Zor

Hello Rick,

I am trying to help based on what I do or what I have done.
Perhaps ohers may chip in with their own experience and valuable suggestions.

I may write things that are already obvious to you or to others. If so it does not do any harm.

So let us remember some fundamentals. This is a plane designed for aerobatics which mean lots of rotational action around all three axis. All rotations take place with the CG as the point of rotations so it is important for the CG to be at the proper place. The design gives a narrower range than most airplanes. The range is only plus or minus 3/8" from its recommended position. The recommended position is 1/8" ahead of the leading edge of the lower wing when the model is in level flight attitude.

The finger method of supporting the model is not adequate in my opinion. We cannot use our fingers in front of the lower wing and the accuracy obtained by supporting the upper wing leads to errors. A proper method is quite essential. I have pictures of how I did it if it may help you. Let me know.

Remember also that the line of lift (wing tip to wing tip) varies with the angle of attack of the wings, thus the narrow range of the recommended CG location.

The rudder mix to the ailerons is to obtain nicely coordinated turns. Remember here that the prop in its rotation is a very effective gyroscope and the effect of this gyroscope is reversed from left turn to right turns. If your transmitter (you did not tell me which TX you have) allows you, you may setup a different amount of mix for left turns as compared to right turns. The amount of mix is best established by flying and observing the results. With this model it is in the range of 5% to 15% of full travel. This also assume that the throws have been set to recommended figures.

The rudder mix should be removable by the flick of a switch because many aerobaic maneuvers need rudder action opposite to aileron control. Check your trasmitter manual as to how to use a switch to activate or remove the mix. You can always not use the mix and coordinae the turns manually by using both ailerons and a bit of rudder to initiate a turn. Establish the banked attitude with ailerons, use opposite ailerons to stop the roll at the desired angle of bank and maintain a bit o opposite aileron during the turn. Remember the overbanking tendency due to the outer wing(s) travelling faster than the inner wing(s). The elevators used to maintain either level or climb or descent rates.

On take offs ___ first check that the angle of attack of the wings with the model just sitting on the ground does not exceed 12 degrees (preferably not more than 10 degrees).well within the stalling angle. A biplane has more drag than a monoplane so it is advantageous to lift the tail on acceleration. That accomplish two things. It reduces the length of the run and allows to rotate and lift off at the pilots control instead of lifting on its own at less than desired climb conditions.

NOTE: The above is what to keep in mind for whoever is interested in smooth and reasonably accurate flying. Many are not interested in this kind of thinking. To each his own.

I have always been interested in experiemntal flying dating back to the old radio control experimentations using home brew equipment. That is not for the majority of today's fliers.

Also there is always the odd fellow who enjoys degrading my outlook on model airplane flying. Their contradictions do not bother me and do not prevent me from enjoying what I do nor my attitude in the hobby. They do their thing and I do mine. All my model flyinghere has been on a private farm using a runway over 2500 feet long and 150 feet wide and a manicured grass surface. We were also flyng in and out with the Piper Twin Comanche.

I wish you all the best with your enjoyment of your model.
Hope the above is helpful to you.

Zor (this short name is part of my real name) Cheers.

Rflyin

My Feedback: (6)

Hello,
today I put together a "CG Sling" to check balance and found I was in the center of recomended range. I moved battery to set it at 1/8" behind center of recomended range. Next flight was ok except right wing dropped as soon as it left the ground. No tendency to drop on landing. I balanced lateraly but will recheck and fly again.

Thanks,
Rick

Zor

Rflyin,

On take off the right wing(s) dropped as soon as it left the ground.
I imagine you did some thinking about what may be the cause.. I may not be telling anything new here but I am thinking about a weight unbalance (right side of the CG beng heavier than the left side. A warp in the wings creating a higher overall angle of attack on the left side. The ailerons not being equally centered with the wing(s) trailing edge.

When checking the lateral balance the straight line of suspension should ideally pass through the CG or very lightly above it (above in the normal attitude of the model as it would sit on the floor). We have to determne where that line is and then suspend the model to establish that line in relation to the CG.

The point of suspension at the front is usually the axis of the propeller. We choose a prop positoning so that there is a minimum of friction (no engine compression and free to turn); We now find a point at the rear such that we can rotate the model around the longitudinal axis such that the model has no tendency to rotate. That makes it easy to find a heavy side. The principle is the same as balancing a prop.

Both points of suspension should be in a vetical plane that splits the model in a symetrical manner. If we find that one side is heavier then corrective action is applied.

Now you can do it your own method but avoid that the C G is above or below the line of suspension.

Have fun,

Zor

Rflyin

My Feedback: (6)

Hello,
After taking some lead off my right wing tip I had 3 beautiful flights tonight. I did expect it to be faster. I read many posts with this motor-prop combo That talked about "unlimited vertical" I would describe it as scale like speed. Any suggesttions on a faster prop? I'm limited to 14" dia.

Thanks,
Rick

Cougar429

My Feedback: (3)

Rflyin, why would you have lead on your wingtip to begin with?

Have to post almost lost the 'bolt today. First flight since the motor probs last week almost turned into a bit of a disaster when I lost throttle control climbing into a loop. Had to fly the rest of the tank out at full bore.

Happy to say for the first time I confirmed my cabane repair in ways I never intended. DANG! This thing scoots at full throttle. Other than a bit of apprehension listening to it rip around, the only problem came at the end of the tank when the motor started to surge. Did not have enough power to stay airborne, and the bugger would not quit completely, so forced it down on the runway hoping the drag from the grass would slow it down enough to allow me to aim it over into the corn. Unfortunately it still barely had flying speed and tried several times to take off again. It was getting a good bit away when I decided to force it over on its nose. The prop finally stopped as it went over on its back, by now almost a hundred and fifty yards down the runway[X(].

Plane is fully intact and found the problem was the ball link on the throttle arm came off. My only complaint on the Saito is the weak arm and flexing allowed the screw to loosen.

Phew! The rest of the day almost turned just as bad, but that's another story[&:].

Rflyin

My Feedback: (6)

Cougar429,
Lateral balance.

Zor

Cougar429 and everyone,

You can now be proud of the emergency training you assiged to yourself as do all professional pilots.

You also learned to never use "ball joints" in a model airplane. They are not reliable paricularly under vibrations. They are devices aimed at making more business for the manufacturers of models. Just remember that I am from the OLD school. Like when we were making our own hinges Hi! Hi!

Of course someone that profits by selling more models may post to contradic me. It would be useless. Nothing is more valuable then the experience gained on the long run. Such experience you are now acquiring and fortunately were able to save your model. That becomes your own reward and as I wrote in the first sentence, you can be proud of yourself.

A refresher for all readers ___
If you are using a control linkage that uses a set screw on a metal rod, grind or file a little flat on the rod removing about 20% of the diameter and make a small recess in the center of the flat with a center punch. Now grind the set screw to present a pointed tip that fits in the center punch mark. If that set screw ever comes loose, you will have some looseness (flop) but the control will not be lost. On the periodic checks that loose set screw will be noticed and retightened.

Periodic checks of a model is like the 100 hours inspection that renews the C of A on a full size airplane.(Certificate of Airworthiness). You can be what ever pleases you. I like to think in terms of being a professional model flier. It does not mean that you have to enter contests to be a professioal.

Some amateur musicians play as well as some professionals without ever participating in a concert on a stage.

In a similar situation concerning engine tuning (so called) remember that the ignition of glow fuel and its timing is a result of the compression in the cylinder which contributes to raise the temperature of the mixture. The firing also keeps the glow plug "glowing" without external electrical assistance. The mixture ratio is of prime importance as well as the temperature that initiates the firing. There is an optimum mixture which is achieved by the settings of the needle valves. Patience and very fine touch up of the low rpm needle (condition of smallest rate of fuel flow) is required to obtain reliable firing and good transiton to higher revs. In the low rpm range the high speed needle properly set for high power has very little effect at the low rpm range. Set the high speed needle first then concentrate on setting the low speed needle properly.

Cheap engines (low cost) may work nicely more by luck than by proper engineering and precision manufacturing. Be aware. I had an engine (brand and model intentionally left out) that could not be tuned reliably. It became very reliable after I took apart the carburetor and polished out the burrs left by fast machinng of the low speed needle openings. Remember that the lower rpm range is associated with a variable opening of the low speed needle valve as you open the throttle.

So much for my "blah, blah, blah" for now.

Have a great day flying your models with the knowledge that all the fine points and adjustments (settings) have been taken care of.

Cheers de Zor

EJWash1

My Feedback: (3)

Since you're limited to a 14" diameter, your experiments will be based on number of blades and pitch. You may want to try some posts over on the Glow Engines, Gas Engines, Fuel & Mfg Support Forums:

http://www.rcuniverse.com/forum/default.asp?forumid=463

You may be able to get some data from modelers running your engine with various props.

EJWash

EJWash1

My Feedback: (3)

Glad you saved your 'Bolt.

Are you saying that the plastic cap popped-off of the metal ball, or that the nut came off the metal ball and the linkage separated from the throttle arm?

EJWash

Cougar429

My Feedback: (3)

The metal throttle arm is relatively easy to bend, so I thing the last round of engine yanks and reinstallations had it flex enough the screw holding the ball loosened in the arm. The ball was still inside the link, dangling from the bellcrank when I went to retrieve the plane.

I have replaced it with a Z-bend in the bellcrank and a regular nylon clip in the throttle arm. should not come loose now, although the threads I cut in the arm may saw away on the nylon center pin. Looking at another arm assembly.

EJWash1

My Feedback: (3)

So the problem had nothing to do with the ball joint itself, just that the nut came undone. A bit of medium-strength thread locker liquid may suffice.

When you mentioned the bellcrank, I went back to your post #477 to refresh my memory of your clever throttle set-up. The ball linkages you use are widely used in R/C helios. If that isn't testimony of a high-vibration environment, I don't know what is. I've used the DuBro cap-style ball joint on four of my last four models (including 2 .60 2-stroke pattern ships) and haven't had a cap pop-off it's ball yet.

EJWash

Cougar429

My Feedback: (3)

As I said, it was that flex that allowed the threads to loosen. With the new setup that should not happen again.

Was going flying again this evening, but my student was beat from work so tomorrow is on the schedule. Now I know the airframe will take it, may push the 'Bolt a bit harder into some maneuvers and see how it goes.

Also fixed my camera so video mode works again. If I can, should have some more vids soon.

Zor

Cougar Hi !

If you soon read this ____
Curious how you are making out with your mdel Bolt in the sky. (lol)

Zor

Cougar429

My Feedback: (3)

So far things are good. New linkage works fine and the plane has a couple of flights under the wheels since the fun. Baffles for the cowling are done, as well. Need to find a fuel "T" and pick up some more epoxy to complete the laminations for the exit dam. Was thinking of replacing the metal throttle lever with plastic. None of my 2-stroke spares will fit.

With all this going on, concentrated on getting the maiden of two amphibs out of the way and the weather has not been cooperating on getting to the field as much as we hoped. Also built dual aileron servos into a PICA WACO I was given for free.

[youtube]http://www.youtube.com/watch?v=uAvzi1GhPQY[/youtube]

[youtube]http://www.youtube.com/watch?v=fVapqznX0fQ&feature=related[/youtube]

To top it all off it was prudent to childproof the build room as the grandson is coming soon. No construction or repair for a week or so, a sacrifice I'm easily willing to make to see the family.

Hope everyone else has been having a nice summer and flying season.

Cougar429

My Feedback: (3)

Cowling is bolted on and hopefully will be able to test cooling soon. On vaca next week. Family is down, but should have more time to do some tweaking.

Cougar429

My Feedback: (3)

Happy, Happy Joy, Joy!

Took the 'Bolt up for a couple of flights this evening. Weather could not have been better. Did some extended runs with the motor at different power settings to check for cooling issues. Nothing evident, but that exhaust gets pretty HOT!

First short flight was a bit cranky, with the motor again starting to poop out, (mostly above that rich mid-range). A bit of work to get it back to the field. Did a bit more tweaking of the mixture and think I finally have it dialed in. Runs as smooth as it's ever been throughout the power range and will idle down to nothing. Oh, yeah, the 13 X 8 prop seems to pull fine, but torque effect on verticals is much more noticeable.

As for the cooling; those two flights ended with no signs of the BBQ stains or fuel/oil crackling I had with the open cowl. Think I can fly with enough confidence and will know what to do when the new cowl is installed on the Pica WACO next in line.

Did find I pulled one Homer. Teed the filler into the carb line. Fine for fueling, but guess what happens when you try to draw the fuel out at the end of a session, (path of least resistance and all!). Thought I would flatten the field box battery before it finally emptied the tank, (or at least I hope so).

Cowl has to come off again to finish the epoxy and glass, so will think about how to solve this one. Want to avoid pulling the tank out again to add another fuel line as it would require a second clunk line and I'm worried it will interfere with the primary supply.

Zor

Congratulations.
Thanks for keeping us posted.

Zor

EJWash1

My Feedback: (3)

Glad to hear that everything is set-up nicely and the way you want it. Nice to be able to go to the field and "fuel, crank, and go."

Been staring at the plans for the Sig 'Bolt now and then and pondering the mods necessary to mount an OS FS-91. Would have to bond-in a recessed firewall like you did. Starting to lean towards just going with a .60 2-stroke. Maybe when I actually start building the fuse, I'll get a better idea.

When you say the "13 X 8 prop seems to pull fine", do you find the performance on the light side?

Pica Waco? Gorgeous plane!

EJWash

Cougar429

My Feedback: (3)

EJWash1, I doubt you would need a recessed firewall for your 91. If planned for during assembly it should work perfectly.

In my case it was due to trying to fit the longer 4-stroke into the stock cowl, (which I believe the original builder bolted it on too far aft) and I was trying to keep his paint and trim aligned.

When I went to fit the F/S cowl I had to hog an excessive amount from the lower surface to give the adequate exit area. This would have not been necessary if the cowl were fit further forward.

Lastly, it would also have removed or reduced the need for lead ballast on the firewall by naturally moving the CofG forward.

All in all, these were lessons I learned late in the game, and would have avoided them altogether if I had waited to do the installation during the winter when I plan on recovering anyway. I may still get a new cowl and take advantage of that knowlege, (and a new Hayes mount) to move the motor further forward.

As for the prop: I have been running it since first spin with the 13 X 6. This is recommended for 3D in the Saito manual, but I found it a bit on the high RPM side. Not really a problem, but I wanted to see how this one would dig in.

Takeoffs required major amounts of right rudder to maintain the line which was my first clue. When I pulled my first vertical it kept fighting me and falling off to the left, (stayed in Low-Rate for these flights as I was concentrating on assessing the cooling). Same story with followups. Loops were also ugly. If left on their own the plane would exit almost 45 degrees off entry heading.

Speed seemed the same as the lower pitch prop, (or actually a tad slower, but I avoided major full power runs until I had some idea of the cooling issue). Vertical also suffered a bit.

EJWash1

My Feedback: (3)

Cougar429,

Thanks much for the intel. This helps.

I have a Hyde mount on an OS FS-91 mounted to a pattern ship. Fantastic workmanship, and it actually quiets things down some. I measured the mount and engine from the firewall to the front of the drive washer - 5 1/2". Laying this measurement on the plan sheet, one option would be to move the firewall rearward during the build 1-5/16". This would push the drive washer 3/16" beyond the cowl (as it's drawn on the plans).

The problem with moving the cowl forward from where it is on the plans is that the top of the forward fuselage slopes downward, so if you move the cowl forward this means that it will be off-center at the engine shaft. As you can see from the plan, moving the firewall rearward would not interfere with the mounting of the cowl in it's location on the plan. A new firewall would have to be fabricated though, and the bottom ply part of fuse inside the cowl (F4) would have to be shortened. There are a few other pieces that are bonded to the fuse sides that would have to be shortened as well. Not a hard mod at all. We'll see.

EJWash

Cougar429

My Feedback: (3)

Yep. The time to plan ahead is when laying up the build. In your case a good piece of heavy ply, (or two thinner epoxied together) should allow you to place the firewall where needed and you should be able to bond to the sides with a lot less work than my mod.

Quick Tip: In some cases if I don't have one heavy enough piece, sandwiching a layer of glass cloth between the thinner ply before weighing the assembly down between thick plexi sheets ensures a nearly indestructible firewall.

Keep us posted when you start assembly. Love to see how it turns out.


Well, I thought of adding a check valve in the carb line downstream of the T, but could not eliminate the possibility of flooding during fill or locate it where the alloy body would not contact the motor casing, (metal-to-metal is a big bugaboo in my book). Bit the bullet and installed a third fill/drain line angled to the port front of the tank. This requires I tilt the plane down during draining, but I can live with that.

Just waiting for the cordless to charge to drill another hole in the firewall and go through the rather enjoyable task of fishing the lines.[sm=bananahead.gif][sm=drowning.gif]

EJWash1

My Feedback: (3)

Thanks for the great tips.

The firewall is made up by laminating two pieces of 1/8" ply. They're the same arched shape on the top, but the inside piece is cut-in more narrow than the other so the side sheets can butt-up against and bond to the sides of it. I built a different Sig kit and the same method was used. I applied a coat of West System epoxy to each firewall piece and clamped them together until they cured. Can't see not doing the same thing here.

EJWash

Cougar429

My Feedback: (3)

Have you ever tried the glass lamination? Works great for strength.

As I suspected, installing the fuel system ended up quite the chore. So badly in fact I had to swap out for a different style 12oz tank to be able to prevent the lines from cutting as it was pushed up against the back of the firewall, (which meant my nicely fabbed fill/drain and vent lines had to go and start from scratch). Have everything back together and pressure tested. Waiting for some epoxy/flox to harden on the cowl. Will do some glassing tomorrow and that should be the end of the work there. Likely won't paint it till I decide the covering scheme. May look as it is now, but removing the painted material should cut a significant amount of weight.

While at that I'll decide if I want to go with ailerons on the top wing, as well.

Hint for users of the Fiberglass Specialties cowls: ANY reshaping or holes need the edges touched up with CA or epoxy to prevent fuel/oils from migrating into the fibers. Don't ask how I know this.

EJWash1

My Feedback: (3)

I haven't tried laminating wood with cloth between before. I'll have to give it a test-run.

I sprinkle a bit of filler in the epoxy to thicken it up a little to cover any voids. I suppose the cloth serves to do the same.

Thanks for sharing the intel on "raw" fiberglass part areas. Makes sense that fluid would wick into the fiber, but not something one would think about.

EJWash

Cougar429

My Feedback: (3)

The glass is more for creating a layer of multi-directional strength. It also prevents the ply from peeling when holes are drilled for mounts, etc.

Try to avoid using Micro to any great amount when doing any structural bonding. The glass balloons add no strength and the higher the content the easier it will be to sand, but more brittle and prone to crack.

For structural fill or bonding I use a material called "Flox", (flocked cotton). We used it extensively in real A/C and my supply remained at the end of a Lancair build. I believe it's available from any A/C supply house, such as Aircraft Spruce. You'd be surprised, a very small amount goes a LONG way.