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Old Oct 31, 2014, 09:26 AM
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Build Log
Fly Fly DG 808 4K

I started "building" this ARF a few weeks ago. I actually posted some pics on someone discussion thread but felt like I was intruding, so I will start a short build thread for anyone interested in this Chinese ARF.

There are quite a few posts here regarding this a/c. I will not bore the masses on what has been done before or with anything but what I have changed. All of these changes come from the suggestions of the great folks here who have taken the time to post their experiences and what has worked for them.

To start, I hate ARFs. I know, that sounds ridiculous because I bought one but its true. I bought this thing with the intention of making changes.

I hate iron on film. I removed all the covering the first day. Good news! The wood beneath was actually very nice quality and very nice lite balsa. The glue work and sheeting was nice quality as well.

I do not like the method of attaching the outer wing panels so I made a small carbon block and permanently glued the outer wing sections on. Also plan to do this with the winglets.

I went lazy and decided not to build a new stab. I did re-profile the tips of the stab, and tapered them to a thinner section at the tips. I also drilled some lightning holes in the large 1/8 thick ply sheet that is used to attach to the fin. All this trimmed a bit of weight.

I added some carbon tow, epoxied down and filled a little with balsa right.

more pics coming on re-hinging the flaps so they go down properly, and allowing for their use to help the minimal ailerons by traveling up a bit.

Neal
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Old Oct 31, 2014, 09:57 AM
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I don't like the monocote type hinges, and as others have noted the method on this glider only allowed for about 30 to 40 degrees of flap movement.

I made a gap seal out of 1/64 ply in a fashion as follows. Sand a small bevel into the balsa at the trailing edge of the wing with a tool like this:

Hmmm.... I have to figure out how to add descriptions to each picture?? I am computer challenged.

Well hopefully these pictures are self explanatory.

The 1/64 ply is sheared to size. I fit the aileron using Robart pin hinges and measure the gap when the aileron/flap is at full deflection. This was about 1/4 inch beyond the trailing edge. I allowed about 3/16 for glue area.

You can see from the pics that the flap is traveling close to 90. I do not believe anything is gained in going all the way to 90, but a bunch of travel will certainly help. You can also see that the aileron can travel up and with full flaps and some crow this thing ought to drop with authority.

I do not like thin balsa trailing edges. I am a clutz and will ding and damage anything fragile. On my larger warbirds I always CA a thin strip of carbon rod to the trailing edge before glass. This can be done quickly in one piece, does not add any measurable weight and makes the thin edge very durable and straight.

I am currently rolling on a coat of fast dry prime and will sand most off. Followed by PPG base clear. I am really trying to keep the finish light. We will see.

I have to take some pics of the stab and start on the fuse.

More to come.

Neal
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Old Nov 07, 2014, 11:10 AM
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Wings are done and made the cut on the nose for the motor!

If anyone cares, the wings are glassed with 3/4 oz glass with west systems very sparingly applied. A single stage high build primer and one coat of PPG ice white base coat and a thin clear. I am sure this will end up weighing a bit more than the plastic film but we will see what the all up weight will be. It took a couple full days to paint these wings. The outer panels and the winglets are permanently glued and faired in.

I hinged the flight controls with 1/8 Robart pin hinges, with the hinge line slightly inset on the flight control. This gives a tight gap and still allows the flaps to go down enough, and also up to aid the ailerons.

It took me a while to configure my Futaba 12fg using "camber" to slave the flaps with the ailerons. You can adjust this onto a switch if you don't want it full time, and you can adjust how must throw you want, depending on how she rolls. I have heard that the ailerons are a bit anemic so I have the flaps traveling about the same as the ailerons right now. This makes for an almost full span aileron and should be more than adequate.

Of course the flaps still work on a slider switch just as flaps alone, but when the flaps are down they will still move as ailerons. We will see how this all works in the air.

I am hoping that by putting the motor up front it will not need nose weight and I will still be in good shape for an over all weight.

No science to the cut in the nose. I just went at it with my dremmel. It appears to me that if placed directly on the nose, the motor will end up slightly below the wing chord line and therefore might end up giving the model a bit of a pitch up with power. I intend a to align the motor so that the thrust line is slightly down. Looks like it only needs a couple degrees.

I am doing the engine mount today so will post more.

Neal
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Old Nov 08, 2014, 12:14 PM
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motor is in! I used a Hyperion motor with the optional rear mount support. I just thought that this looked pretty sturdy and as this motor is 290 grams the thought of it hanging off the firewall made me nervous.

I am probably doing my normal overbuilding here, but most folks here are adding weight in the nose anyway, so at least this weight is doing something.

One thing has me confused about these Hyperion products. They appear to be very high quality and this motor is beautiful. It was only 60 bucks on "clearance". I just checked a few sites and found that the price of this motor in the 1200 kv version is now marked down from 199$ to 17$. Yes, that says 17US$ as in seventeen dollars!! The ESCs are ridiculously cheap right now on closeout. What am I missing? Are these unreliable? This is the 3032 version and it fits real nice in this model. I hope its not a boat anchor!

OH, I ended up using G10 instead of plywood for the mount. You really need to drill cooling holes in the front mount to get air through the motor. I have bought another spinner that allows air to enter the front and travel through the motor and out the back. The holes end up making some fairly thin areas on the small mounting plates and I thought I needed the extra strength from the G10. I know, its heavy. Seems to be a theme here.

I have not figured out how to cool the ESC yet. Ideas??

Pics:
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Old Nov 08, 2014, 04:04 PM
The Fixer
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Well done.
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Old Nov 19, 2014, 04:13 PM
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Finished and flown!

I did the maiden flight today on the FlyFly DG808. As pictured above I have the engine cut in the nose. It is a Hyperion 3032-08. I am running a 4 cell 4000mah battery with a separate 1300 mah for the radio.

I am charging the battery for the first time right now so I will report back how much run time I got. I flew it for about ten minutes with three climbs to altitude.

To be honest.....I tried last night to fly it and ended up breaking my 14 -7 CAM folding prop. I launched it myself and was not ready for the left roll. It ended up doing a nice chandelle with a fairly smooth belly landing. Only damage was the prop.

I only had a 13 -8 prop left and thought this was a little small. When I run it through this static thrust calculator http://personal.osi.hu/fuzesisz/strc_eng/ I was a bit worried as it does not have near the thrust of the longer blades but decided to try anyway. IF you keep it fairly flat, add right rudder for the launch and a bit of right aileron trim it flew out just fine. I will post video when I pry it out of my wifes' phone.

I have ordered a 15-8 and think that will be perfect. The model had plenty of power but since it is heavy (I will weigh it today also) the hand launch requires a pretty substantial acceleration as you do not have altitude to trade. Even with the 13-8 prop and about 5 kts of wind it did just fine. Just don't throw it 'UP". Nice and level until you have a little speed. We will see how the longer prop does.

The air was flat so I did not get to do much soaring. Had a couple real light thermals but not enough for this model. I built it too heavy.

Can I get away with a smaller battery? (smaller than 4000mah) Do I need to go to more than 40C to get more power? I am not sure I can push more than a 4 cell through this set up but I am new to electric so I am really not sure. I have a hyperion 90amp esc that appears pretty heavy duty. Any tips here to lighten the airplane a bit would be appreciated.

OH, I cannibalized my kids Mickey Mouse toy for this model. BUT, being the good father that I am, I switched their Micky Mouse the pilot toy, for the toy in the last picture. It is the new Micky Mouse the mechanic toy! Perfect!

Enough babbleing. Pics.
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Old Nov 19, 2014, 04:39 PM
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correction. I am using 3000mah 4c batteries. My first flight was 3 climbs plus the launch and it is out on the bench right now charging past 2500mah!!? Yikes....
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Old Nov 20, 2014, 02:23 AM
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Quote:
Originally Posted by cabinwacoman View Post
Finished and flown!

I did the maiden flight today on the FlyFly DG808. As pictured above I have the engine cut in the nose. It is a Hyperion 3032-08. I am running a 4 cell 4000mah battery with a separate 1300 mah for the radio.

I am charging the battery for the first time right now so I will report back how much run time I got. I flew it for about ten minutes with three climbs to altitude.

To be honest.....I tried last night to fly it and ended up breaking my 14 -7 CAM folding prop. I launched it myself and was not ready for the left roll. It ended up doing a nice chandelle with a fairly smooth belly landing. Only damage was the prop.

I only had a 13 -8 prop left and thought this was a little small. When I run it through this static thrust calculator http://personal.osi.hu/fuzesisz/strc_eng/ I was a bit worried as it does not have near the thrust of the longer blades but decided to try anyway. IF you keep it fairly flat, add right rudder for the launch and a bit of right aileron trim it flew out just fine. I will post video when I pry it out of my wifes' phone.

I have ordered a 15-8 and think that will be perfect. The model had plenty of power but since it is heavy (I will weigh it today also) the hand launch requires a pretty substantial acceleration as you do not have altitude to trade. Even with the 13-8 prop and about 5 kts of wind it did just fine. Just don't throw it 'UP". Nice and level until you have a little speed. We will see how the longer prop does.

The air was flat so I did not get to do much soaring. Had a couple real light thermals but not enough for this model. I built it too heavy.

Can I get away with a smaller battery? (smaller than 4000mah) Do I need to go to more than 40C to get more power? I am not sure I can push more than a 4 cell through this set up but I am new to electric so I am really not sure. I have a hyperion 90amp esc that appears pretty heavy duty. Any tips here to lighten the airplane a bit would be appreciated.

OH, I cannibalized my kids Mickey Mouse toy for this model. BUT, being the good father that I am, I switched their Micky Mouse the pilot toy, for the toy in the last picture. It is the new Micky Mouse the mechanic toy! Perfect!

Enough babbleing. Pics.
If you can use a 5s lipo (less mah)that is approx the same weight as your 4s lipo,and build a new lightweight tailplane,you will have alot more thrust.I run my reichard nimbus 3.6 metre on 5s/3200 mah 35c lipo/100 amp esc, with plenty of power to spare,although its only 3.1 kg versus 3.8kg plus for the dg808s.Just make sure 5s is okay for your hyperion motor,as it might not be.
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Old Nov 20, 2014, 03:11 PM
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From looking at some of the CAM prop data and info on this motor, I think the motor would be fine, but at 700 rpm/volt it appears that it might exceed the max rpm of these props. CAM is showing a max of 9000 rpm for the 15 inch props. From their data the 4cell is supposed to turn the 15/8 up to 7885. I guess I could put a tach on it with the 5c and see if it goes above 9k. I would sure hate to shed a blade at that rpm.
I am thinking the 15 might do just fine on the 4c. I will do some more tests. It was actually fair with the 13x8, but just don't throw it too steep. I flew again last night and got a bad launch. Now I have to do some repairs to a wing root. Bummer. Should have had patience and waited for the new prop.
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Old Nov 20, 2014, 04:04 PM
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so. cal.
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The chord (thickness) of the aileron at the outermost point looks to be close to 40% of the wing, take a look at the fullsize DG or any glass model out of Germany/Euro, Fly Fly took some big time liberties with proportions. Oh well, as long as it flies.....
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Old Nov 20, 2014, 10:49 PM
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Yes I agree. This is not a scale a/c. It is scaleish, but really not close. I just repaired a little wing root rash that was caused by myself not being patient enough to wait for the correct prop for hand launching this thing.
I discovered inside the wing that this is definitely a Chinese quicky arf. There is hardly any glue in there. The whole wing frame is really poor quality three ply-plywood. Heavy and not strong. The wing tube ends right at the end of the wing rod and then from there outward there is a fairly heavy spar box, but NO overlap. SO when, I rolled to a stop after my failed hand launch the nose hit a hay bale. The right wing decided to keep moving and the wing broke right where the rod ends and the spar box starts . Big surprise.
It was an easy fix and I used same balsa core carbon sheet to bridge two bays where the wing tube ends. This will be on one wing only unless I tear the other undamaged wing apart, and I won't .
I do believe it is strong enough as built/designed but if I was going to aero tow, or do a lot of acro I would remove the covering and put some carbon tow down on the top and bottom skins. As a minimum.
Mine should be up and running again in a day or two. With my new 15-8 prop I will be getting around 900 watts and that should solve my anemic hand launch performance.
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Old Dec 05, 2014, 08:40 PM
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Ever have one of those great motivating flying days? Today was a great day for the DG 808 from fly fly. The jury has been out for me on this model. As you will see here when I post some pics of my latest repair, the quality of this ARF is fair. Not bad but fair. It has an issue with its application here in flat land USA where there are no slopes, and I do not have a tow pilot.

The pod mounted motor limits the size of prop that is usable, and the nose mounted engine limits our launch choices. I have found it difficult at best to hand launch this thing. Turns out a simple dolly works great!

My motivation came from a 30 minute flight today on a single 3000mah battery. I get 2.0 minutes of full throttle on this battery. I am putting a little over 2k back into the battery so I have a little room but not much.

Let me post some pics of my repair and then I will come back and post a video of my successful dolly launch and my long soaring flight. Turns out we had a warm day today in TX and I ended up following a large group of buzzards from thermal to thermal. Those guys are smart lift sniffers. I had to land to pick up my kids from school or I could have stayed up all day! What fun.

A few weeks ago I had an unsuccessful hand launch and ended up rolling into a hay bale on landing. Snapped the right wing root clean off. Here are some UGLY pics.

Inside this wing is some poor quality plywood making up the ribs and spars. The spar caps appear to be birch or something. Not spruce anyway. The spar tube ends and there is a large square balsa spar that continues and tapers outward. It appears weak at the area that the carbon/fiberglass tube ends.

I added a little carbon in there to reinforce my repair and it is stronger than stock. I also added some carbon tow on top of the skin. I did not pick up too much weight, maybe a little from the glue and glass repair. Not too bad, took a couple evenings and was ready for paint.

When the nose hit the hay bale the tail wanted to keep moving also. This ended up snapping the boom right in front of the tail assembly, where they all break! Once in there I found the same rubbery plywood with what appears to be hot glue. The "spar" that is inside the vertical fin was loose and rattling around in the tail. I used a dremmel to cut one side of the fin off and used a carbon/end grain balsa sandwich panel to replace the spar in the tail. MUCH stronger and I think again I should not have picked up any weight except for the cosmetic finish repair.

Repair is DONE and I have about five flights on it since. CG is at 70mm right now. Today was the only day with lift available since I purchased this model. I was worried about its weight and that it would never thermal well but I was wrong. It seems to do great. Speeds from thermal to thermal and I am learning to keep it inside once I find one. I do not believe the model is at fault as I am learning the technique to turn this thing tight and not fall out. Lots of rudder. I have it mixed at 50% and I believe it needs more.

I have the flaps slaved to the ailerons full time and full throw. I believe I will take some of the flap movement out as it is really not needed and probably is a bit inefficient throwing all that out every turn.

It was fun chasing the turkey buzzards today. There must have been a dozen in one thermal that I joined in on. They did not seem to mind. We all hung out together and I rode it up until I was having trouble seeing the darn thing. At four meters wingspan and a red lower wing!

I am currently editing the video. I have two failed launches off my dolly to show, and then I broke the code and got it right and can show the models view of it coming off the dolly. Cost me three prop blades! Down elevator to hold it on the dolly until decent flying speed. I also had to tweak the dolly a bit. That's story is all for my next post.

Later
Neal
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Old Dec 05, 2014, 11:24 PM
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Dolly Parts: My dolly launching learning curve is currently vertical. I have one out of three successful launches. Here are some pictures of my home made launch dolly. It is made from 1/4 ply, 1/20 all thread, some fender washers, some elastic stop nuts and some pipe insulation. A few bucks worth of parts. The most expensive part is the wheels, which I just happened to have laying around. Two from an old crashed 1/4 scale J3 cub and another two off a large scale warbird that I upgraded to scale wheels. These wheels are 5.5 inch dia on the rear and about 4 inch dia on the front.
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The front piece that sticks up prevents the glider from pulling itself off the dolly with forward thrust. I made this adjustable. There is a slot under that fender washer. From the two failed launch videos you see here, I have decided to slide it up another half inch. This will require the glider to fly off with a bit more authority. You can tell on one video I simply did not have enough speed, and from the other it actually fell off and did a little hop over the stop and fell flat on its face!

OH, the green foam piece prevents the glider from tipping forward and running the prop into the ground.

I am going to raise the stop and add a bit more down elevator for the take off roll. I think I can get this thing working reliably. It is MUCH easier to use this thing than to try chucking that almost 9lb monster into the air

Here is a link to my failed launch #1

failed dolly launch (0 min 11 sec)


And the second:

2nd dolly fail (0 min 7 sec)


And finally a successful flight. This flight lasted about 25 minutes with just two climbs and 2000mah put back into the battery. Spotty thermals but some cool friends to point out where they were

AAHHH,,,, its still uploading. I will come back and put it on.

Neal
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Old Dec 06, 2014, 12:14 AM
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My long DG 808 flight. I know, the landing SU%#$#@ed. But not a scratch. I think I had too much flap out or got a little too slow.

Fun flight. Restored my interest in this model. It does actually fly quite well if you can break through getting it up off the ground!

dolly flight trimmed (4 min 29 sec)
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Old Dec 06, 2014, 02:06 AM
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Nice flight.. Glad to hear your to starting to enjoy this model
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