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Old Dec 31, 2012, 05:32 PM
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Minnie Mambo - First Scratchbuild, Many Questions


I got some balsa for Christmas and I bought a Cox .049 SureStart. I am now ready to begin my first balsa scratchbuild. I have printed off and taped together the plans for a Minnie Mambo. I plan to build it two channels - Rudder and Elevator. I may make it three channels if I get a throttle for my engine, but if that doesn't happen it will just be the two channels.

Being that I am new to building with balsa, I know I will have tons of questions.

My first question of many is: How do I cut out the pieces? For the wing's ribs, for example, do I print and cut out the rib template and glue it to the balsa or. . . .?



All help is appreciated.

Thanks,
Nicholas

Link to the plans: http://my.pclink.com/~dfritzke/Minni...o-GeneRock.pdf
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Old Dec 31, 2012, 05:50 PM
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Another questions. . .

I weighed some of my 3/32" thick balsa and sorted them by weight. My lightest sheet is about 10 grams and my heavies sheet is about 21 grams. Should I use the heaviest sheet for the fuselage sides or for making the wing ribs or does it not really matter?
Old Dec 31, 2012, 06:28 PM
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The ribs are usually very light. In some of the kits with 1/16" ribs that I've built, you can barely touch them without damage.
Old Dec 31, 2012, 06:44 PM
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Okay, then I'll use the lightest balsa sheet I have for the wing ribs.
Old Dec 31, 2012, 07:35 PM
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For a constant chord wing I usually cut a template out of thin ply, then simply trace around that with the x-acto to cut out all the ribs.
To make the template glue the pattern onto the ply and cut it close.
Then sand it till it matches the pattern.
For the root ribs I would just cut them out the same, then shift the template down 1/16 to cut the back part where the sheeting goes.

If you don't have thin ply then you could use the hardest balsa you have and harden the edges with CA. You will have to be more careful when you use it to guide the knife.

And for the x-acto use the #11 blades. A cutting mat on the bench will keep the tip from going dull.

Try to match the weight of the ribs on both sides of the wing, and also the two fuselage sides should be of similar weight and stiffness.

Pat MacKenzie
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Old Dec 31, 2012, 07:44 PM
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good luck pyro man keep us posted
Old Dec 31, 2012, 07:55 PM
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Pat, I like your idea much better than the way I did it. I created a page with twelve of the rib templates. I cut 'em out and glued them to the balsa. I then used a straight edge, a French curve, and an Xacto blade to cut them out. They are all very close to being the exact same. I will hold them together and sand them at the same time to get them all to the exact same size and shape.

I will cut the hole where the spar will be after I sand them because I don't want them to be weak when I sand.

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Old Dec 31, 2012, 08:56 PM
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My plans are in my blog
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Here are a few things to get you going...

https://www.rcgroups.com/forums/show...ht=minni+mambo

https://www.rcgroups.com/forums/show...ht=minni+mambo
Old Dec 31, 2012, 11:19 PM
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Thanks for the links Rusty-Gunn. I'll look at those threads later tonight.


So far I've got all the wing ribs cut and ready to go. I also cut the wing spar. I was reading the plans and at the very beginning it says for maximum strength, coat each part with a light coat of cement. and let it dry before assembly. Is this necessary? I want the plane to be as strong as possible for my less than great 'landings'. I am using Elmer's wood glue so should I dilute the glue with water and brush it onto each part?
Old Dec 31, 2012, 11:43 PM
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I would not do it. Just extra weight.
Build to fly, not to crash.

They are talking about solvent based glue like Ambroid, not wood glue like you are using.
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Old Jan 01, 2013, 12:55 AM
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What you are describing is double gluing. We did that when model airplane glue smelled strange--30 plus years ago. Not really necessary with modern adhesives.
Wing ribs are easy to do. Make a template out of thin plywood--1/16 is good--1/8 better. put a couple of thumb tacks through the template at the front and rear. Push tthe tacks exposed points into your rib material and trace around the template as many times as you need to make a set of ribs.
Tapered wings--another story.

BM
Old Jan 01, 2013, 03:13 AM
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Congrat's Nicholas, you picked a pretty rewarding and forgiving hobby. There are plenty of ways to do most things, as you just found out. I too make a sheet of rib copies, but then I print them on a laser jet and iron the ink onto the balsa to transfer the pattern. Not necessarily a better way, but worked better for me.

Measure twice, cut once and when in doubt, ask. One of us will be lurking and ready to give you a tip.

Cheers,
Vince L.
Old Jan 01, 2013, 03:36 AM
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Quote:
Originally Posted by Vince77 View Post
Congrat's Nicholas, you picked a pretty rewarding and forgiving hobby. There are plenty of ways to do most things, as you just found out. I too make a sheet of rib copies, but then I print them on a laser jet and iron the ink onto the balsa to transfer the pattern. Not necessarily a better way, but worked better for me.

Measure twice, cut once and when in doubt, ask. One of us will be lurking and ready to give you a tip.

Cheers,
Vince L.
I didn't know the ink would come off with an iron. I will have to try that sometime. . . Even of just for fun

Thanks, will do.
Old Jan 01, 2013, 02:47 PM
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So I need to cut out the pieces of wood that hold the two halves of the wing together and they also set the dihedral of the wing. They are numbers W4, W5, and W6 and they are made out of 1/8" plywood.

How do ya'll cut out plywood pieces? I feel like it would take forever to cut through 1/8" plywood with an Xacto blade. I can use a coping saw, but I didn't know if you guys had some better methods.
Old Jan 01, 2013, 02:51 PM
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i think coping saw is you only bet unless you take it to a kind wood cutting store that will cut it for you.


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