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Old Dec 15, 2008, 05:24 AM
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Here is a dry assembly of the nose and the fuselage. Parts fit is not bad, but I guess I need to increase the width of the horizontal members because the fuselage cross section is far from rectangular and the sides of these have to be angled accordingly..

Working from laser printed sheets is not very accurate, because the laser printers do not print 1:1 exactly. I had to apply correction ratios while printing, and still they may be offsize a bit. Joining the sheets may bring other errors.

I was lucky that the photos came out well, the camera is not very good - I am not sure if it has any focusing at all - and it depletes its batteries very fast.

Bulent
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Old Dec 15, 2008, 09:49 AM
Two left thumbs
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A work of art, Bulent!

Geoff
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Old Dec 15, 2008, 10:57 AM
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Thanks,

I hope it looks as well or better after gluing

I guess I will try to align the motor bulkhead to be exactly perpendicular to the center line using a laser line projector. That is because the motor will mount directly on the back of the first bulkhead, using a thrust adjustment plate. I will reverse the shaft and make it longer, the original shaft is too short.

I wonder where the battery will go. I am reluctant to lighten the lower second bulkhead, thinking it may be necessary to put a battery cutout there; but probably that won't be the case, because the nose is quite long. Maybe for low capacity batteries forward placing may be more likely. I also want to provide space for A123 batteries that may be used in the future; but those are heavier so they will be placed closer to the CG..

Bulent
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Old Dec 17, 2008, 04:54 AM
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I worked on the nose block and rib cutting template. The shaping of the nose will continue after final assembly.

I am gradually shifting from the idea of using a single aileron servo placed in the fuselage to the more conventional method of two servos placed in the wing panels. Mechanical pushrod couplers seem more difficult to make and use. With two servos, it will be easier to plug the wings in - if servo connectors are prepared properly. Slight weight penalty may result, like 3 grams extra from the servos; but servo mounts and pushrods will be lighter so some of that will be gained. An HS-50 will fit between two ribs.

Bulent
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Old Dec 17, 2008, 03:22 PM
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Great work Bulent - I like the 'laser-cut-look' but without the charred edges
The dual aileron servo method always appeals to me - esp. if your Tx uses two channels - setting up differential etc is so much easier.
Will your noseblock be a plug for vac-forming or be used as is?

Pat
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Old Dec 18, 2008, 10:45 AM
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Hi Pat,

Thanks. I intend to use the nose block as it is, carving the inside and maybe applying light glass cloth; it is around 8 grams at the moment. Somehow it does not look very scale - I noticed that too late. I will try to get it narrower on the lower section. Maybe after final sanding it may look better, though, now the sides are not at the right angle. The nose has compound curves, so I may have to make the side panels from fiberglass material, forming them on foam blocks shaped in place.

This plane is suitable for servo-in-the-wing method, because it has fuel tank surfaces which are flush with the cap strips - on both upper and lower sides. The lower one can be made removable as an access point that is scale..

I should be able to get two channels for ailerons, I have to check. My receiver has four channels; but programming the UH-8 TX for that may not be very easy.

Bulent
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Old Dec 18, 2008, 07:59 PM
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English Wheel

Bulent,

I didn't want to hijack maltone's thread, so I'll bring it here.

An English Wheel of small enough size could be useful for such items as the wheel pants for your F24. Shape them in halves, then I suppose you could epoxy them together. The nose bowl for your cowl might be a bit tedious at this scale, however.

My dad used a rather large-framed English Wheel to shape a nose bowl for a Taylorcraft E2 he was helping to restore for WAAAM . He also said the head of restorations there was practicing with it and made something about the size of a teacup.

Indeed, it would be a neat project for the workbench!

James
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Old Dec 19, 2008, 03:43 AM
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After working out the high level of arithmetic required, I realized that a four channel receiver could not yield two channels for ailerons My 8 channel receiver is an ounce heavier than the Berg , so I should forget the separate aileron channels issue unless the model comes out very light.

James,

Could we use the wheel only on aluminum for model work? Other than steel and aluminum, is there any other metal it could be used on? I had read that aluminum had to be heated frequently to soften it during the process of shaping - it would work harden, or whatever the name for that behaviour is..

Bulent

Bulent
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Old Dec 19, 2008, 08:40 AM
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Quote:
Originally Posted by bmutlugil
After working out the high level of arithmetic required, I realized that a four channel receiver could not yield two channels for ailerons My 8 channel receiver is an ounce heavier than the Berg , so I should forget the separate ailerons issue unless the model comes out very light.

James,

Could we use the wheel only on aluminum for model work? Other than steel and aluminum, is there any other metal it could be used on? I had read that aluminum had to be heated frequently to soften it during the process of shaping - it would work harden, or whatever the name for that behaviour is..

Bulent
Bulent,

I would imagine you could use the wheel on most metals that are reasonably malleable, but work-hardening would be an issue for some projects. I suppose you could use it on brass, for example, but my guess is it would become brittle much more quickly than aluminum and would require annealing more frequently. Pat (maltone) mentioned heating (annealing) the aluminum cowl piece for his Bison several times while shaping that, however he was not using a wheel.

I asked my dad how long it took him to shape the E2 nose bowl, and he said the actual forming on the wheel took about a half hour to 45 minutes (running back and forth to the airplane to check the fit added time! ). He didn't mention he had to anneal the piece for that job. The E2 picture attached is just an E2 pic I found on the net, and not the one my dad worked on. The cowl nose bowl is the same shape, however.

Regarding the ailerons for the F24, I seem to recall my dad said the Fairchild used pushrods with ball bearings at the various bellcranks, resulting in a very smooth feel at the controls! So go ahead and use pushrods and be scale!

James
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Old Dec 19, 2008, 08:59 AM
Two left thumbs
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You don't have to use a computer radio for aileron differential. Setting the servo arms at other than 90° does it, but it's only adjustable by relocating the servo arm.

Fine work so far - keep it up!

Geoff
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Old Dec 19, 2008, 09:55 AM
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Thanks Geoff,

I thought of that way of giving differential also, but the servo arm can be relocated in steps only (depending on its spline), so the differential can have a few discrete values. My transmitter is programmable, but I need a 5 channel receiver.

I have Friese ailerons - if that is the right expression - the aileron LE projects below the airfoil when deflected up, does that reduce the need for differential? Probably that will cure adverse yaw tendencies.

James,

Maybe I can give a try to molding the nose bowl from aluminum; but that will take extra time, which is a luxury I may not have.

I will have pushrods and bellcranks on ailerons, but no ball bearings - and if I can manage it, nothing will show on the wing - the pushrod will be internal. I am thinking of ways to make the servo connector invisible also - by using the joiner tubes - but of course that is needless overkill

I have attached a cross section of the belcrank/aileron hinge, showing throw limits; of course designing is easier than implementing.

After posting this, I realised that differential throw could be given by offsetting the belcrank's neutral position.. The amount of differential action can be finely adjusted in this case, but changing the lengths of both pushrods will be necessary.

Frankly, I have no idea how much differential should be used.

Bulent
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Old Dec 19, 2008, 10:47 AM
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You don't need a separate channel for each aileron. They are connected by a single Y harness. You just make sure that your servos are oriented 180 degrees from each other -- e.g. servo arms outboard, servo bodies in board with respect to the wingspan.

Pete G.
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Old Dec 19, 2008, 11:23 AM
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I know they should be connected with a Y harness, but I was referring to maltone's post #50 above stating that setting up aileron differential was much easier with separate channels on the TX.

Hopefully I can start assembling the fuselage on the weekend..

Bulent
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Old Dec 19, 2008, 12:50 PM
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Quote:
Originally Posted by bmutlugil
I have Friese ailerons - if that is the right expression - the aileron LE projects below the airfoil when deflected up, does that reduce the need for differential? Probably that will cure adverse yaw tendencies.
Bulent, I had Friese ailerons on the Scion and they worked very well to prevent adverse yaw.
That being said, she flies mostly on the rudder and could probably get by without ailerons at all!

Roly
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Old Dec 19, 2008, 12:50 PM
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OK -- didn't connect the dots. The differenntial can be done manually if you do not orient the control arm at 90 degrees to the throw. That gives more motion in one direction than the other. That is how they actually do it on the Tiger Moth.

Pete G.
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