N1EDM

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Thanks, Bob. So far, I've gleaned about 2 pages of build notes from your build (starting on Page 11). I picked that up about the wing boxes, the dowel rods, embedding the hardwood plug into the wing (rather than beneath the sheeting), plywood bottom forward of the step, etc.

I hadn't picked up the parts about the hatch and the aft deck - thanks for bringing those to my attention too. I also want to re-read the posts about the tail post and pylon. I was curious if that was strong enough of a structure to take the stresses of the engine thrust? I will take a closer look at the plans.

Bob

Mustang Fever

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Bob:

The tail post/fin assembly is quite strong, especially if you use epoxy to bond the four pieces of 1/4 spruce or basswood together.
The pictures on page 12 of the thread show the complete pylon building process that was necessary in order to get the 5 deg down thrust.

I seem to remember fiber glassing the whole thing from the base up to the bottom of the nacelle.

I reinforced the area at the bottom of the post with a lot of epoxy and milled glass. I kind of filled that whole area with the stuff, after I got some sheeting on the bottom to hold it all in.

I think the stuff about the hatch came after I had been flying it awhile and had to repair it after some terrible landings.

As of this writing, the fin/pylon assembly and it's related mounting area are about the only parts I haven't managed to break. (My folks always said I was too rough on my toys.)

Mustang Fever

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I decided to strip and recover most of the bottom and sides of the hull, during the ice damage repair process. I'm glad I did, as old RL 205 looks almost pristine, now, after two seasons of hard service.

Mustang Fever

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The "E" Arrow is officially on the boards. I cut the parts last summer, but haven't done much til now.

I'm going to use a Rimfire 32, a 5S 3300 pack, a Flightpower 60 ESC, and a 10x6 prop. Performance should be very close to the glow version: around 65mph and near 6 pounds static thrust.

Mods to the hull to accommodate electric power are minor: you can see the floor and top of the balsa battery box between formers 5 and 7. It will have balsa sides as well, and allows the pack to be installed thru the hatch, between the pushrods. (I built a small electric Arrow a long time ago, and found out that the rear end of the pack has to be even with the step to get the CG.)

The holes in the formers on the centerline are for the motor to ESC wiring. The holes outboard of the centerline are for plumbing cooling air pipes from scoops on the top of the hull behind the hatch.

Bob and Pete: please feel free to post your builds here.

N1EDM

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Thanks for the notes on the pylon - this next build looks like it'll be just as interesting.

Good luck with it,

Bob

Mustang Fever

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Arrows sure build fast. Got the hull framed up, the wing tubes mounted, wing attachment block installed, pushrod tubes installed, and the servo tray built.

The way I do the wing tubes is to 1) Make the holes for them in the hull sides a little bigger than needed so they can "float" 2) grease up the CF wing spars at the wing root so they don't get glued on permanently 3) stick the wings into the tubes and bolt them in place using the regular attaching screws 4) pour the epoxy/glass mix onto the wing tubes, first from below, then above after the first batch cures a little.

I do the servo tray after installing the pushrod tubes, and before the left side of the hull is stuck on. It's just a pair of 1/4 square basswood sticks that fit into 1/4 square holes through the hull sides, with another piece underneath each end for support. (Side note: use the holes that Laddie shows on the bulkhead drawings. The PRs line up perfectly if you do.)

I ordered the 32 motor today so that I can do the stick and pylon sometime next week.

Mustang Fever

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Servos installed and elevons hooked up. I use 4-40 pushrods and have found through experimentation that the best pushrod connection at the elevon end is the Dubro large EZ link (4-40 wire). This allows for very quick and easy wing removal and installation, but the best part is having no threads at the "water" end. (They always rust.) The clipped end of the PR poses no corrosion problem.

Mustang Fever

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Hatch construction. Never have had any luck with cutting parts out of an assembly, like flaps, ailerons, etc. Always ended up with a mess, so I do it like this. Cut the hatch sides out of the hull before it's assembled, then build the hatch in place with some wax paper to keep it from getting stuck.

Pic #2 shows the two blocks for the hold down screws being glued in. The tops are a little more than 1/8 above the former lines so they can be sanded flush with the decking later on.

The bottom of the hull (from the step forward) and forward deck are all in place. I used a little 1/8 ply near the step as specified, but decided to go with 1/8 balsa for everything else, to keep the weight down. I'm hoping that I have enough experience landing the Arrow that I won't do any damage to this one. [8D]

Mustang Fever

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The decking and hull bottom sheeting is all finished back to near the pylon area. When the motor arrives tomorrow, I'll be able to start on the mounting stick and pylon.

Mustang Fever

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I cut the four pieces of 1/4 sq. basswood to 12" - 2" longer than shown on the plans, as I want to make sure it sticks out the top of the nacelle and the bottom of the hull, so it can be trimmed and sanded flush after thoroughly bonding it in both places.

I used Tite Bond water proof glue to bond the sticks together.

By sticking a couple pieces of scrap 3/8 CF tube into the wing fittings, a steel rule and an angle gauge can be used to set the hull at 5 degrees nose up. That way, the stick can be placed vertically against the rear of the bulkhead and the thickness of the wedge required at the bottom can be easily measured.

Mustang Fever

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The wedge needs to be about 1/4" thick at the bottom of the bulkhead, tapering to nothing at the top. At least it does on this model. My aft bulkhead is tilted a little towards the bow.

Mustang Fever

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Quite a bit of progress since the last post: the firewall, nacelle bottom, and both lower and upper fin ribs installed. I earlier had run a piece of string through the bulkheads, and used that to pull the motor wires through from the radio compartment. First time I've used Deans Wet Noodle 12g wiring, and I really like it. Really flexible and easy to work with. Soldering on the motor bullet connectors is next.

Mustang Fever

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I checked the CG with what you see here and the wings on, and using 20 oz of lead to simulate the battery pack in that box ahead of the step. It came out right where it needs to be, and the total weight is about 4.5#. Maybe, just maybe, it will finish at about 5#, which would be ideal.

Mustang Fever

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Motor permanently installed, wires connected, and fin/rudder done (except for one more hinge.)

I've always wanted more water rudder on my current Arrow, so this one is a bit deeper.

Mustang Fever

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Ready to cover.

Mustang Fever

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Ready to fly. I'm going to try it with one of my 3300 4S cells before I commit to buying the 5S. I tested the 32 motor with that using an 11x7 MAS 3 blade prop, and the results indicate 65mph and at least 6# of thrust. Should work well, particularly as the amp useage is only 45 at WOT. That's less than a 32 uses in my Pulse 25E on a 12x5, and that sucker will fly around forever on a 3300 pack.

The airscoops for motor and ESC cooling were made from a old set of glue-the-halves together wheel pants off something I don't even remember. (I never built it.) I just cut the rear tips off three of the halves and voila.

I was gonna make this the same trim as the glow Arrow and the Bullet, with a white hull and orange trim, but got to thinking about the fact that this one is going to see a lot of duty off snow. (If we ever get any, here. Last year at this time we had just got 18" on top of a couple feet that were still left from the previous storm.) So, I gave it an insignia blue bottom for contrast with the snow, and orange on top for visibility during normal turns.

Once the GE silicone hatch sealant cures into a permanent gasket, I can lose the wax paper and go flying, if the lake is clear of ice.

Balance with the 3300 4S pack slid in as far as it will go (until the wires stop it) is just about perfect. I might have to stick some lead in the bow, but likely not. I'll get a total weight check after the silicone cures.

Mustang Fever

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It's blowing 30mph and raining today, so no test flying even tho the ice is probably all gone from the lake. (It's 50 degrees outside)

Some final notes that I hadn't included before:

A divider in the compartment aft of the electronics bay makes sure that airflow through the intake scoop goes forward, and that air will exit through the left hand hole in the bulkhead and leave via the exhaust scoop. The details of the battery retainer and rx/esc installation can be seen in this shot, too. BTW, balance came out perfect with the 3300 pack and no ballast. It's at 14-3/4" forward of the elevon hinge line, about 1/8" forward of where the glow Arrow balances with a full tank.

RTF weight is 6.4#. Watts per pound is 91. With over 6# of thrust on tap, she should perform well, but won't be the rocket that her glow sister is.

I've used rather hard 2-1/2" x 3/8" tapered aileron stock (from BUSA) for the elevons on the two wing sets. They are much easier to make than the ones on the plans, and don't warp in service. When it came time to do the rudder and the skeg below the hull, I decided to use some of it. My rudder is two pieces of the aileron stock glued together. The forward thickness comes to 3/4", which matches the thickness of the fin TE. Perfect. I wanted some more rudder in the water, so I made it maybe 2" longer than called for on the plans. I maintained the 3/4 inch thickness, and made the skeg out of 3/4" balsa. The thick rudder means standard control linkage hardware isn't big enough, so I used a Dubro HD adjustable setup.

Mustang Fever

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She flies great

The handling is even better than the glow bird, and she's easier to slow down and flare for landings. I think this is because the CG never changes, whereas the glow bird gets progressively more nose heavy throughout the flight.

I wasn't happy with the performance at all- I had to fly around at close to full bore most of the time. After landing, the motor smelled hot. I tried it with a smaller prop and it still smelled warm. Then I remembered that this motor always felt tight compared to the same one in another airplane, so I just finished swapping them out and running some prop tests. I'm going to go with an 11x9 MAS GF as it puts a max load on the motor (50A continuous) and seems to be really pushing hard, and the motor is not getting warm at all.

More later. It started raining again so I'm grounded for awhile. (And it's getting dark.)

Mustang Fever

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Even tho I haven't been able to fly with the new motor, I went ahead and ordered a 5S 3000 pack from hobbyking.com. This will take watts per pound from a little over 100, to about 115.

Mustang Fever

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The new motor made a lot of difference- no more getting hot, and acceleration is greatly improved. Still not enough punch for my taste, but the new battery should be here before Christmas.

A note on balancing: I initially set this one up at about 14 - 5/8" forward of the elevon hinge line. After trimming for level flight, this CG causes it to assume an idle power, nose up glide all by itself, indicating that it's a bit tail heavy. I've moved the battery pack about a half inch forward so that the CG is now 14- 3/4" in front of the elevon hinge line. Haven't tested it, yet, as the snow melted away and the lake is all thin ice.

Also, I noticed during all my TOs from snow (at least 9) that she wanted to drop the right wing on initial acceleration, and I'd have to pick it up with a little aileron. I checked the left right balance this morning, and it was definitely heavy on the right side, due to the right wing panel weighing about 2 oz more than the left. I put 1/2 oz on the left wing tip to correct this, before I redid the CG. The trick to determine L/R balance with an Arrow is to put a bubble gauge on the deck, then pick the airplane up by the propeller/spinner only, so that it will assume its balanced state. This would probably work for the Northstar, as well.

This is something I noticed about the glow Arrow: due to the high mounted engine, torque effect is non existent, and the airplane wants to be perfectly balanced left to right or it will drop a wing tip when it can cause the most trouble, TO or touchdown.

Mustang Fever

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The 5 cell 3000 pack arrived today, and what a difference 4 or so more volts makes!

The numbers are, with an 11x7 APC E prop: 11,250RPM 75MPH 5.5# 1.028HP 46A 900W 138W/pound

The thrust and Horsepower numbers are from Thrust HP software, which seems to be quite a bit conservative, so I'm estimating well over 6 pounds of thrust, which is supported by the Watts number.

Can't wait to fly it again. If I can get down to the club field early enough tomorrow, I'll be able to, but the winds are going to pick up later.

N1EDM

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I hope that it stays calm for you, Bob, but we can wait if the wx looks iffy.

My plans from RCM arrived yesterday. I have some other items to work on first, but I'm gleaning a lot of info and tips from this thread. Thanks for showing this to us!

Merry Christmas,

Bob

Mustang Fever

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Back at ya, Bob.

The lake is pretty well frozen, now, and as long as there's enough snow on it, I think I can get down there before the wind gets goofy. (It's about 2 miles from where I live.)

I wouldn't want to walk out on it, but that's why aircraft taxiing was invented.

Mustang Fever

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Well, I'm really glad I went down to the club field, instead of trying to fly off the lake. The motor packed up right after landing. That's it for Great Planes motors. They absolutely will not do what it says on their spec sheets. I wonder what would have happened to it had I attempted to go into the "burst" watts region- would it have caught fire?

I getting a Turnigy 46 replace it.

Mustang Fever

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It took 16 days for the Turnigy 46 to get here from China. Not too shabby.

It wails: It's turning an 11x7 MAS 3 blade at around 11,000 RPM. Right around 700W, 7 pounds of thrust, and over 70mph. All at only 38 amps on a 5S pack. It doesn't even get warm. I'm sold on Turnigy products- I've got packs and a motor so far. I'll probably start buying their ESCs, as the ones available from Tower are very pricey.

The airplane is really fun to fly, now. I landed in a tree at the end of the last flight, but that's another story. (Very little damage. She's RTF again.)

I do have egg on my face over extending the skeg and rudder. On ice, she couldn't rotate enough to take off. I reduced the skeg/rudder length to about 1- 1/4" below the stern, and that cured that.