hllywdb

OK, I'm thinking of building another pacer, especially now with all the lightweight gear. I want to keep it as light as possible and a bit better proportions. I'm thinking of moving the wing an inch higher in the fuse. I plan on using 4 hs-55's (2 in the wing) and micro reciever. Also plan to swiss cheese the stab and fuse. Here is my dilema. Do I shorten the wing by 1 rib and go with my cox TD, or build the full wing, lengthen the fuse by a few inches and use my Enya 09 and another hs-55 for the throttle?

MJD

My Feedback: (1)

Do you figure the Enya is going to give you a net performance gain? I'm skeptical, but maybe. A light model of that size on a good TD is a treat.

MJD

hllywdb

Not absolutley sure on the performance gain. But tank pressure, rock solid needle settings, longer flights, throttle. Has anyone had any luck with pressure taps on TD's?

PeterC

I have to agree with MJD. My old Mach None which was a second generation Pacer flew great with a Tee Dee using old EK servos (2) and an old EK radio.
I can't think why I would want to change the design. If you're up to that type of plane then it's great as it is. I think the weight of a Enya would make it a slug.
My last one was el*ctr*c powered with a BP 21 and a 1250 mah 3 cell lipo and was just as good as the Tee Dee.
If you go with wing mounted servos be sure to put a skid under it to protect the servos.
Peter

fritzke

My Feedback: (1)

Hollywood, this is how planes "evolve"! With all those changes, it will cease to be a Pacer
and be more of your own design. (This is a good thing.)
I'd say stick with the TD or an AP 61, use light gear and, if you must, clip the wings.
A clipped wing might increase the roll rate a bit, it's worth a
try. You never know until you have at it.
I think you are right, the wing loading probably would not be any higher than one from
"back in the day" when the lightweight servos were the 1 ounce Bantam Midgets and a 500 mah
nicad was standard.
Dave

hllywdb

My reasoning behind shortening the wing is to get the fuse/wing span ratio closer to 1:1 and clipping the wing tips seemed lighter than lengthening the fuselage. My old one back in the day used full size servos and a 500ma rx bat, plus an old am 4 channel rec. I have a couple of pattern planes that I fly at the club, but I have a 500+ acre field right across the street that I go over with my kids and fly an old Jr Falcon from plans with a medallion 049, and a scratch built "shrunken" Kadet Senioreta with an 09 medallion with throttle. It's nice to just bring a shoe box with a 1 1/2 volt battery and 8oz of fuel, so thinking another pacer made a bit more modern will fit right in!

DeviousDave

Crap... my post from last night.... I must've forgot to hit "OK".

The best thing you can do for a Pacer is swap the wing for an RG-14 or similar airfoil. As for the motor, Spend $40-50 and get a new Norvel on FeEbay. Weight isn't going to do a pacer a lot of favors-especially with the stock airfoil, so an Enya .09 is not a great idea. You need a 5" or smaller prop, lots of pitch, and lots of RPM.

hllywdb

Hi Dave,
Do you think the Norvel is that much hotter? My TD has Galbreth turbo head, short/lightened piston, texas timers needle, etc. The norvel looks heavier. Is the Norvel 74 better?
Also, I'm doing this from Owen's origional plans with a built up wing, not the ACE. What is the RG-14 airfoil like?
Thanks

Andrew

The original Pacer airfoil is about 16.5% thickness - it's quite plump and may have been thickened to allow the use of the ACE foam wing. The RG-14 is a bit thinner in the waist with a more pointed LE. Here is a pic of a 10% RG-14. It should be quite a bit quicker.

fritzke

My Feedback: (1)

Screenshot from Compufoil:
Looks fast anyway. 2414/2415 is the Ace foam wing airfoil
Dave

MJD

My Feedback: (1)

If the airfoil is the same as the foam wings which I am pretty sure it is, it's a NACA 2415, 15% thick. The RG14 is 8.47% thick, far more slippery.

MJD

My Feedback: (1)

fritzke was posting same time as me. Double whammy.

Andrew

LOL - battle of the foilers.

andrew

DeviousDave

Any of the Norvel 1/2A's will be a step up-they look heavy, but they aren't. TD's might look light, but they have an aweful lot of steel in them. Norvels only have steel in the crank, wrist pin and prop screw.

This is how I'd look at a Norvel for your application:

Big Mig .049/.061: Similar performance to a TD on the same prop, but will make more power with a smaller prop than a TD with smaller props. TD's are best with props designed 40 years ago.

AME .049/.061: Will turn a TD sized prop about the same RPM, maybe a little better. Will blow the doors off a stock TD with a small prop and big hit of nitro. A good AME is like a full blown Kustom Kraftsmanship 1/2hour motor, plus some, and it needles well and has a muffler.

.074: Technically, most .074s were Big Migs with sport porting. The prop to use is the 7-3.5 APC, which it turns with Authority. If you want a vertical 1/2A, use a Norvel. If you want to remove all doubt, use a Norvel .074. (This assumes you build to average weights) The .074 is probably their 'best' motor, but finding plugs is an issue. I'm up to about 30 (got 8 .074's) that I have accumulated over the years watching FeEbay, but there is a commercial replacement plug available now that is reasobably priced-some of the plugs I got were over $30. That leaves needle valves, which can still be had online if you scour hard enough. They didn't make very many .074's

Honestly, if you want an .074 enough to go look for one it would make a great motor for the Pacer. It will be heavier than the TD it replaces, so you may have to move the guts around inside the plane-with today's radios, you will be lighter than the original plane was by quite some margin. Personally, I'd go for a Big-Mig or AME .061. While the Norvel would be a real barn burner on the Pacer, it's not in the spirit of the design-the .074 was mean to go on larger planes that were too good to get a heavy-assed OS .10FP! Best part about the Norvels is that they always run, always draw fuel, always needle well, and the throttles are pretty good too-try that with a TD... It's not like being the fat kid getting the slow gokart!

I can't find it right off hand, but one of the guys here posted a really good video of his SureShark with a Big Mig .061 RC, you should look for it-they performance was quite good. Probably be similar to your pacer given the airfoils and drag profiles of the two airplanes

DeviousDave

The RG14 is a sailplane airfoil, developed to fly at model speeds with chord widths that models use. It's a very friendly airfoil until you give it stooooopid wingloadings like they have in F5D. A friend turned me on to it when he got into Sp400 racing and started making kits. I took over for a few years and most of my airplanes since have used this airfoil. The properties scale well too, My last airplane to use it is a TD .010 powered composite racer with about 70 sq. in. and it flies great.

The AMA Sp400 pylon record was set by one of my airplanes. I never got better than 2nd at the NATs (not saying much given the lack of competition some years), but one year I took a really good pilot (friend's uncle) with me who flies Q500 and Q40 at a national level. He did 75 seconds on the 1/2A course and the airframe weighed about 12.5oz and had 165sq. in. I like the way they fly at about 15 oz. and can't seem to notice a difference in landing speed, though there may be some measurable penalty turning at that weight-I never noticed it-the 2nd place airframe weighed 14.5oz, same airframe as the record holder.

The best way to describe this airfoil would be to say that it is a clean one with a high lift coefficient and a very mild stall characteristic. The main reason we used it was just that it turned so well-some of the other planes of the time had airfoils that were 'faster' when you dove them, but it never translated to being first to finish-especially when they were smaller and had snaproll problems when tuning to keep up in turns. The friendly handling of the RG-14 was jut icing on the cake. It has since fallen out of fashion with the sailplane guys and pylon crowd what with everything being all-molded in CNC machines, but when you compare them to what's hot, they don't deviate a lot from what the RG14 is. The F5D world record airframes from Russia (Avioniks) use the RK-40, which is a thinned RG14.

DeviousDave

Oh, you guys should get a copy of Profili if you like to play with airfoils- it prints out ribs with sheeting, spars etc. and has a full library.

It's free: http://www.profili2.com/eng/default.htm

hllywdb

Won't give me a lot of room for mounting the servos in the wing How much will it change the overall handling of the plane? I'm not looking for fast, just nice smooth pattern style handling with decent vertical

DeviousDave

I can't think that it will change the handling that much, aside from more torque reaction at low speeds. Bigger Prop=more torque reaction. We are still talking about a small bore glow motor, the thing ain't gonna rip out of your hand like a small block chevy powered chainsaw..

I think you'll be surprised at how fast it will be with the .074... It may not swing as fast as the AME's, but it pulls as much pitch and the bigger prop is a LOT more efficient. Prop efficiency falls off a cliff in the 5-6" range, and pouring tons of power to small props doesn't help a lot.

Andrew

See post #9 for a Profili generated rib - it's very inexpensive to register; a good investment to keep the author coming out with improvements. Once registered, you're entitled to new versions as they become available.

DeviousDave

I just downloaded and updated to the new version, it's still free but some of the new features are pay only. I'll flip the guy a few bucks when I refill my paypal account, he's obviously put a lot of work into it.

The only thing I need it for is to generate .dxf files for airfoils to export to MasterCam. I needed them for a twin boom, twin engine .074 combat type ship I have burned brain cells on this week. Starting to look good!

hllywdb

Not looking for fast, just nice light handling with decent verticle. The thing is my TD is a fresh build, just 2 bench runs on the new piston/cylinder/head. There is a AME 049 on ebay right now, but looks like it will take close to 50 to win it.

hllywdb

OK, I'm starting tolike the RG 14. Will Profili let me save the rib plans in anything I can send to my lazer cutter?

Anyone want to way in on the AME 61 vs a hot TD? How much more power?

Andrew

Profili exports .dxf files. I would think your laser cutter would accept those.

andrew

DeviousDave

A stock Norvel with the screen removed and muffler off will run about like a Hot TD. The difference is that the AME's porting runs a LOT wilder, and is meant to run smaller props than the 5-3's and such that used to be hot props for the TD. I like APC's electric props in the 4.5" range, haven't tried all of the glass combat props out there but have a bunch.

One of Andy's videos has a Norvel .061 spinning an APC 5.5-2 glow prop at 26 grand. Obviously, this is not the right prop for a Pacer (wait,... it might be for what you want to do with it) but it goes to show you how lowering the load just a little bit gets the motor farther up into the power curve.

Norvels are pretty common on the Auction Site In The Sky, if this one goes for too much, there will be another soon.

hllywdb

Just put my TD on the bench. Turned an APC 5.75 X 3 at 19,200. Seems like it should be more thrust than a 5.5 X 2 @26k and less prop cavitation. I'm looking for thrust, not speed. I'm thinking a big mig 74 might make some sense, but I'm hearing 14K with a 7X3, does that sound right?