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Old Dec 19, 2008, 12:59 PM
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Probably it will be best to use a screw type servo connector to be able to adjust pushrod length easily, and offset the servo arm as required for differential action. If I give the differential from the bellcrank, it will be fixed and not easily adjustable.

Bulent
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Old Dec 22, 2008, 03:41 AM
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I could not start assembling the fuselage, but I continued with parts cutting to get a longer kit

I first corrected the cross section of the nose block/ motor bulkhead as shown, then removed 1.2 grams of balsa from the wing roots - which will have a 1mm plywood reinforcement glued on.

After that I finished the rib cutting template by putting in all required holes and gluing two pins to hold it steady on the balsa. The brown sections in the photo are epoxy dots that hold the pins on the template - that is some Russian epoxy I had bought decades ago while at an F3B contest in Bulgaria I used a broken razor blade for cutting the ribs, in this way usually no sanding is necessary and one can get a perfect cut - still I sand the parts slightly, thinking it would do no harm. I beleive similar results can be obtained using a sharp X-Acto blade as well, and it would be safer. I did not have any trouble with the razor blades, I am accustomed to this.

The rectangular holes in some ribs are for the bellcank plate structure. These are all the ribs that can be cut using the template, others are different size due to tapering of the wing at root and tip.

Fuselage bulkheads on the back have been cut, except for stringer slots. I also cut the rudder and vertical tail posts, but there is no photo showing these.

Bulent
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Old Dec 22, 2008, 08:17 AM
Übung macht den Meister..
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Quote:
Originally Posted by bmutlugil
I could not start assembling the fuselage, but I continued with parts cutting to get a longer kit

I first corrected the cross section of the nose block/ motor bulkhead as shown, then removed 1.2 grams of balsa from the wing roots - which will have a 1mm plywood reinforcement glued on.

After that I finished the rib cutting template by putting in all required holes and gluing two pins to hold it steady on the balsa. The brown sections in the photo are epoxy dots that hold the pins on the template - that is some Russian epoxy I had bought decades ago while at an F3B contest in Bulgaria I used a broken razor blade for cutting the ribs, in this way usually no sanding is necessary and one can get a perfect cut - still I sand the parts slightly, thinking it would do no harm. I beleive similar results can be obtained using a sharp X-Acto blade as well, and it would be safer. I did not have any trouble with the razor blades, I am accustomed to this.

The rectangular holes in some ribs are for the bellcank plate structure. These are all the ribs that can be cut using the template, others are different size due to tapering of the wing at root and tip.

Fuselage bulkheads on the back have been cut, except for stringer slots. I also cut the rudder and vertical tail posts, but there is no photo showing these.

Bulent
When Pa got my older brother and I started in stick-n-tissue models (I was probably 9 or 10, if I remember correctly, maybe a year younger), the blade of choice was a broken double-edge razor blade! Sure, our fingers got nicks in them, but that was a part of building a model!

James
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Old Dec 22, 2008, 08:29 AM
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Yes, these old techniques were all we had at the time - no laser cutting or CNC. Die cut balsa was invented but we could not buy kits here; even finding balsa sheets was a problem. I had learned these techniques when I was into F3B models around 30 years ago. I am accustomed to plug in wings from my F3B's as well.

I guess it is getting harder to find the older razor blades that were thick and brittle - at least here - so this technique may die. I have some old blades (PAL brand) and when I run out of these I may not easily find new ones. However a blade goes a long way; one may get a model finished completely Newer blades seem much thinner and quite flexible.

Bulent
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Old Dec 23, 2008, 10:44 AM
Übung macht den Meister..
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Quote:
Originally Posted by bmutlugil
Yes, these old techniques were all we had at the time - no laser cutting or CNC. Die cut balsa was invented but we could not buy kits here; even finding balsa sheets was a problem. I had learned these when I was into F3B models around 30 years ago. I am accustomed to plug in wings from my F3B's as well.

I guess it is getting harder to find the older razor blades that were thick and brittle - at least here - so this technique may die. I have some old blades (PAL brand) and when I run out of these I may not easily find new ones. However a blade goes a long way; one may get a model finished completely Newer blades seem much thinner and quite flexible.

Bulent
Bulent,

A2Z Hobbies is a source for thin, double-edge blades. I've attached a pic of their listing for 100, but they sell them individually as well.

James
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Old Dec 24, 2008, 05:18 AM
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Thanks James, that is good knowledge.

If you used any, are these the brittle types that can be broken easily without distorting the blade?

Bulent
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Old Dec 24, 2008, 08:30 AM
Übung macht den Meister..
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Quote:
Originally Posted by bmutlugil
Thanks James, that is good knowledge.

If you used any, are these the brittle types that can be broken easily without distorting the blade?

Bulent
No, I have not used them, but according to the details, they "snap easily to a point."

James
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Old Dec 29, 2008, 04:20 AM
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Some of the developments on the weekend. I constructed the LG box, and started assembling the fuselage, tested motors.

The center of the fuselage is assembled now, I have added the cross members after taking the photos, taking care of aligning them well - I hope

Th LG box will sit as shown in one of the photos. LG wires and strut holder will be pushed in from the sides and secured with the screws - the cabin is large enough to permit screwing from the inside, and doors will be functional. I guess I will use two screws to hold the wings in place as well - I can not be sure the struts alone are enough.

The long pieces are the tail structure elements around the hinge line. They are tapered because a streamlined profile is used.

Bulent
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Old Dec 29, 2008, 04:29 AM
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Here is the motor bulkhead, the thrust adjustment plate and the motor(s) to be used. If the small one is not powerful enough, I will use the larger motor.

The shaft of the motor will be reversed (and lenghtened) so it will go out of the other side. The aluminum thrust plate has 2 degrees down and 1.5 degrees right thrust built in, so the bulkhead has to be dead vertical and perpendicular to the fuselage center line. The plate was kindly machined and donated to me by Nachman Zimet of Israel. That kind of machining is beyond my capabilities. I guess this plate may help in cooling the motor as well.

I have seen that I will have to use a two cell battery, so I may try an A123 setup. That will be heavier, but charging will be much faster. I get tired of waiting for batteries to get charged at the field (when I have no spares). The small motor is just short of 60W at two cell voltages, so it might be marginally sufficient - motors are directly replacable as they have the same screw holes. They can even be changed at the field, if that becomes necessary. The larger motor is the FC 28-22, I forgot to show the label. Both from Hobbyking/United Hobbies : $5.95 each (except mailing). By the way, I just noticed that both photos showing the motors are wrong, the motor and thrust plate should be on the other side. This is the view from forward and the motor should be in the back of the bulkhead

I can use a 10x4.7 SF prop with these, the larger one can even drive an 11 x 3.8 prop, which would be the scale diameter but that would be overkill and a very low pitch.

Bulent
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Old Dec 30, 2008, 05:16 AM
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On weekday nights I can take only small steps, here is last night's work.

LG box was glued between two cross members, this section is nearly indestructible Other cross members of the center section are ready as well. Rubber bands corrected a slight shift, probably they are not needed any more after the LG box is in.

I also preapared the cabin floor on which the servos will sit. Reinforcing strips will be glued below. It does not look like a floor, but the holes save 0.8 grams. Probably the holes can be covered up with lighter stuff, if a scale cabin interior is desired. I have no desire for such at the moment.

I wish everyone a happy new year..

Bulent
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Old Dec 30, 2008, 10:14 AM
I think I can glue that..
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Bulent: how do you cut those nice round weight reduction holes? Brad point drill bits? or are you just really handy with a razor blade?
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Old Dec 30, 2008, 10:47 AM
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Hey Bob,

Good to hear from you. This project has taken precedence over the Dragon Rapide - that may come next. I wonder if you started on a Dragon.

The holes are all manual work. I drill a pilot hole, then enlarge that using tapered grinding stones on a Dremel moto tool - which I slow down so it will not burn the wood or itself A 45 degree conical stone puts a good chamfer on the edges, after the required diameter is reached - of course if the part has some thickness for that.

If the diameter is large enough, I use the Dremel sanding drum to finish the job - before chamfering. That is what I did on the last balsa part. I have found some smaller diameter sanding drums, but ordering them form the States is not very trivial.

Bulent
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Old Dec 30, 2008, 11:28 AM
I think I can glue that..
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I havent gotten anywhere near the Rapide as yet. I still have multiple builds ahead of it... Driggs Skylark (another one of Pat's kits), Gypsy Moth, another heavily modded foamie beaver (I always seem to be building one of those). I plan to do a thread on the Driggs when I start on that though. For all hand cut parts you really do a very nice job!
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Old Dec 31, 2008, 03:58 AM
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Thanks,

I drilled some more holes on the section that goes below the door sills, but no photos yet.

Maybe next year

Bulent
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Old Dec 31, 2008, 08:42 AM
Slow 'n Steady...Grease 'r In
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Bulent,

I've still been watching your progression, but haven't had too much to say because most of what is discussed is over my head. I like your work, though! I would have to agree that, using the tools you have, you make an amazing piece of work! Can't wait for the next update .

KP
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