RICKSTUBBZ

The leading edge of the stab and the stab/elevator hinge spars of this kit are designed to be laminated with two pieces of 3/16 X 3/8 balsa. I am adding a piece of 1/32 ply in between the two. I am doing this because I expect this aircraft to get some abuse. I figure this will add a significant amount of strength and hopefully reduce the amount of flex in the stab and elevators.

Elevator tips are built. There are tabs created with the ply wood that will slide (and be glued) into slots that I will cut in the mating balsa pieces.

I am starting to get concerned about how much weight I have added to the tail feathers. I know it has not been much but adding even a little on the very tail of a plane can cause balancing issues. Don’t want to be hanging any lead in the nose.

WacoNut

Rick I think the gain in strength will outweigh the gain in weight, there should be minimal weight gain from the modification. I have often thought about building this kit, I will be watching
Anthony

jjscott

Does anyone know if anyone sells Balsa USA kits at a discount? A month or so ago there was an ebay seller in northern Wisconsin who was offering Balsa USA kits (a dealer, I believe, but not the company itself). I've searched completed items but can't find him.

Back on subject Rick, you've got a nice build going.

Jim

RICKSTUBBZ

Have not been able to get back to the “Pro” since Friday.

I forgot to mention in my last post—that I was able to use my tile cutting saw (and diamond type blade) to rip the 1/32 plywood stock. I was quite surprised. Had nothing to loose giving it a try. I actually had stopped by harbor freight and picked up a thin (high speed steel) saw blade to use but it did not fit. Anyway good FYI stuff.

I am considering adding 1/4” or so to the nose to help prevent a tail heavy build. Lots of chances to move battery and radio equipment further back but the front of the plane will get pretty crowded very fast. Just thinking at this point. I’ll decide by the time I frame up the fuse.



Anthony,
I agree the extra strength will be worth the weight and work. Also, just to add, I think this is a neat kit. Lots of possibilities. One can build it right off the plans per the book and have a nice bird or you can go do some bashing, to add a personal touch, with out throwing everything away.



Jim
Other than occasional unbuilt kits turning up here or there, I have no idea were to find Balsa USA kits other than from them. They are still a good deal for your buck.

RICKSTUBBZ

I temporarily glued a scrap 3/8 balsa block to the 3/8 dowel that is to be used to connect the elevator halves in order to hold the dowel vertical, horizontal, the same way consistently……you get the picture.

Picture 1 I cut notches out of the dowel in order to “key” it to the 1/32 ply running through the center of the hinge spar. Used my table saw to do this and cleaned up the inside corners with my scroll saw

Picture 2 –- 1/32 ply has been epoxied to the 3/8 dowel.

Picture 3 & 4 –- The notch in the end of the 1/32 hinge spar and how it fits to the new elevator tips.

Picture 5 & 6 – The tile saw I used to rip the 1/32 ply

RICKSTUBBZ

I did the hinge slots the same as I did for the rudder. I can say with out a doubt, pre-drilling was a plus for the elevator/stab spar since I had the piece of 1/32 plywood sandwiched between the balsa.

When building the hinge spars and stab leading edge I decided to drill some 3/16 dia. holes to try out for lightening purposes. These were put only in the inside piece of 3/16 balsa before they were laminated to the 1/32 ply and the outer piece of 3/16 balsa. Don’t have a scale here to weight them before and after. Mathematically it works out to be a reduction of just over 4 1/8” of 3/16 X 3/8 balsa. (Not much, considering how much stock is on this tail)

The bevels on the elevator/stab hinge spar are 20° and were cut using the same set-up as the rudder.

Before starting the build of the stab I clamped the hinge spar to aluminum bar stock to help keep it strait.

The tabs, grooves, and slots I cut for the elevator tips/counter balance worked out really well. I expect this to really stiffen up the counter balance area of the elevator.

Only a couple more pieces of wood to cut and glue and the elevator will be done. Hope to have pictures of that tomorrow.

Picture
1 - shows the holes drilled.
2 – hinge slotting tool I am using.
3 – finished hinge slot.
4 – 56 holes drilled in 3/16 X 3/8 stock.
5 & 6 – Hinge spar bevels.
7 – stab clamped to aluminum bar.
8,9 & 10 –the details of the grooves and tabs associated with the elevator tips.

RICKSTUBBZ

Well, the tail feathers are a long way from done. But I can say all the sticks are glued together. Aside from the obvious sanding, I have to countersink the hinges and figure out the details of the control horns and flying wires/tail braces. Lots of ideas in my head for the braces and horns but nothing on paper yet.

I will start on the fuselage next.

Picture
1 – You can see the 1/32 ply pieces I used to space the counter balance away from the stab.
2-3 – picture of the stab/elevator on top of original plans (moved forward and back) to show how and what I changed on the shape and size.
4-6 – My wife thought it was the wing.

RICKSTUBBZ

First side of the fuse truss is complete.

Before I started building the truss I spliced the 1/4” square balsa for the top longerons. To get a nice fit I stacked the two pieces to splice on top of each other Cut and sanded at the same time making sure to keep both pieces exactly lined up with each other. Then used my aluminum bars and some clamps to glue the splice joint.

Because I decided earlier to have the vertical stab hinge spar extend down and became the tail post of the fuselage I wanted to cut the notches in the back end of the longerons now. Mush easier than trying to do it when everything is put together.

The rest of the truss build to this point was standard stuff. However, I did more or less create a “Frame Jig” for the perimeter pieces of the truss. This allowed me to clamp and/or pin the longerons against something strait. I also used wood glue, carefully applied (except the upright at the firewall it was epoxied) and by doing so I was able to remove the first side without tearing up the wax paper. All of this allowed me to use the same setup for the second side of the fuse without having to build on the top of the first half.

Picture
1- Spliced to longerons
2- Cut for tail post before building
3- How the tail post cuts look after assembly
4- First side finished. Note: the aluminum “jig”.

RICKSTUBBZ

Used my table saw table and a long sanding block to clean up both fuselage sides. First placed them on the table the same way they were built (the side that was down when built is down first for sanding). Due to slight variations in material thickness - both sides were sanded evenly until all the uprights and longerons were the same height/thickness. Then the sides were flipped and process repeated just to clean them up.

I decided to do the triangle brace specified by the kit a little bit different. This was suppose to be an 1/8” balsa piece inside the 1/4” balsa corner. As you can see I opted for ply scrap placed on top of (inside of fuse) the 1/4” balsa.

Picture
1 – sanding fuse side
2 – scrap piece being marked for triangle brace
3 – ply doublers in place with new triangle brace
4 – fuse sides nearly ready to start the joining process

WacoNut

Looking good Rick,
May I suggest you make some gussets out of 1/64 or 1/32 ply to go over the joints on your truss sides. They add virtually no weght and alot of strength to the joints.
Anthony

RICKSTUBBZ

Anthony,
I have been seriously contemplating your suggestion. I first saw this on your WACO post, then again on your Cub thread. I really like the idea, not to mention it looks nice[8D]. Just is, once they are finished (the plane) you don't see any of it. None the less as you stated sure does add a lot of strenth to the glue joint with very little weight cost. I expect this thing will do a snap or two, not to mention a Lomchevac (spelling?) if I can get it to do them. Extra strength will be good[sm=wink_smile.gif].

Cuthie

Hi RICKSTUBBZ.
I am really interested in your comments on building the Citabria Pro. I have just purchased the same kit from Balsa USA and was wondering if I could get your info and pictures sent to me for future reference. This is my first kit that I am building from scratch and need all the help I can get. It seems to me that you are experienced and your pictures and comments would be exactly what I need when building my kit

Thanks
John

RICKSTUBBZ

John,
Would be glad to help in any way I can. This airplane is pretty much a strait forward design and build. Meaning, if it is your first build you should be able to do it. Just don't get in any hurries.
As to pictures and comments, so far everything I have is on this post. If there is something you need that you are not finding here let me know. If at all possible I will post it.
Feel free to post your build here as you go.

Thanks,
Rick

RICKSTUBBZ

It has now been two weeks since I have been able to work on the "PRO". Looks like it will be one more week before I get all my rat killin' taken care of. Then, I hope to be back after it.

Anthony, I will be making gussets for the truss, by the way.

RICKSTUBBZ

After five weeks of not working on the “Pro” I hope to be back on track. I can say in that time I was able to accomplish some RC airplane projects. One weekend went to repair and preventative maintenance to my “Smith Mini Plane”. And some more time went into assembling and setting up my first ARF. 71” wingspan “Carl Goldberg Wild Stik”. It is being used to break in the “Pro’s” engine and radio.

Before I had stopped working on this thing I built a square - jig – box, what ever you’d like to call it out of some luan I had left over from some other projects. I’ll use this for gluing the firewall to the fuselage sides and keeping everything square at the same time. As you can see in the pictures I cut relief in the corners to allow me to get the triangle stock in place while the jig is in place.

This is the beginning of more departures from the way the manual instructs you to build. The book states to some how get all three of the front bulkheads/formers in place at one time and square it all up even though all three formers are different in width. Per the book this also is done after the 1/4 balsa sheet has been added to the outside of the fuselage. By the way, I will not be using the 1/4 sheet. There will be more on that as I get there. Anyway, this way I know I can square up the firewall and the sides and glue the triangle stock with out modifying the angles (of the triangle stock) from 90°.

I also made joiners out of 1/32 plywood (instead of 1/8 X 1/4 balsa) for the bottom longeron splice.

Before I can actually glue the firewall and the sides I will have to finish up some CAD work for the holes that go in the firewall and get them drilled along with cut and glue the gussets that Anthony suggested a few post ago.

Pictures
1 & 2 - The square box I built for a jig
3 & 4 – A mock up as to how I will use the jig also showing uncut triangle stock setting in corner
5 - Longeron Splice doublers
6 - Gusset patterns
7 - This is the glue I use to attach patterns to wood to cut. Allows me to peel it off when done.

Cuthie

Rick,
Thanks for all these hints. They are priceless for someone like me who is building a kit for the first time. Keep it up. As I progress I will send you a picture.

John

WacoNut

Rick,
Very nice clean looking build you have going, I like your tight fitting joints on your truss work. I know how much effort it takes to get that right.
Later!!
Anthony

RICKSTUBBZ

I have cut out the small truss gussets using my scroll saw equipped with a spiral cut blade. Picture 1 Man, that is going to take some practice using that blade. Works good if you have a steady hand.

Picture 2 Shows the mojority of them glued in place. Not as neat and clean as I would have liked but they will work.

As I was working on finalizing my drill pattern for the firewall, I discovered I had the engine initially located .200" too low (in my drawings). This created a couple of minor problems I must overcome. No big deal.

I am running a 16 OZ tank in this thing that extends past F3. Now, I wonder how many guys have this plane with bigger tanks and also have fueling problems. I will be centering my tank to the center of the spray bar in the carburator. As you can see in earlier post my engine is nearly inverted so this creates a even lower tank location mounting it by the spray bar instead of the center of the crankshaft.

Anyway, to get my fuel tank high enough in the airframe, I will have to remove more than a half inch of F3 at the top from where the factory hole is cut. If the engine was side mounted, all most all of the top of F3 would need to be removed.

RICKSTUBBZ

John,

Have you started building yet? Do keep in mind I am bashing this thing a little bit and most of it is not neccesary. I am doing it for fun and for practice.

But, I would suggest checking your fuel tank mounting before building the fuse. Might be worth your while to open up the top inside area of F3.


Anthony,

Thanks on the compliment. I am attemting to do a jam up job with this thing. In the threads that I visit-there are a lot of excellent builders. So, I have set my goals quite high to be able to stand up next to you guys. Only time will tell....

RICKSTUBBZ

I am still working out the details on my firewall. But while the glue was drying on that work here is what I did.

Picture 1
My drawing of F3. The line that is 3/4” up from the bottom edge represents what will be the top edge of a piece of triangle stock supporting the landing gear block. The triangle stock will be an add in not provided by the kit.

Picture 2
This is F5. The line 1/4” from the top represents the bottom edge of the cabane mount plywood.

I posted these two drawings in the case that anyone would like to use them as patterns for drilling lightening holes. I included a couple dimensions to help with scaling at the printer.

Picture 3
This is F3 as it came in the kit with a little sanding done.

Picture 4 & 5
F3 and F5 done my way. Once again, I did not have a scale to measure how much weight this lost. Mathematically it works out to be the same size of the former plywood that is 1” wide and 3 ½” long.


Picture 6
This shows my set up for drilling the holes. I used a combination of 3/8” and 1/4” forstner bits to drill the holes. In order to minimize “blow out” on the back side of my formers I clamped the piece of plywood to the drill press. I think a solid piece of wood that is a little harder would have worked better than this cheap piece of pine. The drill press is set up with the stop so that the drill bit will just touch my back up board.

I printed out the drawings of the formers cut them out at outside edges. Placed the drawings on my formers and used a center punch to mark all the hole centers into the wood. (That’s why the very small circles are inside the actual hole size on the drawing.) No hammer needed. Just push strait down enough to penetrate the wood. Then I was able to float the part in place using the point on the drill bit to catch the punched hole.

WacoNut

Looking good Rick,
I always wandered if it was really worth it to do lightening holes, I will keep an eye on your thread to see how it all comes out. The key to any project like you are doing is to keep your interest up and keep plugging away at it. I always enjoy the little details even when they aren't going to be notice on the finished model, it keeps the build interesting and you will have alot of pride in what you have built when you are finished.
Later!!
Anthony

RICKSTUBBZ

With out a doubt, messing around with the CAD stuff is dragging this out even longer. But, I enjoy that part of this as well. Someday I hope to scratch build something with my own drawings. This process helps get me familiar with some of the design parameters.

Anyway in the process of figuring out all the holes for the firewall, I have located the throttle servo, fuel tank, and the battery pack with in my cad drawings. The plus of having done this even before building… Is I can plan things like my throttle servo plate and make sure that it is built into the plane at an easy time instead of trying to fit it in after the whole thing has been built. Enough of all that and I won't bore you with pictures of CAD drawings today.

Good news is firewall is done and now glued to the fuselage sides. I had to glue F2 in place at this stage of the game because of the mistake I made on engine height. This was because the top two engine mount bolts ended up right at the top of the 1/4” thick firewall. I was not about to remake the engine mount for this. Any way the good thing is this actually worked out better for the build. I added some 1/4” balsa pieces above the firewall and in front of F2 to fill in the void area that would be left. You can see this in the pictures. I drilled the holes for the 8-32 T-nuts with a .220” dia. drill bit, applied 30 minute epoxy around the boss of the t-nuts and pressed them into the firewall with my bench mounted vise. The holes for fuel lines and throttle linkage are .180 diameter. For the throttle linkage I have epoxied the outer casing of a ny-rod into the firewall. The throttle linkage will be .060 wire. However, were it passes through the firewall I will have a piece of the inner ny-rod glued to the pushrod for a bushing. I’ll post pictures of that when that time gets here.

WacoNut

Rick,
Looks like a very clean build you have going, I am anxious to see how the cabane setup is on this bird.
Anthony

RICKSTUBBZ

Anthony,

I can tell you that the cabane and struts of this kit are standard issue stuff. Cabanes are wires stuffed in grooved blocks that are glued to hardwood blocks at the fuse, and screwed to the wing with standard wrap around metal clamps. Struts are basswood or similar with metal plates shoved in slots at the ends and pinned to keep them there.

However it is not my intention to use any of those pieces. The intention is to use streamline tubing and special made aluminum pieces to hold it all together with the help of some all thread. I’ll detail it all out as I get there. I sure hope it works.

iron eagel

I was just going to try to cut something using this type of blade on my scroll saw and read this earlier today...

If I may ask?

Is it because the cut tends to wander because you don't have the toothless part of a blade to keep the cut moving forward smoothly?
Do you have any words of advice?