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Old Jul 19, 2011, 07:24 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
2,388 Posts
Finally (for now...)--the servos in the wings. At this point I should described my radio setup. A friend of mine transitioned from DSM2 to DSMX and bought a new JR X11. As a result he sold me two JR921 receivers (9 channels) for a total of $100... One of them is doing great in my Hobby Lobby Eurofighter. The second is for the T-45... I have a JR X9503, so I'm going to use all 9 channels as follows:

1. THRO
2. AILE-R
3. ELEV-R
4. RUDD
5. GEAR (x3)
6. (AUX1) FLAP (both, Y)
7. (AUX2) AILE-L
8. (AUX3) ELEV-L
9. (AUX4) NOSE Steering

The idea of separating rudder from nose gear steering is credited to X30Pilot. Allows me to trim (and program overall movement range) for both separately.

There is no reversing-Y installed anywhere.
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Old Jul 20, 2011, 04:03 PM
Registered User
Joined Feb 2004
227 Posts
Hi Herb,

I am currently flying with a tailpipe dia of 76mm I set it this way thinking max thrust for grass takeoff, now I'm not so sure. I am led to belive that this large dia is not required, also I am using a lot more throttle just to keep up cruising speed than I thourght I would need. Do you know of any data re; optimum dia for a 90mm? Thinking mainly of a balance between thrust and speed?

regards
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Old Jul 20, 2011, 04:21 PM
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Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,176 Posts
Eddie, 76mm tailpipe sounds a bit big for the MidFan ... I just re-measured mine on the T-45 and it's at ca. 70mm inner diameter, not sure why yours is so big ? I would have thought 70-72mm to be a better number.

But, I think you can live with 75mm or so, the Hawk/T-45 is a fairly draggy jet ... reducing the outlet will increase the efflux a bit, but it will also rapidly increase the load, and thus amps and watts. Is it worth for the T-45, maybe not ?

On the twin 90mm Rafale which is quite a bit faster than the Hawk (low drag airframe) I use 68mm for the Midis, the DS-51 fan can do well with less restrictions as it's a 4-blader with more pitch. On the other hand the Midi handles compressional loads very well, i.e. if you choke down the outlet quite a bit it won't stall.

The JePe 90mm F-16 can do with even more restriction, but that one is a very fast edf. The Hawk is quite a different animal.

If I were you I would try the next flight with the CG moved back to 105mm or so.

The fact that your are using more throttle than you would have expected is just a reflection of the fact that the CMP T-45 is a bit bricky with a small but thick wing and a large draggy fuse ... Mine has the same flying characteristics .

.
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Last edited by Herb; Jul 21, 2011 at 01:28 PM.
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Old Jul 20, 2011, 04:31 PM
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Joined Feb 2004
227 Posts
Hi Herb,
Just doing that very thing now, 105mm it is and from the test flight reduce the airelons as they will become more twitchy with the reward cog. Possibly set the 50% rates that it flew with last time to the new top rate and set a lower one of about 35%. The elevator may become more lively to so rate that down just a little as well. nose leg all repaired so just waiting for the weekend.
I will send you via pm the reply from Jepe to the pipe dia issue, dont forget english isnt his first language
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Old Jul 20, 2011, 04:38 PM
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Joined Feb 2004
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OK give in couldnt figure the PM thing so will just post it.
--------
nice plane !! I am surprized by the scale sound. This scale sound is often the result of a bad airflow in ducting or open (nose)wheel bays. You are throwing away energy for cool scale sound..most people throw it away without this extra sound!
About your nozzle: static thrust is only good for fools, even on the large
15 kg C-5 we use nozzles of some 75mm maximum. Once at speed: with nozzle you can still keep your model going well on only 1/3 throttle, with an open nozzle you always need 1/2 throttle ore more to keep it going..and you fly much shorter. Could be that sound will change too by using an nozzle, my
F-16 tubes imploded behind the fan when they lost their nozzle inair( a nozzle keeps longer pressure in the ducting). Will make on my testbench a test with flexible ducting only and see if I get it back again (have same sound in my F-86, also big pipe without nozzle)
-------------
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Old Jul 20, 2011, 04:43 PM
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Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,176 Posts
Yes JePe nailed it with that scale sound nonsense

Most of the time scale (ie turbine) sound means : bad inlets, bad ducting and poor fan efficiency, or all of the above

Case in point, the new 90mm high blade count fan is perhaps a glaring example, a whopping 9% fan efficiency lost to rather useless sound effects .

Some don't seem to realize that turbine-like noise is just due to very bad turbulence. The sign of good fan efficiency is in fact no sound !!

I had an F-86 with bad ducting that made a fantastic turbine-like noise . Until I fixed the shape of the intake, then it went quiet.
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Old Jul 22, 2011, 06:41 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
2,388 Posts
Can anyone comment on the control throws for this plane? I don't think there is any way I can reach the throws they described (except the flaps, I believe). What did you use for low/high rates? What did you program for expo?

Thanks,

Yoram.
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Old Jul 23, 2011, 01:27 PM
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Joined Feb 2004
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Hi there,

The thorws for my maiden was set up as per the book with the exception of the flaps, I could only get max 30degrees. Airelons proved way to sensitive even on half rate, elevator was just about right on half rate expo was about 20--30% cog as it worked out was at about 93mm forgot to check with the gear lowered!
Have just tried returned from the attempted second flight where I couldnt get the plane to rog didnt try half flap as the nose leg strut broke again my faulty maufacture.
I think even with my now revised cog of about 106mm and half flap about 18dgs a 8.2lb plane even with 2500w will find it hard to rog of shortish grass with the wheels in the kit. I think after the nose leg repairs and new wheels we should be OK but today it didnt seem to even want to pick up speed and stayed stuck to the runway.
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Old Jul 23, 2011, 02:22 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
2,388 Posts
So it soumds like half rates were enough. i can't seem to get full throws with the servo arms installed, and i don't want to put longer arms if i don't have to, as it will leave less torque.
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Old Jul 24, 2011, 06:34 AM
edf flyer
Mannyman535's Avatar
United States, CA, Marina
Joined Feb 2009
1,175 Posts
Im getting another t45 today, wanted to know if there is any other tricks or tips for this bird, i like the canopy mod i seen, where you use only half, ( cut on the first white line)
im going to use some different type of gear, so does anyone have a proven gear that works good, any new tips would be great
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Old Jul 24, 2011, 06:44 AM
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United States, CA, Marina
Joined Feb 2009
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canopy

Brent, how did you do the canopy, and what are you using to attach it to the plane?
Quote:
Originally Posted by corsair nut View Post
heres some pics of mine, still need to finish the cockpit, and some small detailing. some shots showing some mods, like the stab servo location, vg's and stab fences.

also, my maiden report....and a shot of my jhh kfir(needs lots of detail work) 12 lbs..12s 6000...cutom 105mm turbax...about 150-155 mph on a little over 4kw

man, i had a awesome day with the T45!!!!!!! i LOVE this model. its exactly what i was looking for, a nice looking, semi scale model, docile, and fun to fly, and not a flying brick. its all the above! bmiller was there, he was kind enough to lend me his retacts so i could fly it. i think i flew 6 times. loved every one!

first let me tell the setup...
MIDI pro, neu 1415 1.5Y, CC85hv, turnigy 8s 5000.
weight, 8.5lbs
1/8" washout added to ailerons
full 40deg of flap
HK514 retracts, HK trailing link struts, modded JHH sabre main strut for nose strut
hs85's on flaps, 82's on elev, hs...somethin....slim servo for rudder, hs 85 for steering, HXT900's for ailerons
i added VG's to top of wing according to marks in the civering, though i reduced the angle somewhat
wheels/main gear doors stick out a touch
no nose gear doors at all yet (thats a big hole up there!)
CG at 100mm (still feels a tiny bit nose heavy to me)

TAKEOFF: only took about 200ft (if that) using 25deg of flap, model rotates REALLY nice, and climbs at a great angle, just hold a little back pressure, and the model rotates nice and smooth, just like a real one would.
FLYING: SMOOOOOTH...ailerons are nice and crisp, rolls are fairly axial, vertical and loops are pretty dang big...which is good! top speed i would get to be in the 120-125mph range, i might note that im using a really big tail pipe....about 2.9". too big, its taking 65-70% power to maintain a good cruise. but it accelerates from low speeds very well, i can climb at 45 deg angle after touch and go or go around with flaps hanging out. this is a draggy model....coming from a dead vertical power off dive, pulling out at the end of the runway, by mid runway...im feeling the need to add power again...drops speed VERY fast....one draggy mofo! i felt like i had to push on the stick just a bit on the flat, high speed passes, and hold just a little up at low speed. transition to flaps results in no trim change.
LANDING: no brainer! drop gear and full flap on down wind leg, at aprox 200ft, reduce power to 1/2 on dropping turn, line up with runway, 50 ft off end of runway, cut power, and let it slow as it drops to the runway, flare (almost full up just before touchdown) touches down nose high, no sign of tip stall during aproach, or flare. touch and goes are cool, cause if you get back on the power soon enough, the nose stays off the ground while the model rides the mains, then it lifts off and starts climbing out.

changes....going to add nose gear doors, should clean it up a little, and im going to drop down to a 2.75" pipe, has worked great before on other models, and i think it will allow me to cruise at lower power settings. should push top speed to 130 or so.

flight times were 4.5-5 min, the most i put back after any flight was 3300mah, most of the flights were at 2800-3000 mah. not bad. 5 min is great with plenty of pack for a couple go arounds if needed.

all in all, i love it....bruce has some pics he needs to post

bottom line....if your on the fence about buying one...hop on over....the grass IS greener on this side!

WTG CMP.

edit: forgot to mention i used beefier pushrods...
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Old Jul 24, 2011, 09:41 AM
"My grandma wants to fly jets"
heychas's Avatar
Richmond, VA
Joined Feb 2008
477 Posts
Yoram - I noticed from your pictures that you are using the furthest hole on your control horns on the ailerons and flaps. If you use lower holes, you will get longer throws. It works opposite of the servo arm. FYI - I believe Tam recommends to his customers to always use the lowest horn on control surfaces due to planes he has lost caused by high speed flutter using the outer control horn holes... of course w/ jets that will go much faster than this one
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Old Jul 24, 2011, 12:21 PM
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Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,176 Posts
Quote:
Originally Posted by Eddie-extra View Post
Hi there,

The throws for my maiden was set up as per the book with the exception of the flaps, I could only get max 30degrees. Airelons proved way to sensitive even on half rate, elevator was just about right on half rate expo was about 20--30% cog as it worked out was at about 93mm forgot to check with the gear lowered! [...]
My throws are about what is recommended in the manual, and are posted somewhere above in this thread I think .

They work fine, for me. I use around 20% expo on all.

I have +- 9mm on the ailerons, -15mm on the flaps (that's around 30 degrees I think, I no longer use flaps for landing, it lands fine without them), +-14mm for elevators, and +-30mm for rudder.

You need to adjust the linkages so that you get the above recommended throws with a resonable servo deflection

[with properly dimensioned servos flutter has little to do with it, the latter is generally a consequence of poor linkage and/or hinge play & rigidity].

[ EDIT: The CMP T-45 manual says: AIL 15-20mm, ELE 15-25, RUD 20-25, FLAP 10-25. ]


.
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Old Jul 24, 2011, 12:33 PM
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Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,176 Posts
Quote:
Originally Posted by Eddie-extra View Post
... Have just tried returned from the attempted second flight where I couldnt get the plane to rog didnt try half flap as the nose leg strut broke again my faulty maufacture. I think even with my now revised cog of about 106mm and half flap about 18dgs a 8.2lb plane even with 2500w will find it hard to rog of shortish grass with the wheels in the kit. I think after the nose leg repairs and new wheels we should be OK but today it didnt seem to even want to pick up speed and stayed stuck to the runway.
Eddie looks like you need to shed some weight

Larger wheels, correct CG, lower weight and elevator throw could all help with your kind of situation ...

Do you have a lighter pack you can use? The kit wheels are actually not that small from what I remember.

One of the issues with the LG is that the mains are too far back due to CMP's wrong estimate of the CG, so I can see the Hawk might have some difficulty rotating off grass.

I would also look at the elevator throw, maybe you need a bit more (use with care though, pulling on the elevator too hard can cause a stall ).
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