Twistaholics tips, mods, plans, etc. - RC Groups
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Apr 11, 2009, 12:03 AM
Do Da Dippidy
plowboy1966's Avatar

Twistaholics tips, mods, plans, etc.

Welcome T___Taholics and soon to be T___Taholics. This thread is just for essential info and is set up to be a quick reference tool as the regular T___T thread tends to ramble. We like it that way but this will make finding some of the valuable information easier.


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Apr 11, 2009, 12:13 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
Kickin it off...

Engine talk....

TT40 Engines
46 AX ...the standard. Run a 12.25x3.75 on this combo for max performance. 12x4 is ok too.
For a 4 stroke Hot Rod....Os 70 to a Saito 82 with a 14x4, 13x4
OS 61FX for 2 stroke max performance with a 13x4
Waldo's 61 ...."OS 61FX 13x4 and 13x10 for a hoot"
Plow's 61......."I like the OS 61FX/MAS 12 X 7 S2 Series (Scimitar) prop."

TT60 Engines
Ya know, this is a 60 but I dont know anybody runnin a 60
4s choice...OS 91 FS with a 14x4, 15x4
2s choice...OS 91 FX with a 14x4, 14x6
Crazies choice.... up to 125 4 strokes with a 16x4

All of these prop recommendations (of mine) are based on WIDE blades. Run a APC "W" blade or a MAS K-Series prop. Stay with a low pitch. This plane is not a speed demon and I have heard stories of them breaking in the air. High speed flutter is a major possibility also so keep your speed as such.

This is just some basic prop philosophy (IE:just MHO)

Props can be compared to the gears in a car for easier understanding.

Some props are built for speed and some props are built for power.

4 strokes and 3D (hi-alpha) flying have brought on the advent of basically "wider" available blades. These have a wider profile from the front (leading edge) to the rear (trailing edge)

Master Airscrew (MAS) are called "K-Series" props
APC uses the term "W" and will sometimes use the word "Wide"
Generics usually use the term "Wide"

The diameter of your prop is applicable to YOUR aiframe, landing gear, engine specs, etc. but the performance you want OUT OF the prop to make the airframe do what you want is a relationship to "pitch".

Think of it this way....

1st gear......a #4 pitch of the "WIDE" variety.
2nd gear.....a standard #4 to #6 pitch prop
3rd gear......a #6 to #8 pitch pitch prop
4th gear..... a #8 to #10 pitch prop
5th gear (overdrive) a #12 pitch prop

Things to keep in mind. 1st gear doesnt have much speed, but you get there quick! Remeber you ALSO SLOW DOWN JUST AS QUICK! The massive blade profile on these type props also have massive air CATCHING abilities when slowing. This same profile also harnesses the massive torque provided by our 4-strokes in order to hang your plane motionless in the air.

A torque monster motor (todays 4-strokes) really shines with these fat blade props and 3D flying. You want immediate power and power to do massive tricks (like hanging on the prop and flying on the prop in hi-alpha, to pull out of a spin, etc) so it becomes a match made in heaven. You dont particularly want the speed and you dont get it with this high torque low RPM set up.

2nd gear is a compromise....and most the time a happy one. Little speed and a little power. Longer roll out with a #6.

.....usually moving to high RPM 2 strokes at this point...

3rd gear is getting out of our catagory (of TwisTing) and more into sport. Moderate speed.

4th gear gets us to the Warbird catagory. 8's and 10's. Looong rollout. High speed. As is true with the 4Wide on braking, the opposite is obviously true here. With an 8, 10, 12 your prop braking will be virtually nil.

5th gear overdrive....speaks for itself

Waynes Prop Load Factor (PLF) chart is invaluble, as are the other tips in his post...FOUND HERE

Structural changes
Reinforce your rear fuse areas shown n the piccy's
Also reinforce your landing gear block with some tri stock or something.
Go with a sullivan tail wheel from the get go, or eventually the tailwheel will snag and tear your rudder off.
Battery mounted behind wing saddle (maybe not at first )
Below are some pics of a hatch that you create right behind the wing. This allows you easy access to the area you need to beef up. This also allows access to where your battery will (eventually) be. It becomes nessessary to mount the battery in this area in order to achieve a perfect balance for engines in the 5-60 2c range and for 4c engines in the 70-80 range.
Last edited by Dad_Roman; Apr 17, 2011 at 02:45 PM.
Apr 11, 2009, 01:16 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
Plans for a neato airplane.

Big thanks for these go to "NoMatta"
Last edited by Dad_Roman; Jul 13, 2009 at 09:54 AM.
Apr 20, 2009, 10:46 AM
Do Da Dippidy
plowboy1966's Avatar
Originally Posted by Crazy Eddie
Can someone list the most popular engine/prop combinations for the Twist 40?



I like the OS 61FX/MAS 12 X 7 S2 Series (Scimitar) prop. The OS 46AX/APC 12.25 X 3.75 flew very well for me too. Those are the only two engines I've used on this airframe so far but the four strokes look good also.
Apr 21, 2009, 12:30 AM
I meant to do that
littlewing78's Avatar
Right now I have a Magnum 70 4stroke on mine. Its fun and flies well but could use lots more power. I did have an os surpass 91 on it for a bit. Flew much better but was a little heavy. A Saito 72 or 82 would probably be great.
May 07, 2009, 12:43 AM
Cookies Good - Bacon Better
NoMatta's Avatar
Hey gents. I ran across this vid some time back, but could not remember where. Just ran across the below thread with the vid at the top. Looks very promising. I'll be trying it soon.
May 07, 2009, 02:12 AM
rccardude04's Avatar
I'm a few days behind but...

Twist 40 ARF

Saito 82/APC 15x4W/30% heli fuel

Graph-Tech UCD46 landing gear


TP1320 2s/Castle BEC @6v


I think my CG is ~5.25". It's pretty good. Lifts the nose just slightly if you try to let it stall.

Flies NICE. Still need to work on rudder-to-aileron mixing to get rid of the very bizarre couple, but other than that, the thing flies amazing. Rudder-to-grass tail touches are no problem all day long. Pulls straight up like a rocket. It's great.

Also, landing technique:

Let the airplane float in. It almost likes to come in high-alpha. 3-points are super easy. Don't try to *grease* it in like a pattern ship or warbird though. She'll just take off and keep flying again when you let go of the sticks.

Edit: I now have an OS 70FS Ultimate and 13x4W prop. I broke it in half and had to glue it together, but I really like the OS 70. I don't think it has the pull that the Saito did, but I think it sounds better and seems to have more consistent throttle response, especially out of a hover.

Last edited by rccardude04; Apr 29, 2010 at 10:09 AM.
Jun 02, 2009, 08:43 PM
Do Da Dippidy
plowboy1966's Avatar
If you are just setting up one of these, the neutral position for the ailerons will be the centerline of the wing. A straight edge is as good as anything for finding the centerline on the outer end of the wing. Some like to mix a little spoileron or flaperon in just for kicks but it is absolutely not necessary. The CG will be a bigger factor on how she lands. Most end up with the plane trimmed in such a way that she will settle down into a nice three point landing. Happy landings!!
Jun 11, 2009, 01:00 AM
Walk of Shame Season :)
Waldopepperaxe's Avatar
Crazy Eddie, the first Picture shows the screws, I screwed 2 servo screws into the back of the cover into a piece of balsa ply I doubled under the frame towards the rudder. there is a tongue on the front of the cover Picture 2 I just slide under the exsisting lightning hole. quick and simple. make sure you use a spacer the same size as the cover inbetween the tongue and cover.

Sorry it took so long to respond I forgot we had this page lol.

Os 70 4 stroke surpass II 14x4 13x4 12x8
OS 61FX 13x4 and 13x10 for a hoot

Servo placement to go with Tweplica plans
Last edited by Waldopepperaxe; Aug 30, 2009 at 10:25 PM.
Jun 11, 2009, 02:22 PM
Walk of Shame Season :)
Waldopepperaxe's Avatar
The best Mod for the T_ _ _ T 40 is this
Jun 12, 2009, 01:25 AM
Do Da Dippidy
plowboy1966's Avatar
Waldo, you crack me up.

Okay, we forgot to mention that the engine mount rails need to be shaved on the inside in order to fit a suitable (meaning really large and grossly overpowered) engine. The crankcase will be larger than the manufacturer intended so instead of plugging the holes and redrilling the firewall just bolt the mount to the firewall and start shaving the inside of the rails until the engine will sit down all the way. Then mark and drill the holes to mount the engine to the engine mount. Remember to mount large engines as far back as possible as CG will be an issue.

Please remember to restrain your airplane before starting the engine. Tie it down or use a tailhook or wing stops. Whatever you have to do to insure that the plane is secure before you start it up. If you don't, I hope you are really tough.
Jul 06, 2009, 07:52 PM
linkadrip's Avatar

Twist 40 61FX Tuned pipe

Well thought id add my mods here since i have had a few of these planes.

The first PNP Twist i had Was great Had an Evolution .46 NX on it only mods to it were the landing gear, prop and tail gear.

Landing gear.

Tail gear.

Used the stock JR servos bought longer control arms for it.

Control arms used 2 sets Since the longest control arm were only 2 in the middle. I'm sure there are better ones out there.

Propeller that seemd to work the best for me.

Was great plane taken out buy a Crow..

Then i moved onto the Arf version since i had most the stuff, but i didnt have to much luck with the evolution engine and wanted that raging Power so i Switched to a bigger engine. Same airframe components just a bigger enigne.


And for even more power i had to go with a tuned pipe.

Pipe.8.5cc (.45-.60)12"2.0 oz56.951150
HeaderO.S. .61 FX & SF, .75 AX
O.S. .60 FP & LA(bolt through)
Evolution .61 NT
Jett .67L & .76L (not the .60L or .65)
Magnum .61 Pro
MDS .68-.78 FS Pro
ThunderTiger GP & Pro .61
Webra .61-.75 P5-H 2860286128622863

Propeller. I use on the OS .61 have to remember it's what works best for me. Alot depends on were you fly your plane. I live in the mountains and the air is thin here so a prop with a low pitch is better. High pitch props Stall and dont pull as well. Need low gears in the mountains.

This plane has broke in half on one landing after it had 50 or so flights on it.
So i peiced it back together and Beefed up the Area behind the cockpit were they all break sooner or later.
And thats about it.
Using a hitec optic 6 radio with the Hitec RX for my Radio needs.
Been happy with mine and fly it every chance i get Seems to be the only plane i have that flys right.
Update 1/18/2010
Since i last posted here i have made changes put the stock muffler back on the OS. 61 FX too many complained about the noise. Low end thottle response with a tuned pipe is sluggish and not good for trying to Hover have to have quick low end throttle response.
And switched prop to a 13X4 Narrow tip apc prop. Seems they dont make a 13X4 wide prop.
Planning on adding 3 inch wheels and a 14X4 Wide prop.
Last edited by linkadrip; Jan 18, 2010 at 04:05 PM.
Jul 13, 2009, 09:57 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
Originally Posted by gws_003
Hey guys,,thanks DR for the plans,,gonna scale ...
OOoohhh...glad you said that. All I did was post the plans.

The big Thanks go to "NoMatta"

I have updated the earlier post to give credit where credit is due

Cant believe someone hadnt caught that

Edit:Posted 1-3-11

Ok, its a year later and the synth vs Castor debate rages on. Seems like a petroleum engineer would be the right guy to listen to, especially one that flew R/C.

Here is a great article I found on the subject. hope you enjoy!

Originally Posted by Originally Posted by From a Conoco Petroleum Engineer
Read "Castor vs Synthetic". It discusses some pros and cons, but keep in mind it is 2-stroke info, not 4-stroke.... is also an excellent read on castor oils, but again, it's two-stroke info:

By Bert Striegler.

Back in 1983 there was quite a controversy in magazines about the tests that were necessary to measure the "lubricity" of various oils that might be useful in engines. Castor oil was used as the benchmark, but it was obvious no one knew why this was so. They apparently got a lot of info on various industry tests of lubricants, but these were really designed for other purposes. This was my answer. I will remind you that I was a lubrication engineer and not a chemist, but I drew my chemical info from Bob Durr, the most experienced lubricant scientist in the labs at Conoco.

Bob worked with my group on many product development projects and I can tell you that he is one smart hombre! Small changes were made in the text, but surprisingly very little has really changed since this was originally written. Here goes with the answer:

"I thought I would answer your plea for more information on castor oil and its "film strength", which can be a very misleading term. I have never really seen a satisfactory way to measure the film strength of an oil like castor oil. We routinely use tests like the Falex test, the Timken test or the Shell 4-ball test, but these are primarily designed to measure the effect of chemical extreme pressure agents such as are used in gear oils. These "EP" agents have no function in an IC engine, particularly the two-stroke model engine types.

You really have to go back to the basics of lubrication to get a better handle on what happens in a engine. For any fluid to act as a lubricant, it must first be "polar" enough to wet the moving surfaces. Next, it must have a high resistance to surface boiling and vaporization at the temperatures encountered. Ideally the fluid should have "oiliness", which is difficult to measure but generally requires a rather large molecular structure. Even water can be a good lubricant under the right conditions.

Castor oil meets these rather simple requirements in an engine, with only one really severe drawback in that it is thermally unstable. This unusual instability is the thing that lets castor oil lubricate at temperatures well beyond those at which most synthetics will work.

Castor oil is roughly 87% triglyceride of ricinoleic acid, [ (CH3(CH2)5CH(OH)CH2CH=CH(CH2)7COO)3(OC)3H5 ], which is unique because there is a double bond in the 9th position and a hydroxyl in the 11th position. As the temperature goes up, it loses one molecule of water and becomes a "drying" oil. Another look at the molecule. Castor oil has excellent storage stability at room temperatures, but it polymerizes rapidly as the temperature goes up. As it polymerizes, it forms ever-heavier "oils" that are rich in esters. These esters do not even begin to decompose until the temperature hits about 650 degrees F (343 deg C). Castor oil forms huge molecular structures at these elevated temperatures - in other words, as the temperature goes up, the castor oil exposed to these temperatures responds by becoming an even better lubricant!

Unfortunately, the end byproduct of this process is what we refer to as "varnish." So, you can't have everything, but you can come close by running a mixture of castor oil with polyalkylene glycol like Union Carbide's UCON, or their MA 731. This mixture has some synergistic properties, or better properties than either product had alone. As an interesting sidelight, castor oil can be stabilized to a degree by the addition of Vitamin E (Tocopherol) in small quantities, but if you make it too stable it would no longer offer the unusual high temperature protection that it did before.

Castor oil is not normally soluble in ordinary petroleum oils, but if you polymerize it for several hours at 300 degrees F (149 deg C), the polymerized oil becomes soluble. Hydrogenation achieves somewhat the same effect.

Castor oil has other unique properties. It is highly polar and has a great affinity for metal surfaces.

It has a flash point of only 445 degrees F (229 deg C), but its fire point is about 840 degrees F (449 deg C)! This is very unusual behavior if you consider that polyalkylene glycols flash at about 350-400 degrees F (176-204 deg C)and have a fire point of only about 550 degrees F (288 deg C), or slightly higher.

Nearly all of the common synthetics that we use burn in the combustion chamber if you get off too lean.

Castor oil does not, because it is busily forming more and more complex polymers as the temperature goes up. Most synthetics boil on the cylinder walls at temperatures slightly above their flash point. The same activity can take place in the wrist pin area, depending on engine design.

Synthetics also have another interesting feature - they would like to return to the materials from which they were made, usually things like ethylene oxide, complex alcohols, or other less suitable lubricants. This happens very rapidly when a critical temperature is reached. We call this phenomena "unzippering" for obvious reasons.

So, you have a choice. Run the engine too lean and it gets too hot. The synthetic burns or simply vaporizes, but castor oil decomposes into a soft varnish and a series of ester groups that still have powerful lubricity.

Good reason for a mix of the two lubricants! ( " 927 " is a mix as described here!)

In spite of all this, the synthetics are still excellent lubricants if you know their limitations and work within those limits. Used properly, engine life will be good with either product. Cooked on a lean run, castor oil will win every time. A mix of the two can give the best of both worlds.

Like most things in this old life, lubricants are always a compromise of good and bad properties. Synthetics yield a clean engine, while castor oil yields a dirty engine, but at least now you know why! "

Bert Striegler

Bert was the Sr. Research Eng'r. (ret.) at Conoco Oil Co.

Classic Exerpt from Clarence Lee...Castor vs Synth

Originally Posted by From Clarence Lee, engine clinic column, page 72, in the July 2004 issue of RCM

Contrary to what some of the synthetic oil manufacturers would have you believe, a synthetic oil has yet to be produced that can equal castor oil for high temperature or lean run protection. Hence, many of the synthetic oils have a small amount of castor or other high temperature additives added. Most of your synthetic oils have a flash point in the 450F range which is the point where the oil vapors ignite and go up in smoke. Klotz synthetic has one of the highest flash points of 510F. Castor, on the other hand, has a flash point of 535F, and upon burning, leaves a varnish or glaze that further protects the moving parts. This is something the synthetics do not do and just adding more synthetic oil will not be a substitute for the benefits of castor, especially on those lean metal melting runs fellows oftentimes subject their engines to.

Great Article from RC Model Reviews Castor vs Synth
Last edited by Dad_Roman; Feb 14, 2016 at 01:04 PM.
Jul 29, 2009, 10:32 AM
Registered User
u2builder's Avatar
Could someone tell me what the typical weight of a Twist 40 is (with OS 46) and what the wing area is? Approximately.
Jul 29, 2009, 12:52 PM
Suspended Account
my scale is nota good one but with the floats it is about 7lbs

Funny the t---t 60 as i remenber it was not much heavier?


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