ArildDJ

I’m finishing all wood work of my scratch build DNU these days. All equipment is in house and I have just started to get concerned about the dry weight of the DNU.

I’m going to have 4 ch. Setup with rudder and throttle ring on my Cox SS.

Equiment is:

4 HXT 900 Servos
Spektrum AR7000 receiver
Sanyo 250mAh NiCad receiver battery
Sullivan Slant 1oz tank
As pushrods I’m using Sullivan Red ones

Weight with all wood (not sanded, not covered) and equipment is about 365 gram or aprox. 12,87oz / 365g. I’m planning to get one layer of dope on the surfaces with contact to the covering. Covering to use is Microlite.

Do I need some modifications to lose some weight?

alcarafa

I 've build one DNU final weight was 340 grams ( 12 oz ).
Covered with ultracote light.
3 HEX 900 servos. aileron, rudder, elevator.
Spektrum AR6100 reciever ( 3 grams )
S ony 3000 Mah AAA batts. for reciever [X(] - (made the pack myself).
CF pushrods
Reed valve COX .049 slightly modified (polished to mirror inside and Doug Galbreath conversion head and Nelson HD glow ) this lil beast screams out loud
2 oz sullivan tank
Drill as many holes you can to save weight without compromising structure.

You ' ll love it.

longdan

I honestly think a rudder is a waste of time on a plane like this. You certainly don't need it for turning as the ailerons/elevator do this just fine. It may help for a few aerobatics but other than that its just extra weight - and its a tight fit in there for just a 2 channel set up let alone 4.
Mine came out at just over 11 oz ready to fly less fuel. My setup is 2 x HS-55 (ele, ail), Worn out Cox TD .051 (no throttle) 270 mAH NiMh rx battery, 2 oz round du-bro tank, GWS 6ch nano rx.
Its a blast to fly. I tried a Norvel .061 (throttle wired wide open) but it was a bit quick, and the norvel was a bit heavier than the TD, so went back to the TD. I love the way the TD unloads in dives and its got all the power this plane needs. Never felt that I needed a rudder. I use Tornado nylon props - cut down 6x3 or 5x4. They last forever and dont break on landing like APC or MAS props.

flying poodle

Mine came in at 12oz

TD 051
Fuji film tank
Four 9gram servos (dual ailerons)
270 niMA
full size futaba rec
bolt-on wing


I have to dissagree about the rudder. It allows knife edge, snaps, and flat spins. Its also fun to point the plane in the wind and let it "kite" up about 500' and flat spin down.

ptulmer

My Feedback: (5)

The DNU doesn't seem to suffer too much until after 15oz AUW. Rudder control with the original rudder is fine, but an ultrastik type rudder might work better.

Alabama Racer

Sorry for the ignorance but what is a DNU. Anyone have a photo to post?
brad

ArildDJ

Well thank you all for replying!

My plans for the DNU is to let it be as aerobatic as possible. That’s why I decided to apply both rudder and throttle. With some checking with the kitchen weight I’m now suffering a little with the all up weight for the DNU. I could do the “Swiss cheese job” and drill out holes in wing profiles, ailrons, rudder and stab, but I’m not shore about the savings for this. I have decided to change my receiver to the Spectrum AR6100. I would really hard try to get under 13 oz for the all up dry weight since I believe the Sure Start isn’t a powerhouse. I got some Tee Dees laying around but I have other plans for them over time (one of them is NIB and I really don’t think I ever gonna start it).

Do you think approx. 84 holes in the DNU is the way to go, or do I just weaken it for a very little weight save?

ArildDJ

DNU = Das Not Ugly Stick by ptulmer.

I haven't taken any pictures of my, but if you do a search you will find a lot of them.

blvdbuzzard

Mine came in at 14 7/8 oz with 5 servos and a heavy 2oz plastic tank. I used (3) 3.7 gram servos. (2) for ailerons and (1) for throttle. I used 8 gram servos for elevator and rudder. Mine is covered in cheap cote. I need to run the AP .061 more. I also need a smaller prop. I am running a standard 6X3 MS and YS 20-20 fuel. Steerable nose wheel is nice too. People were surprised that I could taxi such a small plane. Even at almost 15 oz mine just floated when I was gliding it in.


Dru.

alcarafa

Rather than drilling holes on ribs and ailerons, drill big holes on fuselage that 'll help more to reduce weight more than lil ones .

82 holes are more than enough !!!!

KidEpoxy

I saved weight on one DNU by having a friend help me build it.
I had him stand next to me,
and every glue joint he would thwap me in the head and say "Too much glue."

ok, kidding aside, he only helped me setup the ribs like that,
but he did make me sponge/wick a lot of excess glue off the plane

ChicaWolverina

I say to Viva La Rudder! Go beyond simple Yank-N-Bank mentality!

K...


><
Tomasina ChicaWolverina!

chevy43

Sulivan tanks are pretty heavy. The stopper is heavy just by itself. You could save some weight by using a bubble bottle tank. Are you using a battery switch - the solder on micro swiches at the electronics store are the smallest and lightest. 1/2 a control horns with screws are bigger than nessasary too. I like the little ones you just stab in and glue in place.

ArildDJ

I put just the wood on the weight and it weighted in for 116g / 4,09oz. I think that isn’t too bad. I must reconsider my equipment before I do the drill job. Maybe a Fuji tank and some other equipment.

ptulmer

My Feedback: (5)

Combatpigg (of course) once said something real witty about drilling holes in balsa to save weight. Wish I could remember what it was... Anyway, it's an exercise in futility. Use good, light balsa and you'll be fine. And 4oz for a fully built (bare wood) airframe sounds pretty darn good to me!

Hey Kid, my airframes weighed much less when I stopped gluing myself to them.[sm=lol.gif]

Oh, Chevy is 100% right about those tanks. They weigh exactly what they hold, 1oz! Unfortunately, when the DNU left the drawing board it was setup for a 270 nicd battery and sullivan tank under the front hatch and a surestart up front. Cheap and easily available was the mantra at the time. Balance issues arise quickly when other combos are used. Get creative placing components and usually everything works out.

ArildDJ

Ready for covering!

Saving weight as ptulmer said, just by removing the builder from the plane ;-)

ArildDJ

Finally it’s done!

Weighted in for 13,47 oz.

It ended a little on the heavy side but since I would make as 4 channel I guess I got some extra weight. I ended up with a little nose heavy but not so much that I need to balance it with lead in the tail.

Here are some pictures:

combatpigg

My Feedback: (3)

DNUs all across the WORLD! [X(] The Sun never sets on the DNU EMPIRE!! Still waiting for a DNU from Africa, though.

ArildDJ

”The Empire Strikes Back”

Well I got a short flight with the DNU yesterday. My buddy throw it of and it started to fly immediately. It didn’t need any trim at characteristics was brilliant. Thanks to ptulmer for a real nice plane!

My engine leaned out so it wasn’t a long flight. I got to learn more about this small Sure Starts. I think it’s getting way leaner in flight than on ground. The negative was the belly landing. On hard snow and some ice the covering got some damage. I therefore decided to give it an undercarriage. Total weight with the undercarriage is 14,22 oz, but when flying the DNU I think it can manage the weight very well. Here are some pictures of DNU with home made wheels (I will change them later)

combatpigg

My Feedback: (3)

Very Nice! It is obvious that you built a very accurately put together plane.
Make sure that the fuel system has no kinks in the lines and is not drawing air. Air bubbles can form inside the tank in flight from vibration, so do your best to look into that.
I like having a 2 oz. veterinary supply syringe around for both fueling and to help troubleshoot fuel system troubles. Monoject is the brand and I press a short length of 3/32" brass tubing into the tip so it can be used with small or large fuel tubing. It is also a good idea to put a couple of short sheetmetal screws into the back of the syringe body to act as "stops" so you can't accidentally pull the plunger out.
If the whole system of engine, prop and tank is working well together there should be no special tricks needed to get a good needle setting that works until the tank is bone dry. You should be able to launch it within 1000 rpm of peak and the worse case would be watching it suffer through a "rich" flight.

windy city

VERY NICE DNU!
And yes ptulmer has a CLASSIC there!
Mine is almost one year old and electric, it goes out to the field every time and still makes me smile!

windy city

ArildDJ

Thanks!

I look forward to try the DNU again with landing gear. Right now it’s dark at the afternoon and freaking cold… I so done with the winter in Norway…

longdan

I feel I have to pipe in here - maybe a little too late, but I fail to see how someone can build this ship to be overly heavy. When I built mine, I built it mostly as per plans, using standard balsa from the LHS, Hardwood wing spars, plenty of epoxy round the fuel tank area and put shear webs all the way out and some cheap translucent chinacote to cover. Basically, I didn't try to save weight anywhere. And Mine came out at about 11.5 oz ready to fly. But I think I did gain a major weight saving by using aliphatic resin for all the glue joints except for the firewall where I used epoxy. Aliphatic is basically PVA (both are about the same strength), but with a few better properties. Seek and ye shall find. I can't be bothered going into the pros and cons of aliphatic, except to say that I think it is far superior to CA and epoxy when used to stick an airframe together (except for the aforementioned firewall)

And another thing worth mentioning: when sheeting the centre section, there is NO reason to have a join in the centre of the sheet. The sheeting can run from end to end in one piece. This adds tremendously to the strength of the wing - unlike a glue joint in the centre. This can be achieved even on wings with a small amount of dihedral. Just 'wet & forget'. That is another advantage of aliphatic glue - you can glue wet balsa cos aliphatic uses water as a solvent. And cleanup is too easy.

The bottom line here is that epoxy just weighs planes down, especially small ones like 1/2A.

ArildDJ

Thank you for hints

Well I see your point. Mine is glued all together with CA. I like the CA and Kicker… The only place I use epoxy was for gluing in and coating the firewall.

If I had taken away all my heavy stuff like rudder, throttle, Sullivan tank (build in bladder or Fuji can tank) and landing gear it would weighted in for 11,67. Maybe I could saved a little more if I had used some of the aliphatic glue to. And I did for sure sheet the wing without any unnecessary cuts and joints.

Unfortunately I don’t have any flying fields with good green grass for belly landing. Therefore I decided to add landing gear witch wasn’t a part of the plan when I started to build the DNU. With 4 channel and landing gear I will be happy if the DNU doesn’t show up with some characteristics like heavy plane sometimes do…

longdan

Have you ever heard V8 fans say "there's no replacement for displacement"?

In 1/2A the saying should be "there's no replacement for a light airframe"
I know it doesn't rhyme and is not as catchy as the V8 one, but it is just as relevant.

It sounds like you built a light plane. Pity you weighed it down with so much gear. But the test is in the flying.
If you like the way it flies then stick with it and enjoy it.