DonStegall

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I have already started a thread on RCU about a new Quickie 500 I am designing for mass production. The thread is at New Q-500 ARF design.

I have completed the initial design for the Screamer and am going to start making the first prototype today. The first one will use a Viper 500 wing so I can get it in the air as quickly as possibly. Next weekend is my target for the first flight.

I will be making a jig to ensure the fuselage is straight and to make building the prototypes as quick as possible. I will post many photos along the way.

Protecting a Quickie design is next to impossible. So I will be very open to those who want to participate in the prototyping and testing.

Jim Duda

Don - just for grins, try doubling the size of the rudder on one of your test models so the sport fliers can do some additional maneuvers...we can always decrease the throw for racing.

DonStegall

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I took the family to lunch and stopped by the local HobbyTown USA to pick up some wood and glue. Before lunch, I had finished the drawings for the fuselage outlines and printed it on letter size paper. I use tick marks every 4" so I can piece the paper together. I used some 3M77 and glued the template to a piece of 3/4" MDF for the fuselage jig.

After I got home, I seeded the takeoff pad on the field, then got back to the jig. I needed 30 pieces of 1/4" dowel for the alignment pins. So I cut them and beveled the edges on a belt sander.

I took out my contacts because drilling the holes for the pins has to be accurate. In fact I missed in a few places. I just chose close by locations that would have minimal effect on the shape.

After drilling the holes, I tapped in the pins using a rubber mallet on one side. It is good to check yourself and make sure you get the shape you want before committing all of the pins. It looked fine with pieces of 1/8"x4"x36" balsa and 3/32"x4"x24" basswood for the doublers. I couldn't find any 2mm or 3/32" light ply or I would be using that. But the basswood is close enough in weight and strength for the first prototype. So I tapped in the rest of the pins.

I put both sides in and measured the width. It was only about .010" over the minimum, and the covering will add just a little. But there are pins at the wide point, and I don't think width will be an issue.

All looks good. Now I have to cut out the fuselage sides, doublers, formers, landing gear block, and wing hold down blocks.

vicman

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Dang bro, thats quite a bit of work there! I like the idea since you can bang one out in a few minutes of glueing. I did something similar a while back for the 3DF F-18.

Nice job.

DonStegall

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This morning I cut out a stack of 4 doublers.

I bonded them with a light coat of 3M77 and let it tack before putting the pieces together.

fizzwater2

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looking good - we'll be watching your progress, Don. Thanks for sharing all this with us.

heliothiszea

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Don - Just ran across this post! I'm very impressed! I really like the jig, never thought of building one like that . . . awesome - Seth

DonStegall

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Seth, the jigs are cheap. All it takes is a $5 piece of 3/4"x12"x48" MDF and a couple of bucks of 1/4 dowels. You do need a drill press. I use a $100 Delta from Lowes. Every racer needs a drill press. I've seen them at the low buck hardware stores for as little as $50.

I'm short on time and can't locate the threads I did on the Smasher on RCU. Check out these articles:

http://www.rcpro.org/net/ThreadView.aspx?threadid=354

http://www.rcpro.org/net/ThreadView.aspx?threadid=419

http://www.rcpro.org/net/ThreadView.aspx?threadid=407

DonStegall

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I had a long week at work and didn't get anything done. But I'm getting started back up today and will be posting photos through the weekend.

I started this morning by bonding 4 pieces of 1/8"x4"x36" balsa using 3M77. And I'm getting the fuselage side pattern ready to put on the stack.

fizzwater2

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So you're using the 3M77 to hold the stack together and gang cut 4 sides at once, right?

Darn that work thing anyway, it gets in the way of getting any good modeling done!

DonStegall

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That's correct. I like to cut at least 4 pieces at one time because it make the cutting on the bandsaw easier. And it is a lot less work. You have to be a little more careful or you can mess up a bunch of balsa in a hurry.

The trick is to only spray a light coat of the 3M77 cement on one side that you want to temporarily hold together. And you have to let it sit for a minute or so until it tacks. Then put the pieces together. If you spray the cement on both surfaces, they will not come apart.

The new job is fun. I'm doing mobile device development for Windows CE devices. These are hardened industrial Pocket PC devices that get used for everything from gasoline truck delivery to donut delivery. It's a really cool company doing cool software on cool devices. Microsoft has continued to evolve the Pocket PC and there are many more in use than I realized.

fizzwater2

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a friend of mine just went to work for Radix ( I think that's the name) - they make those small ruggedized handheld PC's. Their final assembly and test used to be in Salt Lake City, I believe, but they were recently purchased and are now in the Kansas City area. The board house that was doing their contract PC board assembly bought the company. He's responsible for building up their test department at this point.

vicman

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Glad you are working again Don.

Back to the stacking thing.
you are only cutting two pc at a time, right?

DonStegall

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Vic,

I'm cutting 4 pieces for 2 fuselages. I almost always build 2 prototypes at the same time in case one bites the dust too early.

I have the fuselage sides cut out. Now I have to cut the stab slot before separating the pieces. Cutting the stab slot will be a little tricky since the jigsaw is only 16" deep. So I will have to cut it as close as possible and hand finish the slot with files.

vicman

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Hate to be dense but how are you stacking & cutting 4 pc at a time but only glueing one side of each? Seems the middle two would have glue on both sides.

I usually use T-pins and do the same thing. Especially for wing ribs, for a straight wing I can cut, sand, and fit the spar on all of them at the same time.

DonStegall

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Sorry ... I was not clear ... I'll try again.

If I'm doing four pieces, I spray a light coat on one side of three pieces. Let it tack, then stack them.

Then I spray a light coat on the pattern and attach it to the stack.

If you spray one side of all four pieces, you just put the pattern on the top piece. Never put glue to glue.

The great thing is that you can sand the edges and get everything done as one unit. Then you just peel the pieces off.

It works MUCH better than pinning.

DonStegall

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I cut out the fuselage sides. Then I cut the stab slot using a scroll saw.

Next I drilled some 1/16" holes on the thrustline. I did this at the formers and one spot at the tail. These holes will be used for alignment when the parts are put on the jig.

I then separated 2 sides and 2 doublers. I also cut some 1/16" basswood to use as doublers on the tail. Instead of cutting the parts, I just glued them on and will cut them after the epoxy hardens.

DonStegall

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The fuselage is built upside down in this case so that the bottom sheeting can be put in place while the framework is still on the jig.

I lined up the thrustline at 2.5" from the jig surface. I then used shims made of manila folder to get the sides tight to the formers.

I found out that I need additional pins between F3 and F4 because the doubler keeps the side from bending enough. But it was close enough for a prototype and I decided that I was not going to add the pins and re-jig. That's why I cut parts for 2 prototypes at the same time.

Vic, the 3M77 method works where T-pins don't. I cut two sets of 1/8" light ply formers at once.

I used CA to glue the formers in place. Thin first, then a small fillet of medium. The trick is to not glue anything to the jig. Also, give the CA plenty of time to cure before moving the framework. I did use kicker to make sure the formers would stay in place. I will add small fillets of epoxy once the whole thing is off the jig.

Tomorrow I will glue in the landing gear block, raise it up, and sheet the bottom.

HighPlains

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Don,

Great thread you have going. The concept of designing a competitive quickie around standard sized servos for the average novice racer is so obvious that it has been missed by all. A standard tail is not a handicap when the problem for most is just flying the course.

If I could offer a couple of suggestions -

The landing gear takes a lot of abuse, even by the best of us. It would be far stronger if it's mounting plate extended forward under the F2 bulkhead, thus transferring landing impact loads up to the wing directly through the plywood bulkhead. Just gluing it to the rear of the bulkhead placing the glue in shear is not nearly as robust. I would also extend it rearward too so you have a glue line of 3 to 4 inches on each side.

I don't see the front and rear wing hold down blocks on the top view, but if they are "U" shaped, it adds a lot of torsional stiffness. This really helps the engine to transfer power.

Bob

DonStegall

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Bob,

Thanks. the threads on this plane have benefitted me greatly. Having the input, questions, and comments have made this a fun little project. The guys who put down the internet and these conversations are simply wrong.

I used your 3 to 4 inch glue line suggestion and cut a U out of the landing gear block. The great thing about this is that it helps hold the shape of the fuselage there as well. Plus with some triangle stock inside, it will be very strong.

I couldn't do what you said with the bulkhead because I already had the bulkhead in place. Also, it would cause an issue with the size of the tank opening there. Assuming a tank is inserted ahead of the bulkhead. If a bladder tank is used and butts up against the bulkhead, it may be doable. I could make the bulkhead the way you say, and the user could grind out the bottom part if needed to get a tank in.

DonStegall

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I determined that the shape behind the former (F3) at the wing trailing edge was going to make the fuselage too narrow at the wide point. The 1/4" dowels were not holding the shape because of me not having enough alignment pins behind F3.

So I cut a piece of 1/8" balsa to the shape in the topview and glued it in right behind the doublers. This fixed the shape problem, and I will be able to remove it after the bottom is fully sheeted. Then the servo tray will also hold the shape.

HighPlains

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Don, a few other thoughts for the readers of the thread

I use a parabolic cutout on the landing gear pad, both in front of the bulkhead and behind - notches in material are usually stress risers, it's easier to cut out, and it provides nearly the only curves on a quickie fuselage.[&o] I make it out of 1/8 ply with two 3/8" wide strips of 1/8 ply glued on top of the pad behind the bulkhead to double the glue line and provide the thickness required for the landing gear screws. Triangle stock goes on top of the strips.

I'm a big believer in 1/8" birch aircraft plywood, that and the amazing strength of balsa in fuselages. Lite ply is great for selling that next ARF, but very weak in shock loads. Throw in the thinner birch plywoods for doublers on the fuselage sides and top and bottom of the nose of the fuselage and you end up with a plywood box on all six sides of the nose section.

The weakness of many quickies in the nose area has lead to frustration for many. We've all seen landings knock loose the firewalls, mostly because the firewall has a very small glue line plywood to plywood. Adding plywood doublers to the top and bottom skins ahead of the wing and from the landing gear pad forward doubles the firewall glue line strength. That and using two or three layers of 1/8 ply to form the firewall (more layers of wood by using thinner ply to build up the firewall, gives it has a higher percentage of glue in the wood matrix.

For the truly paranoid, got to have the absolute maximum strength, add a couple of 1/8 dowels through the outside fuselage surfaces into the firewall on all four sides (making sure to miss where the engine mounting holes will be) adds more strength, and finish with a nice wrap of glass top to bottom and side to side of two oz cloth.

Of course the inside of the nose is also framed with triangle stock until no right angles exist where plywood meets plywood. Just because there is a lot of glue surface with all the plywood and triangle stock, does not mean there is a lot of glue used to build it. Epoxy only requires a good fit and a thin film between parts.

DonStegall

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The fuselage is fully sheeted on the bottom while still on the jig. I used medium CA for the bottom which is planked with 1/8" balsa. I will probably switch to the metric equivalent of 3/32" for production.

I took the fuselage off the jig and trimmed the sheeting with my bandsaw.

Now I can see how to fit the servos, pushrods, wing hold down blocks, and the tank.

These will be the last photos for a little while.

DonStegall

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Bob,

Gotcha on the materials. Thanks for the thoughts on the details that can make a big difference. Layering plywood so that only the areas that need thickness is a great suggestion.

The firewall will be made of a thinner piece of plywood that is tabbed and locked into the sides. Same thing for the wing hold downs. I didn't do it for expediency on the prototype. The manufacturer will laser cut the pieces, and I just can't do the precision and complexity that they will be able to do. So I will pin the firewall and hold down blocks.

HighPlains

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I forgot to mention that the balsa sheeting to the nose on top and bottom is far stronger if the grain of the wood runs the long axis of the fuselage instead of cross grain. The wood has better compression strength in that direction and improves the fuselage resistance to the big crunch on muffed landings.

Cross grain behind the wing and landing gear gives the best torsional stiffness to the tail section.

Oh yeah, one of my fuselage jigs, easy to make. I glue graph paper to the base and plot out the fuselage curves and dowel pin offset. Again a drill press is a great tool (unless you have to move it).