SrTelemaster150

I'm about to pull the trigger on the CMPro 91" J-3 Cub ARF.

I see posts where the recommended engines are over kill. I have a saito FA 91 on C&H SparK ignition that is putting out about 6% more power than stock glow ignition & I am looking for an IMAA legal high wing ARF to be powered by it.

I also have an FA 150 on spark that's putting out nearly what a 180 does on glow, but it would probably be overkill. It would still be a plan "B" if the 91 is inadequate.

W/the 91 would I be better off W/the Great Planes 1/5scale 81" J-3 Cub?

I would like to keep the engine (inverted) within the cowl if possible.


EDIT: I found that the 90" Great Planes J-3 Cub KIT is listed @ 9-12# max W/.70-.91 4-stoke recommended.

The more I investigate, the more it seems that CMPro is overpowering W/its recommended engines.

GarySS

My Feedback: (13)

I would vote for your .91 Saito. Glow .91s put out about 10 pounds of thrust which on a 12# cub seems about right. Throttling back for a quiet cruise is satisfying while still having some reserve power.

SrTelemaster150

Wow 10# of thrust in a 12# airplane should have pretty good vertcal @ WOT when it's pulled up @ speed.

The 150 on spark (8850 RPM W/an 18X8) puts out more than 1 1/2X that! THAT would be INSANE!

GarySS

My Feedback: (13)

I get this data from a R/C Report magazine test using a zinger 14x6 prop. R/C Report was located in Huntsville, Alabama where the altitude isn't extremely high so that helps the numbers.
The test showed 162oz. thrust at 9,100 RPM or ten pounds.

My OS Max .52 with a 13x5 in a 7 1/2 pound 1/5 scale cub produces about 6 1/2 pounds of thrust. There is not much up side performance and I have to really get a head of steam before looping it.

SrTelemaster150

I'll be running it on C&H electronic ignition. EI helped my 150 pull another 150 RPM W/a Dynathrust 18X8. (over propped)

Hopefully it will help the 91 as much.

I'm not looking for 3D performance but as long as I can pull some vertical for hammerheads W/WOT from level flight & loops from a shallow dive I'll be happy.

If the 91 won't cut it I have an FA150, an FA180 & I'm working on a high compression 180 conversion on a 150 case that will have 15.1:1 CR running EI. The HC 180 ought to be able to take it out of sight!

nitro wing

My Feedback: (1)

put the 150 in if it fits,
Then you can fly around at 1/2 throttle and nudge the stick a bit for a nice climb.
The larger prop will also look much better than a little 14 incher

SrTelemaster150

That's what I'm beginning to think.

SkyPilot101

SrTele, have you ever posted info about your spark conversions, I posted looking for info in the Glow forum, but did'nt get much response. I'm interested in doing the same thing, steady low idle & more power is what I'm after.

SrTelemaster150

http://www.flyinggiants.com/forums/s...9&postcount=11

Sorry, this site won't let me post a link on F-L-Y-I-N-G Giants.com You'll have to go there, scroll down to the Nitro Power forum & look for " E85 Mix For EI Converted Saito 4 Strokes? " thread, post 11 has some limks for sources. You can also google C&H Ignition & there is a phone # on the page. Contact Adrial & C&H (he is also onhere as C&HSparkGuy. He's active on the Engine Conversions forum.


There's more, but it will take me some time to find them.

http://www.rcuniverse.com/forum/fb.asp?m=11027721

http://www.rcuniverse.com/forum/fb.asp?m=11014049

Texastbird

I vote for the .91. A Dave Patrick Cub is well over 100" wingspan and it flew great with a Saito 1.50 and had much power to spare. Now, if it needed the nose weight to balance, then stick in the bigger engine and set up the idle REAL slow so it will land, ha, ha.

SrTelemaster150

On spark ignition, the 150 idles @ 1400 RPM.

According to this calculator http://personal.osi.hu/fuzesisz/strc_eng/index.htm

The 150 turning the 18X8 @ 7850 RPM will generate 17.64# of static thrust. That should be enough to hover W/an 11.76# airplane.

daveopam

My Feedback: (9)

The .91 will fly it fine, but you may need the extra weight of the 1.50 in the nose , so why not. My only Cub experience is with a 1/4 scale kit built Balsa USA. It flew with a 1.20 OS Gemini. PLENTY of power. Your .91 should make as much if not more power than the 1.20 twin. The CG was an issue even with the twin out front. The nose is so short on these. It needed the flight battery and the battery for the on board glow in front of the dash to balance.

david

SrTelemaster150

Well, AKM just called me a while ago & informed me that they were out of the CMP 91" J-3 Cub. Since the price from them was already stretching my budget, another $40 for the similar from Nitroplanes is out of the question. Especially W/all the bad press concerning their poor product support.

So, it looks like I'll be opting for the 1/5 scale 84" J-3 from "The Wings Maker'. (World Models 1/5 J-3) $179.99 shipped! The $60 savings ($100 over NP price) will more than pay for a super kewl scale engine kit from Top Notch Products.



I'll even have some left over for a 1/5 scale main gear from Robart for when the weak OEM gear goes bad.

As far as needing weight in the nose?

The ignition module & battery pack will add plenty & since the 1/5 J-3 is almost 4# lighter than the CMP 91" J-3, the 91 W/the extra HP from electronic ignition should be able to pull through loops & Cuban 8s. It should also have enough vertical snot to pull vertical for stall turns.

daveopam

My Feedback: (9)

I full scale Cub will do a stall turn. At least with correct preceding down line. lol

david

SrTelemaster150

Yeah, but I want to pull 500' vertical before I throttle back & kick the rudder.

I'm hoping an electronic ignition fired 91 will do in an 8# 1/5 scale Cub what a glow ignited 180 does in this 16# 1/4 scale cub.

[youtube]http://www.youtube.com/watch?v=tN1_-xmVLIo[/youtube]