HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 29, 2012, 11:42 AM
Registered User
WestTexasKing's Avatar
Monahans TX
Joined Sep 2010
1,925 Posts
Higher expo means that stick travel in the center moves the controls less, and concentrates max deflection toward the limit of stick travel.
0% expo is the same as not having any expo at all.
Think of expo as an arch, in the center it's almost flat, while the sides begin to exponentially increase the farther out you go.
That means in normal flight you have more room to wiggle the sticks around without banging them to high deflections.
In aerobatic flight it's just a small departure from low deflection to high deflection (so if you're at 50% deflection on the stick, the next 50% till you hit the stop will give it far more travel).
Works out great if you don't need high deflections for anything other than aerobatics.
In other words, the higher the expo (numerically), the slower the reaction time and easier it will be to make fine movements on the stick...which equates to a smoother flight in most cases.
Some people don't like expo, some do, and there's valid arguments for both sides.
I've used 80% expo on some planes, and negative expo on others...it's all about getting the sticks to make the plane fly the way you think it should, or having "balanced controls" as FS pilots would call it.

The lower the number on travel means the control surfaces move less (ie 70% means you get only 70% of the full travel afforded by the servos)
WestTexasKing is offline Find More Posts by WestTexasKing
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 30, 2012, 06:43 PM
Registered User
meanangel's Avatar
Joined Mar 2012
94 Posts
Quote:
Originally Posted by WestTexasKing View Post
Higher expo means that stick travel in the center moves the controls less, and concentrates max deflection toward the limit of stick travel.
0% expo is the same as not having any expo at all.
Think of expo as an arch, in the center it's almost flat, while the sides begin to exponentially increase the farther out you go.
That means in normal flight you have more room to wiggle the sticks around without banging them to high deflections.
In aerobatic flight it's just a small departure from low deflection to high deflection (so if you're at 50% deflection on the stick, the next 50% till you hit the stop will give it far more travel).
Works out great if you don't need high deflections for anything other than aerobatics.
In other words, the higher the expo (numerically), the slower the reaction time and easier it will be to make fine movements on the stick...which equates to a smoother flight in most cases.
Some people don't like expo, some do, and there's valid arguments for both sides.
I've used 80% expo on some planes, and negative expo on others...it's all about getting the sticks to make the plane fly the way you think it should, or having "balanced controls" as FS pilots would call it.

The lower the number on travel means the control surfaces move less (ie 70% means you get only 70% of the full travel afforded by the servos)
I see Thanks for the info
meanangel is offline Find More Posts by meanangel
Reply With Quote
Old Oct 30, 2012, 08:37 PM
Registered User
Cubber1's Avatar
Norway, Hordaland, Årstad
Joined May 2009
1,185 Posts
Quote:
Originally Posted by WestTexasKing View Post
Higher expo means that stick travel in the center moves the controls less, and concentrates max deflection toward the limit of stick travel.
0% expo is the same as not having any expo at all.
Think of expo as an arch, in the center it's almost flat, while the sides begin to exponentially increase the farther out you go.
That means in normal flight you have more room to wiggle the sticks around without banging them to high deflections.
In aerobatic flight it's just a small departure from low deflection to high deflection (so if you're at 50% deflection on the stick, the next 50% till you hit the stop will give it far more travel).
Works out great if you don't need high deflections for anything other than aerobatics.
In other words, the higher the expo (numerically), the slower the reaction time and easier it will be to make fine movements on the stick...which equates to a smoother flight in most cases.
Some people don't like expo, some do, and there's valid arguments for both sides.
I've used 80% expo on some planes, and negative expo on others...it's all about getting the sticks to make the plane fly the way you think it should, or having "balanced controls" as FS pilots would call it.

The lower the number on travel means the control surfaces move less (ie 70% means you get only 70% of the full travel afforded by the servos)
------------------
You explain it all very well, but in addition it could be mentioned that not all radios are the same, is it not futaba and spectrum that have opposite ideas of what positive and negative expo is ?
Cubber1 is offline Find More Posts by Cubber1
Reply With Quote
Old Oct 30, 2012, 09:19 PM
RC Logger Support
jlcamp7's Avatar
United States, WV, Hurricane
Joined Jan 2010
3,293 Posts
Correct. Some radios using negative on the expo is the same as using positive on others. All spektrum radios use the positive adjustment for less movement around center.

So I'm finally joining the club. Picked up a nib banana hobby (red paint scheme) here on the forums. Set to arrive on Thursday. Can't wait!

For any of you that have had the BH version have you had the same issue with brittle decals?

Also do you guys really feel the carbon spars in the wings are necessary?

I want to put it together right and do the correct mods along the way but don't want to do anything if its not really necessary.
jlcamp7 is online now Find More Posts by jlcamp7
Reply With Quote
Old Oct 30, 2012, 11:30 PM
Registered User
WestTexasKing's Avatar
Monahans TX
Joined Sep 2010
1,925 Posts
Quote:
Originally Posted by Cubber1 View Post
------------------
You explain it all very well, but in addition it could be mentioned that not all radios are the same, is it not futaba and spectrum that have opposite ideas of what positive and negative expo is ?
I have a 9X and spectrum, and never noticed anything like that.
I guess I was looking at the product of what the buttons were doing to the controls instead of what the numbers were doing on the display.
Or maybe it was just self-explanatory I dunno...
Easiest way to tell is to go to max expo one way or the other and see what the controls do.
If they move slowly at first and then rapidly toward the end...to me that's positive expo.
If they move rapidly at the beginning and then slowly toward the end, that's negative expo.

Negative expo is mostly used when one of the primary controls are sluggish compared to another, and the responsive control feels right to you (ie you don't want to use any more expo on the responsive control).
For example, if the ailerons don't have much effectiveness without lots of deflection, and the elevator is very responsive, I'll use a bit of negative expo (or neutral if I have lots of expo on the other) to liven them up proportional to the elevator...that makes both the elevator and ailerons seem to have about the same level of responsiveness.
I've used it on the rudder of a Blade MSR that was a bit sluggish (the tail motor took some time to spool up, so it wasn't on par with the other collectives).
I also used it on the sttiP before I realized I was moving the aileron clevises the wrong way, actually reducing travel
It helped, but realizing what I did and fixing it made a much bigger difference LOL

The end result is that your controls wind up feeling balanced, so that in a coordinated turn you're using about the same amount of stick deflections (aileron, elevator, rudder).
Of course, it's all a matter of personal preference...if you don't like the way your model flies there's no valid reason why you should stick to someone else's rules or recommendations.
Find what you like and make it work for you, it's a hobby designed to be fun, that's the way I see it anyway
WestTexasKing is offline Find More Posts by WestTexasKing
Reply With Quote
Old Oct 31, 2012, 01:03 AM
Registered User
WestTexasKing's Avatar
Monahans TX
Joined Sep 2010
1,925 Posts
Quote:
Originally Posted by jlcamp7 View Post
For any of you that have had the BH version have you had the same issue with brittle decals?

Also do you guys really feel the carbon spars in the wings are necessary
Yes and yes.

The BH decals are like a film that keeps flaking off.
Some spots hold ok, but others flake off just being touched by your hands.
Same with the HobbyLobby version as well.

The carbon spars aren't necessary, but it would be silly not to install them considering the benefits and ease of installation.
I flew my first one for lots of flights without spars.
The second one lasted about 10 flights.
Both had noticeable wing flex and caused less than desirable flight characteristics.
So if you don't feel like doing anything more than what's required, be gentle with it and fly it like your grandmother was in the cockpit.
Otherwise, take heed of all the in flight structural failures (some in level flight!) and numerous praises for the spars.
It only takes 30min to do, and it's EASY.
No special tools required and you don't even have to be precise.
Just cut a slit in the foam, tap the spar in, and pour CA over it.
It's easier than replacing a servo (see example below).

Some other tips if you don't feel like reading the entire thread:

Buy a different prop or use a 4S battery.
They'll accomplish about the same thing.
The sttiP has plenty of thrust, but flies way too slow.
It needs to have a bit more speed so the wings will provide adequate lift.
A 10x8 works great, a 10x6 works good on 4S too.
Be sure your power system is up to the task though.

The battery compartment will handle a 3S 2200mah battery with some modifications.
You'll have to open the front of the rear battery tray big enough to push the battery in at an angle into the front compartment.
The battery will sit at a 45deg angle inside the fuselage...it sounds weird but when you study it for a few minutes you'll see the way it's done.
It doesn't fly all that sluggish with the 2200 either, but you have to adjust your aerobatic style to accommodate the extra mass.
Rather than relying on lots of thrust to maintain altitude or speed, keep your airspeed up more and use energy conservation (building up speed to make large loops and using the mass to throw the plane around as an example).
With a smaller battery you can just pin the throttle and you'll get your airspeed or altitude back whenever you want it.

The tail surfaces can benefit from larger servo horns affording more travel, and at the very least you can locate the pushrod on the outermost hole (it appears there is no such thing as too much travel on the sttiP, except during your maiden flight LOL)
You can access the tail servos by removing the canopy and pulling out the printed seats, the servo compartment is located there.
Just remove the screw on the servo horn, move the pushrod to the outer hole, then reinstall the horn (be sure to index the horn to the servo).
The aileron linkages are old school torque tubes and not a precision setup.
To increase aileron travel, locate the clevises on the innermost hole of the torque tube actuator and the pushrods on the outermost holes of the servo arm, then check end travel to be sure there's no binding.
If there is, you have several options:
-Adjust clevises and/or pushrods to reduce travel
-Program in servo endpoints on your TX, either with the servo endpoint menu or dual rate menu.
-Trim wing and/or ailerons to allow more travel (see below)
You can also install dual aileron servos located in the wings for much better control and more travel with some wing trimming (the ailerons will only go down so far before they contact the wing itself, binding the servo, trim this portion of the wing or aileron and you'll get more travel out of them)

The cowling is a bit fragile, and they're almost impossible to source.
With some modification, a PZ Stinson cowling can be used to give it a radial engine look (really cool! see pic below).
Others have made molds for new cowlings but that was a while back and I have no idea what came of it.

Landing gear is flimsy, if you bounce it good enough to bend the landing gear just remember that bending it back will eventually work harden and break the steel wire, and it really doesn't take a whole lot of less than perfect landings to bend the gear.
It uses plain old steel wire as the gear, so if you can source a spare set of gear from maybe a PZ supercub or similar they should fit right in without much alterations (older foamies were pretty much exclusively sprung like this, so there's plenty of them still around).
Some have beefed up the existing gear by adding another wire over the gear or braced the gear legs from underneath the fairing, there's plenty of options on this matter.

The sttiP's CG envelope is a BIG one.
CG is perfectly safe between the two plastic top wing attachment screws.
Ideal CG is just in front of the rear screw.
Theoretical CG limits are ridiculous...I've successfully flown the CG past the trailing edge of the top rear wing (over an inch past recommended CG limit) and all the way to the leading edge of the wing without any undue hardships associated with improper CG.
Basically, if you keep it between the screws, you're golden!

The carbon spars, prop and/or 4S power will really compliment this model.
I'd recommend starting out with a 10x6 prop, get used to it, then jump up to the 10x8 or a 4S battery.
The other mods can be done down the road, as they're not nearly as important, but the sttiP will reward you with every bit of affection you give her



WestTexasKing is offline Find More Posts by WestTexasKing
Reply With Quote
Old Oct 31, 2012, 08:28 AM
RC Logger Support
jlcamp7's Avatar
United States, WV, Hurricane
Joined Jan 2010
3,293 Posts
Wow WTK!

Thanks for all of that. You just took me through almost the whole thread. I really appreciate the help and not only sharing all that info but also it gave me key words I can search when wanting to know more about it.

I will do the spars. It also sounds like I should go ahead and do the minwax process as well if I want to keep her looking good.

Mine is coming with two 1800 3s packs specifically made for this plane and some apc 10x8 props so performance wise should come out okay. Also have some 1000mah for other planes I'm going to use as well. Shorter flight times but hey since I got em might as well use them.

Also I have a 30a and 50a esc so I'm going to install one of those. Probably 30 since the 50 would just overkill.

Thanks again WTK
jlcamp7 is online now Find More Posts by jlcamp7
Reply With Quote
Old Oct 31, 2012, 11:32 AM
Yes it was Abby Normal
Joined May 2012
2,068 Posts
WTK,

The sttiP looks outstanding!!! Very nice job on that cowling, really changes the entire plane.

TwistedGrin
TwistedGrin is offline Find More Posts by TwistedGrin
Reply With Quote
Old Oct 31, 2012, 02:27 PM
Registered User
Joined Mar 2010
1,337 Posts
Expo helps reduce or eliminate control cross coupling.. When added to elev/aileron you can control one without the other moving because the stick is 'dead' around neutral. The larger the expo number the bigger the dead zone is...
rtbates is offline Find More Posts by rtbates
Reply With Quote
Old Nov 01, 2012, 10:54 PM
Registered User
WestTexasKing's Avatar
Monahans TX
Joined Sep 2010
1,925 Posts
jlcamp...no problem, always glad to help a fellow sttiP owner

Twisted...
That was an old pic, I've since changed it up some and added the PZ Stinson's motor so I didn't have to cut half the radial engine mock up out of the cowling.
The cowling itself is farther forward as well to improve handling (in relation to thrust...the farther the prop is away from CG the better it handles when you hang it on the prop) and to compensate for the bigger and farther forward motor, I installed the tail servos in external bays directly in front of the horizontal stab.
The servos now have more room for bigger arms, which equate to more throw on the control surfaces.
Dual aileron servo mods are next, followed by shaving the lower wing's "belly".

On the drawing board is a somewhat scale single seat open cockpit located at the rear of the current cockpit, using the existing turtledeck, along with longer gear legs with a bit narrower fairings and topped off with slightly larger tires.

The upper wing is going to be more of a challenge.
The Samson has a straight upper wing that matches the lower wing, without any sweep.
They're also stubbier, so I'm going to clip the wings somewhat and round the edges back out.
I have the wing from my first sttiP and I've test fit to see if it'll look ok...which it does.
The hard part is going to be lowering the wing closer to the fuselage with all new struts and hoping the modification doesn't adversely affect handling.
Hesitant to redo the struts because I'm worried about not getting everything rigged up straight and true.
I guess the plan with those are to simply cut them down shorter to hide the use of CF strips buried into the top and bottom wings, which will bear the stresses instead of the flimsy plastic.
The whole point is to modify the sttiP into a Samson without having to custom build portions of the basic structure.
I hope to be able to use existing parts (whether they're from the sttiP or from a different model, like the PZ Stinson) with just a few simple modifications making them look the part.
Here's a photo of the original Samson which I'm attempting to re-create:



A good shot of the straight wings:



The gear legs can be strengthened by using an additional wire running to the center of the fuselage from the bottom of the gear legs.
I'm planning on using thin gauge steel wire tied to a set of springs installed on the center of the fuselage to stiffen up the gear without making them completely rigid...all in keeping with the scale details of the Samson .

WestTexasKing is offline Find More Posts by WestTexasKing
Reply With Quote
Old Nov 01, 2012, 11:49 PM
RC Logger Support
jlcamp7's Avatar
United States, WV, Hurricane
Joined Jan 2010
3,293 Posts
Got the Pitts in today. Looks great and I'm looking forward to putting her together.

A few questions before I start putting her together.

#1 What size carbon rod should I use for the wing spars?

#2 I've never done the minwax process before. Seems simple enough. Grab a can and 5" foam brush and go to town with light coats. My question is should I go over everything or should I keep it off of plastic items like the bottom compartments and cowl? Just didn't know if there were certain things I should keep it away from including the exits for the pushrods.

Other than that I think I'm set. I'll probably pick up some larger Dubro wheels since I'll be using a runway with short grass.
jlcamp7 is online now Find More Posts by jlcamp7
Reply With Quote
Old Nov 02, 2012, 07:51 AM
Registered User
United States, NC, Charlotte
Joined Jan 2007
1,203 Posts
It is water based so it will not harm plastic but I see no need to coat plastic parts, but no harm if you get it on plastic.
I would upgrade landing gear before installing larger wheels on flimisy stock gear.
Tim
Quote:
Originally Posted by jlcamp7 View Post
Got the Pitts in today. Looks great and I'm looking forward to putting her together.

A few questions before I start putting her together.

#1 What size carbon rod should I use for the wing spars?

#2 I've never done the minwax process before. Seems simple enough. Grab a can and 5" foam brush and go to town with light coats. My question is should I go over everything or should I keep it off of plastic items like the bottom compartments and cowl? Just didn't know if there were certain things I should keep it away from including the exits for the pushrods.

Other than that I think I'm set. I'll probably pick up some larger Dubro wheels since I'll be using a runway with short grass.
w4yn is offline Find More Posts by w4yn
Reply With Quote
Old Nov 09, 2012, 12:25 AM
RC Logger Support
jlcamp7's Avatar
United States, WV, Hurricane
Joined Jan 2010
3,293 Posts
Finally got spend a little time on the Pitts today. Installed carbon strips and also put on 3 coats of minwax. Should have her back together and ready to go hopefully this weekend. I do have one more question. I have two 1800 mah packs that are made to perfectly fit in the first compartment on the bottom. I plan to put a Popsicle stick in the open hole to keep the lipo from falling through the opening. My concern though is that even though it slides perfectly in, just above the lip it's a pretty cavernous opening and the battery just kind of flops around in there. Is that how everyone else is flying or are people doing something to get rid of all the play of the battery in that compartment?
jlcamp7 is online now Find More Posts by jlcamp7
Reply With Quote
Old Nov 09, 2012, 05:25 AM
What goes up must come down..
Canada, QC, Saint-Laurent
Joined Jan 2002
1,724 Posts
I have used a pce of foam with velcro on both lipo and that foam that is glued inside the fuselage ..later I add a small wood dowels and rubber bands on one sttiP once I flew a larger lipo (2200) and the lipo did slide out under the G forces and lost control broke the plane in 1/2 just in front of the lower LE ( I was not having rubber bands mod. then) so yes make sure you have the lipo well secured prior to put G forces!
just my 2 cents here.

WTK when you put the 4s did you use the original esc that came with your stiiP ? mine is having only the writing 10A x 2 doesn't say how many lipo's :-(
rodair is offline Find More Posts by rodair
Reply With Quote
Old Nov 10, 2012, 07:19 PM
Registered User
Canada, ON, Toronto
Joined Jan 2012
127 Posts
Has anyone tried Parkzone Stinson landing gear or something else with wheel pants? The stock legs are bending every flight now but I hate the look of the SuperCub gear.
AirbusDriver is offline Find More Posts by AirbusDriver
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Herr Engineering Pitts Special crashnburn Sport Planes 9 Aug 16, 2003 01:41 PM
Robbe Pitts Special JeffD Aircraft - Electric - Airplanes (FS/W) 3 Nov 13, 2001 07:29 PM
Herr Pitts Special rubber-to-electric conversion mkirsch1 Sport Planes 11 Oct 25, 2001 11:59 PM
Robbe Pitts Special GMILL47 Scale Kit/Scratch Built 3 Oct 03, 2001 10:15 PM
Herr Engineering Pitts Special crashnburn Sport Planes 7 Jul 05, 2001 11:06 AM