RICKSTUBBZ

RC wings,

Several guys on this thread have wrote to build this baby by the book. I tend to agree with them. As I recall the stock build puts right and down in the firewall. When I built mine, I thought “I don’t need that” and built the firewall square and it was a hand full to fly. Flew it that way for a while shrugging it off as a small short coupled airplane. [:-]One day out of curiosity and experimentation I added the down and right into the motor mount. Suddenly the plane was much better behaved. (For the NAH sayers out there) You still need to know how to use the rudder even with right thrust.

I have no idea how it will act with the ST.51 since I have not got there yet. If I get it done soon I’ll grab some video and show you. But in all honesty, even with the OS45FSR I never fly or flew it at full throttle except in climbing maneuvers. I even once had an old K&B .40 in this thing. It flew the plane just fine. But if you wanted to loop you had to dive first. Probably very scale like performance.

What I like about the .51 is you can run a bigger diameter prop with less pitch by comparison. Somewhere in the 12X5 maybe even 13X4 range. As I mentioned before I hooked my son up with that engine on a GP Super Decathlon fully enclosed in the cowl (rotated engine to 135°). That plane is as short as this one. Works good so far with the props mentioned.

One thing I will say about the “Smith” it will be in your interest to get aileron differential by whatever means makes you happy. Either use modern day two servo setup or create it using mechanical setup. Other wise it kind of barrel rolls and does not do a true axial roll. Mind you - mine is still set-up without differential and I enjoy flying it just the same.

rc_wings

[/quote]

Several guys on this thread have wrote to build this baby by the book. I tend to agree with them. As I recall the stock build puts right and down in the firewall. When I built mine, I thought “I don’t need that” and built the firewall square and it was a hand full to fly. Flew it that way for a while shrugging it off as a small short coupled airplane. [:-]One day out of curiosity and experimentation I added the down and right into the motor mount. Suddenly the plane was much better behaved. (For the NAH sayers out there) You still need to know how to use the rudder even with right thrust.
[/quote]

The book calls for no right or down thrust - which I found a little odd. Will build some in as well as neg incidence on the top wing (approx -1.5 ???). BTW - I AM a rudder man!

[/quote]

I have no idea how it will act with the ST.51 since I have not got there yet. If I get it done soon I’ll grab some video and show you. But in all honesty, even with the OS45FSR I never fly or flew it at full throttle except in climbing maneuvers. I even once had an old K&B .40 in this thing. It flew the plane just fine. But if you wanted to loop you had to dive first. Probably very scale like performance.

What I like about the .51 is you can run a bigger diameter prop with less pitch by comparison. Somewhere in the 12X5 maybe even 13X4 range. As I mentioned before I hooked my son up with that engine on a GP Super Decathlon fully enclosed in the cowl (rotated engine to 135°). That plane is as short as this one. Works good so far with the props mentioned.
[/quote]

I figured the .40 would fly it nice, a .45 would be good, but the .51 was only a couple bucks more and since I would like to have it go vertical and have enough to power to loop without diving, the .51 sounds perfect. A sweet but costly little 4 stroke would have been nice too but double the price even after the Pitts muffler. A little throttle management may be in order. No need for 3D on this one as it is not the bird, but did not want to be short on power.

[/quote]

One thing I will say about the “Smith” it will be in your interest to get aileron differential by whatever means makes you happy. Either use modern day two servo setup or create it using mechanical setup. Other wise it kind of barrel rolls and does not do a true axial roll. Mind you - mine is still set-up without differential and I enjoy flying it just the same.
[/quote]

Understood and will build in mechanical diff as will only use one servo as per plans.

EscapeFlyer

My Feedback: (1)

Actually, I wonder if the full scale bipe isn't the same. Has anyone seen one up close?

Yes.

Iterresting- for what it's worth:

When I flew my Mini at the MAS club in Denver, this bipe snap rolled blindingly fast. Then I moved to the Twin Cities. What a difference about 5000 ft make!

I'm at 780 ft now and comparatively, it's a dog! - Not to say it still isn't one of the most fun airplanes I've ever flown. I think I will add top ailerons to try and recreate what it could do in Denver.

RICKSTUBBZ

rc_wings

Have a real close look at the plans. I am pretty sure they have you add an extra piece of 3/16 or 1/4 stock on the front of the left side of the fuselage (right thrust) and I am pretty sure the firewall face is not square to the "datum line" (down thrust). I could be confusing it with a different build. But I am pretty sure that is how the plans and book are on this one.

rc_wings

Nope....plans show the firewall and mount "square" and the book states on page 3: "The original models used no engine offset to the right or down and this gave good results".

So unless my plans and manual are an older revision....this is what they call for. The book (although I have quickly scanned it over at this point) makes no mention of wing incidence, but the plan seem to indicate that none is called for.

So, I was relying on recommendations posted on this thread, and a couple others regarding incidence and thrust. I was going to "build in" -1.5 degrees incidence on the top wing, 2 degrees down thrust and 2 degrees right thrust so was wondering if this combination would be a better starting point? [sm=confused.gif]

Sorry if I keep repeating the question, but was hoping to build this and avoid shims in the beginning so want to be sure the above figures is an ideal starting point, contrary to the plans and manual.

All feedback is much appreciated!!!

RICKSTUBBZ

I pulled out my plans and book this morning. I also set the Smith up on my table saw, pulled out the scales and incidence meter and got after it.

First and foremost let me say I stand corrected. I was obviously remembering a different build. Now I did originally have this plane built with 0° engine thrust. And did do as I said a few post ago - experimented at a later time with right and down thrust. In fact when I recovered it is when I put in the spacers for the engine mount.


Rc_wings and all,
Here is the measurements from my “Smith” .

Top Wing 0°
Bottom Wing 0°
Stab with elevator “strait with stab” 0°
Elevator has 5/16” down trim for level flight (measured with a scale laid flat on stab and measuring the distance to the top of elevator at it’s longest point. With the elevator at this point and putting the incidence gauge on it (trailing edge of elevator to the leading edge of stab) the measurement = 3° to 3 1/2°
Engine down Thrust 3 1/2°
Engine right Thrust 3 1/4° (9/16” difference right to left with 10” prop measured to elevator hinge line.)

Balanced per the plans - 3/16” to 1/4" behind the leading edge of bottom wing.

Travels
Elevator
Low Rates Up 7/16”
Down 9/16”
High rates Up 3/4” This is almost too much travel on high rates
Down 7/8”
Ailerons
Low Rates Up 9/16”
Down 7/16”
High rates Up 11/16” Ailerons could use more travel on high rate. And still need more differential.
Down 1/2”
Rudder 1 3/4”

With the 45FSR and a 10X6 prop the RPM related pitching of my plane is alright. I set it up to fly level at my cruise (around half throttle) it will drop the nose and sink reasonable when I cut the power and it will climb at full throttle. For me the elevator travels feel like they are maxed out. The Ailerons could use a little more travel on high rates. The rudder on this radio does not have dual rate and this amount of travel feels right for me. The only thing I use the low rates for, on this plane, is take off and landing and those travels are perfect for me. The airplane will snap roll like nobodies business but aileron rolls are at best a fast slow roll (corkscrew). I have flown this thing a little heavier on the tail than it is right now. If you are on top of your game you can get away with it and the snaps and spins are even crazier.

I can say, if I were to build another “Smith”, based off the info I have from this one I would alter the stab incidence to be at least a couple degrees positive. I’d maybe even dabble with adjusting a little negative in the top wing as has been mentioned. In fact I might do that to this one just to see how it acts. Another learning experiment.

Now it’s time to go pack up for a trip to the flying field. Later....

EscapeFlyer

My Feedback: (1)

I think you'd be right on the money.

It's still a blast the way it is too.

Have you tried a large open loop? Does your Mini tend to want to ignore elevator input as it reaches a full vertical attitude? All my Minis did this and when I fed in more elevator it squared the loop. Every one at the field blamed it on the airfoil, but I wonder if your horizontal incidence suggestion would help that as well.

rc_wings

Thanks RICKSTUBBZ and ilikebipes! I now have a good idea of what needs changing as a starting point to make the SMP a little better.

RICKSTUBBZ

Ilikebipes

It is hard to elaborate on this much without seeing it happen. Too many variables. One thing that comes to mind is the question of airspeed and/or prop wash?

RICKSTUBBZ

rc_wings

Which “Bisson” muffler (part number) did you buy for your ST 51? I am concerned that the one for the 40, 45, 51, is going to be too small for the 51. Even though I’ll swing a bigger prop at lower RPM.

By any chance do you have a way to weigh your “Bisson” pitts muffler? I could not find a weight for it (on the web) at “Bisson” or on “Tower”.

I ask because I started working on my “Smith” last night. Pulled off the OS45FSR and weighed it and the ST51 along with their mufflers. Long story shortened the ST51 and muffler is 3 1/8 ounces heavier than OS45FSR and muffler. With out mufflers the ST is only 1 1/2 or so ounces heavier. I say “or so” because I don’t have the numbers in front of me right now.

The good news is… I will be able to get rid of the 1 3/8 ounces of lead I had in the nose. I am bummed at this because my plane is already overweight in my opinion. If I can figure out how to lose about 1 1/2 ounces in the muffler then I’ll be at the same weight as it has been with the current set-up.

Anyway, if you can get a weight on that muffler I would be very appreciative.

rc_wings

RICKSTUBBZ,

I purchased the Bisson Pitts PN 2140. It weighs 87g (3.1 oz approx) with the included mounting bolts on my old [] scale. Have been looking for a new digital, but have not found one I like and is decently priced yet. I suspect it is pretty close though.

Here is the link to Bisson...but no details there in terms of weight.

http://www.bissonmufflers.com/en/muf...ting_id=114065

Hope that helps.

RICKSTUBBZ

Thanks,

By the way for the digital scales, check out the discount department stores ( I cant stand ?all-?art) in the cooking section for food scales. They have some chinese made stuff that works OK that does not cost very much.

rc_wings

I have not put too much effort into it yet....but the few places I did visit, they did not seem to suit my needs for one reason or another. Will have to go on a mission one day as really need a decent scale, especially for my smaller electric stuff.

EscapeFlyer

My Feedback: (1)

RICKSTUBBZ,

Don't be worried about the weight. I've had a mini that wieghed 7lbs (most finish around5.5-6lbs) and flew as well as the 5.5lb mini. It landed slower than my trainer does. This is not an exaggeration. I think it was so fat because I added stringers on the fuse, and used a heavy way to attach the N struts on the wing (I used brass inserts.).

Brian

rc_wings

RICKSTUBBZ,

I was at the LHS today - picked up another kit - GP RV-4 . Love the RV-4 and wanted the kit for some time...unfortunately the queue is getting longer for builds. Have SMP, two versions of the Citabria Pro (small electric 30", and the Balsa USA), GeeBee, Mustang, FW190, and now the RV-4, along with a couple fixer uppers....Hmmmm and what is next..might have to quit my job in order to have time to build.....wishful thinking, but, no!

Anyways, while at the LHS, they have a Bisson Pitts for a ST-61, which I was able to compare side by side with the same one I bought for the my ST-51, and it is almost the same size in terms of volume. The "can" part is identical in diameter and length that I could tell, the only difference is due to the larger cylinder on the 61, the "manifold" part is slightly larger to fit the bolt pattern of the 61. I did not check the pipes, but assume they would be slightly larger...but can't recall now. [] So, either the Bisson muffler for the 51 is large for that size....or the 61 is extremely small???? I suspect on these engines, it really will not make tooooo much difference in performance. Since our application will not require us to squeeze out every available RPM possible, we should be fine for the most part. Now if we were talking Quickie 500, that would be a different story, and would likely be running different engines with pipes to get that wonderful adrenalin rush for a minute or two. Just thought I would pass on as found it interesting that they would be very close in size. I am using a Bisson Pitts (same style as on the ST-51 only larger obviously) on a Webra 1.20, and am very happy with the performance so far. Still breaking in the engine and playing with prop combination to get it right for my requirements....but so far so good, and expect good results from the ST-51/Bisson Pitts combo....but will find out soon enough I guess.

Cheers.

rc_wings

Very nice!!!!! I just luv the original colour scheme, and will likely cover mine similarly.

RICKSTUBBZ

Ilikebipes

Your "Smith" looks good in that picture all dressed out in the red and white.

RICKSTUBBZ

rc_wings

Thanks for the side by side comparison on the Bisson mufflers. That is helpful in my consideration whether or not to buy one. With my plane being a patched (and botched) sport flying version and not scale I am considering another concoction I have for a muffler. You never know what I might do.

As to the building queue,,, I hear you…I have a list of 10 or so that are piled up waiting on me. I have recently talked myself out of buying several that I want.

RICKSTUBBZ

For the sake of conversation, here is a picture of what caused the aileron failure on my "Smith". I am wrestling with it now trying to get enough mechanical expo out of this set-up.

rc_wings

This is the first time I have seen such a failure. Usually those horns are indestructible. Did it get bumped hard in some way that may have stressed it?

EscapeFlyer

My Feedback: (1)

I'm wondering if it isn't some sort of defect.

I hope you don't mind me saying this, but I'm not a big fan of ball links for flight control surfaces. Is it possible the ball link popped off and wedged itself under the bell crank somehow? That would probably be a bit far fetched. I don't know if your servo is strong enough to do that kind of damage.

I'm going to go with a factory defect, with consideration to the amount of info given so far.

I'm sorry to see that.

RICKSTUBBZ-

Thank you! This is the scheme my dad and I used when we built my first biplane (Yes, It was a Sig SMP)! I'm rather fond of the scheme, sentimentally speaking, too.

andrew66

I was always told that ball links were no good. it is just too easy to pop them off. since you have already cut into the wing, why not do dual aileron servos. Eliminates one extra potential problem.

RICKSTUBBZ

I did say for the sake of conversation,

I am not sure where to start[sm=confused_smile.gif]. Let me say first, remember this airplane was originally built in 1985. It was recovered sometime later I think around 1990. Admittedly it has not flown all of those years. Until the aileron failure it had been flying 3 weekends out of four for a year getting an average of 3 or 4 flights each outing. Ultimately I expect to retire this plane permanently soon. I more or less retired it after the aileron failure. But I have decided to bring it back for at least a little longer.

That said, all the hardware is original (24 years old) and the set-up and radio is from that era. I also know that in reality all the hardware should be replaced at this age and I have no one to blame but myself if the hardware fails.

I mention all this, or should I say I admit to all this to support the case for how durable this stuff really is. Or at least the stuff made in the 80’s.

In this case the ball link did not fail. I would not consider putting ball links on anything bigger than this. Nor would I use them on something this size intended for 3D type controls. In fact if new, I would use the current swivel ball links instead. http://www3.towerhobbies.com/cgi-bin...&I=LXD907&P=SM I might even use them on this repair.

I have slept many times since the day of the aileron failure. But I do recall smacking that side of the wing on a touch and go prior to noticing the plane being sluggish on ailerons.

As to putting two aileron servos in this thing…. No reason not to. Mechanically it is surely easier. If I was building a new one maybe I would. But this one is set up with one servo and I have no problem with that. Nor do I wish to remove enough of the covering to make holes in the ribs for the servo wires to run.

rc_wings

andrew66 brings up a good point re aileron servos in each wing. I was going to go with the stock configuration due to the small size of the ailerons, and did not want to add any additional weight (well debatable I know!!). Will give it some more thought, as originally thought it would be fine as is.

Wonder if the new SMP kits have laser cut parts? I hate cutting out the parts from the 1/4" inch sheets... [:@] Having said that....the build has officially started..although no glue has hit any wood yet. Will be trying out some new stuff (for me anyways) over the usual CA I have used for many years. Some stuff from "Deluxe Products" named "Super Phatic". A gentleman was selling it at a local swap, and his demo was impressive. Thought this would be a good project to try it out on. Only thing I did not take into consideration is that it dries a little slower, which will slow the building process down.....just when I thought I could not get any slower!

Cheers

rc_wings

I have used Ball Links on many occasions (on my earlier builds) and have never had a failure. Come to think of it I have NEVER had a mechanical failure......any mishaps, were, well, how shall I say it, Pilot error. [:@] Last night I was doing a little mod on my CG Ultimate I built (1.20 Saito and this is the KIT, not the ARF!) and was looking at the ball links I installed about 16 years ago on the rudder servo for the pull/pull system and still holding like a champ. I put this plane through it's paces, so if anything can stress those ball connectors, it would be in this bird. Had a heck of a time trying to get them off, so not sure that they would ever come off in flight. I do use different connectors now....just cause I have more experience and now have a certain preference, not because I fear they will fail.

Like anything, I guess these components have a lifespan. Plastic may become brittle and break over time. I had a plane, one of the first RC birds I built and flown so much, that I was afraid something WAS going to give resulting in a crash. It was a very aerobatic plane, and I did a THOROUGH check on it before every flight. Unfortunately it was lost in a mid-air collision at a fun fly. At least it was a spectacular ending to a great plane as opposed to a linkage or control failure. [&o]