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This thread is privately moderated by Herb, who may elect to delete unwanted replies.
Nov 16, 2010, 02:43 PM
speedin n da weeds :)
sikky's Avatar
Hey Herb how deep are the retract wells?? What's the tallest retract that can fit in the wing??
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Nov 16, 2010, 04:24 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by chalmrast
Please PM me if I'm bothering you on your Build log...
Not at all, on the contrary, as long as vaguely related to the subject in question (CMP T-45), Hawks & T-45's in general, EDF's in general - or jets of any type for that matter

Yes those parkzone pilots are just the right size (1:9), and will look reasonably good when repainted.

.
Last edited by Herb; Nov 16, 2010 at 04:39 PM.
Nov 16, 2010, 04:28 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by sikky
Hey Herb how deep are the retract wells?? What's the tallest retract that can fit in the wing??
The question is, with ot without proper mounts ? With proper mounts it's about the depth of a Springair 602, or ca. 21-23 mm.

https://www.rcgroups.com/forums/show...9&postcount=43

Keep in mind that the wing top surface is just a layer of thin balsa. One little accident and you are out on the other side with your retract mounts ...
Nov 16, 2010, 04:34 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by chalmrast
... I don't see why this plane won't fly great on a nice 6S, 2000W setup. It will be in 6.5-7.0lb range. ...
Yes I kind of agree - but I prefer to have a bit more performance than a bit less.

If you look at the numbers for a 2000W 6S setup, that's 2000 W/(6 x 3.55 V) = 94A. So you are pulling a good amount of amps.

With the safety rule of keeping a 20% headroom on the esc, that computes into a 120A esc... Of course if you have one already & have the packs etc then go for it.

But on 8S you get something like 2200/ (8 x 3.55V) = 78 A so you can get away with a slightly bulkier esc - maybe.
Nov 16, 2010, 04:38 PM
Lithium Member
Herb's Avatar
I got my carbon tape & carbon tow from cst today in the mail, so will be doing some taping soon ..

.
Nov 16, 2010, 07:28 PM
Gilbert, AZ
chalmrast's Avatar
Looking forward to seeing how you will do the canopy. I'm scratching my head after looking at the instructions showing the canopy screwed to the fuselage
Nov 16, 2010, 11:18 PM
Lithium Member
Herb's Avatar
I will glue the canopy to the canopy tub with silicone. Then put a wood dowel or wood tongue in the front, and a simple latch in the back.

I usually end up doing maiden flights with the canopy taped on with masking tape

Parkzone pilot before & after tamiya acrylic work

.
Nov 16, 2010, 11:23 PM
speedin n da weeds :)
sikky's Avatar
Those look nice ,like the shine!!
Last edited by sikky; Nov 17, 2010 at 02:07 AM.
Nov 16, 2010, 11:24 PM
Lithium Member
Herb's Avatar
Looks like these guys went to the Rodger International School of Ducting

I added a bit of carbon tow to prevent flexing of the intakes. Might not be necessary but I prefer it this way ... it adds no weight.

.
Last edited by Herb; Nov 20, 2010 at 06:17 PM.
Nov 16, 2010, 11:58 PM
Renegade Fun Forever!!
rvincent's Avatar
Nice Herb. What do you use to glue the carbon tow on the ducts?
Nov 17, 2010, 12:15 PM
deltas are cool
AIR SALLY's Avatar
Herb ducts look good ...CST is just down the road from me, i do use there tow on some of my Ducts too ...Bob i use "flex zap on mine ...thick (pink lid) to tack it down ...then follwed by the thin (blue lid) to soak the tow ,wipe off the excess and set aside to cure on it's own ..no kicker.
Nov 17, 2010, 06:14 PM
Registered User
jonnyspeed's Avatar
Sorry to post on your build thread Herb, but every other thread about this plane is closed... Feel free to PM me if you want me to delete this.

I just ordered mine yesterday I'm thinking of power systems. I think there is a trend on this board for people to way overpower airframes. I also think that there are a lot of times when a lightweight setup would work just as well as a heavy high power setup. Having said that... This plane looks like it was designed with the Changesun 90mm fan in mind. That fan is rated at 2600g thrust on 1600W and 70A from a 6s pack. That should work out to over 220W/lb and roughly a .88:1 Thrust:weight ratio. I don't have a ton of EDF experience, but those numbers sound respectable for a scale/sport plane. I fly from grass and I find that the lighter the plane the easier it gets up. I would like to try a 6s or 8s setup, but I'd like to see what others are doing first. Have you decided on your power system yet Herb?
Nov 17, 2010, 06:33 PM
Gilbert, AZ
chalmrast's Avatar
I'm leaning toward 6S too.... but we'll see.

I have the Changesun Fan with a 1900kV motor on marginal 6S packs in my HobbyTopGun L-39. It does about 1700W at 72A. The Efflux with a 76mm diameter exhaust is about 140mph.

I dopplered the top speed at about 87MPH. This jives with other Efflux vs. top-speed ratios my flying buddies and I have seen. The plane will fly about 60-70% of Efflux depending on airframe size, style, and construction.

A large foamy with big cheaters like a FlyFly or HobbyTopGun will be more towards 60%. A smaller, smooth, composite airframe may push more towards 70%.

Below is my HobbyTopGun L-39 with the aforementioned setup. As you can see, it flies scale. It weighs 6.5lbs.

Also attached is my buddy's ProEDF Mig 15 on 6S 90mm. It is very similar in size to this T-45. He was radared at 120MPH! His exhaust is choked down a little more than mine so he has a higher Efflux. And of course the smaller, smoother airframe contributes to the higher speed!

HobbyTopGun L-39 2nd Flight (2 min 59 sec)


Matts Mig 2-15-10.mpg (4 min 8 sec)
Nov 17, 2010, 08:14 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by rvincent
... What do you use to glue the carbon tow on the ducts?
Quote:
Originally Posted by AIR SALLY
... I do use their tow on some of my ducts too ... Bob i use "flex zap on mine ... thick (pink lid) to tack it down ...then followed by the thin (blue lid) to soak the tow, wipe off the excess and set aside to cure on it's own .. no kicker.
Yes CA probably works just as well - i can't stand the fumes.

I used Z-Poxy laminating epoxy ... I pull the carbon tow tight around the ducts with masking tape, then applied & spread with a finger a light bit of epoxy diluted with alcohol. I am allergic to regular ca and it sticks bad to my fingers.
Nov 17, 2010, 08:31 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by jonnyspeed
... I think there is a trend on this board for people to way overpower airframes. I also think that there are a lot of times when a lightweight setup would work just as well as a heavy high power setup. ...
I agree completely I am a big fan of lightweight setups, they tend to be so much more enjoable - to me. I fly on a short grass field and like to do some aerobatics, otherwise I get terribly bored.

Having said that, the Daniel Schuebeler Hawk is about the same size ( 48'' ws) and weigh class (7.5 lbs rtf on 8S 3700). Typically it flies on 2000W give or take a couple of 100's W. Arvid flies his on 1600W and loves it.

So that would suggest a sensible power range for the CMP in the 1800-2200 W ?

If one scales up the power from Sapac Hawk / T-45 (33% less wing area than the CMP T-45) and agrees that that one flies well on say 800-1200W , then one ends up with a power estimate for the CMP of +33% of that or around 1600 W give or take a few ?

One thing to keep in mind is that my Sapac Hawk (59oz rtf) has a wingloading of 31oz/ft2, whereas the CMP one has @ 7.1 lbs rtf a wingloading of 45 oz/ft2 which is substantially higher ...

So related to this last point is my worry that the low speed handling and the mains retract mount issues are such that a lighter setup would be preferable ...

Right now I am leaning towards a lighter setup with < 2000W ...

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