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Messerschmitt P.1091


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  • 2 weeks later...

Cold and a bit late, but otherwise perfect conditions today for some real test flights. I changed the center of gravity a bit to get to the optimum point. I think two positions for low and strong wind will be suitable with the small tail. And I increased the butterfly deflection to decrease the glide path on landing (which is quite long). Further I optimised servo movements a bit.

Several short flights and landings showed good flying characteristics. There's a little upwards tendency on an otherwise easy hand launch, which is just minor but I want to check that another day. Otherwise no flaws, although I think flying in rough conditions will be more interesting. Forward cog could help, of course. Glide angle is superb and I'm looking forward to good thermal conditions. Rolls are fine and loops and circling can be really tight. Aileron reaction supported by flaps is good, rudder a bit weak and has to be increased, elevator is fine but can be optimised, too. Stall tests on both cog positions were satisfying and better than expected, just the nose is going down and speed quickly regained. No tendency to flip over one side.

 

The AG35 airfoil is definitely a fine one. Easy to built with flat bottom surface. Easy handling, good performance.

 

Timo

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Cold and windy but dry at least, so more test flying yesterday and today. As expected it wasn't perfect flying in rough conditions. I had problems finding a good elevator trim, being either too high or too low. Either too much sink rate or loosing too much speed when turning into the wind. I also found out that the ESC voltage regulator has problems with the increased butterfly flap. 3A should be enough for six small servos, but this time I used digital servos on the wing and that could be the reason. There's a chance that they need high current at the same millisecond. And Kavan fast'n'eze hinges are more stiff than the traditional ones. Another task to optimise.

 

This morning I made several small changes. I increased angle of incidence a little bit by adding layers of tape to the fuselage. I moved elevator linkage to the inner hole of the servo horn. I also moved that servo and resoldered the clevis on elevator side to get a straight wire which is moveable with small force. Finally I put a light 3S3000 accumulator inside, COG a bit more forward than yesterday. Still more aft than originally calculated but that helps for finding thermals. Accumulator position is now perfect on the center of the accumulator board and easy accessible from the hatch, so that estimation was good.

 

Flying was different right from the start. The little up and down after hand start was away, just a perfect straight acceleration at a light upward angle. Flying was smooth despite the once again windy conditions. Only landing took full concentration. I had to land down the slope on the narrow grass patch with unsteady wind. Decceleration was too high at first, adding power for a second then lead to a long glide path at the same angle as the slope. So half butterfly once again to bring the model down while working on all rudders to keep the 1091 straight. Maximum deflection is fine since rolls and loops are possible, but for the next flight expo on aileron and rudder is zero and only 10% on elevator. 

 

So now I'm coming to the point where I can recommend building this model without bad feelings. More flights willl follow, of course, but it seems I'm on the right track. Finding good settings for a new model is always interesting, especially in this case with many servo functions and the double role as motor and glider plane. With scale models you have to make the best from what you have, no chance to alter the original design too much.

 

Timo

 

 

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Edited by Timo Starkloff
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  • 2 weeks later...
  • 2 months later...

Last weekend there was the meeting for plan & self built models in Huttwil, Switzerland. Last year it was not due to covid so this time much more people than usual appeared with a great range of models. If there's interest, I'll post some pictures in the events thread.

 

With my 1091 I've had a great formation flight with an Yokosuka Ohka someone built after my FMT plan of the same 1/12 scale. 180 cm compared to 45 cm. It wasn't easy to follow that small plane but the yellow colour helped a lot.

Right to the airfield is a steep slope which provided me with perfect conditions to fly the P.1091. Low level flying over the airfield combined with soaring along the nearby ridge.
I'm still undecided if I should test increasing wing angle to improve gliding angle, but it already is a fine flier. A bit weak on hand start and a long gliding path even with flaps deployed, but otherwise unsual looking and flying fine.

 

Timo

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Edited by Timo Starkloff
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  • 3 months later...

After being a bit lazy during summer, I resumed working on plans and CAD again. Not much to do with the P.1091, I increased the tail a bit and also the angle of incidence. Otherwise it's "just" sorting parts and rework text and explanations. Nethertheless it takes some hours of work.

 

It still is an unusual model and much fun to fly. A month ago I had to change motor and esc. The previous one with around 180 W got too hot one day in summer. Now the motor is capable of up to 25A according to the datasheet, although only short duration. I'll try to fly not at maximum power for long periods. There is not much cooling for a small motor inside the fuselage. But center of gravity and accumulator position is perfect and a heavier motor would make changes necessary for my model.

 

Timo

 

 

 

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  • 4 weeks later...

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