Bleriot XI

[Birgir]

Good to hear that your Bleriot is back on its feet again, David. It didn’t take you long to get it fixed. Lost 800 gr of weight, where is the CoG now?

I fly mode 2 and if there is no aileron I have elevator and rudder on right. My first plane where three channel Kiel Kraft Mini Super with that setup, later I added aileron.
**LINK**

What size prop are you using?

B.

[David Germany]

CofG is now at 120mm back, about 35%. Prop is 11 x 6 at the moment.

I have my controls set up as you, effectively flying on the right stick. I use this on hand launch rudder/ elevator gliders with no problems, but I did have a rudder/elevator Taube which I flew infrequently and invariably tried to track on the ground using the redundant rudder stick, with the inevitable untidy take-off.

David

[PatMc]

Posted by David Germany on 17/07/2016 22:51:20:

but I did have a rudder/elevator Taube which I flew infrequently and invariably tried to track on the ground using the redundant rudder stick, with the inevitable untidy take-off.

David

David, mixing the redundant "rudder" stick with the operational right stick cures that problem. I use between 30% & 50% mix with several vintage models. Solves the inadvertant wrong stick input as well as oversteering issues on take off.

[David Germany]

Any flights yet Birgir.

Have managed three short flights with mine. First flight was decidedly scary, 2 circuits and a fairly hard landing, luckily no damage. Checked CogG and realised it was too far back. Re balancing to the 120mm mark took another 200g of lead. Second flight a bit easier but definately hangs its tail and fairly reluctant to turn. Increasing rudder has a limited effect up to a point at which the model suddenly banks over needing a fair bit of opposite to level again. Climbs steeply under power, and descends rapidly when the throttle is closed. Made a pretty good landing, rolling along nicely on the main wheels. Went for a third take-off, a few circuits and another reasonable landing.

So, in summary:-

Needs a fair bit of speed and a long take-off run to get airbourne.

Applying elevator to get airbourne seems to result in dropping a wing, which is controllable if you keep the power on.

Flies a bit faster that I had anticipated.

Needs a fine balance on the throttle to maintain level flight, too much results in a steep climb, to little sees the nose drop into a fast descent.

Drags its tail in turns,

Reluctant to turn and drags its tail up to a point, when the inner wing drops sharply as if going into a spiral dive. Opposite rudder brings it back, if a bit untidily.

I think some of the issues are down to my limited skills and it may be a matter of mastering the somewhat sensitive control responses. I rather nievly expected this to be a relaxing calm weather model, but possibly this is not the case.

I may mix down elevator to throttle to help minimise the climbing under power.

Anyway, the windy season seems to have returned so it's back in the loft at the moment.

Dave

[Birgir]

Congratulations Dave!!!

This is very interesting to hear. I’ve not been able to have spare time and calm weather meet yet but this news makes me very restless. Hopefully I can find a time on a calm August evening soon.

Thanks for the description, it will help me to build courage for my first takeoff.

B.

[Don Fry]

David, have you considered the thrust line of the motor, I would suggest that you consider a bit of down thrust might balance the climb/dive issue.

Edited By Donald Fry on 03/08/2016 19:15:21

[David Germany]

Good point Donald, I've did have down thrust as per the plan but I may have inadvertently changed this when I replaced the motor. I'll check it out before flying again.

David

[Birgir]

At last, at last – the first flight of my Bleriot tonight!

Birgir

[David Germany]

Well done Birgir, that looked a lot less scary than my first flight. What were your conclusions afterwards ?

Where did you finish up at regarding CofG and all-up weight ?

David

[Birgir]

Well, it still felt at least a bit stressful 

Actually I flew two flights. The first flight I left Luis on the ground (56 gr.) but added 100 gr of lead up front, having total of 700 gr. ballast. The power was very marginal and it felt more of a problem to keep the nose up rather than being tail heavy.

So the next flight I skipped the extra 100 gr and put Luis in again (about 2630 gr total, I think). I also noticed that the elevators seemed to have moved on their axes. I corrected that, tightened the screws holding the middle and took off again. That is the flight in the video.

After not so graceful landing I realized that the elevators had moved again and where not in line with each other. The aluminium pipe is not glued well enough in the elevators and can be moved. There were just a minor damage to two of the balsa pieces in the side of the fuselage.

The lesson learned is.
a. CoG about 12 cm from the LE looks ok at present
b. The power is marginal but ok with 10x4 prop
c. The split elevator does its job well, but needs fixing
d. This was great fun!

Birgir

[Birgir]

Hi

I ‘m still doing some exercise and learning to control the Bleriot. I’ve realized that in the first tries one of my mistakes was to use the elevator to keep the fuselage wheel on the ground. My thought was that keeping the fuselage wheel on the ground would help the control on ground and at the same time ensure that the model would not nose over. I was also worried about the tail being set too high so the take-off incidence of the wing would not be enough.

I have now learned that it is better to relax on the elevator, keeping it neutral on the runway. The model soon lifts the tail getting into the correct fuselage datum line (I think). There is no danger of nose-over and it is much easier to get up speed. When suitable speed is acquired a small pull on the elevator stick gets it airborne. When in the air it is very important to keep the model straight into the wind using the rudder against the direction the model tends to go to. If not, it will drop a wing and go back to the repairing table. This is where I am at the moment. No major damage, just small fixing here and there.

Any comments and advice are very welcomed

B.

[David Germany]

Glad to hear not too much damage.

I've also consciously tried to hold the tail down on take-off for the same reasons. Next time I'll try leaving the elevator neutral until lift-off.

Regarding holding directly into wind I very much agree. I have just crashed my 84 inch Aeronca C1 due to not putting in enough rudder to keep directly into wind on take-off, It dropped a wing and spun into the ground. (No major damage).

David.

[Birgir]

Hi everyone

 

Today there is a fairly calm weather in Iceland, about 5 m/s, so I decided to practice a little more with my Bleriot

 

Better tuned engine and also more running time has increased the power a bit but it still is very scale like. I have also put neoprene tires on the wheels – thanks for the tip David.

 

The wind was a bit swift and the model was swept side to side. The take-off went very well, I have taken PatMcs advice to mix the left stick 30% to the right rudder stick and it works well.

 

When in air the rudder and the split elevator do have a very good control over the model. Even when a sudden side gust almost rolled the model 45 deg. full rudder could level it off and for a short time it looked like the model was flying sideways, at least compared to the ground.

 

I hope there will be more opportunities to practice later this autumn – this is very much fun even though the wind is about the limit the model and I can handle.

 

B.

 

[David Germany]

Good to hear Birgir, I must admit mine has been languishing in the loft waiting for the ideal weather, which is obviously not coming. I will increase the down thrust before flying again and will program in PatMcs rudder stick mix as well.

David

[Birgir]

Today we had yet another calm day in Iceland, - what is the world coming to.

I did some more practice on my Bleriot and now I have two tasks at hand.

The first one is fine tuning of my SC30FS. When I run it full throttle for some time it tends to take a brake and stops delivering full power for five to ten seconds. If I relax on the throttle it picks up again. I’ve tried to lean the mixture, quarter of a turn clockwise, but that increases the problem. If I make the mixture richer, turning counter clockwise I’m not getting as much power. Does anyone have experience of this? Could this be something that disappears with a little more running in?

The second task is trimming. As I´m getting better at controlling the model in the air I now have started to trim for levelled flight. It looks like the model only has one speed, full throttle, and needs 5 degr. of up-elevator to keep constant height. Considering that the elevator area of the split stabilizer is quite big, (68 sq.in.) this is considerable amount of up-trim.

There are probably two main factors to take into account. The first one is the down thrust of the motor. I haven’t been able to test this properly but it feels like the model slows its speed and loses height very rapidly when the throttle is pulled back, not pulling up as I would expect if the down thrust would be too much. It is as per D. Boddingtons plan.

The second factor is the Centre of Gravity. At present I have got 600 gr of lead up front and the CoG is about 12 cm from the LE. On D. Boddingtons plan the mark is about 10 cm from the LE. Would it be right to presume from the flight experience that the ballast is still a bit too much and would be ok to move the CoG one cm further back or so?

My intentions now are to remove 50 or 100 gr of lead and have a try.

Does that sound sensible?

Any thoughts, comments and ideas are welcomed!

B.

 

 

 

Edited By Birgir on 16/10/2016 18:45:35

[Don Fry]

Behavior sounds like an overheating engine, may disappear with more running.

CG is too far aft, take weight out, but suggest say 25 grammes at a time. When the CG gets to its critical point, 25 grammes is a lot. As the weight comes off, you will find the under power issue tends to reduce, which removes the overheating issue. We hope.

Edited By Donald Fry on 16/10/2016 19:59:59

[Birgir]

Thanks Donald

But I‘m a little confused. When you say “too far aft” do you mean “too far forward”?

I will take 25 gr. out at a time.

B

[Don Fry]

Sorry mate, senile dementia setting in, I mean too far forward. The way I would do it is to make a hundred grams of your ballast easily removable, in 25 gram lots. Two minute flight, decision, land, remove 25 g, another 2 minute flight, repeat, etc..

After 4 flights, remove 100 grams of permanent ballast, and repeat with the 25 gram lots.

Edited By Donald Fry on 17/10/2016 09:33:56

[Birgir]

 

Following Donald’s suggestion, I switched 100 gr of lead with 3 * 25 gr and took off.

 

Everything went ok but it didn’t seem to make much difference. So, I landed, removed 25 gr more and took off again. Everything still ok, a little change for the better, not as much elevator needed to maintain constant height.

 

Next decision: remove another 25 gr. Now, my courage was increasing and I had a new idea. How about different style of landing. Until now I have always landed on half a throttle, flying the plane in, aiming for a smooth landing. What about having the motor idling and gliding in for landing?

 

Well in just a few second I realized that Bleriot XI is no glider. Under cambered short and wide wings are not at all similar to gliders wing. The model came down more like an elevator than a plane.

 

When landed, I realized that somewhere before, I had seen a picture of similar landing.

Talking about scale

Luis Bleriot’s first landing in UK was probably very similar to mine.

Only minor damage and already fixed, further adjusting of CG must wait another day.

B

[Birgir]

I‘ve been thinking (yes, it does happen) about prop types and sizes. Earlier in this thread there was an informative discussion about prop sizes. After some testing with a very primitive testing method, rubber band and a ruler, I came to the conclusion that a 10*4 was giving the most pull and decided to stick to that prop size at least while solving other problems (CoG, weight and better wheels)

I understand that a higher pitch gives more speed and more diameter gives more thrust. So if I want to keep load on the motor constant, I can get more thrust with more diameter and smaller pitch, but that would, in theory, give lower speed. For my Bleriot and SC30FS it appeared in my rubber band test that 10*4 would work best. That was actually suggested to me much earlier, i.e. aiming for thrust rather than speed. (Thanks Jon)

I have been using nylon props, Robbe Dynamic, for all my testing and flying because they don’t brake easily and can survive a nose over or two. But from aesthetic point of view a wooden prop would look much better on a Bleriot and it has also been suggested that a wooden prop would max performance.

So now to the actual question.

If I go from Robbe Dynamic nylon prop to Turnigy Type A Beech Wood Propeller, can I use the same diameter and pitch?

Jon Harper has pointed out that those A type props run really fast and therefore I might use 11*5.

Based on my limited experience and knowledge I would think that 11*5 would put more load on the motor demanding more thrust and speed than 10*4, especially if it spins faster due to thinner blades.

I would welcome any explanation, comments, suggestions and tips about the difference between using wooden and a nylon propeller.

B.

[David Germany]

Can't help with prop selection Birgir, I tend to use trial and error. If you are thinking of using wood how about an XOAR WW1 Scimitar, I have one on my Flair Puppeteer and I think it looks better than the normal wood prop.

[Jon H]

The trick with props will be to keep the rpm in the working range of the engine. In your video the engine seems to be really screaming but you aren't really going anywhere so that suggests it needs a bit more prop. If you have a tacho I would choose a propeller that runs about 9000-10000rpm on the ground. You don't really want it revving like mad as its not as efficient like that. The symptoms you mention about the engine are typical of an engine getting a little too hot but I would not be worried. cooling will improve in flight so if it hangs on for 10 seconds on the ground in the air will be just fine.

I used 10x5 master airscrew props with some success in the past and now the engine has some running time this might work well. 11x4 master or 11x5 turnigy A would also be worth a try. Its possible a 12x5 turnigy might work if they do one. The master props should be very cheap and easy to get and will be more robust during your testing phase.

[Jon H]

I just read your post again and I didn't really address one of your questions.

The simple answer is that there is no simple answer. Choosing a propeller is not easy and predicting its performance is also not easy.

For example, using my saito 45 for reference I recorded the following figures

13x5 turnigy type A - 8600rpm
13x5 turnigy cherry - 6200rpm
13x5 Master airscrew K - 7000rpm

Again, my Laser 180 recorded this:

Master classic 18x8 - 7500rpm
Master wood scimitar series - 7200rpm
Turnigy type A 18x8 - 8000rpm
Menz wood 18x8 - 7400rpm

So, not only is material a concern but so is the brand. In the case of my 180 the prop with the slowest rpm (master wood) was the one that gave the best performance. The Menz was next and then the turnigy and the classic fought over last place with the classic being very noisy. RPM is not everything and if the prop has no bite on the air then you will loose performance.

But

being able to turn a larger diameter at the same revs as a smaller prop will give higher thrust, so the type A series that normally run fast will usually give back more than they loose because of their inefficient blade. In the case of my 180 this didn't happen as I did not get enough of an rpm rise, but on the saito it worked very well as the rpm rise was so large.

As david has already said its about trial and error at the end of the day, and its about compromise. For example the lovely xoar he has on his pup there is not the most efficient as it puts a heavy load on the engine. That said, it looks great and while the engine might not give its best performance using it, if the performance is enough then its not an issue.

As I don't know how the props you are using perform I cannot really judge which brand would be a step up and which would be a step down. All I can say is that my old tiger moth flew well using the master 10x5

[Birgir]

Hi

The weather here in Iceland has not been very suitable for my Bleriot project lately. Never the less I’ve been able to do some flights. As some of the readers of this thread may remember there are two main tasks at hand at present. The first one is adjusting the CoG losing some of the lead up front and the other one is to select the best prop to be able to get the most out of the rather small SC30FS.

On D. Boddingtons plan the CoG is marked about 10 cm from the LE. To get the CoG to 11 cm I had to put about 600 gr of lead on the landing gear and therefore it was very difficult to get the model up to speed on the runway with the rather small engine. When in the air I had to use a considerable amount of up elevator to keep it level. I took Donald’s Fry advice and took off 25 gr of lead after each flight. Now I’m down to 425 gr so I must have had more than eight flights until now. The model still needs an up elevator, but considerably less than before.

During this time, I’ve only had two crashes, not counting some hard landings and minor injuries. Both was of course my own fault. The first one was fixed by re-gluing the landing gear but the latter one was more drastic. The reason for that crash was that once again I didn’t follow the rule of heading directly into the wind until suitable height is reached. If you allow the model to turn to early it will drop a wing and tip stall into the ground. (I needed three instances to get this; understand, practice and remember.)

The model is already fixed and ready for take-off once again.

I’ve been using 10*4 prop but as the engine runs in, it gets more power and I have now switched to 10*5 and by that I’ve got a little more speed for take-off.

It might be wise to try 9*6 or 10*6 as I could still do with a little more speed for take-off.

Now I´m off for Texas for a fortnight so further test must wait a bit.

B.

Note to moderator:
To my surprise this thread has had more than 10.000 visits even though it has been buried deep in the forum. I wonder if it is possible to see where the bulk of those visits come from. Is there some website with a lot of Bleriot enthusiasts out there on the internet?

Edited By Birgir on 03/07/2017 10:34:29

[cymaz]

I’ve been using 10*4 prop but as the engine runs in, it gets more power and I have now switched to 10*5 and by that I’ve got a little more speed for take-off.

It might be wise to try 9*6 or 10*6 as I could still do with a little more speed for take-off.

Now I´m off for Texas for a fortnight so further test must wait a bit.

B.

Note to moderator:
To my surprise this thread has had more than 10.000 visits even though it has been buried deep in the forum. I wonder if it is possible to see where the bulk of those visits come from. Is there some website with a lot of Bleriot enthusiasts out there on the internet?

Edited By Birgir on 03/07/2017 10:34:29

I'm sure not only Bleriot fans read this but engine owners, builders and fliers who might learn something from reading the excellent blog