flyingagin

Starting to lay out parts placement, so I can draw up my fuse. Just going to be a rough drawing.

I started by printing out the tail feathers. I have downloaded a PDF of a RM 19. it has 230 square" of wing. So I needed a little more than double the stab area. I had calculated that if I printed it out (the stab) at 1.45% I would end up with about 84 Square" or about 22% of wing area. So that is what I did and I actually ended up with 90 square" close enough. I will cut the tail feathers from 1/8" sheet balsa. So the stab is 6.25 wide at the root and 18.5" long. The vertical is printed to the same scale.

I naturally want this thing to balance with very little to no lead added. I will be able to shift the engine some while the fuse is still roughed in. I do not have enough parts finished to hang them and see where the cg ends up at and the shift. So going with my best guess and past experience. The cg could be off by this method. We will see.

The engine is a Super Tiger .34 rc @ 12.8 ounces with muffler. Same weight as a OS .35AX, 2 more than a .25. I will likely use a 11x5 prop.

So here is the placement measurements.
I am referencing everything from the back of the prop.

Prop to bottom wing L.E. =8.5"
Wing stagger will have the top wing L.E. 1.5" forward of the Bottom wing L.E.
Prop to Stab L.E. will be 25" and T.E. of bottom wing to stab is 8.5"
Prop to T.E. of elevator or fuse end is 31"

Ready to cut tail feathers now.

I am really enjoy working at this desk vice that wiggly card table. I am feeling more productive.

Ken

flyingagin

They say confession is good for the soul, they also say measure twice cut once.

So I have a confession. I did not measure twice when I laid out the elevator. Not sure how I goofed up like this. The template was printed out for one side. I then traced it onto the wood flipped the template and did it again. The stab is correct, but I sure screwed up tracing out the elevator.

So the elevator is scrap. It might find it way into a bulkhead or something.

And I was so proud of myself for only using one sheet of wood for all the tail feathers, stab, elevator, vertical stab, and rudder.

Oh well I will cut another.

I am sure I will make more mistakes on this build.

Ken

flyingagin

It was suggested that I glue the scrap piece back onto the short elevator side.

So after I got home from work I went into the workroom to rummage the garbage can AND AND AND the garbage can IS MISSING!!! So "hey Hon where is the garbage from the work room?" She had switched out the can for a bigger one and not put the new one back. (Is she trying to tell me something?) So anyway I found the scrap piece. The cut was fairly clean but proud of the line (cut slightly bigger), and the elevator has since been sanded to final shape, But the scrap piece is still close enough I can make it work.

Ken

flyingagin

A little filler, some sanding, and once it is covered it never happened, right?

Ken

flyingagin

Today it seemed like run, run, run. I was off today for a couple of doctor appointments. First was a spinal injection for my bum back. Dang it that is most unpleasant. Unfortunately it won't last long. Had a friend drive me as no driving afterwards. And no food or water before so I was starving by the end and was suffering coffee withdraws. This afternoon a second related Dr. app. At some near point down the road they are going to start burning the nerves, and install and implant to help with the pain. This getting old crap sucks big time. But God will not give me more than I can handle, but he might make me toughen up some more yet.


The work I got done was just planning and drawing. I changed the dimensions I posted earlier as it was just to short coupled. Looked real bad. So I lengthened the tail some. I think it looks much better than it would have. Still subject to some changes.


I also laid out the side view plan (actually the only plan so far) the struts, both interplane and cabane struts.


I am going to go with a side winder engine install, due to much easier to center the fuel tank on the carb spray bar.


The new stab placement is now 29" from back of prop or 13.25" from bottom wing T.E. It was 25" and 8.5". The vertical will stay in the same relationship as before i.e. rudder T.E. at the elevator L.E. just as a normal RM. is.


Please feel free to jump and and suggest changes. Comments most are welcome.


Ken

flyingagin

Did not get anything done Saturday, all kinds of things sucked up building time. But I did get a bit done Sunday and this evening.


I basically designed and mad ply doublers and the firewall. I only managed to cut out one side, but it will now make a pattern for the other side, so should be faster.


The bigger doubler is 1/8" light ply. There is a whopping big difference in weight between the finnish on and the unfinished one. The little doubler is 1/16" birch ply. The firewall and first bulkhead will glue straight on it.


That is as far as I can go tonight. But I was really anxious to see how the would come out, how much weight I could remove. Well over half.


Ken

flyingagin

The front doublers are done. I waited to finish the other side till I got my band saw, versus carving them out by hand. I cut a slit through the doublers to make the inside cuts. I then filled it back in with a sliver of birch ply. That is not very strong but there will be a ply bulkhead there and that will reinforce the slit doubler. So no problem.


I have been saving my tip money for about 6 months now. I only occasionally get a tip and usually only a couple of bucks, but I have once in awhile received a nice one on some of the longer runs I do, like 30 to 60 minutes each way.


I got 10% off at Lowes today when I should them my Military Retiree Card (Navy, 20 years) and real nice thank you for your service from the cashier.


I drive people to medical appointments.


I used to have a nice full size Sears 13" floor band saw (maybe it was 12", I don't remember that well) I had to part with it and my big radial arm saw about four years ago on when we left Iowa for Texas. Oh man I loved my big saws, but I could not have them in an apartment. Kept my drill press and disk/belt sander as they are bench top tools. In fact they are set up in the 4'x5' storage closet on the patio, and see plenty of use.


I think the wife is going to make me put this out there also. I will just surprise her tonight. I will lay it on her side of the bed tonight. So if I end up in E.R. tonight from a iron skillet to the head you won't be surprised.


Now me happy happy!!!!!!


I will have to spend some time doing alignments and adjustments to it.


Ken

flyingagin

The front doublers are done. I waited to finish the other side till I got my band saw, versus carving them out by hand. I cut a slit through the doublers to make the inside cuts. I then filled it back in with a sliver of birch ply. That is not very strong but there will be a ply bulkhead there and that will reinforce the slit doubler. So no problem.


I have been saving my tip money for about 6 months now. I only occasionally get a tip and usually only a couple of bucks, but I have once in awhile received a nice one on some of the longer runs I do, like 30 to 60 minutes each way.


I got 10% off at Lowes today when I should them my Military Retiree Card (Navy, 20 years) and real nice thank you for your service from the cashier.


I drive people to medical appointments.


I used to have a nice full size Sears 13" floor band saw (maybe it was 12", I don't remember that well) I had to part with it and my big radial arm saw about four years ago on when we left Iowa for Texas. Oh man I loved my big saws, but I could not have them in an apartment. Kept my drill press and disk/belt sander as they are bench top tools. In fact they are set up in the 4'x5' storage closet on the patio, and see plenty of use.


I think the wife is going to make me put this out there also. I will just surprise her tonight. I will lay it on her side of the bed tonight. So if I end up in E.R. tonight from a iron skillet to the head you won't be surprised.


Now me happy happy!!!!!!


I will have to spend some time doing alignments and adjustments to it.

This will speed up some work big time for me. It will be so much easier to make parts now and stack cut ribs. I am going to have to build more planes.


Ken

flyingagin

I finished the rear doublers that will secure the stab properly. I then glued up the front doublers. Then after much double checking that had I had the correct side so I would end up with two opposite sides and not the same (yes I have made that mistake in the past), I glued up everything Only 15 minute epoxy used for these operations.


Next I will have to make two more bulkheads, and then I can start glueing up the fuse.


Oh and I forgot to mentioned I reshaped the rudder so I could round off the back of the fuse and have it all blend in. I added a 1/2" section to the rudder to give me some room to reshape the back of it.


Ken

flyingagin

The front half of the fuse is joined.


The 2 bulkheads behind the firewall are light ply. The rest will be 1/8" balsa. There will be a bit more structure tie in on the bottom for the bottom wing.


Looks like I need to relieve the first bulkhead cut out a bit for a looser tank fit.


Hopefully I can bring the rear half of the fuse together this week.


Ken

flyingagin

I just had to see what it looked like with the wings.


Ken

flyingagin

I did a little work tonight.


Brought the aft end of the fuse together. Had to add 1/8" filler stock above and below the ply doublers. I jigged the fuse on my magnetic building board. then glued the back together. At that point I just had to go a little bit further and add some bottom sheeting. At this time I have to leave it open from just forward of the stab L.E. Work to do in there later.


And that is it for now bed time. Another early start time tomorrow.


Ken

gene6029

Moveing right along there Ken! I have the same band saw & it does just fine for my hobby work. I took the time to set it up and adjust it & dont have any problems with it. By the way THANK YOU for your service to our country.......Gene

flyingagin

I get to work on it a little sporadically Gene, But I am trying to move at a somewhat reasonable pace nonetheless.

I glad to hear your report on the bandsaw.

Ken

flyingagin

Back on the wings


First I made use of my new band saw and ripped to pieces of 1/4" birch aircraft plyas center section doublers behind the L.E. I then epoxied in. These will also serve to add strength to the wing mounting.
The I stated carving the the 1/2"sq L.E. I went at it with new exacto blades. I shaped one side and the flipped it and whittled the other side and just kept eyeballing the work to ensure I was even and centered. Just eyeball work here. I the rough sanded one wings L.E.


Here was maybe my biggest and stupidest mistake yet. I failed to go find my dust mask and wear it. Asthma attack. I have hit my rescue inhaler twice and other meds. I am moving a slow physically on purpose right now so as not to run out of air. Boy was that stupid. I know better. Dang me. Balsa dust is some nasty stuff, so fine and lite.


So I thought I would stop every thing for a bit and do an update. I am OK, just stupid.


Ken

flyingagin

I stopped work and went and bought some supplies


# one supply DUST MASKS!!!!!


I also picked up some aluminum tubes. Bigger than what use I used for the bibe wings I bought some that are 1/2" and thicker walled, very stiff, still only 3' long. Where do you find some that are 5' or 6' long?????? I got these for future building projects.


I also decided to try one of the new LED light bulbs. They are kind of spendy. I got one that is = to a 60 what incandescent bulb. Reall nice color from it, plenty bright.


Any way back to to the wings With a dust mask. I used a 2' long sanding bar with some 80 grit and got the L.E. I really leveled the L.E. out and then a small 180 grit foam block. I really like the L.E. shape.


Ken

flyingagin

Working on the wings. Some tedious slow detail work, fixing problems.


Some of the ribs trailing edge end were a bad fit. Some were under size, some a near prefect fit. Numerous ribs were considerably thinner than the trailing edge stock. Not all though. And I forgot that the inner 3 ribs had to be sheeted with 1/16" center section sheeting. I needed the trailing edge, leading edge and spars to be 1/16" proud of the ribs.


First I addressed the ribs that were to low. They were only low at the rear. I basicly cap stripped them with 1/16" by 1/4" wide strips. This made then a little taller than the T.E. Next I trimmed the cap down to the width of the ribs, 1/16". Followed by some careful work with a sanding bar to make them flush. It worked pretty good I think.


For the center section I made a marking block or gauge. Just two pieces of 1/16" scrap sheet. It basically is a cross with the one piece glued on top of the other. Lay it on the ribs and start marking. Then a bit of careful whittling and sanding made the 3 center ribs ready for center sheeting.


Now that I have a band saw I wont run into these problems again. I will just make to templates and stack cut the all at once. It was just to hard to make template ribs with a coping saw.


But problems solved.


I I have only dome one wing, the one that is going to be the bottom wing. And only one side at that. This is time consuming. The top wing has on additional problem. The trailing edge stock is not perfectly square with the wing. It is at a bit of an angle. I made it first, and tried to align it with a gauge. Thought I had it. But on careful siteing down the length I found it to be misaligned. The bottom wing I eyeballed into true. Got it right. I will have to cut the T.E loose on the top wing and realign it. Then I get to spend a few hours fixing rib fit on it also. I am only doing the center sheeting to the top of the bottom wing and then to the bottom of the top wing for a while. I have mounts to install in the centers. For 6/32 wing bolts on the bottom wing. And cabane strut attachments on the top wing.


I am trying to get to the point were I can attach the bottom wing to the fuse, so I can judge the struts length and angles. Still a heck of a lot of decisions to make.


I only work for short stretches of time, and then my back will start to scream and I retreat to the lazy boy.


They pictures are not the best. I had trouble getting close enough and still reasonably focused. Not a real good camera.


Ken

flyingagin

I finished fixing the rib problems on the bottom wing. And I have added vertical shear webbing to the spars. The wing feels a heck of a lot stiffer and stronger now.


Ken

flyingagin

I fixed the misaligned T.E. on the top wing. It was alot easier and faster than I thought it would be. It was a little more than just tacked on to the ribs so I was able to get enough C.A. off the joints to fix it with out much effort. I think I had spotted the problem as soon as I removed the wing from the building board, and so just left it alone; didn't add more glue to the joints.


It only took about 30 minutes.


After that then I fixed the ribs to T.E. sizing just like the bottom wing, and installed the vertical shear webbing and bottom center sheeting on the wing.


So both wings are now at the same point.


I need to set up the bottom wing to fuse mounting, and add the mount points for the struts to bothe wings. Then I can add the rest of the center sheeting to both wings.


I will wait to do the wing tips till after both wings are mounted and alighned.


Bottom wing on the left.


Ken

flyingagin

Made more good use of my band saw and cut some bolt and nut plates from 1/16" and 1/8" birch. The 1/16" is to reinforce where the bolts pass thru the bottom wing and the 1/8 to receive the blind T nuts. I will have to add a real small piece to the nut plates so that the little spikes on the nuts have enough material to bite into. I am using 4 6/32 bolts to attach the bottom wing.


A real surprise the bottom wing is dead on square to the side of the fuse. I did not have to tweak anything at all.


Ken

flyingagin

The bottom wing is now held by two bolts 6/32s. I made a 1/16" birch ply pate that I then epoxied to the bottom of the T.E. In the fuse there is a piece of 1/8" birch from one side to the other. and two 1/4" lite ply pads on top of it. A T Nut into each, I needed the 1/4" because the 3 little spikes would have protruded there the 1/8" ply. The wing is aligned in all directions right now but needs the front two bolts installed to lock it in place.


I just had to get a glimpse of what it is going to look like. The stab is not glued in at this time yet. It is stuck into it's slot, a snug fit.


Two more to install in the front part of the wing.


I will get some pictures of the bolting details later but it is bed time for me. Past bed time.


Ken

flyingagin

Trials and tribulations. Lack of foresight on my part.


I have the bottom wing temporarily bolted on.


I installed the rear bolts and hard points first. And about a day later decided I had really screwed up. That I had the perfect recipe for loss of aircraft the way I installed the nut plate in the fuse. Not enough to hold it in there.


The nut plates are 1/16" birch ply with 1/4" on top to receive the blind nuts. It is in the 1/16" ply plate that the problem lies. There is just not enough surface area to hold it in there in negative high g turns. It is flush with the bottom of the wing saddle. It is about 1.5" long by 2.5" wide.So there is a total of 5.5" by 1/16" of area epoxied to the inside of the birch inner doubler. on top of it I glued two 1/4" thick by roughly 1/2"sqaure peices of ply for the blind nuts to sink into. They don't have enough glue area with the fuse sides and none with the aft bulkead. I am afraid that just wont take the loads.


I intend to leave the 1/16" plate be, but the 1/4" pieces have to be removed. I will try a real hot xacto blade and see if I can cut the epoxy.


I will then replace them with a one piece 1/4" ply piece for the blind nuts. And epoxied to the sides and rear bulkhead. I will then pin it with two small screws through into the sides. I will use a pair of servo mounting screws through the fuse sides and into the 1/4"ply plate. Counter sunk through the balsa fuse sides There is then the 1/8"light ply and 1/16" birch ply fuse doublers that the screws will be in and then the 1/4" blind nut plate. My wordage here really sucks. I hope you get the meaning of what I am trying to do though.


Now the front 1/16" birch ply nut plate is done the same way but I used nearly the same size blind nut plate that will be pinned with servo screws. I think this fix will now hold and not pull out of the bottom of the plane.


I epoxied a 1/16" birch ply pate onto the trailing edge of the bottom on the bottom. the bolts then go through this.


For front bolt pass through plate I spent about a week thinking about it. I don't wont the plate pulling through the top of the wing.


My answer is a 1/8" birch plate (sort of a very flat U shape) epoxied to the 1/4" leading edge doubler, with a nice lip under it that the bolt pass through plate sits on, plus it is epoxied to the L.E. doubler. I think there is plenty of glue surface area here to hold solidly. I also epoxied a piece of 1/8" by 1/4" birch ply on it's side on top of the upper spar inside surface. The bolt pass through plate is the epoxied on top of this and the lip of the U shaped L.E. peice.


I think this will take the loads.


For sure feel free to jump in and correct me on this.


I am not to sure I have described things well, but here are some pics, so between them and my write up I hope you get the ideal. And if you think it is still lacking or if you think I over did it let me know please.


Ken

straitnickel

flyingagin,
I don't see a problem with what you have there. I've only built a few kits for experience here, but I don't see the wings coming off.

flyingagin

Back on track. I now have the nut plates properly secured.

Those 2 little nut plates in back cam out with very little effort. I used a hot exacto blade to cut the epoxy. I think I spent at tops 30 minutes removing them.

I then made one nut plate and epoxied it into the back section.

I did the front right from the beginning, so no problem.

I then ran the servo screws into the nut plates, 4 each. They are counter sunk and will be puttied over.

I think the nut plates are now up to the task.

I think at this point I will jig it to my building board . One to get the stab slot trued and primarlily to get the wing struts built and the top wing aligned.

Ken

Lou Crane

Ken,

Last night, I replied to your Q: about bellcrank mounting, which was forwarded from here to me email.

I just ran through your build-sequence thread again. Several impressions...

You are creating about twice the wing area of a standard Ringmaster. (Except, of course, for the reduced efficiency of two wings operating in the same air space. See below.)

The addition of surface spars to the wings increases their strength very nicely!

As it is a biplane, you might consider mounting the bellcrank through the fuselage, instead of within either wing. Why? Vertical CG location is important, too. If the lines reach internal leadout guides, or possibly a guide on a strut between upper and lower wings, at the wrong height, the model wil try to fly "rolled" to the attitude where the pull force DOES aim at the vertical CG. The wings are above and below the place where the eventual vertical CG will be...

If you haven't yet, consider a strut at, say, the first rib inboard of the tip rib. that can be as simple as a 1/16" ply piece about 1/2" wide, pocketed into the wing surface. E.g., on the rib, some 1/16" balsa ahead of and aft of where the strut goes, and a 1/16" balsa strip joining them, inside the wing. The strut can then be added after covering, simply by slitting the covering to open access to the 'pocket.' It will also help aligning the two wing sections parallel... For symmetry, put another such strut at the same relative position outboard....

Another piece of 1/16" ply, about 1/2" by 3" ply can be glued to that strut at a height where the model hangs straight vertically. The leadout guide piece can be clamped onto the strut - e.g., with a reversed clothespin clamp so you can find this location vertically. The leadouts should have their mid-point at about 3° to 5° aft from the CG. (Sin 3° =.052; Sin 5°= .087.) The 'guides' can be small brass grommets or short lengths of tube...

Multiply the distance from fuselage centerline to the leadout guide by the Sin value to find where the CENTER between leadouts should be, aft of the front-to-back CG. (The model should hang at that 3° to 5° nose down, in other words.) This allows for the sag aft of the lines due to their drag, If no allowance is made, pull will aim ahead or behind the proper point, and the model will fly nose-in or nose-out accordingly. Some nose-out tendency is acceptable, but we've overdone that by too much for decades. Too much brings other problems, which are very hard to ID and solve.

AS the total area is about double that of a stock Ringmaster, have you considered enlarging the horizontal tail area appropriately? Biplanes are less efficient in their use of wing area than monoplanes - the air from each wing interferes to a degree with the air the other wing flies through. Figure that this makes the total area about one and three quarters the total of one wing. To have the same effect as the stock Ringmaster's tail, area should be proportionately larger.

The area of ellipses is about 3/4 of the span times the max chord - 0.75 (or so - closer to 0.7854.) We can acceptably assume that the front and rear parts of the tail are approximate ellipses. Since area is span times chord, each should increase by the square root of the area increase needed. IOW, a bit over 1.3 times the stock Ringmaster size. That, btw, keeps the same 'shape.'

These ideas seem to be still possible for you to include in your model with minimal complication. For interest, if you find a bunch of plan (top) views of several full-size biplanes, you WILL see that the tail area looks disproportionately large. It isn't disproportional!

You are into a fascinating project. The problem with so many of those is that you may run into problems which you could not expect, and even if the model survives early flights, which are hard to identify and resolve. I hope i'm offering thoughts that might avoid some of that. ALL models need to be trimmed for best performance, but there are some ways to get them closer before first flight. I HOPE my comments bring you that joyful success, to be finalized according to how the beast flies...