Dynaflight Decathlon - DA 50

[Trumpetman]

I thought that I would put up the world's shortest build thread for a Dynaflight Super Decathlon that I built in a couple of months this past winter. I wasn't planning on doing a full build thread but I did take some pictures as I went along.

A few specs:

89" wing span with 1237 sq. in of area
69" fuse length
advertised weight of 16-18 pounds.
calls for the following engines: 1.08-1.80 2 stroke, 1.20 - 1.60 four stroke or 25 - 35 cc gas

I used a DA 50 with Mejlik 20 x 12 x 3 blade prop (gives me good clearance). Except for throttle and choke, I used 5955TG's all the way around (overkill but I like the security). JR R1221 receiver with dual power input (used (2) 5 cell 2000 Mah NimH for the receiver and one 4.8 volt for the ignition). To be honest I did not weigh the finished plane. I will do this if anyone is interested but I simply made sure that the CG was correct before doing the maiden. I know that the plane is over powered but I made what I felt were prudent upgrades to the front end (ie. I ditched the light ply laminated firewall and installed 3/8 arcraft ply with additional bracing etc.) to handle the extra power. I live at about 3200 feet above sea level so there really isn't such a thing as too much power (you can always throttle back!).

The first few pictures show the interlocking light ply structure that forms the fuse as well as the framed up wing. Nothing out of the ordinary here but pay attention to the use of a 3/16th sq stick of balsa under the ribs which dials in the required washout.

[Trumpetman]

You will notice from the size of the 1/2" by 1 3/8" by 42" block which forms the leading edge that there is a fair bit of carving to be done with this kit! Make sure you have a good razor plane before you take this one on!

The wing tip blocks are massive: 2 2/2" x 2 3/4" x 14 7/8" !! It helps to have a band saw to do the initial shaping of the block. I also hollowed out the block as much as I could to try and reduce as much wing tip weight as possible.

I used a lot of clamps and some sighting sticks to keep everything parallel when I pulled the tail of the fuse together. The interlocking structure works well to help keep things aligned as well.

[Trumpetman]

I like it when the pieces start to come together and look like an airplane! Knowing that I was going to over power this thing I added some additional gussets to the Rudder, Fin, Stab and Elevators. I paid close attention to the fit and finish of each joint and I pinned a few of the higher stress locations with tooth pick sized dowels. The cowl is a two piece unit of ABS plastic which is a pit of a pain in the a** but it turned out OK.

One of the pictures gives a bit of an idea of what I did to the front end to shoehorn in the DA 50

[Trumpetman]

I told you this would be the shortest build thread on FG!!

Misc. building notes: the quality of balsa in the kit was overall very good. I threw out the tail wheel unit from the kit and used a carbon fibre tail wheel scavanged from a crashed QQ Yak. I beefed up the landing gear mount plates with aircraft ply and some additional gusseting. The plane was covered with Monocote and the white trim/stars were ironed on and then outlined with blue trim tape as per the full size scheme. Make sure to build in the right and down thrust for the fire wall as my first flights showed it to be just about perfect. The only issues with the kit were the abs cowl and wheel pants. I cobbled the cowl together and it turned out OK and I threw out the wheel pants. I may repace both of these shortly with some fibreglass units that are readily available. As well, the windshield cracked across the top where it bends down next to the wing. This happened after only two flights. I may have stretched it slightly in that area and the vibration from the DA must have started the stress fractures. Overall, a good kit and an easy build for someone who has a few kits under his/her belt. BTW for those of you who are thinking about this combination of plane and engine, that small hole on the left side of the cowl was the only cutout on the side necessary to clear the invered Pitts style muffler on the DA.

First flight notes: The snow in Calgary had cleared enough by last weekend that I was able to take it out for a maiden flight. The DA was used on previous planes and is running well. After a thorough systems and range check I taxied out and took off. No lack of power!! Two clicks of down trim and one or two left aileron trim were needed. I was surprised with how axial the rolls were. This would be an excellent first giant scale gasser and it could do well in IMAC Basic at the local/club level (this is hard to say when I have seen 40% Compy's flown in Basic!) The weather window closed on us quickly and I have not been able to get out again with it but I will try to get some video and flight pictures in the near future.

Thanks for lookiing.

[IMACmike]

Very Nice! Looks like high quality workmanship, too! I have one of those kits, but I was thinking more of an ol' Q35 that I have laying around to power it. Reminds me of my father's 7KCAB, except his was blue/white.

[Trumpetman]

Thanks, I'm kind of old school and I like building when I get the chance. My dad was a carpenter by trade so I feel real comfortable with wood. The Q35 should power it in a nice scale like fashion. I'm not sure how much those engines weigh but I balanced my plane by putting the rudder servo and both elevator servos in the tail (just under the stab). No additional tail (or nose)weight was needed to balance the plane.

[tombrez]

hey gordon nice job...

[Dumorian]

Very nice!

Have you tuned the CoG on this plane yet? If so, where did you find it flies the best?

[Trumpetman]

Thanks for your comments. I have left the C of G where recommended on the plans. It flys well and lands nicely at this setting. The rolls are unbelievably axial for a high wing plane (use the recommened aileron differential) and when I put it into an inverted 45 degree climb and let go of the sticks it will gently fall off. It takes almost no down elevator pressure to hold an inverted line. As I fly it more I have come to believe that this would be a great IMAC plane for a low time pilot interested in flying Basic. Snaps are weird and I havn't figured out the right amount or sequence of control inputs to make it snap nicely.
Although it has more than enough power there is no point in setting a 3D type of rearward C of G because the ailerons are way out there on the end of the wings and completely out of the prop wash. This thing needs forward airspeed for good roll control. If I were to build another one I would extend the ailerons inward almost to the root. I think this would give you a 3D capable plane (especially with the DA50 up front.

[Dumorian]

Thanks Gordan!

I built flaps on mine. I used another 4 bay areas... so not quite to the fuse. I figure I'll run full span ailerons and can play with that percentage. I did build the flaps just like the ailerons, so I'll be able to have equal up/down travel.

I am doing a tug release, which was the primary purpose for the flaps... for those times when an earlier takeoff works best with a particular glider.

I also plan to put mine through the paces and am looking forward to having the extra aileron/flap authority. I'm putting a 36cc on mine... a bit lighter than your 50! It should hold vertical, but might not climb. I am coming down the home stretch. Not a lot more to do before starting the covering. I have done several things different. Pull/pull on the rudder, CF rods for the elevators, (I never cared for flex cables on control surfaces under that much stress), bomb bay, flaps, tug release, upgraded LG and LG mounting plate and then just generally added a few bits here and there where I thought a bit of added strength was a good idea.

Mostly I have some more sanding left, mounting the bomb and tug servos, creating a new slot for the CF control rods, the bleach bottle cowling (I'm about to talk myself into ordering the FG one) and just a few more finishing touches before I should have a beautiful nude! Then comes the pearl white and orange covering.

Thanks for the flight report. Sounds like the CoG is pretty much spot on if your inverted is that near to neutral elevator. I might have to add just a bit of weight to the front darnnit! I thought the gasser would be enough. I'm at the backend now and still have more going behind the CoG than in front. When I tested it I didn't have wing servos installed nor as I said, the tug or bomb bay servos. All that was lacking up front was the EI module and the cowling... not much weight there. I guess I'll be trying to get my batt packs into the front of the cockpit.

Again, thanks. I'm getting pretty torqued about getting this into the air and flying season is coming on strong now.

[Trumpetman]

Sounds like you are building a real utility fun plane! Using the coupled flap/aileron setup should take care of the issues I have experienced with the stock ailerons locations. The plastic cowl in the kit is a bit of a pain but it can be made to work. The 36cc that you are planning to use should work well at the altitude that you fly at. I'm at 3200 ' ASL so I need the extra power. Please post some pictures of the various mods that you have made to your plane. I would be interested in seeing the mechanism you used for the glider tug release and the bomb bay doors.

I put my fuel tank right on the C of G and used the space just behind the firewall for two batteries (the ignition and one of the dual receiver packs) This way I balanced the plane without adding any dead weight and the balance does not change during flight as I use up fuel.

[Dumorian]

It is going to be both a fun plane to fly and also one with several purposes. The bomb bay is huge, comes up just under the windows and is about 6 inches long by the width of the interior. If I can get a banner made of thin material that can fold/roll up to fit that space, I can also do a banner drop so to speak. I'll be able to harness it to the tug release, down each side to the banner inside the bay. So, I'll be able to take off with no banner, drop the banner out and fly around with it and then drop the banner from the plane before landing. Of course the candy drops. Easter eggs filled with flour, small paratroopers and I bought a case of Peeps. Nothing like dropping little yellow chicks from a big bird in the sky!

I toyed with the idea of lights, but I just want to get it flying at this point. I really don't need to invest another several hours off in yet another direction. It would be pretty neat though to use like 10mm LEDs for marker lights and such. I'm not really trying for scale... and was even thinking about retractable landing lights... but again... more hours and more plugs during assembly. I think I've done enough.

As of the moment after a bit of time on it today, my wings lack only the filler pieces that fill in next to the windshield and four little places to sand down a tiny bit of wood filler, and they are then ready to cover! Yes! The fuse in the meantime has been patiently setting over to the side waiting for the wings to get out of the way.

I really like your gas tank idea. Wish I had given that more thought from the start. I will more than likely run lipos though for my flight packs.... and I like to balance charge them, so they need to be removed from the model for charging, so, I guess I'm still on the right path. I did put my gas tank on a slide out tray though. No way, I'm going to rubber band something like that into place and then cover up the only way to really remove and reinstall it. I also had a leftover composite LG... very heavy duty, with a bit broader and a bit higher stance. So, the weak aluminum one gets left for maybe a lighter project in the future. I also beefed up the LG plate inside, using 1/4" baltic ply with some CF pins in strategic locations. So I think I'm good to go there. Much stronger than stock.

Yes, this model should wind up being a really fun plane to fly. Hearing what you say about yours really is incouraging. This seems to be the general consensus. I wanted a nice size tug first. The other bonuses are always positive! I'm sure I'll be just flying the model much more than using it as a tug.

I had originally planned to use a CRRC 40cc on it, but it doesn't have a close fitting Pitts muffler available and as I was working towards having one made, this Brillelli came along. I've heard great things about this engine. It's sad that the company just didn't make it. It has a very compact muffler system. It works out that the carb will be cut through the side of the cowling and I'll be able to actuate the choke due to the angle of the carb... pointed downward a bit and the adjustment screws are aimed right at the muffler cutout, so it should be a very clean install. I just hope it's enough power. I really hope I don't need to go to something as large as a 50, or I'll be wanting to redo the firewall as I just don't think the light ply is quite good enough for a 50. Very early on, I was actually considering a 50cc twin! That could look pretty neat!

I had planned to get some shot of it today, but batteries... it seems that something is always on charge around here, yet the one thing you want to use has dead batteries! So, I charged up the camera batteries and maybe I'll be able to take a bit of time to do that tomorrow. I want to take it outside and let it set on the ground for the first time and then get some really good nude photos of her. I'll be sure to get some shots of the 'working' areas and mods.

Thanks for your responses.

[flying skunks]

we flew a pair of those years ago , we found that when you opened up the ailerons two ribs , it would make the ail. very effective when doing 3D , truely a fun plane to fly , been thinking of building another ..... the plane would do one of the best blenders ......also make sure that the wing struts ARE Functional ..

[Dumorian]

	Quote: Originally Posted by flying skunks
	we flew a pair of those years ago , we found that when you opened up the ailerons two ribs , it would make the ail. very effective when doing 3D , truely a fun plane to fly , been thinking of building another ..... the plane would do one of the best blenders ......also make sure that the wing struts ARE Functional ..

Good input! I thought the standard method on both ends of the struts was a bit on the light side... if one plans to wring it out and I do. I added side supports to the blocks in the wings, which span across to the next rib. It just looked like those mounting blocks could twist out too easily.

At the fuse, as I said, I did a 1/4" plate for the LG with side that turn up inside... making basically a u-channel. I used some CF rod to pin these together and it's all epoxied into the fuse. It seems very rigid. My struts will mount to those. I also plan to use metal straps instead of the plastic and threaded rod provided standard. I'm afraid mostly that the threaded rod would strip out of the end grain wood.

I'm also doing a full flying wire set and have tossed the idea of using flex cable for the elevators, and have instead fabricated CF tube push rods... This forced me to exit the fuse about 8 inches in front of the stock slots, but should provide precise response. I'm doing a pull/pull for the rudder.

I'll get to play with full span ailervators, tuning them to what feels the best. I'm running a 12Z radio and have lots of options for tuning this and/or setting up multiple rates for the flap portion of what really is an aileron in this mode.

The model is getting close enough to finished at a time when good flying days are happening here, that it's really starting to bug me that I can't seem to go any faster! As of last night though, all I lack are the fillers by the windshield and I'll be ready to cover the wings. The fuse is not very far behind being in the same state.

[Dumorian]

Here are some nude photos of my Decathlon!