A different approach
 

I caught the last pattern contest at my local club last year and decided to build a 2X2M Laser for pattern competition in 2011. With all the rain we have been having I have been able to make some decent progress. The fuse is all but done and I spent most of this morning on a motor mount. The gear I ordered is too long so I am going to move the gear mount up a few inches. At this point with everything pictured including two 5S 5000 MAH batteries it weighs 6.8 lbs. Getting concerned about the weight.


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RE: A different approach
 

Wow over 200 views and no comments? Don't be shy guys. this is my first pattern build and first big electric, would love some feedback good or bad

RE: A different approach
 

Maybe is because your plane is sooo.. (cough cough).... "unusual" since the actual trend in F3A.
I suggest you to riconsider totally your way of mounting the engine. I think it's a litte under designed for the massive torque of these motors. Try to take advantage of the full width of the firewall.

RE: A different approach
 

Keep posting the build photo's, it was not that long ago when we first went to the two metre rules that there were quite a few stand off scale types getting around.

It may not fly as well as a purpose designed F3A, but if you enjoy it, and it gets through the sequence, well that's what it is all about.

I would have a good look at the mounting as Roberto suggested though, it could undo all of your good work if it is not strong enough.;)

RE: A different approach
 

Yes it is a bit unusual but my hopes are that it will fly well enough to be competitive up to Advanced class in my region. I do still fly IMAC and wanted a pattern airplane that flies simular. I will investigate the mount a bit more however it is much mose sturdy then the mount the motor came with. My biggest concern right now is the weight.

RE: A different approach
 

Are those nylon bolts with nylon standoffs and nylon locknuts for the motor mount?

RE: A different approach
 

yes that is nylon hardware. I am a little surprised about the responses I have been getting about the motor mount. If this were a gasser, I would never have attempted a mount like this but being electric I think it will work without being over built. I work in a composites shop that builds military hardware and the techniques in that mount are utilized inthose productsquite often. All the glue joints are a high grade epoxy with milled fiber added and heat cured at 180 degrees. Themating surfaces were abraded well and cleaned with acetone. I will however be doing some stress testing before the motor spins just to be on the safe side. As just a little side noetpeople have been mounting 150-170cc engines with 1/4X20 stainless hardware for years without problems.


I do appreciate the feedback

RE: A different approach
 

1/4 - 20 stainless and 1/4 - 20 nylon are totally different. The sheer numbers aren't in the same world. I would not use nylon for this purpose, regardless of the size.

Just my .02

Arch

RE: A different approach
 

Ask and ye shall receive. The only reason I mounted YSs and Hyde mounts with 6-32 screws was because the mounting holes were too big for 4-40. I don't ever use nylon in any shear application, and that's what you'll be getting with the torque of the motor.

I know I don't doubt the construction integrity of your motor mount, and it's doubtful that others on here do as well. The the professional appearance of the construction of the mount is a testament to your composites background. I just think the thing is too damn complicated. It's neat, appears to be built well, and is definitely outside of the box thinking. However, I think most would agree with me that you would have been better served to extend your motor box sides a couple more inches further forward and bolted the motor directly to the firewall using standard (4-40, 6-32) hardware.

My only other comment regarding the airplane is the batteries appearing to be mounted in the bottom of the airplane. From what I've seen, this is not the optimal arrangement. Primarily for a lazy person, like myself, I don't like flipping my airplanes over. To have to do that every flight stinks. Secondarily, and probably more relevant to the discussion, I've never been crazy about the way pattern planes fly with the batteries so far off of the fuse centerline by being bottom mounted. I've seen several Japanese pattern planes that were retrofitted to electric with batteries in the belly pan, and I did not like the way that any of them presented. The airplanes all appeared to fly with the nose down and did not track straight. My thoughts are that this is a function of vertical CG. The same aiframes that were either glow powered, like they were originally intended, or that were modified to have the batteries sit closer to the fuselage centerline appeared to track much better and the fuselages sat at a better angle in straight and level flight.

This commentary is worth what you paid for it. I am very impressed with your work, as you appear to be a heck of a craftsman. Kudos to you for taking the path less traveled, as well as utilizing a design that has fallen out of favor due solely to its lack of being flavor of the week, on top of adapting that to a 2M airframe.

Good luck with your project, and I for one look forward to seeing its progression.

RE: A different approach
 

You probably can save some weight by not sheeting the fuse all the way to the tail, to avoid secifically the "tail weight". Some weight can be saved also if the turtle back is constructed by some lighter/thinner wood or foam.

There is a 2m wood pattern construction article on AMA a while back. It is for gas power but should give some idea on how to save weight.

RE: A different approach
 

Ryan, thanks for the feedback, most useful.

I hear you about having to flip the airplane over to install batteries. I was going to make a stand to ease this. The biggest reason I went to the belly was it seemed that I would be able to get the most airflow across the batteries and controller. Obviously I did not consider the vertical CG. It may be difficult to to tell from the pictures but the batteries are actually 4.25" below the wing tube ( Center of battery to center of tube ) it you feel this is too far off the cernter line then I will take your advice and move them to under the canopy and work on getting better airflow to them. I am also going to construct a couple more plates with the nylon hardware and see just what kind of shear force it takes to make it fail. starting over again I would extend the firewall. I originally intended to use an OS 160 . After seeing and talking with a few of the pattern gurus in my district I made the jump to electric.



Nonstop, The fuse is actually quite light. Without the motor mount landing gear it is 1.9 lbs. The fuse is not really sheeted, the 3/32 balsa sides are structural, The fuse is built with these sides as a box if you will with cross bracing to eliminate flex then the formers and stringers are added top and bottom. The turtledeck us 3/16 square spruce stringers with the formers being 1/8 med balsa. I did consider a balsa sheeted foam unit because it would look much nicer but in the end the stringers were chosen because it it lighter.

RE: A different approach
 

Vertical CG would have nothing to do with what angle the fuse is in level flight. In fact, lengthwise CG has very little to do with that. The only thing that will control the angle the fuse flies at will be the angle of incidence the wing is mounted on the fuse. But Vertical CG has a lot to do with what the model will do in a vertical upline. Most models that have been originally designed for IC engines need the batteries in the belly in order to have the vertical CG in the designed location. Think about the IC engine cylinder sticking down, then the exhaust system on the bottom. If the packs are located too high, the model will pull to the canopy in an upline, requiring more downthrust.

RE: A different approach
 

Where did you mount the batteries for your Partners?

RE: A different approach
 

I suppose the final resting place for the batteries will be determined to where they are located in some of the current F3A airplanes in relationship to the wing tube. The good news is depending on where the batteries sit to get proper CG may allow me to try both locations. I have been flying a 50cc Laser for a little over a year with the engine inverted. Initially on an upline it did tuck to the gear. A tad of up thrust cured that but I do wonder everything else being equal if the CG was closer to the thrustline would it have tucked? Of course airplane trimming is a whole very long topic in it's self.


Tony F Now there is a name that has been around. I remember you first working over at Indy and the first time we met was at an IMS show where you were flying a Heli boy for Walt.

RE: A different approach
 

Hi Ryan,

I first mounted them up near the wing tube. The model pulled to the canopy in an upline. I moved them to as low as I could get them, which with the way the gear mounts in a Partner is pretty low, and the pull went away. No other negative things felt when I made the change.

Hi speed,

I never worked in Indy but I did work at World Engines in Cincinnati. I did fly for Walt at a few demos.

RE: A different approach
 

OK Yes now I remember. That was when World was the distributor for OS Max. looks like I will go ahead with strapping them in through the bottom for now. I know it will be inconveinent having to turn the airplane upside down but the cooling will be much better. I am fairly new to electrics but I do know that heat is lost effeciency. Probibly overkill on the 5000 MAH batteries but I would rather end up with some practice packs as opposed to packs that won't get me through the sequence.

I did manage to get everything wired up and did a short 1/2 throttle run up. Scary power is the only thing that comes to mind. And I for years have thought nothing about flipping a 150cc gasser

RE: A different approach
 

I managed to get some work done today. Mounted the wheel pants. They are off a H9 Funtana and are the perfect size. For the 11.00 I paid for them I just couldn't justify laying up my own. As for the cowl and canopy / hatch thats a differnt story. I need to finish up on the canopy plug and get a mold made from it. Then I can make up all the glass parts over a week end. Still have to cut the wings. Does anyone know of a good and easily obtainable material to cut templates from? I have been using 1/8 ply and then rounding the edge followed by a coat of thin CA and finish sand but still having minor issues with the wire dragging.

RE: A different approach
 

That's a good looking airplane!

What landing gear is that?

RE: A different approach
 

Formica kitchen counter top materiel makes excellent templates. The hot wire doesn't melt or burn the edges and the glue side is easily marked with a pencil. Rough cut on a band saw and sand smooth to your outline. You usually can get scraps from a cabinet shop for free.

RE: A different approach
 

Thanks Ryan, the gear was found on Ebay of all places. I'm fairly sure this outfit is subcontracted by many ARF manufacturers. The gears and spinners I ordered from them look identical to the ones that come with the Pilot ARFs.

http://cgi.ebay.com/F3A-100-Carbon-f...item33637d029c



Burtona, I have heard of people using formica, thanks for the reminder. I will give it a try.

RE: A different approach
 

A good friend of mine has just received a set of that gear from the same supplier, we compared them to my ZN gear and they are virtually identical in all axis, the only small differences are the weave of the carbon cloth and the thickness of the finished legs. The height, rake and spread are all identical.

RE: A different approach
 

I used the same gear on my E-converted Sequel. The gear is pretty strong and light in weight. I wish they could provie a set with reduced height measurement.

RE: A different approach
 

Not much new as the holidays are over and it's back to the day job. Out of curiosity I did pull the hatch and cowl off my 50cc Laser and threw them on for a look. The fit wasn't very good but gave me an idea of what to expect.

RE: A different approach
 

A little more progress. The past couple weeks I have managed to move the landing gear to the bottom of the motor box. I think I should have put it there from the start but you know how works in progress can be. I got the tail fairing and cowl layed up and loosly in place. The canopy plug is almost ready to paint and then I will have that mold ready to make a part as well. Gearing up to do the wings next week. Foam and 1/16" balsa sheeting is just sitting in the shop waiting for me.

RE: A different approach
 

Got the canopy plug finished. Next week I will be lay up a mold from it and then by the end of next weekend have a finished glass part. What are you guys using for battery straps and where to get them? I have tried the usual hardware and electronics store and have come out empty handed so far.

RE: A different approach
 

Check out the Xtreme Battery Straps by Puretech at http://www.puretechproducts.com/products

They are excellent quality.

RE: A different approach
 

Thanks, Those are just the ticket!

RE: A different approach
 

Looks good. what are you using for the canopy plug finishing? Are you going to vac-form a canopy off that too?

RE: A different approach
 

Thanks. The canopy plug has been painted with Klasscoat epoxy paint. Very simular to the old K&amp;B epoxy paints. The next step is to wax the plug with Part All wax then apply a coat of PVA mold release. A surface coat of resin with black tint will be brushed on and when dry a layer of 2 oz cloth followed by 4 layers of 6 oz cloth. The mold will then be pulled from the plug and be ready to use for the actual part production. When I designed the canopy I used a canopy off a Comp ARF Extra 330 3M to make what would be the clear section. If I decide to go clear rather then paint I can just order a Comp ARF canopy and fit in the same fashion as they do.

RE: A different approach
 

Home Depot and Lowes carry a nice selection of Velcro straps and adhesive backed Velcro. It is usually located in the hardware (bolts, nuts, fittings) area.

As for your question about material for templates. I use(d) hard balsa with a length of small diameter piano wire ca'd to the edge. After ca'ing the piano wire on, sand the outside edge with very fine sandpaper (600-1000 grit) and the nichrome cutting wire will slide in it very well.

Woodie
Team Acme LG
Team Blenderm

RE: A different approach
 

Not much progress, work has really picked up so models have had to take a back seat. Still hope to have her flying by April. I did manage to get the canopy mold made and laid up the canopy and mated it to the frame.

RE: A different approach
 

Not alot of time lately to work on thew airplane but that changed some this week. My fiancee and I cut some cores and I got the wing sockets installed. Today I glued on the wing root ribs and will be sheeting the wings over the weekend. I will post some more pictures and a bare airplane weight sometime next week. I have been reading that most of you guys are using 3900 to 4400 MAH batteries? Pretty sure I went overkill with my 5000 packs. Need to shave some weight, as of right now it looks like I will be at around 11.5 lbs

RE: A different approach
 

I realized I hadn't really kept up with this thread. Finished her up a week ago sans color. After the test flight tomorrow I will start adding the trim as time allows. With a 2200 mah RX battery and a pair of Zippy 5000 mah batteries she weighs in at 11 lb 3 oz. Switching out the batteries and a few minor things will get me below 11 lb. So far I estimate I have just slightly less then 800.00 total investment. This includes all the electronics less TX

RE: A different approach
 

Very cool. You will probably find that you can go much smaller on the reeceiver pack. Most guys (and gals) flying 2 meter pattern planes are using 1 700 to 900 mah lipo or 2 450's on a regulator For a full 8 minute pattern flight a 2 meter electric bird only pulls 50 to 75 mah out of the pack.

Stuart

RE: A different approach
 

Stuart, yes I agree my RX pack is way overkill. What I have found after 13 years of IMAC flying is that the big gassers bounce the control surfaces quite a bit and that is the major power draw. I have a 900 mah lipo RX pack and a couple 5 cell 4500 mah batteries on order and that should get me to legal weight. If the airplane works as designed I will be able to fly a little slower then I have observed some of the newer pattern ships flying. I have seen some mighty thin airfoils out there. It's funny, we have gone that route with the big IMAC types to be better snap performance because the IMAC sequences are full of snaps. In the pattern advanced sequence there are only two snaps and one of those, the avalanche has the airplane loaded positive so poping a neg snap is no issue with the thicker airfoils I am using. The second is on a 45 degree downline so a quick pop of up elevator followed by rudder and aileron will get the job done there too. I'm pretty excited about the test hop tomorrow and will report back with my findings.

RE: A different approach
 

Got in 3 flights today. Needs a little tweaking. The main thing is the CG is a little aft. Other then that and the 19X12 APC prop didn't give the vertical that is needed for the advanced sequence but that was expected. The motor and speed control temp was checked after each flight and were barely warm so the system will handle a bigger prop without issue. Being a 230KV motor, I doubt that it will handle the usual 21.5X14 that most guys seem to be running so I am looking for some suggestions. I was thinking 22X10 or 22X12.


I would like to extend a big thanks to Luke for letting me use 3 of his battery packs to do the test flights!

RE: A different approach
 

IMHo, She needs some taller gear to get rid of the Weiner Dawg look!! lol

Nice to see some handicraft applied though!!

Keep us posted on the flight test and maybe a vid??

RE: A different approach
 

Congrats on the first flights. My guess is the 22x12 will be a pretty big load on the motor/esc combo. It was the prop of choice several years ago when the lure of electric was the very slow flight with great braking on the downlines. However, for the outrunners in the 225+ kV range it is a lot of amps. You might consider the 20x13 or 21x12 props. More load than your 19x12 but shouldn't be too much for your motor.

Good luck, hope to see you at BARCS.


Woodie
Team Acme LG
Team Blenderm

RE: A different approach
 

Very nice work! I have been following your progress eagerly. Love when someone takes the path less travelled.
I missed what motor you have. It looks like an Axi F3A. Many have used an APC 20.5x14 very succesfully on that motor. It will draw around 90A but it can handle it. They recommend a 20x13 which is a little slow on most airframes. I would try the APC versions of both and then order the one you like best in carbon to help you make weight. The Falcon CF props are very nice but a little pricey to experiment with.

RE: A different approach
 

Anthony, here is the link to the motor I have.

http://www.hobbyking.com/hobbyking/s...idProduct=2129



I picked up a 22X10 at the local shop but will order a 21X12 to try. I'm thinking the 21x12 will work the best. For the most part I had good speed at level but not quite the vertical I wanted. Being all white it was a bear to see so I think I am going to pass on the BARKS contest and go to Fresno in a month. That will give me time to get some color on her and get everything dialed in.