dabrown

Put it together yesterday to see how it looked and to check the weight and balance. Not good news. 17 lbs and tail heavy. Will need a lb or more ballast to get the CG to where it's shown on the plans.

Other than that, only a few minor things to do before I take it out and crash it...

Dave

Nothrottle

Not an economical suggestion, but a powerful one, add the weight up front. A larger engine! There are the same Decath's out there with 40cc gas and up. My bird weighs in @14 lbs. with 17lbs. of thrust powered by a well used Magnum 180 4-stroke. The rudder and elevator servos (3) total and the 5 cell battery all hug the back of the fuel tank. The servos mounted an easily removable rails for maintenance. I built with the balance in mind using the light 4-stroke. Not scale lol, it will hover!

do335a

dabrown,

I see that you've already mounted the battery and servos as far forward as possible. Mine has that feature as well. Even so, this plane has lot of wood in the tail so it's very easy to come out tail heavy. Adding that special scale style tailwheel which you've installed increases the tendency. Yes, I used one of those too - as well as the tail brace wires and hoped that I was compensating adequately by moving everything that I could far forward.

Overall weight is easy to build up too, especially with a fabric and dope finish. My first attempt was Coverite with paint. It failed for a number of reasons before completion. Trash about $200.00. Second go, which you see in the pix was Ultracote. Add about another $125.00.

I don't remember which engine you have in yours. However, the engine weight was also a consideration for me. I knew that the extra heavy ST 2500 would help the balance. The final result was no added balast. My overall weight is about 16+ lbs - close to you. Dynaflight suggests a finished weight of 16-18lb, so you are still within the claimed range.

Another item which helped my balance but hurt my overall weight is my particular finishing of the cowl. As most of you know, if you've seen my numerous earlier posts, I am not a fan of this kit or manufacturer support in any way. And you all know that the supplied ABS parts are not great. My solution was to trash the interior kit, which was an extra cost waste, as well as the wheel pants and somewhat modify the existing cowl. Parts fit was very poor, with many significant gaps and holes where the parts were to be joined. I glued it all up, filled the seams with bondo, sanded and filled forever and then fiberglassed the entire cowl on the outside. Countless hours later, although it looks great, there's a fair amount of weight there. That's probably what saved my balance though.

BTW, my plane has been retired temporarily after only one 5 minute flight. Engine had problems with the con rod at the big end. Such is life. I could not believe that the flight required almost full throttle. The performance of my OS 1.08 in my Sig clipped wing Cub at about 15 lbs. was far superior. This could have been due to the engine problems though.

A seven year build project, followed by one 5 minute flight and subsequent retirement!!

dumorian

My Feedback: (6)

I was pretty near 18lbs with mine. But.... flaps, bomb bay, powerbox system, heavier LG, and a 36cc gasser... it added up. My tail servos are mounted in the standard location. I almost had to do this as the bomb bay fills the back half of the cockpit. I did need to move batteries a bit forward. The Brillelli engine is not a flyweight.... but I balanced without adding 'lead'. I am only concerned with needing to strengthen my firewall still. I plan to do aluminum straps inside and outside. Doing these inside is going to be a real chore as the top bolts go through just under the deck. I'm happy I did the gas tank tray. That has been a lifesaver... but it will still be tough getting to the top of the back of the firewall.

I have had recent running problems with my gassers. Turned out to be bad advice on 2-stroke oil and mix from a vendor. I just last week 'finally' figured out what was going on and am cleaning pistons on everything now. The Decathlon has been sitting to the side waiting for this answer and a new LG. The composite one I used had some minor cracks when I selected it. Those have grown larger and I'm not sure I want to fly it. I plan to have a custom aluminum gear made for it.

Good luck DAB... the plane flies fine at that weight. You'll need a little throttle just before touch down as it does start to drop at the very end. Mine really likes to be 'horsed' around and really shows its character best when flown hard.

Nothrottle

Commencing at the very beginning of assembly of the tail feathers: Ripped 75% of the 3/8" wood and used the remaining 25%. Simply cut the 3/8" sticks (ribs) longer. Removed from the stab center wood on both sides of the vertical fin mount area. Gussets reduced. Dorsal fin and top spines made of foam. These procedures enhanced removing enough tail weight to allow the Magnum 180 4-stroke engine for proper balance. Ultra Cote was used for the covering, saving more weight. Not scale, intended aerobatic as possible with the Decath.
I agree the pre-cut parts fit was not perfect. The kit has been in production for decades and punched wood does not compare to laser cut. I was doing arfs for years and craved doing a kit last winter. I thoroughly enjoyed the kit bashing of this plane and the results were fantastic. Flight # 31 and on this weekend and many more in the future! (Crosses fingers)

dumorian

My Feedback: (6)

Excellent NoThrottle! It sounds like you have a very good build. Mine likely has around the same number of flights, including one 'unscheduled' landing? I managed to get all twisted up on takeoff... tried to leave the ground before it could be done... better than traveling into the brush at that speed... or so I thought. I stalled it... just about pulled it out, but didn't have quite enough and put her down 'very hard' on it's wheels over in the weeds. 0 damage, other than those aforementioned cracks in the LG getting larger. I was totally amazed. This thing is a tank that positively will take at least some abuse. I did however add some extra reinforcement here and there, like a 'real' LG plate... some tri-stock. I was expecting a major repair job and after a check out.... flew it again that day. Just used more care for gentle landings. But alas, those cracks have increased... and another inspection just now leaves me with the official stance of 'this LG is retired'. Time to order my new gear.

I also have struggled with the tail gear. The weight of this model does require a heavy tail gear. I tossed the OEM gear... used the heavier Dubro equivalent and the spring on that is not even enough to hold the wheel straight. I picked up a gear at a swap last summer. This will go on in the mod process. It may require some work up inside the fuse to have some backing. Another of those not so easy to do task.

dabrown

Thanks for all the inputs guys.

The engine is a Saito 180. We can't fly gas at our field during the summer, so I'm stuck with glow.

I moved the rud/elev servos up front, in anticipation of the CG problem, but don't think that helped much. Doing so meant the metal 4-40 pushrods were longer, and they are heavy. If I could find some carbon fiber rods, that would help quite a bit.

Also, like do335 said, going against me is the tail wheel hanging way out. It's a fairly light unit but nonetheless a long way from the CG. I did that to be more scale like.

The wood in the horizontal stab is especially heavy as Nothrottle mentions and I could have done more to make it lighter. After I crash, I'll rebuild it lighter: o

Another thing is the paint. The Klasskote epoxy I used doesn't give up much weight when it cures and I put it on too thick...and there's alot of surface area in the tail fins.

For now I'm leaving the tail braces off. Plenty strong as is.

Anyhow, if I can stay under 18 lbs, should be OK. No intention of any 3D performance, just hope it's not a lead sled!

Dave

do335a

As for a lead sled...

I'll say that in my case, when the engine flamed out, it required immediate nose down. And it sinks pretty fast. Very steep descent angle once the fan stops.

Nothrottle

With my 180 on the nose, hovering should be @ 100 feet minimum. When it falls out, it does so rather quickly with momentum the 89" wing creates and at least a 50' lost in altitude before recovery. Rolling circles or harrier, are very big, lazy and graceful using max throws. Knife edges require a strong servo and 45 degrees of rudder throw. Once in position, minimum effort to hold.

dabrown

Well, I flew it yesterday. Despite the fact that it weight 19 pounds after adding the nose ballast, it jumped off the ground and the Saito 180 pulled it around very nicely. Unfortunately I didn't have the idle low enough for landing and ended up ballooning and crunching the landing gear.

So now I'm looking to either beef up the gear like other folks have done, if I can bend it back straight. Or going to a machine shop and see if they can make one. If I do that, what do you think, 1/4" aluminum? Steel, maybe 3/16"?

My local hobby shop guy said I should be able to find someone to make a custom carbon fiber gear, but I'm thinking it would be very expensive.

Dave

stevo revo

Good to see this thread is still rolling.

I finally installed carbon fiber landing gear on my Decathlon, and all the bent aluminum landing gear nightmares are gone. I contacted Mike at graphtechrcshop.com , imho the best cutting edge carbon fiber rc aircraft landing gear on the market. A few club members have contacted him to make or buy lg to replace their shoddy stock landing gear on their planes. These guys are very helpful, and stock alot of gear for alot of birds, that they hand lay up themselves here in the states....

Anyway, this is what I got....... http://www.graphtechrcshop.com/produ...8&categoryId=4 ........ They modified it for a 1" thickness, and section roughly 5/16" thick, enough to support a 20 lb plane on a rough field. (although I'm under that ...... It cost about $15 more than the advertised price to make it custom, but so far it has been WELL worth it. Very nice to fly my Decath this year with trustworthy gear.

Other things I'm pondering changing, are replacing the OS 1.60 with the new DLE 30. The 1.60 is a great running STRONG engine, but I'm tired of wiping slime off my pride and joy. When I do that, I'll probably pick up a new cowl from Fiberglass Specialties. My factory cowl is doing ok, but it's quite heavy, and not the most scale. Speaking of which, has anyone bought this piece yet? I'd like to see some photos of it.

The motor and cowl swap will be a project for next winter. I'll keep flying her this summer for now.

I have some vid of a flight from a few weeks ago, sporting the new gear. Note how on takeoff and landing, how well it absorbs the bumps on our less than perfect field.
http://www.youtube.com/user/TrollHDT...12/Ln0f9AQyx8U

Here a a few photos with the new gear too. I like how they look with the carbon prop too

dabrown

Stevo,

Excellent video and a sweet airplane! Your gear does look pretty stout and didn't seem to flex too much. Looks good too. I believe I will contact them.

Our runway is smooth but it's hard surface (textile/fabric) and it's somewhat short, so with an airplane like this and no wind, you have to be right on speed and touch down on the numbers. I figure I'll be able to do that say, 1 in 10 times. OK, 1 in 20...

Thanks alot for the info.

Dave

kwhite.6

How important is the washout in the wing? I finally have mine ready for covering but it's only got 1 degree of washout and I can't figure out how to get any more. Any suggestions?

beepee

As long as you have 1 deg and it is the same on both sides, I would go with it. Trying to add more is a major effort. You will need to be careful during first flight to check tip stall tendency at a recoverable altitude. I suspect it will not be bad, but it is a good thing to check with any new airframe.

Have fun!

Bedford

kwhite.6

I rechecked and I've got 1 degree in the left wing panel but 0 in the right. Is there any way to twist it so it's the same on both sides?

dabrown

You could try laying the wing on a flat surface and shim the tip trailing edge up with some weights holding the leading edge down to try to induce some additional washout. Possibly wet the balsa with water and keep the twist in until it dries.

A 1 degree difference isn't much and you should be able to easily compensate for it with trim. Also, your measurements might be off too since it is difficult to establish the chord line for the tip and root exactly.

But, I'd say go ahead and try to add some twist then finish it and fly it. I never really checked the washout on mine but when it flew the first time it was pretty much rock steady.

Dave

secatur

Hi, I've got over 200 flights on my Decathlon...It's a great model (Moki 1.80 Gas) And EXTREMELY GOOD VALUE for Money ! !!!! Just a shame DYNAFLITE is winding down !!!![img][/img]

secatur

Is FibreGlass Specialities still operating ? I can't seem to access their website ?
Thanks,
Steve

stevo revo

Try this........... hope it helps.

www.fiberglassspecialtiesinc.com

mooseflyer

Hello all. I recently received my Dynaflite Decathlon from Tower. It's been about 12 years since building a kit (not counting the hundreds of Guillow's and Dumas FF kits I've built over the years just to pass the time). I got stuck in the ARF "groove" and got tired of "modifying" and saying, "I would've done it this way" every time I inspect a new model. So, I did some research and read countless reviews and forums looking for a good refresher kit. I've been wanting to get into larger scale aircraft, so the SD seems like an ideal project. I look forward to starting the build, and I plan on posting progress pics as I go. I was going to post a pic of the box (it just arrived today via UPS), but I think we've all seen it enough to know....unless someone wants me to post a pic just so they can say, "ah, I remember that day".

mooseflyer

Here we go!

do335a

Mooseflyer, looks like you're off to a great start.

Now that you are at the stage where you can do something about it and those of us who have already complete ours are beyond that, I would highly recommend that you lighten the tail. There's a lot more wood there than you need, especially in the stab, vertical fin and rudder.

If I were doing it over, I'd cut those down by about half their width and simply lengthen the ribs. In many other places, I'd chuck the lite ply for balsa - even make balsa plywood if necessary since it's at least as strong and much lighter.

Another thing to watch is to check and double check everything before gluing. You will find that unless the kit has been changed, there are bulkheads which are a different width as drawn full size on the plan and where you see them on the top view of the fuselage. You'lll also find that the fuselage sides are not actually parallel between the front and rear cabin bulkheads, although they may at first appear to be so. That means do not glue the forward bulkhead perpendicular to the fuselage side. And on, and on, and on.

Check everything. Doubel check and be certain before you glue.

mooseflyer

Thanks for all the advice...that's why I subscribe to these forums before starting a project. I did, however, begin the stab before I read your post. I am planning on making it a gasser; do you still think it will be tail heavy?

dumorian

My Feedback: (6)

I did a 36cc Brillelli on mine. I did the stock build with rear servos as per plans. What I did different was add a bomb bay and flaps. Each of these added weight, but just to the aft of CoG, so not a lot of effect on CoG. I am at the most rearward CoG and have worked to get more up front.

Yes, if you can trim weight from the rear... excellent, even as a gasser. 1 ounce off the rear equals 4 ounces off the front. You should be able to trim a lot from the elevators and rudder. I sort of like that beefy stab and fin.

If I had it to do again, I do think I'd consider making the rudder maybe 1/2" to 1" deeper. The model loves rudder in flight! And a bit more for better ground control wouldn't hurt anything either.

Either toss the LG, or add the music wire dealy. Bennett built has some neat fixtures for the music wire install. Also, if I had it to do all over again, I would positively dump the plastic bits and buy the fiberglass cowling and wheel pants from Fiberglass Specialties. Yes, the plastic bits can be used, but getting there... Frustration comes to mind.

OH, also positively do a tray system for your gas tank. These need plumbing work every few years when the tubing gets hard. I have no idea how you could do this with the tank built in per plans.

And... LOL... this might be the last of it. If I had it to do again, I would positively toss the light ply laminated firewall and build a firewall out of hard aircraft grade plywood. The soft ply is just too soft. Engine mounting bolts compress into it easily and that's no fun later. If you do decide to use it, plan some metal plates on each side where the bolts pass through.

mooseflyer

Thank you, and if you think of anything else, please let me know.