|Jul 26, 2010, 04:04 PM|
Tim, I get the impression that most of the problems with these types of planes (pylon racers in general?) stem from the launch ... would it not make more sense to launch these types of planes (pylon racers) with bungee type launchers as they do EDF jets ... or am I missing something here?
|Jul 26, 2010, 04:36 PM|
Hi Colin. Thanks.
I've considered the bungee and a few others have suggested it as well. The first problem I see is the possibility of the cord getting caught in the prop. But I guess you could try it motor off. The other problem is mounting a hook, but all you would have to do is reinforce the bottom of the fuse with some lite-ply I suppose, so that's not much of a problem. Truith is, I just haven't experimented with it. Anybody else out there? Also, I think I've got my launching technique down. A few of the launches were in dead conditions. That, with poor technique and a heavy model (from repairs) is a bad combination. I think under most circumstances there should be no problem. Maybe someday we'll have to give it a try.
|Jul 27, 2010, 06:27 PM|
I got one last monday! I walked in a new LHS that I never went to before to get foam safe CA and kicker to complete my Splash 3D when I saw this box (a Rifle) on the wall. I got so excited. I knew I wanted this plane, it was BO everywhere, but there was one available! It wasn't planed in my budget, but I thought "Hey, it's your birthday soon" When I got home, I realized that I forgot to buy the glue!!!
I'm glad I found this post before I maiden my new Rifle. Good thing I had to wait for my motor to get in. I found this thread because I was trying to find out if I could fit a 28mm motor in the nose.
Here what I'm planing to put in my Rifle.
The motor is going to be either a HXT 2835 3900kv inrunner or a Scorpion HKII-2213-14 (3585kv). I was planing to turn a 4.1x4.1 or a 4.75x4.75 prop in combinaison with a Plush 60 esc and Rhino 2150 3S 20C packs. Servos are probably going to be Futaba S3114's.
This setup should put the Rifle in the 150mph range. Of course I'll do all the mods suggested in the thread (wing spar, tab and firewall reinforcement).
I would like to have feedback about my power setup. Are the 3114 servos going to be strong enough? Maybe I'll need higher C rating lipos? My goal is to use as much as possible the electronics I have in my "junk" bin.
Thanks guys for all the info posted here, it is very usefull. Never been through a whole thread that long before
|Jul 27, 2010, 07:37 PM|
My personal experience with the 3114's is that they are good servos, but strip "very" easily. With something going that fast, you don't want to have any doubt...or...at least as little as possible.
|Jul 27, 2010, 08:13 PM|
Yeah... better off throw in a few extra $$$ for good small digital servos with MG.
I just realized that the wires of the outrunner could (will?) cause problem. Anyone's using a 28mm outrunner in the Rifle?
|Jul 27, 2010, 10:12 PM|
I'm getting to like metal-gear servos too--especially if going beyond the 120mph barrier.
I'm going to post a wing modification page tomorrow--at least the way I did it and it's worked for me and my setup is 290 - 330 Watts.
|Jul 27, 2010, 10:25 PM|
I was looking at your motor choices. The Turnigy from Hobby King may be a good choice, but the kV sounds pretty high. As long as the motor can handle whatever prop you decide upon. Even with the reinforced wing I wouldn't push the airframe over 330W static, so be certain to use a Watt meter once you start experimenting with props. As far as the inrunner goes, we were looking at a similar motor at work and it would be difficult to get those wires to fit in the nose. Finally, you need to keep the Rifle light, so your 2150 battery is a larger than I would prefer (heavy). Try to stay within the 1300 - 1500mAh range.
If using motors in the range you suggested I would reinforce the wing--as I stated I'll post the way I did it tomorrow with photos. As far as the LE tab, go a few pages back and see my post about that. I sincerely and strongly feel the tab is MORE than strong enough. Honestly, I've been flying my Rifle with the wing tab partially cut through from the sharp fiberglass (the ply former was not all the way back against the fiberglass in the notch in the fuse, so for a couple of flights the fiberglass was all that was holding the wing tab until I noticed this and fixed it). I have about fifty flights on my Rifle and the tab, even in its damaged state, is holding up fine. For the firewall, all I would do is add three or four drops of thin CA to the back of the firewall around the inside of the fuse.
|Jul 27, 2010, 11:08 PM|
Marco_ul, that turnigy 2835-3900 motor is nasty, its a statorless design and is horrifically inefficient, I did some testing on it a few months ago on a 4.1x4.1 it was about 60% efficient, and the more load you put on it the more it turns to custard. Thats means that On a good 3S 40C pack itll make 32000rpm on a 4.1x4.1@400W, Thats 1500rpm less than an arc 28-37-2 makes and the arc only takes 350W to do it.... I would be impressed if it would crack 100mph in the rifle with that motor.
If you want a good inrunner, you gotta pay good prices. Looks at ARC's, Megas and Neu's.
If you want a mind numbing fast speed400 pylon plane, the rifle is NOT the airframe you want anyway!
|Jul 27, 2010, 11:35 PM|
Thanks for the advices guys.
Tim, I'll make sur that the slot in the fuse to hold down the tab is correct. I will fill any gap with epoxy, if needed. I can't wait to see your wing mod.
I know that the turnigy motor is not good. I just wanted something to fit in the plane and see how it goes. I just got into "fast" planes, after flying 3D parkflyers over 3 years now. The scorpion outrunner will go in my SpeedWing Dart.
The Rifle is going to be my test plane. If I like the experience (I'm sure I will), I will surely get a potent inrunner, not the cheap one you can get from Hobbyking. I was considering the the Neu 1105/2.5Y combined with a CC ice lite 50 esc in a VIP-1 or something similar.
That's also the reason why I wanted to use my 3114 servos. On the other hance, I know that if you cut too much on quality of components you're looking for trouble. Failiures happend even with the good stuff!
|Jul 27, 2010, 11:51 PM|
Thats sounds like a better plan
The ARC 28-37-2 is a good motor, and relatively cheap option @ $50US http://lightflightrc.com/ , itll smoke those HK 2835 inrunners (I gave the ones I bought away, they are that bad!...)
If you wanna go down that path, maybe run the ARC on light 2S pack with a 4.75x4.75 on the nose. It'll make the rifle easier to launch with a low AUW and more thrust from the larger prop, and will still scare most! Then transplant the motor and servos into the new faster airframe.
Futaba 3154s are very very nice speed400 pylon servos, You dont need high torque or speed in most fast planes, throws are very small and most have tiny surfaces. You need high resolution and low amounts of slop, which means carbon/nylon gearing is a better choice than MG. MG's gearing develops slop much faster than the "plastic" geared stuff, which eventually leads to sloppy feeling controls in flight and then flutter.
|Jul 28, 2010, 04:41 PM|
2S…interesting. I never considered that before, so I had to go out and bench-test it my self just so I would have some data. So I ran my ARC 28-37-2 on an APC 4.75 x 4.75 with three different 2S battery packs. Here are my readings (using the Watt’s Up Watt meter): With the first ElectriFly 1800mAh 25C I got 26A, 200W @ 21,300rpm. On an identical battery (just for confirmation) I got 28A, 210W @ 22,000rpm. With a 1500mAh 25C I got 25A, 180W @ 21,000 rpm.
While we are talking about good, lightweight setups, I remembered that we tried our own lightweight setup a while ago. It was a 24-33-2500 Ammo with an APC 4.5 x 4.1 (on 3S). We didn’t get any speed readings, but the Rifle flew just great and the speed was definitely acceptable for a beginner/intermediate (I’d have to estimate around 80 to 85-ish, 90?). It was the first time I flew my Rifle full-throttle the entire flight and it was a thrill! With this setup we were running an ElectriFly 3S, 25C 1300mAh battery which produced 16A, 185W @ 24,000rpm (don’t forget, 4.5 x 4.1 prop).
So, with the ARC you’ll be getting a little more Wattage, but I guess I’d have to fly the two setups back-to-back see if any differences in speed (and thrust—important for launching!) are detectable—and of course the outcome also depends on the condition of the batteries. But the 28mm ARC motor weighs 3.0 oz. while the Ammo weights 2.2 oz (.8 oz difference). However, the difference in the 2S vs. 3S batteries discussed here is .3 oz (3.9 oz for the 1300 3S vs 3.6 oz for the 1800 2S, but I’m not quite comparing apples to oranges because of the different capacity ratings of the two batteries).
Finally then, the ARC motor with a 2S setup weighs 6.6 oz while the Ammo with the 3S setup weighs 6.1 oz — .5 oz lighter with the Ammo/3S setup.
Obviously though, you’re maxed-out with the Ammo motor as you wouldn’t want to go any larger on the prop because you’re already pushing the published maximum current limit, but with the ARC you’d have “room to grow” and it wouldn’t even know it’s running on 2S! (I mean it would run plenty cool).
But gee, I was pleased with the Rifle with the lightweight Ammo setup and am intrigued by how light the Rifle would be with the 2S ARC setup and how well it would probably (obviously) fly—for an intermediate pilot.
I think any viable motor/prop/battery combo in the 180-200 Watt range would be ideal for budding ‘pylon’ pilots—with a setup like this you should be able to get the Rifle down to a ‘feathery’ 16 – 16.5 oz.
(I just looked up the weight of a Flight Power 2S 1300mAh 25C and it weighs 2.8 oz. What a combination that would be with the ARC motor for a lightweight setup!!!)
I can’t stop my self…I just bench-tested the 24-33-4875 Ammo on 2S. I tested it with a 4.75 x 4.75, 4.7 x 4.2 and the 4.5 x 4.1. The current draw is a little high with the first two props, but with the 4.5 x 4.1 and a 1500mAh battery I got about 28 Amps at 190 Watts. With a 1800mAh battery I got 32 Amps at 235 Watts. Now, the static Amp draw is too high (the motor is rated for only 20A constant), but the numbers I get from other trials show that current draw drops about 35% in-flight putting this setup right at the edge (18 to 21 Amps). But of course, the Amp draw also falls continuously during the flight, so I think this would be a worthwhile combo to test for an ultra-lightweight setup. You could save as much as 2 oz. with a 24mm motor and a 1500mAh battery! I’ll have to give that a try in-flight and give a report.
|Jul 28, 2010, 04:48 PM|
And here's how I reinforced the wing on my 'jalopy' Rifle:
From the Rifle instruction manual, page 3:
‘IMPORTANT SAFETY PRECAUTIONS’
6. While this kit has been flight tested to exceed normal use, if the plane will be used for extremely high stress flying, such as racing, or if a motor larger than recommended is used, the modeler is responsible for taking steps to reinforce the high stress points and/or substituting hardware more suitable for the increased stress.
This in mind, along with some of the accounts posted in this thread and the fact I am flying my Rifle with a motor/prop combination that provides 290W to 330W static (depending on the battery), has lead me to reinforce the wing on my Rifle too. The plane has become pretty beat up from a few bad hand-launches and another landing mishap, but the reinforced wing has withstood all of this, plus about fifty flights flown constant, full-throttle with aggressive, full-elevator pylon turns.
This modification isn’t endorsed by the company—it’s what I came up based on my experience and a few posts I have seen in this thread. I have not tested this modification to failure, so I do not know what is the limit, but I am satisfied given the power setup I am using. Finally, Great Planes cannot control the materials you will use or the quality of your work, so again, this is not endorsed or recognized by the company.
Cut one 11” spar and one 14” spar from Midwest .057” x .177” x 24” carbon fiber strips (MIDR5742). (Do not use the razor saw you will be using for cutting the slots in the wing because the carbon will dull the blade). http://www3.towerhobbies.com/cgi-bin...?&I=LXJDR4&P=7
Bevel the ends of the spars. Use medium-grit sandpaper to roughen the spars so glue will adhere. Wipe the dust from the spars and set the spars aside.
Use a straightedge and a fine-point felt-tip pen to mark the cut lines for two 1/16” slots on the bottom of the wing as shown.
Cut and fill one slot first and allow the epoxy to harden before cutting the second slot. Otherwise, you may distort the wing.
Use a metal straightedge to guide your razor saw cutting one of the slots—keep the angle low so as not to cut far into the foam.
Use a hobby knife to cut across the ends of the slots joining the two cuts, then peel out the fiberglass strip. Use a sharp #11 blade to cut the rest of the way through the foam up to the top skin—it’s okay go lightly guide the tip of the blade across the inside of the top skin, but use great care not to cut into it.
Use the back of the hobby blade to dig out most of the foam, then use 220-grit sandpaper over a piece of 1/32” plywood to clean out the slot the rest of the way. Lightly blow any remaining particles out of the slot.
Test fit the spar, then remove.
Mix a batch of 30-minute epoxy or finishing resin—stir slowly so as not to introduce too many air bubbles. Mix in milled fiberglass (micro balloons or possibly no filler at all may work, but I used milled fiberglass).
Pour the mixture into the slot, then coat the spar and insert it into the slot. Fill the slot the rest of the way with your epoxy mixture. Allow the epoxy to settle for a few minutes puncturing any air bubbles that may appear. Before the epoxy hardens use thin cardstock to wipe the epoxy flush with the bottom of the wing. Do not disturb until the epoxy has hardened, then cut and fill the other slot with the other spar.
After all the epoxy has hardened wet-sand any remaining epoxy over the slots smooth and even with the bottom of the wing.
This may be enough to do the job, but to be certain I wanted to mate the bottom skin across the slots:
Cut an approximately 12” x 18” sheet from a plastic bag or MonoKote backing and tape it to your workbench.
Cut 11” and 14” strands that are approximately 1/4” wide of Dave Brown carbon fiber tape (DAVR2000 -- also known as carbon tow or tow). Use care not to twist the strands and handle them carefully so they remain thin and flat.
Lay the strands over the plastic, then pour a line of epoxy/resin over the strands. Also lightly coat the bottom of the wing over the slots.
Again using care to keep the strands flat, work the resin into the strands with an epoxy brush, then lift each strand onto the wing over the slots. Use another thin piece of cardstock to squeegee out excess epoxy and smooth the carbon strands. Dip your finger in denatured alcohol to smooth the carbon even more—the strands will be thin and flat enough so they will not even interfere with the fit of the wing to the fuselage. Wipe excess epoxy/fingerprints from the wing and allow to harden. After the epoxy/carbon has hardened lightly wet-sand with 220-grit, then 400-grit sandpaper.
|Jul 30, 2010, 04:05 PM|
Well, got in a few flights on my ultra-lightweight Rifle setup today. This isn’t my same, overweight ‘jalopy’ Rifle riddled with repairs, but our test Rifle back at the shop that hasn’t a scratch. The plane was outfitted with a 24-33-4875 Ammo and an APC 4.5 x 4.1 prop. I flew it with 1800mAh and 1500mAh 2S batteries. First two flights with Eagle Tree data logger and thermo probe. Then, two more flights without the Eagle Tree just so see how well it would fly at its lightest. WOW!!! VERY enjoyable, pleasing to fly! I’m absolutely astonished. With the 1800 the plane was PLENTY fast—especially for a beginner. No radar, but I’d have to say 80mph straight-and-level easy. Same with the 1500, only definitely slower and less flight time (4 min timer with the 1800, I’d set my timer to 3 min with the 1500—this is full-throttle the entire flight). The best thing was the hand-launches. The first two flights (with the Eagle Tree) my assistant launched. Then, I wanted to launch my self after we gathered data and took out the Eagle Tree (with the 1500mAh battery the Rifle weighed only 15.4 oz!). With both setups the plane flew away effortlessly pretty much straight-and-level. No anxiety what-so-ever. And power off, full-elevator the thing would not even drop a wing tip. It would just float there slowly sinking. With either battery the plane was tail-heavy—with the 1800 it was balanced precisely at the aft recommended balance location, but with the 1500 it was another 1/8” aft of that, but with the lower wing loading I think you can get away with a farther aft C.G. so the plane was still very friendly (however, it would snap, but not until the second of two consecutive fully-banked, full-elevator circles—but you could still turn it hard, quick 180 with no problem). Also, the Rx and servo were mounted farther aft to make room for the Eagle Tree, so putting those two up where they belong would help the C.G.
However, upon examining the Eagle Tree data back at the shop it was revealed that we were pulling too much current and the motor was getting a little too hot. With the 1500 the temp rose about 45 degrees and was pulling about 22A in flight, but the motor is rated for only 20A constant, so that’s a tad too much. And with the 1800 the temp rose about 65 degrees and the motor was pulling about 25A. I think a guy would be okay with a 1500mAh battery, but there isn’t much room for error, so I don’t think I could recommend this setup, but gee how pleasant the Rifle was to fly and how many more people could get started in ‘pylon’ with any setup like this.
However, this does reveal how well the Rifle (and probably any other plane like it) flies with a super-light wing loading and reduced power (for the novice). This brings me back to what started this whole thing—jackosmeister’s suggestion of the ARC 28-37-2 on 2S with the 4.75 x 4.75. Even though the ARC is a 28mm motor and is slightly heavier than our Ammo 24mm motors, you’re still saving considerable weight just by dropping a cell and going to 2S.
Maybe I’ll try our same 24mm Ammo with an APC 4.1 x 4.1 to see if I can find a decent 2S setup…
…Just bench-tested with the 4.1 x 4.1…about 29A static (19A estimated airborne) 215W with the 1800 pack and 25A static (17A estimated airborne) 180W with the 1500mAh pack. Sounds encouraging, but won’t know ‘till I get her airborne. I’m guessing it’ll be a little too much on the ‘lame’ side with the 1500 but pretty nice with the 1800. Probably give it a try next week. I’m just so pleased with how this lightweight setup launches which would be great for beginners. This weekend I’ll be flying my own Rifle with my ARC 28-37-2.5, 3S, 4.75 x 4.75 (290 – 330 Watts!).
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