marko509

I am currently building a Model Airplane News plan designed by Paris White for a DC-3. The plan suggests using two .50 to .60 two strokes. I am thinking of taking this project a little further but I need some input from some of the more experienced engine guys out there. I would like to also build a matching scale Dakota or Horsa glider to tow behind (take off, releasing the glider in flight, with another piolt landing the glider). I do not know if something like this has ever been done or considered before, but if so, would I need to ramp-up the engines some, and if so, what would be a good starting point? I have no desire to break any speed records while in flight, so I am looking for something that will comfortably get the glider off the ground. This is a project that I will be taking my sweet-old time to complete, as my workload in my profession will not allow me to devote a huge amount of time at any given time to work on it.

Thanks for the suggestions-
Mark

Edwin

My Feedback: (2)

I have those plans too. You wont get too many responses, there just doesnt seem to be very many built. I am planning on using saito .56's in mine. Have you seen anything on the CG for these plans? I couldnt find it anywhere.
Edwin

jaka

Hi!
How big is the DC-3
I have two OS .26 fourstrokes in my Marutaka DC-3 (span 211cm, weight 3,6kg))

Edwin

My Feedback: (2)

I believe its about 93" ws. I've done some calculating and what I come up with is around 37% to 40% at the wing root. This is also confermed on a 56" ws set of Cleavland plans I inherited. But it just does'nt look right that far back. Jaka, where did your cg end up percentage wise! If this conversion program worked right I believe it says yours has about an 83" ws, correct? Its been awhile since I looked at the plans but I think it stated .40 2-stroke engines. Its a pretty old design. I'm planning on dropping about 10 fire jumpers from mine. I have an idea to use a rotating spring that should pop them out one at a time. Easier to picture than to explain, just dont have a picture.
Edwin

jaka

Hi!
Yes! My DC-3 is 83" in span.
If you have a DC-3 with a span of only 93" ..that's around 2.36m (236cm), two 6,5cc (.40) four strokes would be perfect for it.
If you choose twostrokes I would recommend OS .40 LA. Not a ball bearinged engine.
I can't understand why they recommend 10cc (.60) engines as this is way way to much power and will only make the DC-3 heavy and difficult to fly. Perhaps it was the only reliable engine size in the sixties...or that people didn't know better....

The C of G om my DC-3 is around 25% total wing area, as on most other airplanes. I haven't checked out the percentage on the side wiew though

Edwin

My Feedback: (2)

Before I forget, Nice job on your DC-3. I've seen it in the past when you've posted before and have always liked the finish you have.
Edwin

MinnFlyer

My Feedback: (4)

I can't comment on the engines, but I will throw in a comment on the glider....

Towing a glider can really be fun, BUT I would strongly recommend that you attach the glider's tow-line to the CG of the Tow Plane - not to the tail.

In full-scale glider flying, the first thing you are taught is to keep the glider down. You see, because the glider is a high-lift aircraft, the tow plane is pulling it faster than it wants to go. Therefore, the glider will rise faster than the tow plane.

Now think about it, you have a glider attached to a string, lifting up on the tail of a tow plane. Unless the glider pilot can keep the glider down, he's going to pull the tow plane's tail UP

Pull the tow plane's tail up, and the tow plane's nose goes DOWN, and once the tow plane has gone into a dive, it will pull the sailplane faster - creating MORE lift (See where this is going?) there's nothing the glider can do but go down with it (Or release - but this usually happens on, or shortly after take off, so there often isn't time).

If you attach the tow rope to the tow plane's CG, as the glider rises, it will just help to lift the tow plane.

marko509

It has a 94" wingspan. The listing on RCStore.com says the length is only 49", but that has to be incorrect... I would imagine that I might want to substitute one of the 1/8" balsa formers to plywood, maybe double it if I am ever going to tow a glider. The top attachment makes sense. I wonder if it would be possible or adviseable to modify the airfoil of the glider to negate this bad tendancy. There would have to be a tradeoff at some point.

Nowhere on the plans or in the included article did it ever mention where the CG is located.

Edwin

My Feedback: (2)

Only the glider pilot can control that. Might as well tow sport planes with no engines if you change the airfoil. I have about 10 hours in full scale sailplanes and my very first takeoff leaped into the air. Scared the cr@p out of me. Even thought they told me it would happen, you never really expect it like that. The instructor just laughed and said he had it. I quit cause I just couldnt afford it anymore. Like Minnflyer says, speed on the glider creates a lot of lift.

Yep! CG has been what kept mine rolled up on the back burner. Not very much info on these plans.
Edwin

OsmanKhan

Hello,

Great to finally hear people who have actually got the Paris White DC-3 plan. I have been working on this project for quite some time now. Its almost ready and with some effort will probably fly in a month or so. Not a great plan to work with and very few details given in the accompanying literature. But it does give the CG location. I have bought two .51 ASP engines (2 stroke) for the bird. I did add an inch to the wing's center section so as to cater for a bigger prop (like an 11" or 12") which otherwise would cut into the fuse. I have also gone and made scale retracts that will be operated with springair retract mechanism. As for the fuel supply, i will install a 2oz hopper tank in the nacelle area fed by a main 12oz tank to be fitted on the center section (one for each engine). I will post some pics next time to let u guys see where the project stands as of now.

Osman

Edwin

My Feedback: (2)

So where is the CG!
Edwin

OsmanKhan

The CG as per the plan is given 135mm from the leading edge of the root rib. I guess you can work out the percentage from this value.

Osman

Edwin

My Feedback: (2)

Where did you see this listed on the plan! I've been looking all over these plans for a few years off and on and havent found it.
Edwin

OsmanKhan

Hi Edwin,

I guess we should have the same plans. I got mine thru mail from MAN. It has two sheets. One with the fuse and wing layout, the other with all the formers, ribs, nacelle, and tail section detail. On the page with the fuse layout, they have marked the CG with a typical circular CG logo on side view of the nacelle and wing area shown below the fuse. The root chord is around 355mm and measured from the leading edge the CG spot is exactly 135mm. Let me know if that is correct.

Osman

Edwin

My Feedback: (2)

God I hope I havent been this blind all my life. Will have to check that at home tonight. I got mine from MAN too. Either way, Thanks for the CG. Another guy PMd me about the nacell formers. I havent even looked at that. I pull the plans out 2 or 3 times a year thinking I'll stumble across the CG. Been doing that for about 3 or 4 years. Sometimes it hits you like a phone book in the face. DOH!!
Edwin

OsmanKhan

thought would be easier for u to locate the CG with this image

Edwin

My Feedback: (2)

Hmmm! My plans dont have that. From just the little bit I can see there, it looks like the same plans. Will be checking when I get home tonight. Either way, now that I have it, its going to be marked on my plans. Any other issues I can work out. Thanks a ton.
Edwin

jaka

Hi!
I don't want to upset you in any way but those .52 twostrokes will make your DC- 3 fly like a pattern plane.
20 years ago a friend of mine built the same DC-3 as you are building from M:A:N plans and he used OS .45 FSR:s and those where way too powerful.
I would recommend smaller and lighter engines like the OS 32 or OS .40 LA using 10x5-10x6 three blade props.

marko509

My plans also do not show this CG marker... Well, at least Osman's picture and info will put this issue to rest. Osman, I'm also glad to hear of your tank idea- those "ronson lighter" gas tanks just look too darned small! One other question... on the sheet with the fuse there are the rudder pieces on the bottom of the sheet. One of these is marked R13. There is no R13 marked on my plan. Just looking it over I think that it may be the bottom of the leading face (angled) of the rudder, marked as "1/4" sheet." Is this correct?

I think I may need to get my money back on this one... who knows how much other info is missing?!?

Mark

Edwin

My Feedback: (2)

Well THIS is interesting, take a look. It says Paris White on the plans. Finally, after years of looking, someone got it. I was almost going to give up and sell the plans. Osmankhan, when did you buy your plans. I bought mine about 4 or 5 years ago. I'm not set on any particular engine. I just know that I want to use 4-strokes. Thanks for the heads up Jaka. The saito .56's were some engine I had on hand ment for another project that just died away for lack of interest.

Osmankhan, Definately want to see some pictures and hear about the maiden flight. Until now I think you're the only person I've heard of that actually started on it. Now I've heard of two. Not very popular is it. Thanks for resurecting an old project. I love DC-3's but the ziroli is just out of my league and a budget buster.
Edwin

OsmanKhan

I got the plans way back in 1998. I suppose some details just faded away on the master copy till they send it to you guys .

Mark you are right about the R13 rib for the rudder. It is exactly the part you guessed on the plan. Don't give up on the plans. I'll be happy to help you out with any missing info or other details you would want when making the plane. The ronson can fuel tank kept me bogged down for quite a while, 'cause it wasn't available here and the thought of permanently sealing a custom made tank inside the nacelle was too unsettling for me. Eventually I have altered the wing design so that the outer panels are removable from the center section and the hopper tanks inside the nacelle area are accessible for maintenance from the end ribs of the center section.

The all up weigth for my machine is going to be in the 12lbs range, owing to heavier scale-looking retracts, 9 servos (2 aileron, 2 throttle, 2 flaps, 1 retract, 1 rudder, 1 elevator). I think two .51s would give me the leverage to not worry about being short on power if other fun stuff needs to be added (like the paratrooper dropping thing). Also I have a feelilng that the whole thing will come out tail heavy and I would rather have heavier engines up front than some dead weight in the nose.

Osman

Edwin

My Feedback: (2)

Osmankahn, Thats a real fine job there. Really looking forward to your maiden. What paint scheme are you planning on? I was thinking about doing one I saw setup as a fire jumper (forest fire paratroopers). Still fine tuning a means to drop about 10 fire jumpers. A WW2 scheme towing a troop glider would be cool too. In a way I'm glad I delayed this project. Many years back before I quit drinking I saw a show that had flying Elvis's jumping out of a DC-3. In a drunkin stupor I thought that was what I wanted to do. Glad I didnt.[sm=lol.gif]
Edwin

marko509

Osman, you have done a fine job so far on yours! I'm not sure if you realize what kind of trouble you're in now that you offerred to answer any questions I might have! Engine-wise I was thinking about using two Evolutiuon .46's... I have one of those Hangar 9 P-51 PTs's, and that is a pretty slick and reliable engine. Should be plenty of power. As I said before, it will be a long time before mine even approaches this stage of completion due to my work load in my job.

This may be a dumb question, but are hopper tanks absolutely necessary?

Mark

OsmanKhan

Hi Mark,

To be very honest, I have not installed the fuel system yet. The hopper tank system was suggested by one of my friends, basically for making sure that the engines always have an uninterrupted fuel supply. The hopper tank eliminates the chance of any air going in the supply line since the clunk in the hopper tank stays in fuel all the time. Theoretically it feels like an added factor of reliability. My plan is to make a mock up of the complete installation and bench test the whole thing with and without the hopper tank to see which scenario is better.

Believe me you don't have to be concerend about the time scale for this project. I have a seven year old son who is younger than this plane. I have been doing this project with a lot of long pauses due to various reasons. But as luck would have it you can do it much quicker than that and I would be more than happy to share any info you may want in order to speed up the project.

As I mentioned earlier in the thread, my AUW will be around 12lbs, or half a pound more if nose weight is required to balance it out. With this kind of a setup I would always want to have the extra power available than rather be low on it with a smaller sized engine like a .32 or .40. Also the heavier engines in front of the CG will compensate for any dead weight that might be required for balancing it out.

Osman

oldtimer143

Hi guys,

I'll throw in my .02 regards the aero-towing.... A friend and I did some aero-towing back in the late 70s (I have a feeling we were perhaps the first in Australia to do this but can't prove it!!). He had a .61 sized Stafford Super Chipmunk and towed my home-brewed fibreglass and foam slope soarer. We had an absolute ball and I can tell you that it isn't nearly as difficult as you might imagine... The following details will help (hopefully).

1. We used a simple release on BOTH models. This was a safety feature we figured we needed in case there was some reason either radio couldn't release.

2. We started with a simple 20 foot piece of 60 pound fishing line with a 12" segment of 1/4" bungee as a shock absorber. This was too short and got a little hairy - not enough time to react comfortably. We finally settled on a 50 foot length of fishing line with the shock absorber. Worked fine.

3. We used the tail of the tow plane with absolutely no troubles. This will be scale of course for your C47 and I would recommend you go with it. However, with the Horsa, I believe they were attached to the tow line by a Y-yoke so the attachments will be at the wing leading edges or probably the struts. You will obviously have researched that.

4. We found that with a VERY slick glider, it was difficult to stay behind the tow plane!! I had no trouble staying in low-tow position on takeoff, but the eventual technique that worked for us was to basically climb at maximum angle to keep the glider in position. This will obviously not be as big of a problem with a more draggy (scale) glider such as the Horsa, but you might be still surprised at how little extra power is needed to tow it. In fact, I would venture to say that you probably won't notice the drag very much at all.

5. To put your mind to rest about the glider climbing uncontrollably - it won't. That is why the glider pilot has an elevator stick after all! Yes, he/she will need to keep forward pressure on it as the glider will be more comfortable at lower speeds, but it will remain completely controllable. If you really wanted to be certain, just build a semi-symmetrical section for the glider instead of the more usual high-lift item. The glider will still have more than adequate performance and will be easier to tow...

6. It is probably obvious but I'll say it anyway - make sure you build the glider with ailerons and don't rely simply on the rudder for turns - it is too slow to react this way and you won't be too successful.

7. Get used to the glider pilot landing before you and being there at your shoulder asking how long before you can tow him again! It's too much fun to just do once!

Hope this helps. Feel free to ask any question you need.
Cheers,
Greg