Balsa USA Smoothie RC Plane Kit Build No 5 Wing Construction Part 3 Dihedral

In this video I continue with the construction of the wing of the Balsa USA Smoothie, which includes joining the wing halves together and setting the wing dihedral. To set the wing dihedral I need to cut and sand the main spars, leading edge and trailing edge to the right length and angle. It's not difficult, but can be a little tricky. I also add some plywood reinforcement to the main spar area and trailing edge area to make the wing join stronger. Finally the wings are joined using 30 minute epoxy and held together with clamps and allowed to cure.
The Balsa USA Smoothie kit is a 40 class (size) sport plane and has been around for a long time and is still readily available on the Balsa USA website. For this balsa kit build I will use traditional rc plane kit build techniques.
In each build series episode I will focus a different aspect of the build including the wing, fuselage, tail section rudder and elevator, engine mount, landing gear, tail gear, engine set up (OS Engines .46 AXII), fuel tank, servos and receiver (Futaba), control rods and horns, Monokote covering, carving and shaping wood, using CA glue (Zap CA glue, Starbond CA glue), epoxies (JB Weld, Bob Smith Industries, Z-poxy finishing resin), tools and everything thing else involved with building a radio control plane kit (RC Airplane kit).
I have been building, flying, crashing, modifying, and repairing radio control planes for many years and enjoy sharing what I do with the radio control plane community, so I started RC Plane Tech channel for fun.

[@tonymccarthy9273]

hi mate very interesting build video, just a a suggestion, I wouldn't have bothered with making a slot for the front center rib , I would have just cut the tab off the rib and epoxy it in , it would,my have made much difference in strength, thanks for your videos,

[@JamesRCPlaneTech]

Thanks! Always good to hear suggestions.

[@mab0852]

Just use 3 dots of CA to fix the parts so they don't slide. Quick and light.

[@conrayjones9290]

to stop parts from sliding you can drill two very small holes and fit tooth picks as aligning pins. they can be cut off and sanded

[@JamesRCPlaneTech]

Thats a great tip! I know dowels are used to help secure parts, cut off and sanded flush. But I never heard this one with the toothpicks for this application. Great tip!

[@Jimmyzb36]

This is the way I plan to build my future balsa rc kits when I hopefully get to retire! I've been stashing kits for 20 years. Thanks for the video. Jimmy KN4UXO

[@SomeGuyInSandy]

Nicely done so far!

[@Vdubin64bug]

Excellent job on the build.. You motivate me to get out in the shop.. I have two wings to build.. I need to get going on them..

[@JamesRCPlaneTech]

Great, thanks!

[@normhalliday3969]

Enjoying the build series. If you raised each wing 1/2 inch would you achieve the same dihedral as if you raise one side 1 inch? Seems the geometry of the join angles would change a bit?

[@JamesRCPlaneTech]

Thanks. It would be the same outcome. If you set one wing flat on the table and raised the other an inch and cut the angle to join them. Then lowered the wing 1/2 inch, the other wing would raise 1/2 inch. The wing angle cuts are relative to each other not to the orientation relative to the table. For example if you were making a picture frame you would cut 45 deg angle in each piece and join them to make a 90 deg connection. It wouldn’t matter if you laid one flat on the table and connected the other vertically, there would still be a 45 deg cut in each. Hmm it is something to think about..

[@waetos]

Now that you added another dihedral doubler, you will have to modify the 2 front inner ribs because they are supposed to go into the space that doubler is now taking up. That's why they only supplied one doubler- it goes behind the main spars. You could slot the ply but IMO, it's unnecessary. Flatten the rear of those ribs and epoxy them to the dihedral brace. It'll be less work and just as strong.

[@JamesRCPlaneTech]

I’ll have to review the vid again, been a while since I did this step, but I believe thats what I did, I trimmed the spars a little.

[@marcobuonavita2757]

Otto lavoro sempre istruttivo l'anno nuovo ti porti grande vitalità , un grande saluto

[@JamesRCPlaneTech]

Grazie Marco, spero che tu abbia un grande anno nuovo. Divertiti a costruire e pilotare aerei RC!

[@jeffallen3382]

Just found your channel! I like the idea you used on adding that 2nd joining plate. I tend to think of ways to build strength in the frame as I know my la dings are not the most graceful.

[@JamesRCPlaneTech]

Thanks, yes adding a little extra support and strength can be very helpful. Thanks for checking out my channel.

[@JamesRCPlaneTech]

And as long as we don’t go overboard, a little extra support here and there is not going to add significant weight. Thanks again for the comment

[@rcnatec64]

When gluing pieces together that could possibly drift, sprinkle a little bit of salt on one side. It prevents the parts from slipping while your clamping them.

[@JamesRCPlaneTech]

Wow, thats a nice tip, I see how that would work. Cool idea

[@rperry70]

You could always add a .25 x .25 stick on the T.E. . This would give a good place for hinging, and also add strength back there. yes, you would add that width to the chord, but it would not matter. Then just modify the fuse to accept the xtra width.

[@JamesRCPlaneTech]

Thats a good point and good idea. Balsa USA should really address this. Something should be done no matter what.

[@skymaster547]

Hi James, I've been through your smoothie build a couple of times and enjoy it. I am currently building mine but I'm stuck on step 12 of the wing. In the paragraph it reads "use a 1/8 block under the spar and a 3/8 block just forward of the LE sheeting to avoid building a twist into the wing". I totally get the 1/8 spacer, but the leading edge sheeting isn't on yet. I don't see anything in your videos about that. I have built many a plane back in the day so I'm confident that I can continue on, but wanted to ask you what you did as "just forward of the LE sheeting" is basically just "air". Love the series and so glad you posted it. Steve

[@JamesRCPlaneTech]

Hi Steve, thanks for the comment. I will need to go back and look at the instructions myself to remember what I did. Ill check it out and get back to you.

[@JamesRCPlaneTech]

Ok, so to start I will say that I found the instructions hard to follow at times,especially with the wing. I went back and looked at my video and the instructions q12, and honestly I can’t remember if I caught the 3/8 block note. But I read it over and over .. this is what I think: if you look at the picture they referenced in that step (photo w11) , there is a block just in front of the trailing edge sheeting. As you say, there is no leading edge sheeting yet. So I think the “LE” is a typo and should be “TE” for trailing edge, and the 3/8 block is supposed to go just forward of trailing edge. This makes more sense to me, because a 3/8 block would be too small to support the leading edge. So I think you have the 1/8 block supporting the spar, and the 3/8 block supporting the rear of the rib just in front of the trailing edge sheet. This would prevent the wing on the plane from twisting while setting the dihedral? I think this is what it means. There is no way I can see how a 3/8 block could support the leading edge. And the picture, I can’t see any block at the leading edge, plus as u said, there is no leading sheets yet. This is my best guess. You are right, I did not mention it in the video, because I overlooked this. I just lined up everything and checked for proper fit and joined the wings. I don’t remember using the 3/8 block. Tell me what you think after you read this, I still could be wrong.

[@JamesRCPlaneTech]

Also… I did not like the pictures in the instructions and found them to be challenging at times to understand. Thanks for your comment, Im glad you pointed this out to me.

[@skymaster547]

@@JamesRCPlaneTech Thank you for going to that trouble for me. I kind of figured it out. I unpinned the stick propping up the wing at the rear and slid it over to the left a little which propped up the center rib, serving the same purpose as a block would have done. So, if your right, and I think you are, it's a done deal there. On to the next step when I get time. Thanks again, Steve

[@JamesRCPlaneTech]

Great , Im glad it worked out one way or another. I think even In instructions, there are sometimes more than one way to skin a cat, and sometimes i omit or modify a step here or there, and work things out that may make more sense. That being said, Im guilty of mistakes along the way, hopefully not too bad. Good luck with the build!

[@alexherrera3918]

Great explanation. what would be the strategy with a smaller wing (30in).? the same? i found it very difficult to put degrees. any advice?

[@JamesRCPlaneTech]

Hi, I imagine a smaller wing would be the same. But Im not clear on what your question is? Are you trying to set a dihedral based on kit instructions or estimating? Also may depend on what type of plane it is, sport, trainer, scale etc. they will all have a different degree of dihedral or even no dihedral depending on the style of plane. Are you building a kit, and does it give you a dihedral amount in instructions? Sorry, I’m not clear on the question.

[@rperry70]

Too bad 2 center ribs were not designed into the wing. Then you can set the angle on those ribs, say 3-4 degrees. Then trim the spars to the ribs. I understand this is an old design, but this is how you see most wings built.

[@JamesRCPlaneTech]

I agree, there are a few quirky things on this kit, and I found this center section a little odd, that the ribs go in after the wings are joined. How you describe it had been my experience also (the Barnstormer kit I built was like you said). This kit also has no trailing edge solid stock piece, just the sheeting coming together like a hollow triangle. I found that odd also. This kit has been around since the 70s at least and one would think they would have updated it a little. I agree with your comment, thanks

[@glennroberts461]

Man you made things difficult for little strength value.

[@JamesRCPlaneTech]

Haha, ya some say I don’t need to do these type of things, but I guess I worry a little about how this wing is joined together. I’m sure it would be fine per the kit instructions, but I find myself doing these things when I build.

[@kennethturner8212]

Rc plane tech…. I don’t blame u at all. If I build this kit, I’ll will do exactly what you just did. Makes sense to me!