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Plan Modifications

Old 01-09-2017, 05:59 AM
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Default Plan Modifications

Here is the plans of the wing I am scratch building. I got them enlarged and was looking at them last night, I started wondering if this plane was worth making. I started doing some research on it, I found one built, and the guy who built it says it flies great, so I will take his word on it. The plans were published in 1980 in RC Mag, so there is some credibility to them. I am wondering why the designer did what he did, an example.... why the use of all the bellcranks, why not use servos. So my question is are these designs so strict you cant make any changes to them. I am sure the guy took the time to figure the weights and balances of the plane, maybe not, this being my first scratch build, I really don"t know if I can make modifications, like moving servos. I don't think it will effect the CG.

While I am here, I started making a few wing ribs last night, I was cutting six at a time. I took the paper stencil, glued it to the balsa sheet, then glued six sheets to it. I tried several different glues, I watered down some white elmers, tried one of my grand kids glue sticks, I really didn't have much luck separating them I was able to get them a part, but was a *****. I searched it on line, and someone mentioned a 3m product, spray adhesive, I think M85. i couldn't find it at lowe's, wal mart, home depot. So what do you use to do this, I hope its just a mater of maybe using too much glue, I can't see cutting 1 rib at a time, when 30 of them are the same size.

Thanks for looking and taking the time to answer.
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Old 01-09-2017, 09:16 AM
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Sure you can make changes. In 1980, there weren't as many strong, small, light servos as to day so often belcranks were used.

I cut ribs by stacking balsa blanks, holding the blanks together with two 1/8x3/4 strips of double sided tape. Tape holds but comes off easily. Good luck.
Old 01-09-2017, 03:14 PM
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Double sided tape..... of course. Thanks for the help
Old 01-09-2017, 05:45 PM
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RCM Seneca II? Back in the day servos cost $30 so it was too expensive to have two do something one could do. If you had a buddy box cable you were considered rich. Not kidding. Just the way things were done. I remember it made news when someone showed up with two aileron servos on their pattern plane and the first pull pull on rudder. Update to your needs.
Old 01-10-2017, 04:48 AM
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Yes, Seneca Piper II. I think I built my Morrisey Bravo around that time. It has two servos for the ailerons, I will have to see what I did with the flaps. I'm not really concerned about the flaps on this plane, I will use two servos for the motors, and ailerons. Now that I think about it, the bravo, has a push pull cable for the tail wheel.

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Old 01-10-2017, 08:23 AM
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You can use rubber cement to bond the layers together, 3M #77 spray adhesive (very lightly), or similar. Use Ronson lighter fluid to remove the adhesive. When cleaned-up, there's not enough residue left on the wood to worry about. You can also use re-stickable glue sticks to hold the layers together.

Lots of alternatives.
Old 01-11-2017, 04:25 AM
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The other solvent that removes 3M 77 spray very nicely is mineral spirits.
Old 01-11-2017, 07:46 AM
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I prefer to have one aileron servo for both ailerons up to about 60 size. The servo only needs to be powerful enough to roll the wings so there isn't much stress on it. I also like bellcranks and haven't had problems with them. These days it's fashionable to put an aileron servo in each wing half. Do whatever blows your skirt up.

As far as modifying plans, the skys the limit. I modify nearly every plane I build just a little.

Here's how I do wing ribs: Trace the rib over the plans using tracing paper. Cut this out leaving a little paper outside the lines. Lay the paper down on the garage floor and very lightly (LIGHTLY!)spray it with 3M 77 spray. Next, invert the can and spray to let it clear out so the nozzle doesn't clog. Place the paper template over the wood piece that will be a rib and rub it down with your finger. Now stack as many pieces of balsa as you need ribs on top of one another and tape them together with masking tape in several areas. Cut out your ribs on the bandsaw being sure to retape areas that were just cut to hold the stack together. After you've cut all around, check to make sure you have a nice fit for your spars then remove the remaining tape and admire your work. The top rib template you glued down should remove easily but don't let it stay on the wood for long. Note that I said to spray the 3M77 on the template, not the wood.

As an alternative, you can use double sided carpet tape to hold the wood pieces together but my experience is that type of tape is really really really really hard to remove and you will wind up cussing it and possibly breaking a rib or two trying to remove it. When I don't have a better alternative, I cut that carpet tape up into tiny pieces so it will be easier to remove. But I still don't like doing that.

Good luck. Building from plans is very rewarding.

Old 01-12-2017, 03:59 AM
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Thanks for all the help, along with being my first scratch build, it is also the first multi engine plane I have ever built. I am not really worried about the bell cranks, except for the eng. I know they will work for the eng, but thought I would be able to control the throttles better with the two servos.

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