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Cermark Sukhoi SU-31 "Version 2" ARF opinions

Old 04-05-2008, 10:35 PM
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root
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Default Cermark Sukhoi SU-31 "Version 2" ARF opinions

Has anyone heard anything about the flight qualities of the newer, cheaper 2nd version of the Cermark Sukhoi SU-31 ARF?

Version 2 specs
Wing Span: 68 in Wing Area: 816 sq in
Length: 60 in Fly Weight: 9.5 lb
Tank: 450cc with 3color silicon tubing Radio: 4 Ch, 5 Servos
Engine: 90 to 120(2C), 120 to 140(4C), Gas Engine 23~26cc


The video from Cermark is really impressive.

The guy is doing 3D stuff with a BCMA-SPE26 in the nose.

http://www.youtube.com/watch?v=8vErQ...?TID=14&PSN=21

If this link expires or quits as they all seem to do after a while then go to Cermark's web page and you'll find it advertised.

I'm interested because my G23 with a Bennet single pipe needs a home and its very affordable at $170.

root


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Old 04-06-2008, 07:32 AM
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soarrich
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

That is a pretty plane.
Old 04-06-2008, 07:34 AM
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RhyanO
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

I just saw a review on this plane in the May 2008 issue of Model Airplane News.
The review was favorable to the plane as are basically all reviews by this magazine.
They used a 26cc SPE gas engine in the review plane. For ~$170 it seems like
a fairly in-expensive airplane that one could use a gas engine on.

Let us know if you find anything else out.

Ryan
Old 04-06-2008, 08:42 AM
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root
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

Another forum has a thread about it but the pilot hasn't maidened it yet due to weather/wind conditions.

He says:
-The bottom of the entire airframe is grey. Almost impossible to see unless it`s a very clear sky.
-The spinner is no longer included.
-Gone are the aileron sockets and pin hinges. It now sports Cya type hinges with huge,draggy, park flyer type bevels.
-The covering is no longer cut at the factory for the servos or stabs.
-The hardware is subpar to say the least. The wing bolts were so poorly molded, they were square. At least three pieces were missing from my herware package all together.
-Unfortunately, the manual is still for the first version so I`m not even sure if the missing parts are supposed to be in v.2 or not.

Don't forget the price went down about $120. I can deal with upgrading some of those things listed for the savings.

I'll keep us posted as the owner of version 2 actually winds up living in the next county and we started e-mail correspondence.



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Old 04-06-2008, 06:41 PM
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aussiesteve
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

My son has the version 2 fitted with a Saito 1.80. He has about 30 flights on it so far and hasn't managed to tear it apart in the air (This is a good thing - his flying style would normally do that, it is way overpowered with the 1.80).

All of the comments by root are valid - especially regarding the grey underside and the poor quality hardware.

This airframe builds very light. The 1.80 is way too much for it but a teenager who likes to try 3d loves to have the extra power.

We have been considering putting a 26cc gas on it. I think it would be a much better fit than what we have but my only concern is the lightness of the frame The engine would need to be well run in and tuned for smoothness. I think it would also be an excellent candidate for e-power. (which is something that is not my personal preference but there are plenty out there who do like that option)

Having said that, it is an excellent flyer and as root has mentioned, the cost of the ARF certainly allows room to fit better quality hardware (Which I do on just about every ARF I build anyway).
Old 04-06-2008, 08:39 PM
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root
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

Thanks for the positive "hands on" information.

I notice the 1.80's are around 3 to 4HP and range from 38 to 48 ounces in weight
If you can remember, tell us what brand of 1.80 your son has and do you remember what was done to get the CG correct?
Did you have to add nose weight or move the battery up front?

I'm just wondering what I'll be doing with my G23 being on the hefty side of 50+ ounces. I don't want to spend the 100 bucks getting a conversion done to save/shave 13 ounces if I don't have too.

My G23 is only rated at 2HP but can swing a 15x8 APC around 9200 rpm. It's transition from low to mid to high is pretty smooth so I'm optimistic that it should do just fine for sport flying but I haven't heard of any G23 doing 3D stuff.

The SU-31 demo video on the Cermak webpage uses a BCMA SPE 26 and it's doing major 3d stuff. My club's members who owned factory stock SPE 26's have all had carb problems and weren't able to come close to the performance of the average G23.

Should I be that much more optimistic to expect the same 3D sort of capabilities in the right hands?

Any comments would be appreciated.
root
Old 04-06-2008, 09:17 PM
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Default RE: Cermark "Version 2" Sukhoi SU-31 ARF opinions

He's using a Saito 1.80 on it. (about 35 oz by memory)
I didn't do the build on it but I think he has it mounted on the standard mount that came with the kit.
We are running an APC 16/6 prop on it.

He installed the battery (5 cell) etc towards the nose. I don't think he added any additional weight to get it to balance but I would have to check on that one to be sure (He's a few thousand miles from where I am at the moment). I'll get him to Chime in on this thread.

I think your G23 would be just fine. His is way overpowered and it has unlimited vertical at less than half throttle (it teaches him throttle constraint)

He has used the recommended throws for low rates and has maximum throws on high rates with 65% Expo dialled in.

He is using Hitec 645MG's all round on it for servos (we use them as our standard sport servos)
Old 04-07-2008, 04:38 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Friends,

I ordered my Su-31 today from Cermark.

Regina the sales rep told me that the $149.99 version that was advertised in March magazines is no longer available.

In the newer "Version 2" (or should they now say Version 3) for $169.99:
-the fuselage has been modified to be lighter and stronger
-the aileron and tail''s control surfaces have also been modified for better aerobatics.
-there''s a different manual.

It''s an added $24.95 for shipping to NJ from California with an expected 3 to 4 business day arrival.

The tech support calls for a HS-645 for the elevator, 625''s for the aileron and rudder and a 425 for the throttle.

root
Old 04-08-2008, 08:05 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

I called Cermark today find out why the 645MG servo was recommended on the elevator as opposed to the usual rudder position.

This time I was speaking to Steve and he said because there's only a single servo used for the elevator, one with higher torque should be used.

According to Steve:

The manual is not a new one. The way that the belly pan is mounted is incorrect and the tail servos are in a different spot than the manual shows them. These corrections didn't warrant the hassles of creating a brand new manual.

He also suggests using better hardware than what is supplied.

The control surfaces are bigger on version 3 for more 3D maneuvers. This change was made to meet the higher demand for 3D type arfs.
Old 04-09-2008, 09:13 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

I have an older version of the Sukhoi powered with a Saito 180. Flys great.......after I added 1lb. of weight and moved the battery to the nose. Used digital hard hi torque.
Old 04-09-2008, 09:52 AM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

The blue one??

So what do you think the All Up Weight is now with the 1LB added.

Can you tell us anything else about the plane?

Old 04-09-2008, 10:15 PM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Root....... my Suk has been parked in the back shower for some time as the engine is now in my Goldberg 67" Yak. But to answer your questions, it flew well and I am the owner of two such Sukhois. The spare still remains in the box, unopened to this day. One day I'll knock off the dust and fly it again. My Suk is probably 3 years old.

I ordered blue and received "red". My flying buddies call it pink. The included hardware was junk of which I upgraded. It's been a while and I believe that I modified the elevator to have the " carbon fiber duel elevator pushrod control" system as offered by Central Hobbies and used a hitec 180 in/lb servo as on both rudder and elevator. My aileron servos were analogue 100 in/lb torque. Flying wires on the horizontal and verticle stabs.

Love how the ailerons were recessed in the wing. Did not like the "slab" elevator and would have prefered a true airfoil. Slight pitch and roll coupling that I did not bother to mix out. But 1.0 lb. in the nose to balance as recommeded by the manufacture??????????? I cannot explain

To me, Suk's & Yak's are attractive and great flying airplanes.
Old 04-10-2008, 01:56 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Thanks, ****sheee.

I'm getting great reports from a new flying buddy from a nearby club that this plane is a real keeper.

"It slowed down really well.
Stalls are just a mushy dip of the nose. A little power and your out of it. No wing dip.
Even with the control surfaces at the minimum throws it was very responsive without being twitchy.
Inverted flight with the CG at the back of the range needed almost no down elevator."


This third version that I bought also has extra firewall bracing.

root aka Bob G

p.s. THANKS for the photos, Shawn.
I'm lovin' this plane more and more every time I see a picture of it.

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Old 04-10-2008, 02:36 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

What the hay - as long as you're looking - courtesy of me and a simple google search.

Sukhoi Su-31

The Sukhoi Su-31 is the latest single seater from Sukhoi. It has the highest performance of any piston engined aircraft made today. As well as being flown by members of the Russian aerobatic team it has been ordered by the 1994 World Aerobatic Champion, Xavier de Lapparent, as well as the then current Swiss, French, Italian, Spanish, Australian and South African champions.
Although the Su-31 is physically similar to the Su-26, it is actually really quite different. The main difference being that the entire fuselage, ie everything behind the cockpit, is composite rather than tubular steel. This reduces the weight by some 30kgs, which is very significant in an aircraft of this sort. Other differences are:
The aircraft has a similar fuel system to the Su-26 in that it has a fuselage 70 litre tank, which is the aerobatic tank. Long-range fuel tanks can be installed in the wings (total of 206 litres extra), which is very convenient, but with some weight penalty. Conversely, the extra fuel can be in long-range detachable ‘belly tanks’ of up to 200 litres.
There are 3 additional luggage areas built in the Su-31, which make it quite exceptional for an aircraft of this sort:
1. A bay behind the pilot
2. A separate compartment in front of the pilot, above the fuselage fuel tanks.
3. In a separate bay in front of the instrument panel, where a specially designed ‘suitcase’ can be quickly installed and then carried away from the aircraft.
In terms of flying qualities, the –31 is designed to be somewhat more unstable than the Su-26 – although this is only really a matter of degree – which makes it more suitable for free-style flying, and certainly a great deal easier to snap-roll than the Su-26.
The canopy is side-opening, which means that it can be opened with the engine idling, which can be a great benefit in very hot weather while an aircraft is waiting for take-off.
Like all other Sukhois, the Su-31 can use either the 360hp M14P or the 400hp M14PF, as well as the more powerful 430hp M9F and 450hp M14R engines, although as a practicality most aircraft have the more powerful engines fitted.
The Su-31 has continued the extraordinary competition track record of the Su-26, winning successive World and European championships in both men’s and women’s categories as well as successive Breitling Championships.
Production of the Su-31 continues (but extremely slowly) at the Lukavitzy factory, and some thirty-five aircraft have been manufactured.
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Old 04-11-2008, 12:13 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Forget to mention that I probably installed a pull pull rudder system
Old 04-14-2008, 11:20 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Just got done putting the SU through it`s paces. Twelve flights now and liking it more every day. The 26cc gas engine is a good match for this airframe.
The speed range is incredible! You can tell they did their homework when they made the new version geared more towards 3d/freestyle.
Will hold knife edge with barely 1/4 throttle and the slow rolls are rock steady. Snaps seem a bit sloppy but this is probably more to do with an out of practice pilot on a new plane.

Root, you`ll most likely want the CG at the rear limit in the manual to start. Even that seemed a bit nose heavy for me. Mine is 1/4 inch back from that.
This is a very stable plane
Definetly happy with it!!
Old 04-14-2008, 01:28 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Great to hear about your success.

What specific servos did you use and what was their specs?

root
Old 04-14-2008, 09:55 PM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

I just bought this plane and it arrived on Saturday. I just started building it today. This plane is a breeze to put together. I''m nearly finished after just a few hours.
I''m upgrading all the hardware too and am installing the BCMA 26 in it as well. I have installed the engine upside down. So, I feel cutting the cowling is going to be the biggest challenge. Do you or anyone else have any good photo''s of how the cowling was cut with the BCMA? I''d like to make it as clean as possible.

Also, during your 12 flights did you try to do the hover thing? Does it get unlimited vertical? I have high hopes after seening that video on the Cermark website. What prop are you using? I plan to put a Xoar 17x8 on it first.

Thank you.
Old 04-15-2008, 06:44 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

There`s plenty of power for hovering. I started with a power point 16x8 but it did`nt load the engine up enough and switched to a Zinger 17x8. Vertical is unlimited with both props.

If I get a chance, I`ll snap a couple photos of the cowl. I had to make the holes for the exhaust and spark plug pretty long to be able to slide the cowl all the way back.
Old 04-15-2008, 08:05 AM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Great to hear about your success.

What specific servos did you use and what was their specs?

root
Old 04-15-2008, 08:36 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

I used Hobbico CS-70mg servos for the tail surfaces and CS-64`s for the ailerons. The throttle is one of the 821s that come with the Spektrum radios.
The CS-70s are metal geared with 106oz of torque.
The CS-64s have 69oz.
Old 04-15-2008, 11:03 AM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Just got mine in the mail.....yowser what a long cowl!

The manual states nothing weaker than a 75 ounce-inch servo for any of the control surfaces. I''m glad I didn''t over do it. By the way - obrienhobbies.com have the 645 and 625''s for under $30 w/$8 shipping as of 4/14/08.

On 1st impression, the tail wheel looks a little wimpy...

in fact, I noticed at the end of the xeroxed manual, the "minuses" mention it being weak around the wheel section of the rudder...

has anybody changed it to an aftermarket brand?
-looks like a Sullivan tail wheel bracket & spring system will work.

root

ps Are there ANY other installation issues I should be aware of or do I have to rough it like the guys before me?
Old 04-16-2008, 08:07 PM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Here you go 19.99, high speed, high torque. http://www.hobbypeople.net/gallery/440701.asp
Old 04-16-2008, 08:25 PM
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions


ORIGINAL: root



The manual states nothing weaker than a 70 ounce-inch servo for any of the control surfaces. I'm glad I didn't over do it. By the way - obrienhobbies.com have the 645 and 625's for under $30 w/$8 shipping as of 4/14/08.


root

ps Are there ANY other installation issues I should be aware of or do I have to rough it like the guys before me?
The Club House forum has an extensive thread on the "O'Brien Hobbies experience". A word to the wise.
Old 04-16-2008, 09:59 PM
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root
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Default RE: Cermark Sukhoi SU-31 "Version 2" ARF opinions

Wow, that Cirrus Servo sounds great and for the price of only ONE Jackson especially.

Never had any dealings with Cirrus yet. Maybe it's time.

I never dealt with O'Brien either except just to see their prices on the web, which seem the lowest.

I'll have to look up both the Cirrus and the O'Brien forum feedback to be sure.

I'll be puttiing together my SU-31 over the weekend and I'm sure to be back here.

I already experienced the same gap in the wing halves as did the girl that reviewed the old version on the other decent RC website/forum.

I'll be testing my pectoral muscles being the human clamp after the epoxy is spread between them. The wing halves that is.

root

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