Here is a list of all the postings PatMc has made in our forums. Click on a thread name to jump to the thread.
|Thread: Keil Kraft Caprice CoG|
It's actually the other way round. The rearward cg was meant to take advantage of a "lifting" tailplane. In fact it's a concept that doesn't really add up, at least for rc flight.
Edited By PatMc on 13/07/2019 23:20:34
|Thread: Electric conversion Bowman's Sunduster|
A couple of years ago I built an Amigo 2 (about the same span as the Sunduster) modified to take this 1050kv motor. Lipo used for first flights was a 3s 1400, lately I've been using a 3s 700 for flat field & the 1400 when slope soaring in light wind conditions.
There's also an 860kv version of the same motor which should enable a faster climb rate, if desired, using a bigger prop at the same current & power.
Edited By PatMc on 11/07/2019 21:54:49
|Thread: What to use on a Cub|
You're right, Martin.
Martin, you can scale the weight & power pretty accurately around this size model of a light full size aircraft. Also the power to weight ratio should be the same for all scales regardless of prototype's weight.
According to the specs for the original Great Planes Electri-Cub the RTF weight should be 3.3 - 3.5 lb. Note that's with a brushed motor & 7 - 8 cell 1700 - 2000mAH nicads. The nicad battery would be more than double the weight of a typical 3s 2000 lipo. It would seem reasonable to expect a brushless + lipo or an OS15 powered version to weigh around 3 - 3.3 lb.
Dunno which OS 15 Denis is referring to that can produce 500W.
The model to be aprox 1/7 scale Piper Cub. The full size nearly max loaded take off weight is around 1200lb & max power is 65 bhp (48.5kW) At 1/7 scale this equates to 3.5lb & 0.19 bhp (140W)
IMO the model should cruise around nicely in a livelier than scale fashion with the OS15 at 1/2 throttle, whichever version it is.
|Thread: The demise of. ASP/SC|
Because electric motors are always capable of doing they were designed to do.
|Thread: Prop selection for glow to electric conversion|
If the 10x6 draws 27A on 7.4v then that limits the power to 200W. A smaller prop that draws the same current on 11,1V will increase the power by 50%. Even though the smaller prop is less efficient at converting this power into thrust it will not be 50% less efficient so you could reasonably expect a significantly better performance by using 3s rather than 2s.
I think it's this 1500 kv motor 7738 is the Graupner part number.
It seems to be rated at a max of 30A but it's not stated if this is continuous running. OTOH max output at nominal voltage (7.4v) is 148W, which suggests that the max continuous current is actually 20A .
|Thread: Dismantling and cleaning|
Good result glad it wasn't my doomsday scenario.
|Thread: Mercury Aeronca Sedan|
The rigging angles of the full size Sedan WRT the datum are : wings +1⁰ (note that's through LE to TE, not the section's flat bottom), the tailplane : -3⁰ , thrust line zero.
IMO the full size angles with a flat section tailplane would make a better RC model than the Mercury plan especially when it's being built to a substantially bigger scale.
This article from Flying Scale Models suggests that the working strut fixings are fine for FF but it's necessary to modify them if converting to RC.
John, I built my Robot for ic using a paxolin plate to mount the motor to the wood bearers. I tried several different glow & diesel engines including a PAW19, Yin Yan 2.5cc, Fox 15 & Enya 09 III. The Fox & Enya were best power/weight match with the Enya slightly less powerful but better throttling.
As you will see it has ailerons as well as elevator & rudder. Never broken a prop yet even when I damaged the nose area.
BTW mine originally had the downthrust as per plan but I found the nose lifted when power was reduced, when I repaired the nose I zeroed the thrustline & it's fine. Can you not just use throttle control as a substitute for elevator when under power ?
Edited By PatMc on 24/06/2019 18:01:38
|Thread: Dismantling and cleaning|
Have a look at this thread posted by Gordon Whitehead last year.
|Thread: Spinners for brushless.|
The prop saver linked fits straight onto the 3mm shaft it would be instead of the adaptor. I don't think you'd be able to use a spinner with the prop saver. Perhaps a folding prop would suit you better, spinners for them here. There may be more spinners on the Robot birds site [The owners of BRC].
|Thread: Ben Buckle Junior 60 build|
Andy, I wonder if by "wallowing" you're referring to a "dutch roll" - this is the model repeatably rolling about 20⁰ - 40⁰ one way then the other ?
I can understand needing more elevator authority with the BB version, mine is probably more powerful than the normal Flair ones because of the rearward cg but still not oversensitive by any means.
BTW if you normally fly aileron & rudder equipped models you will no doubt be using the "aileron" stick for rudder on the Junior but be used to normally steering with the other stick on rudder control during take off.
Edited By PatMc on 22/06/2019 23:29:25
|Thread: Transmitter / receiver issues, help needed pls|
Daire, the problem is probably because the ESC has a linear mode BEC.
Some ESC's have switching mode BEC's. SBEC's reduce the voltage in, as you might guess, a switching process that I'm not going to explain further other than to say it's much more efficient, produces less heat & is much less restricted in servo current against I/P voltage.
AFAIK most ESC's below about 40A rating only have linear BEC's. However I received an email the other day from Hobbyking advertising the launch of a new range of their Turnigy Plush brand ESC's that all claim to have SBEC's fitted. As yet I've not bought one from this new range so can't recommend them on experience but I have used Turnigy Plush ESC's from their previous range with no issues.
PS other than being a customer I have no connection with HK.
Edited By PatMc on 22/06/2019 22:10:04
|Thread: Ben Buckle Junior 60 build|
Cymaz, raising the wing LE would raise the motor thrustline by the same angle exacerbating any pitching up with power tendency.
Andy, to cut the 0 - 4mm wedge shape - cut a piece of balsa (1/4" ?) the desired length by about 8cm - 10cm. Split down the length near the centre angled at the 0 - 4mm. Now cut straight down the grain of each piece to give 2 of the desired wedges. Best done using a small table saw or bandsaw.
Sounds like your first flight antics could have been caused overcontrol due to too much control movement being available, especially the elevator throw.
For comparison I've measured the elevator chord & rudder bottom chord on my Jnr 60 also the control throws & permanent down trim setting of the elevators.
Elevator chord = 35mm, permanent downtrim = 5mm [8⁰] , full up from perm trim = 10mm [17⁰] , full down from perm trim = 7mm [11.5⁰]
Rudder chord = 98mm, throws EW = 43mm [26⁰] .
The rudder is more powerful than necessary because I like to do a few uncharacteristic Jnr 60 aerobatics when I get bored with the normal sedate pattern. Elevator is less powerful but still enough for loops & to hold inverted.
Edited By PatMc on 21/06/2019 23:29:55
Looks great, Andy
Once you've flown it a few times & are happy with the trim you could try removing the lead incrementally, adjusting the elevator trim as you do. My Junior has the cg 1.3 inches rearwards to that shown on the plan & has been flying without problems since 1986. The rearward cg improves the glide & widens the speed range.
Control the rate of climb with the throttle & the speed with elevator trim. Don't worry if you end up with some permanent down elevator when you've established a comfortable cruise setting, it will have no ill effect. With the tx trim at neutral mine has 1/4" permanent down elevator which gives a nice cruise setting at about 1/4 - 1/3 throttle.
The Junior is quite responsive to rudder & even though the BB version rudder is much smaller than the Flair the rudder control should be more than adequate.
|Thread: Confirmation - The World Really Has Gone Mad......|
The lady who collided with the cyclist is a 28 year old Yoga teacher called Gemma Brushett. The papers have got hold of 2 pin up type photos of her posing as she performs stretching exercises whilst dressed in a bikini.
|Thread: Futaba 6EX 35 MHZ not transmitting|
You are the only one who has descended to using sarcasm, Percy.
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