Posts: 290
Joined: 8/17/2004 From: tulsa,
OK, USA Status: offline
Well I just got back from flying mine and it too was a little strange. First flight of the day was perfect. Engine started up no stumble, ran perfect whole flight and I couldn't get it to stumble or sag. Next couple of flights same old deal -- cut out on a slow roll. Never did die, but made me nervous. I am going to try the tube idea and hope it works. Just seems strange to me that it would start this after this many gallons of fuel. Then again -- this is my first DA100 and my first round cowl airplane.
Posts: 2008
Joined: 10/21/2003 From: Oak Harbor,
WA, USA Status: offline
I just want to make sure that no one here thinks that the WH Su-26 is the reason to blame for my engine troubles. I never thought that.....only came on here to ask help because of all the others that are flying it successfully.
I really believe that the way I installed my throttle servo was 90% of the problem. Never stray from what has worked on every plane prior!
I look forward to getting the Su-26 back in the air and final trim done for the IMAC season.
Posts: 12012
Joined: 2/25/2002 From: Central, CA, USA Status: offline
I know this is a silly question to ask, but I haven't read all that has gone before. The engines have been tuned I presume? The low needle is not causing the problem, especially on the DA that has a lot of fuel through it? Don't bristle please, just asking
The stumble/sag issue is fairly frequent on Yaks and Sukhois and generally a diaphragm thing.
_____________________________
If you can''t fix it with a hammer, you have an electrical problem.
Posts: 290
Joined: 8/17/2004 From: tulsa,
OK, USA Status: offline
No offense taken here. Yes the engines have been tuned and re-tuned. I also suspected the diaphram especially since the problem just more or less came up recently.
To that end I pulled the diaphram and inspected it with nothing being found. That doesn't mean there isn't somethin wrong with the diaphram as I doubt I could have seen a very small problem. I plan on giving DA a call tomorrow and probably just replacing the diaphram. I really think that will fix the problem but the pressure relief mod that Tom showed above will probably help as well.
On the plus side I got some pretty good flying in this afternoon even with a cranky engine.
Posts: 12012
Joined: 2/25/2002 From: Central, CA, USA Status: offline
Typically there will be nothing at all wrong with the diaphragm, only the manner that it's sensing air pressue. If it is sensing higher or lower pressure air than what is seen at the venturi, the burbal issues begin. If the engine worked well in the same plane for a long time and suddenly started being cranky look at any changes that have been made inside the cowl as the potential cause.
< Message edited by Pat Roy -- 11/21/2007 1:17:55 AM >
_____________________________
If you can''t fix it with a hammer, you have an electrical problem.
Posts: 2008
Joined: 10/21/2003 From: Oak Harbor,
WA, USA Status: offline
In my case the plane had worked fine in other planes......a russian composite Su-26 and an AW Extra 260.
For the TOC motor I'm using I suspect some leak issues on the motor as it appears that the orginal motor is now working with the linkage change.....I'll test fly Thurs or Friday.
Posts: 679
Joined: 3/26/2003 From: St Helens,
OR, USA Status: offline
Hey guys , thought i'd jump in here real quick and show the CF gear graphtech made for my sukhoi. It's extremely strong looking and i don't think that it'll give me any problems , but it was a total pain in the A$$ geting it to line up. It took me two full night of fabbing things together to get them to fit! Anyways........they don't look like the way i wanted them too ( they are not bowed!) but who the hell cares.....i already lost an entire summer of flying because it took 4-1/2 months to get the damn gear here. I only have 4 more servo's to buy , a spinner , throttle cutoff and a couple misc little things , and she's ready to go. Just in time for it to sit all winter until probably march or April! I do have a couple more gasser's coming in the next few weeks to a couple months that i'm going to build as well , so the winter should be full of fun.
Posts: 2008
Joined: 10/21/2003 From: Oak Harbor,
WA, USA Status: offline
Hey......mines together and has been for months. If I could only get the engine working (which it appears I have finally).......I'd get to fly mine too.
Looks like I will have to delay until next weekend the engine test. I'm having to go out of town for a death in the family over Thanksgiving.
Posts: 679
Joined: 3/26/2003 From: St Helens,
OR, USA Status: offline
Sweatpea.....your running the 3W-106 correct? How did the airplane balance out.....pretty well? I am curious to see how your Suk fly's and how the motor runs inside that big round cowl. I think i may be switching over to the 3W-106CS version for my Sukhoi. Also.......with the 3W in there , what was the length of the motor from firewall to where the prop bolts up? I'm looking to get about 1-1/4" clearance between the prop and the cowl , like i did on my BME 115 , but i beleive my engine mount block for that motor was like 2-5/8". I know the BME is shorter , just wanted to know by about how much.
Posts: 2008
Joined: 10/21/2003 From: Oak Harbor,
WA, USA Status: offline
quote:
ORIGINAL: JEFFRO503
Sweetpea.....your running the 3W-106 correct? How did the airplane balance out.....pretty well? I am curious to see how your Suk fly's and how the motor runs inside that big round cowl. I think i may be switching over to the 3W-106CS version for my Sukhoi. Also.......with the 3W in there , what was the length of the motor from firewall to where the prop bolts up? I'm looking to get about 1-1/4" clearance between the prop and the cowl , like i did on my BME 115 , but i beleive my engine mount block for that motor was like 2-5/8". I know the BME is shorter , just wanted to know by about how much.
Yes I'm using a 3W106B2
I'm not sure how far out spaced it needs but I used 3 of the Aeroworks alum spacers on it. I also felt that mine needed about 1.5 degrees of right thrust and 1 degree of down thrust and used thin washers for that. A scale Su-26 actually has the prop quite far from the cowl. 1 reason is that the prop is small compared to the cowl so it gives the air time to get around the cowl.
CG was set to the leading edge of the wing tube for the maiden, but WOW was it nose heavy. I had to add 2oz to the tail.
I'm using pefa cans so that might be the issue. I put my rudder servos in the tail also and I was still nose heavy. I moved my batteries back behind the hatch (there is a picture on here from someone else that did the same). I also used an R/C blimp graphite tailwheel.
From what I saw on the minimal flights so far.......
-rolls are axial and not much throw needed....but you can really wrap it up with more throws -stalls were pretty easy -it climbed well but pulled to the left (hence the thrust change) -I'm using 28x10 Mejlik -Inverted flight was normal -knife edge is going to require some mixing (havne't got there yet) -downline required 9% on my 10x to the elevator as it pulled to the canopy (pretty standard here) -the landing gear is a little weak but with the brace supplied it keeps it from spreading. Keep about 1 click of throttle in until your ready to touch down then to idle and it will just float in. I've had 2 deadsticks so far and the plane floated to the runway quite easily and landing was harder than normal but no damage. -not sure of my overall weight as I typically don't weigh my planes....I'd say around 28lbs (I wasn't trying to keep it light)
The bottom of the wing is going to require some kind of change in scheme......a little bit hard to see on cloudy days for IMAC.
Flys the sportsman sequence just fine. I'm sure it would be good upto advanced as is now. Once I finalize the trimming I'll let our Unlimited pilots try it out.
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RE: ... - 
And sweetpea's probably right.......hopefully i'll enjoy it more!!