably needs more ballasting up front. Which is what I will try next, and if that is succesful I will tackle the side/down thrust.

Thanks for the comments, cheers,

Max.

(btw, love your little Sipa jets )

Edited By Max Z on 13/09/2018 20:26:09

[Stephen Jones]

No problem Max, looks like you have got it all in hand .

Thank`s btw

Steve

[Max Z]

Two more flights today, with (very) marginal improvement. I did move the motor forward by 10 mm, and also bent some toe-in into the undercarriage to assist in running straight during takeoff. Both measures improved things slightly, but it still flies tail down. On the second flight we stuffed some extra lead on top of the battery, and again there was some improvement, clearly pointing to the way to go.

As I said before, the problem will be where to put the extra weight to have the best effect. I probably have to do some surgery to the forward-bottom to get to the void beneath the battery support.

The main thing is that with very carefully moving the sticks flying and landing can be managed, and it is still undamaged.

Max.

[Stephen Jones]

When it is sorted i am sure it will fly as well and as predictable as mine do, it is a trait of tandem wings.

Steve

[Marc Webster]

Hello Max Z,

I found this build when searching for the HM.16. I have a 1yr old baby and my wife is French so I want to build an HM.16 as a pedal car for my son. We live in Los Angeles CA area. Anyhow, I am having trouble finding a good 3 view or even RC plans as a starting point. I am a solidworks user and curious if you would be open to share your CAD assembly as a basis for me to design the pedal plane. If you used another CAD program saving it as a Step file would also work. If you are open to this or helping in any way even if just sending a good 3 view than please reply to this post and we can exchange contact info.

Take care and looking forward to your reply.

Marc

[Max Z]

PM sent.

Max.