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Sep 02, 2019, 11:03 AM
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Build Log

AVRO Arrow, the third.


This will be the third Arrow build, the first 64mm fan version is grounded awaiting a new fan. The second had twin 70mms, 48" span: it was big, beautiful, and perhaps my finest build in 30 odd years. But it was under powered, and on it's second flight, a stall sent it into the ground hard, rookie mistake. Worst of all the plane wasn't mine, it was a gift for a friend and I was working the bugs out of it.





https://www.rcgroups.com/forums/show...wo-Avro-Arrows

Arrow number three replaces that aircraft. It will not be as monumental, we want to have it flying before the snow hits, but it is a fair size, 35" span, built lighter with a single 80mm fan. It will not be under powered.




AVRO ARROW.
35" span.
55" long.
Weight unknown, guessing about 3 pounds AUW
Fan: 80mm, 11 Blades.
Construction: plastic covering over foam.
Five channel with retracts.
Last edited by foamnpacktape; Sep 09, 2019 at 10:30 AM.
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Sep 02, 2019, 11:04 AM
Build it, don't buy it
foamnpacktape's Avatar
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The Build,
Won't be as thorough as other build logs, but I will provide the highlights.

Sept 2, Five hours,
Wings are cut, leading edges glued on. Fuse slabs are cut and I have begun shaping them. Will update with pictures tomorrow.
Another 4 hours, Wing pieces all glued together, elevons cut and sanded. Currently working on the wing saddles.

Sept 9, 20 hours,
Wing saddles cut from wing cutting discards and glued into fuse sides. Fuse glued together, intakes and exhaust ducting begun. Exhaust nozzles cut out with outlet at 90 FSA. Nose roughed out.
Basic soft outline of the aircraft is complete except for the canopy and top fairing.

Sept 15, 20 hours,
Nozzles attached, fan mount and most of ducting completed. Cut out canopy and fairing, and built the vertical stab. Inlets reinforced with balsa and sanded to shape. Slot cut into wing that will contain battery and electronic components.
All airframe components are completely cut out, hard points, spars, electronics, and finishing remain.

Sept 16, 2 hours.
Some more filling and sanding. Began building battery/electronics compartment into fuse. Sides glued in place and top of tray finished.

Sept 20, 5 hours.
Finished up bottom of equipment tray, glue ducting pieces in place, shape nose where it goes into fuse. Build in hard points to attach rear wing bolts. Glue sides onto vertical stab, shape to meet upper fairing, and adjust sweep.

Sept 23, 8 hours,
Installed wing dowel hold downs at front of wing, and reinforced rear section for wing bolts. Bored a hole to the rear of the wing for the motor wires. Installed spars in the wing, and did some work on the wing saddle for a good fit. Took care of a few small details with the intakes and blended them into the fuse.
Abandoned retracts, not enough pros, too many cons. This simplifies things, and should cut a week or two from the build. By going with a fall away dolly for takeoffs, the flying weight will be around four pounds rather than over five, which is significant, and the drag reduction will also result in a better flying aircraft.

Sept 25, 4 hours,
Finished up wing spars, filled and sanded them to conform to wing contours. Cut servo bays, and conduits to equipment tray. Worked a bit on fallaway takeoff dolly, mostly figuring out breakawy servo connection, will be using small magnets with wires soldered to each one. This should provide a solid electrical interface with dolly servo, yet come apart relatively easily once the dolly and aircraft part company.

Oct 1, 12 hours.
Been a little remiss in posting my progress, jumping ahead a bit, time estimate is very conservative but close.
Magnet connection did not work out, kept losing contact, have replace that with three spring loaded contacts and three strips of copper as the interface, it seems to be working alright. Airframe is complete, bare without covering came in at 15.5 ozs. Began covering last night and got the bit of the fuselage done before I ran out of white, hoping one roll will be enough to finish the plane but it is going to be close.

Oct 7, 22 hours
Covering is done, radio and fan installed, Balance point determined, and came out within a quarter inch with no weight added. Saturday and Sunday morning I worked on it every waking hour to have it ready for Maiden. Brought it out to the field and had it on standby while hoping for the gusty conditions to subside but they never did, Maiden pending..
Last edited by foamnpacktape; Oct 07, 2019 at 08:48 AM.
Sep 02, 2019, 11:05 AM
Build it, don't buy it
foamnpacktape's Avatar
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99 hours,
100 bucks into the airframe, but 1/2 of that was already on hand. This does not include electronics.
Airframe, 21 ozs,
AUW, 68 ozs.

Maiden pending.

This is turning out to be a relatively quick build should come in at around 80 hours which is a far cry from the 250 hours I had into the last one. Not as much thinking involved after finishing two in the last year already, practice doesn't make perfect but it sure saves time.

I have a set of retracts for it, as it is being built for Adrian, and we often argue about the merits of retracts over hand or dolly launch. Might have to have that discussion again, I hate adding the weight, complexity and fragility (The mains will be very long to get below that fuse hanging under the wing) of retracts for a a few seconds on the ground for takeoff and landing.

Had the discussion about retracts again, but didn't put up much of an argument, it gets retracts. I suppose I should have one plane with retracts in my portfolio anyway, and get that off my bucket list.

Having issues with the retracts. shape of the wing and the long length of the struts, put them in a position 2-3" behind the center of gravity, which will likely impeded rotation on take off. Also would benefit from a shorter front strut, as the one I have is twice as long as required.

Had the retract discussion with Adrian, just shared the issues I was having and he suggested going to a fall away dolly like we did with the last one. This is ideal, I didn't want to broach the subject. This build just got easier, and the end result will be a better airplane.
Last edited by foamnpacktape; Oct 07, 2019 at 08:51 AM.
Sep 02, 2019, 03:10 PM
Really?
dll932's Avatar
Looks great!
Sep 06, 2019, 09:46 AM
Build it, don't buy it
foamnpacktape's Avatar
Thread OP
Quote:
Originally Posted by dll932
Looks great!
Correction: looked great, not so much anymore.
Sep 13, 2019, 08:30 PM
Really?
dll932's Avatar
Quote:
Originally Posted by foamnpacktape
Correction: looked great, not so much anymore.
Ouch! What happened?
Sep 16, 2019, 08:30 AM
Build it, don't buy it
foamnpacktape's Avatar
Thread OP
Quote:
Originally Posted by dll932
Ouch! What happened?
Although nose heavy, and underpowered, after using the length of the entire runway, the maiden was uneventful. Brought it down, added some weight to the tail, greased the wheels, and the next takeoff was much better.
Ended up stalling it about 75' up, rookie mistake, not enough time to recover before she lawn darted. Could have been rebuilt, I have fixed worse, but decided to make a clean start.
Sep 16, 2019, 05:56 PM
Really?
dll932's Avatar
Quote:
Originally Posted by foamnpacktape
Although nose heavy, and underpowered, after using the length of the entire runway, the maiden was uneventful. Brought it down, added some weight to the tail, greased the wheels, and the next takeoff was much better.
Ended up stalling it about 75' up, rookie mistake, not enough time to recover before she lawn darted. Could have been rebuilt, I have fixed worse, but decided to make a clean start.
Ah well, I wish you success next time.
Sep 17, 2019, 08:30 AM
Build it, don't buy it
foamnpacktape's Avatar
Thread OP
Thanks,
It wouldn't be so bad if the plane didn't fly well, or some mechanical/electrical gremlin took it down, but pilot error.... especially with so much time and money invested, is hard to take.
But, it did survive maiden, so there is that.
Sep 19, 2019, 06:02 PM
Really?
dll932's Avatar
Quote:
Originally Posted by foamnpacktape
Thanks,
It wouldn't be so bad if the plane didn't fly well, or some mechanical/electrical gremlin took it down, but pilot error.... especially with so much time and money invested, is hard to take.
But, it did survive maiden, so there is that.
Been there a few times.
Sep 21, 2019, 05:20 PM
Onward and Upward.
CatManDu's Avatar
Any news?
Sep 23, 2019, 09:22 AM
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foamnpacktape's Avatar
Thread OP
Just a note, I often update the 2nd post build log without commenting and giving the thread a bump.

Build is progressing quickly, which is good because winter is coming, we have snow forecast for the end of the week. but we should still get a few nice flying days before winter sets in completely.

I have most of the airframe complete now, only a few details to take care of, should be able to get enough accomplished this week to begin covering on Saturday, and maybe get the electronics installed. Maiden next Sunday is possible, but probably overly optimistic.

Spent last Saturday, trying to get the retract issues sorted, and they have been abandoned. With the shape of the wing, the mains would have to be well back of the center of gravity, causing issues on rotation at take off. Further, one gets extra drag, and they will add at least a pound to a 4lb aircraft. Instead, I will set it up with a fallaway dolly for takeoff and belly landings. This will save at least a week of build time.

Did some adjustments to the CoG and lateral balance on my first Arrow, the 64mm fan version. With a few clicks of trim, it is flying rock solid, and bodes well for this Arrow's maiden.
Sep 25, 2019, 09:09 AM
Build it, don't buy it
foamnpacktape's Avatar
Thread OP
Anticipation is killing me, all the pieces are now cut out and the airframe almost complete. Should be able to finish up the construction by Saturday, and then spend most of the day filling and sanding to prep for the covering, might even get most of that done. Then all that remains is to install the electronics, the fallaway takeoff dolly components, and the graphics. Might even have Sunday available to work on it as we are expecting snow this weekend and our Sunday fly day might be better relegated to a build day.

Maiden is only a couple of weeks away, unfortunately they are cutting power to one of my buildings on the 6th, hopefully it will not last the allotted time, 8hrs, and I can get out to Adrian's for the maiden.

Build will come in under 100 hours, less than half the time of the previous Arrow.
Sep 30, 2019, 11:57 AM
Build it, don't buy it
foamnpacktape's Avatar
Thread OP
Airframe is complete, 15.5 ozs without covering.
Had time to work on it quite a bit over the weekend. Not a lot else to do, unless you like shoveling.

There is over a foot of snow in my backyard.

Spent too much time trying to come up with a break away connector for the steering servo on the fall away dolly. Tried using 3 small magnets with a wire soldered to them, and a steel contact in the dolly for each one. Should have worked well but had a difficult time maintaining a connection to the chrome on the magnet. Eventually gave up, and late last night broke up a few old relays and made up a pad with three strips of copper on the plane I will add three spring loaded points on the dolly to contact and that should solve the issue (fingers crossed).
Will do that tonight then tomorrow should begin the final filling and sanding, and cover as I go. Still hoping for a maiden next Sunday.
Sep 30, 2019, 06:10 PM
Registered User
KarlHeinz57's Avatar
I had done something similar in the past with my Horton 229 and its dolly.

I mounted on the airframe the female end of a servo extension so its opening was pointing down with the bottom of the model/wing. Then on the dolly I carved away some of the material from the steering servo's male connector so that it would slide out of the female end with just a little tug.

I left a bit of slack on the servo end so the connection would remain even if the model shifted on the dolly as it was apt to do. Once the Horton lifted free of the dolly, the male end of the steering servo cleanly disconnected from the female end on the bottom of the wing and it was smooth sailing from there.

Perhaps I've just described what you're creating but I thought it was worth adding.


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