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Hello! Explorer build

#1
Just saying hello, first post. Finishing an Explorer.

It's the water-resistant type. Everything is built, I'm painting now. Krylon primer seems to stick well after some light sanding with #320. It does take several coats and a few spraycans to defeat the brown paper. Will finish with a semi-gloss. Eventually, I'll probably get an airbrush so I can customize paintjobs, but I'll hold off until I after I discover how crashy I am.

I've been seeing on youtube, and reading here, that the wing tends to fold up if not flown gently. I used a tip given here and added carbon fiber arrow shafts to the wing structure. I worked out a process for doing this that made it fairly easy.

Does anyone happen to know if there is a way to unwrinkle the paper? I suspect not, but it would be neat if it turned out that there was some magic method, say, spraying on alcohol and hitting with a clothes iron while thinking good thoughts magically removed them or something.
 

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#2
Finished. With the sport wing, it's much too tail-heavy to balance on the dots even with a 2200mAh battery all the way to the front. I shoved the tail boom in an extra couple of inches, which helped, but not enough.

It took 5 cans of spraypaint to cover the brown paper.. much of which went into the breeze anyway as I had to paint outside.. but I can't imagine a uniform paintjob could cause it to be this tail-heavy.

My carbon fiber arrow reinforcement added maybe an ounce including the glue, and right up against the back of the spar I don't think it could affect CG that much by itself. Knowing what I do now, I think I'd try to put it in front of the spar next time.

I can add a larger battery and a small camera.. but i suspect the CG will be too low for the thrust angle. I'll hang it up tonight and find out where the true CG currently is.
 

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buzzbomb

I know nothing!
#3
I'm sorry I can't answer your questions. I am a complete newb at all this. I'm just chiming in to say that's a really good looking build. That's almost Bixler level.
 

ElectriSean

Eternal Student
Mentor
#4
I think the batteries they used in that build video were really heavy, I always had to add a bunch of nose weight to get mine to balance. It flies well though. Nice build :)
 
#5
I'm sorry I can't answer your questions. I am a complete newb at all this. I'm just chiming in to say that's a really good looking build. That's almost Bixler level.
Thank you! Paint does a lot for the appearance. The process was all fun, too. I haven't even flown this one yet, and I'm already trying to decide on my next one.
 
#6
I think the batteries they used in that build video were really heavy, I always had to add a bunch of nose weight to get mine to balance. It flies well though. Nice build :)
That makes me feel better. Right now I don't have any way to weigh the plane accurately. I'm hoping to find a (cheap) several-kilogram scale with single-gram precision. Doesn't have to be NIST or anything, I just want it to give relative weight for making adjustments and determining the impact of glue, paint, paper, etc. Hanging scale? Countertop? Not sure.
 

Seahunter

Active member
#7
Finished. With the sport wing, it's much too tail-heavy to balance on the dots even with a 2200mAh battery all the way to the front. I shoved the tail boom in an extra couple of inches, which helped, but not enough.

It took 5 cans of spraypaint to cover the brown paper.. much of which went into the breeze anyway as I had to paint outside.. but I can't imagine a uniform paintjob could cause it to be this tail-heavy.

My carbon fiber arrow reinforcement added maybe an ounce including the glue, and right up against the back of the spar I don't think it could affect CG that much by itself. Knowing what I do now, I think I'd try to put it in front of the spar next time.

I can add a larger battery and a small camera.. but i suspect the CG will be too low for the thrust angle. I'll hang it up tonight and find out where the true CG currently is.
Mine also came out tail heavy using a 2200mah. I got a tub of the kids Crayola air dry modeling clay at wally world and use that inside the nose to balance it, after I get the CG right I cover the clay with packing tape to prevent it coming loose and causing a horrible accident! Most of my paint jobs were only two coats, so at five you must be doing a very light spray, that's the right way, just seems to take more paint. Would love to see pictures of your carbon arrow spar method on your next build. Nice work!
 
#8
I typically fly my Explorer with a 2800mah, that could be why I've never ran into a problem getting it to balance.
I did find that my Bronco was quite nose heavy, I had to put the battery uncomfortably far back into the fuselage. My solution to that was create new skewer wing mounting holes further forward so the fuse mounted further back. Now to get the plane nicely balanced, the battery is in a more normal position. Maybe moving the wing position is an option for you?
 

Chappie66

Active member
#9
Mine also came out very tail heavy even using a 2700mAh battery pushed as far forward as possible. I added lead weight inside the nose piece to get it to balance.

Your build is awesome...

Mine always wanted to plant itself in the dirt when hand launching and required a fair amount of up elevator to compensate while it built air speed.
 
#10
I wish I had taken photos of the process I used with the arrows. If I do anything similar I will be sure to document it that way.

An idea about balancing weight on the nose - obviously extend the nose so you don't need to add as much, but you could achieve the same thing with a weight at the end of a wooden skewer projecting from the front so you don't need to add as much total weight. You could also mount this higher up, say from the top of the wing, to bring the CG up a bit and more in line with the thrust angle. Of course, you need to be careful you haven't made a flying javelin :)

Could also cut holes in the longeron structure back near the tailplane to shave some grams.
 
#11
Got to fly it yesterday at a local field, tested both wings. Some notes:

My Explorer was significantly overweight. Weight without battery was 684g, while spec is 493g. My non-standard accessories included in this weight were the carbon fiber wing reinforcement (28g,) an external SBEC (13g,) and 4 or 5 cans of Krylon spray paint. The paint must have been the major contributor here.

I ended up having to add 60g to the nose to get CG to line up, for an AUW with battery of 915g, spec is 683g.

Wing loading is supposed to be 23 g/dm2, mine is 31 (10.1 oz/ft2.)

That is super porky, and while it still flew well on the 3ch wing - it had plenty of power to climb at 50° indefinitely - the sport wing was where the weight was really felt. It took a lot more throttle and most of my available elevator trim to stay level in cruise. When the low-voltage-cutoff kicked in and cut my power to 30 percent, I made an error in judgment by setting my flaperons full down for landing. It did not have enough power to stay afloat and dropped below the horizon short of the runway. This was pretty dumb on my part, because I was approaching a hilltop landing into a headwind at low groundspeed and didn't need flaperons at all. The downdraft coming over the hilltop sucked it in and beached it down the hillside out of my view. However, it was apparently a gentle nose-in as there was absolutely no damage. My motor was still spinning, dragging my battery down into the danger zone.

Some notes for myself:
- Set up failsafe to set throttle to zero so it shuts down in case I lose line-of-sight again. My field is at the top of a hill, so any crash will be NLOS.

- I have two settings for flaperons, weighted 25 and 50. The 50 setting is way too much (it's about equal to the full 12-degree aileron limit) and slams the brakes on pretty hard. I'll reduce the range on these.

- There was a ton of tail authority, even though I doublechecked the CG before flight. Very pitch sensitive. I ended up changing elevator expo from 30 to 40 to get it more managable. My first step toward putting this thing on a diet will be to shove the tail boom further into the core so I can dump some of the lead out of the nose; it just doesn't need that much tail.

- My second step will be to extend the nose a couple inches, as I've seen someone else do, so I can move my battery forward and dump yet more lead.

- I wish I had put my wing spar reinforcements either in the spar, or just in front instead of just behind. That would have helped a bit with respect to the tail-heaviness.

- For my next build, find some light alternative to spraypaint. Someone said airbrushed ink? That brown though is hard to keep down.

- Total success on the wing reinforcement. I did some hard high-speed loops with both wings. All good!

All in all, an exciting first flight for me. Despite my inexperience, I had little trouble flying and landing except for that last episode. I'd like to thank the San Diego Wingmasters for welcoming me in at their airfield, and for their help and guidance. I'll be back next weekend!
 
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#12
Another note.. launch this one at 50% throttle, not full. One of my three launches I tried at full-throttle, and it nearly got shoved into the ground.
 
#14
@rmzalbar , I had a heck of a time launching pushers until I saw this video:
Heh, I just happened to see that video this morning. Very helpful. I knew it might be an issue yesterday, because I located the vertical CG with a plumb-bob and saw it was well below the thrust line, so I was careful at first, but for #3 I just had to see so I nailed it just after release. That video made me feel better about the high thrust line, as far as the Explorer isn't unique in this and there is probably a valid reason not to have it lined up. Efficiency?

Club members were kind enough to do all of my tossing for me.
 
#15
I've managed to rip both wings in half in crashes and then glued them back together, so the Explorer is still kicking, and I took care of the tail-heavy problem for good my extending the nose 3 inches, enabling me to get rid of my fishing weights and giving more room for cameras and such.

I just finished a Mighty Mini Fokker Dr.I. This is a very nicely detailed little plane, and very satisfying to hold and look at when complete. A bit of a challenging build with regards to making sure everything is straight. Definitely make sure you "look ahead" in the build video before gluing things up. I got burned when I installed the landing gear bent to the wrong angle before I realized the axle skirt needs to fit between them, then creased my undercarriage and dented the underside of my wings with my stupid thumbs trying to fix it in-situ. Well, I can always make new undercarriage struts to replace the rumpled ones before I paint. But before I paint, I'm going to make sure it flies tomorrow.

I ironed the leading edges of the airfoils to round and seal them. Very pleasing result there, but I also did it to the side-facing edges, and kind of wish I hadn't done those because made it look somehow less appealing to me.

EDIT: Not today, neighbors across the street are having their roof replaced apparently, so the entire street is filled with ladder trucks beeping back and forth and a bunch of guys hollering at each other while clanking stacks of terra cotta roof tiles around. So I drove in to the office to work in (relative) peace. Maybe I'll give it a quick buzz early in the morning before I head to work.
 

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#16
I used a heat pencil to loosen and reposition some glued seams, and unfortunately melted the foam under the paper in a few areas, resulting in sunken areas under crackly unsupported paper. I'm wondering if it's possible to carefully peel the paper back, replace the damaged foam sections, and then glue the paper carefully back down so there's no break in the finish? I'll try a small section tonight.
 

buzzbomb

I know nothing!
#17
I used a heat pencil to loosen and reposition some glued seams, and unfortunately melted the foam under the paper in a few areas, resulting in sunken areas under crackly unsupported paper. I'm wondering if it's possible to carefully peel the paper back, replace the damaged foam sections, and then glue the paper carefully back down so there's no break in the finish? I'll try a small section tonight.
I "liked" that post, because honestly I haven't a clue, but I'd do the same. Just give it your best shot, and see if it works. Please let us know.
 

Headbang

Master member
#18
My Explorer came in at 750g with a 2200mAh 3s. I built it with gorilla glue, and air brushed with cheap Walmart acrylic craft paint after a coat of minwax. I would imagine hot glue would have added another 100g to 150g. The light paint and light glue could be why mine balance perfectly. I reinforced the wing using packing tape after painting. Few strips on top and bottom the span of the wing.
 
#20
I've managed to rip both wings in half in crashes and then glued them back together, so the Explorer is still kicking, and I took care of the tail-heavy problem for good my extending the nose 3 inches, enabling me to get rid of my fishing weights and giving more room for cameras and such.

I just finished a Mighty Mini Fokker Dr.I. This is a very nicely detailed little plane, and very satisfying to hold and look at when complete. A bit of a challenging build with regards to making sure everything is straight. Definitely make sure you "look ahead" in the build video before gluing things up. I got burned when I installed the landing gear bent to the wrong angle before I realized the axle skirt needs to fit between them, then creased my undercarriage and dented the underside of my wings with my stupid thumbs trying to fix it in-situ. Well, I can always make new undercarriage struts to replace the rumpled ones before I paint. But before I paint, I'm going to make sure it flies tomorrow.

I ironed the leading edges of the airfoils to round and seal them. Very pleasing result there, but I also did it to the side-facing edges, and kind of wish I hadn't done those because made it look somehow less appealing to me.

EDIT: Not today, neighbors across the street are having their roof replaced apparently, so the entire street is filled with ladder trucks beeping back and forth and a bunch of guys hollering at each other while clanking stacks of terra cotta roof tiles around. So I drove in to the office to work in (relative) peace. Maybe I'll give it a quick buzz early in the morning before I head to work.
This little bugger ran off the bench at full throttle while I was programming the ESC and gashed the hell out of my hand. I must have read "leave the propeller off while setting it up, for reals moron" 30 times, so I knew better. Sitting in the ER right now waiting for my ride back home.