ULF,
Yes I think building the wing upside down like a Kaos wing is the best way short of having custom foam cores cut (lol). The air tank will probably go in to the fuselage in the compartment above the forward part of the wing so it can be accessed and removed easily. I found the picture below in a thread about the ARF available through COX and will probably do something similar. I think the guy that did this installation's name is Bo Ingram.

I'd have to look at the plans but am wondering about wash out when building the wing upside down. The plans call for a balsa stick or something to be laid at a wierd angle across the back half of the wing while building upright. Or is there any washout in the MK II wing? It seems like the Pica version had 2 degress at the tips.

Just curious, thanks.

Tim, I'll have to look at the plans but I believe it called for a 1/4" x 1/4" balsa stick, like you said at an angle on the trailing edge of wing.

No washout in the MK2. The 1/4" stick is there to give the symmetrical wing a second place to contact the plan in addition to the main spar. The reason it is at an angle is to compensate for the taper in the wing from root to tip. I verified this before gluing parts by checking that the centerlines I drew on the ribs were level at both the root and tip. If the stick were not at an angle you would build twist into the wing.

The inaccuracies that proliferate in this wing are largely a result of a worn out drafting machine used by the person that drew this plan. While I can compensate for them once discovered, it has been time consuming and a lot of work to say the least. If I were starting the wing from the beginning I would employ the aid of a clever CAD tool I just discovered to draw and print the wing ribs. It's called Profili 2 and heres the link:[link]http://www.profili2.com/eng/default.htm[/link]

Before you groan about a steep learning curve, forget it. This software is so intuitive and, frankly brilliant, that I had the whole Duelist wing laid out and a rib schedule, complete with lightening holes and built in tabs to aid in building, within an hour. I didn't even need to refer to the help section! After struggling with my 500 page TurdoCAD manual that was refreshing.

I've just begun working with Profili 2 but already anticipate a whole new world of design possibilities. The software is specifically made for model airplanes and their low Reynolds numbers. It has a database of thousands of airfoils that can be compared to one another using different performance parameters like angle of attack and airspeed.

For example, if you wanted to import the stock Duelist airfoil into the program and compare it to others within its performance range you may be able to improve the speed envelope drastically with a slightly thinner wing(from 15% down to 14% thickness ratio for example). There is even a provision for designing flaps!

Interesting you mention that. My son-in-law stumbled across that same program recently and I downloaded it this weekend. One of my biggest issue with the plan for this plane was how the wing ribs were stacked and did not line up. Some of the lines on the odd ribs cross over and you have to be creative when cutting the templates.

How do you know what the airfoil is of the Duellist or any wing for that matter?

We better be carefull with this thread it is straying into the "Twin and mutli" or "Scratch Building" forums!! [sm=red_smile.gif]

I didn't get to play with Profili enough to get as far as you did but would be more inclined to build another with a better set of rib templates to work with.

TCB,
From what I understand so far, symmetrical airfoils are most often described by their thickness ratio (max thickness as a % of chord) and the distance from the l.e. where it occurs (also a % of chord).

Looking at the side view of the fuselage with the wings cross-section drawn, I found the root chord was 14 5/8". I also found the max thickness occurred at 4" from l.e. and was 2.244" thick. So you could say it is a symmetrical airfoil with a 15.3% thickness ratio occurring at 27% of chord. I don't know if Platt made it up or grabbed it out of a book yet but I can upload it's dimensions and begin comparing it to other airfoils in the database. Take a look at the Eppler 477. It's a bit thinner than the Duelist but looks interesting.

This is very interesting, but I'm afraid it is way over my head.... [&o]

It would be nice if we could have a pattern made of all ribs used on the Duellist that are accurate and not distorted...

Ulf, the plan ribs will work, it just takes a bit more time. Profili 2 is free to download; play around with it before you decide not to pursue it. It makes ribs you can download using your printer at home.

I began sheeting the top of the wing panels yesterday. I'm not sure if it's the best way but it worked.

First, I carefully sanded the leading edge bevels using the guide lines I scribed on the balsa leading edges before the wing was built.

Second, I pinned the wing panel to the plan top side up with the 1/4" stick in place so the wing wouldn't have any twist. At this point I glued from the trailing edge to the main spar and just pinned the sheeting to the leading edge. After that was dry I removed the leading edge pins so I could reach in and take out the pins holding the wing to the board!

Third, I glued everything else including the leading edge. While pushing the sheeting down tight against the leading edge using the building board as a straight-edge, I tack glued the sheeting to the l.e. with ca glue.

Mike,

I have good news, today I started building my Duelist....

I decided to start with the fuselage first, I bought a pine board (1" x 3" x 6') for a building fixture and glued all formers F-1 through F10 on the board. It definetly helps to keep everything aligned, next I installed 1/4" x 1/4" stringer on top of formers from canopy back to F10, next I was going to install crutch on both sides but decided to wait untill I have both pushrod tubes installed, don't know if I should glue them in permanently yet or wait untill the 1/8" sheeting is dry fitted?
Tomorrow I will install the crutch on both sides....

I'm using Tibond Carpnters glue so it is going to take more time waiting for the glue to dry, I try to stay away from CA Glue if possible, fumes are getting to me.

I'll try to post a picture tomorrow.

So how is your project coming along it has been very quiet here latley...

Ulf,
Glad to hear another Duelist is taking shape. I haven't been working on mine much the last couple of weeks. Spring and the yard chores have been consuming the free time. I'm also doing a lot of flying right now before it gets real hot here.

If you plan to do your pushrod guides like I did I recommend gluing them prior to sheeting the fuse. Having them glued at each bulkhead will make them a bit more stable and less likely to come loose and cause problems.

Funny, my planes never seemed to last more than about 50 flights so I never worried about wear or access. Now that I'm not as crash-prone I spend much more time setting them up and contriving easier methods for future maintenance. I should be back on this one in a couple of days.
Mike

Mike, here is a picture of my project, hopefully it will look like a Duelist when done...

Question for you Mike, did you get any written building docmentation with your plans?
I'm working strictly off the plans, some of the detail isn't clear especially the front half of fuselage, but thanks to your pictures it has helped me quite a bit, Thanks....

I'm dreading when the time comes to prep the fuselage for the side sheeting, there is some sanding shaping of the top and bottom 1/4" sheeting that runs from the canopy and back and from the trailing edge of wing to the back.
Did you cut out the wing saddle and cokpit area out of the sheeting before you glued it to the fuselage?

I'm open for any sugestion that you might have, by the way this is my first build working strictly off the plans...

Thanks
Ulf

Ulf,
Nice! I just reread my fuselage sheeting description and it's not real clear the way I wrote it. I beveled the top and bottom pieces of the fuse before attaching them to the fuselage but thats probably not critical. I would suggest marking light guidelines with a straightedge so your sanding ends up nice and straight. After making the sideskins from sheet stock I marked two points on each that I could locate on the plans and on each side of the fuselage. I chose the center of the crutch at F3 and F6 bulkheads. I also marked a reference line the full length of the sideskin to mark the center of the crutch so I would know where to place holding pins and to help establish a reference line later when I set the wing and stab incidence. Next, I traced a paper template of the wing saddle off the plans that included those two points, lined up the points of the template with the same on each sideskin and cut the saddle out before attaching it to the fuselage. I didn't do any other trimming to the sideskins prior to attachment because I felt I would need something to grab onto while coaxing the skins around the bulkheads. If you are using 3/16 sheet it'll be much easier than mine was and you might find it convenient to trim some off the lower part of the tail. Still, have thin CA and rubber bands on-hand and soak those skins good! I trimmed off excess sheeting as I went. When you align the sideskins to the fuse press a long straight pin through each reference point on the skin, then with the skin an inch from the fuselage, get the point of the pin into the fuselage at the same reference point. This makes the wing saddle line up nicely with the fuselage on both sides. Mine came out perfect (much to my surprise). I wish the wing ribs....um, nevermind.

There was a two page article with my plan but it had nothing in it regarding construction. It was all about what inspired him and some of the things he did when developing the thing. If you PM me a fax I can try and send you a copy.

Good luck with the build,
Mike

Thanks for the reply.

I'm going to use 1/8" balsa skins for my fuselage. I plan on using Ultracote so I think that I need the extra strength, I don't want to get into fiberglassing...

When you skinned the fuselage did you do it while the fuselage was still attached to the building board?

You don't need to Fax me the information (I don't have a Fax machine), I was hoping for some detailed building information, but like I said before your pictures helped me a lot.

My other plan is to use spruce spars when I get ready to build the wing for a little extra strength, do you think it is an overkill?

Here is a few pictures of todays work...

I'm getting a little closer almost ready to skin the fuselage.

I made a test sample using 2 types of wood glue, I'm gluing together 3 pieces of 1/8" balsa together and then I'm going to soak them in water and see what happens when I bend the sheeting.

Titebond 2 = Weatherproof according to the manufacturer.

Titebond 3 = Waterproof according to the manufacturer.

Here is another picture, it would not fit on previous post....

Ulf, your doing a great job. My main concern when sheeting the fuse was keeping the thing straight. There is a lot of force required to bend everything together even in a soggy state so you must have the structure attached to the board and bend each side at the same time to cancel out the forces acting on each side of the plane. I started at the saddle and pinned along the crutch toward the tail, then turned around and pinned toward the nose. next I forced the sides together just aft of the cockpit area and while holding it in one hand, tack glued it in place with thin CA. I repeated this toward the tail, always pulling on each side with equal force. You will probably want to trim away excess sheeting as you go so you can see where your tacking. I also felt better checking eyeballing the fuse from the tail periodically to make sure I wasn't building a bannana!

In regard to 1/8" sheet, if you have light stuff it's probably no biggy. Much of mine was kinda heavy and stiff so I really had a tough time with it. My fuse is built like a tank! Let me know how that Titebond III holds up in the soak, I'm running low on II and will switch if your happy. Regarding spars, again, my wood was on the heavy side so I put the densest balsa on the lower spar and the less dense on the upper. (Airplanes pull more positive G's than negative during their service life.) Instead of spruce, you might put some 1/16 shear webs on the back side of each main spar pair with the grain vertical. That would be lighter, much stiffer, and possibly stronger than spruce substitution. One place that should be strong is the stabilizer leading and trailing edge. At high speed soft balsa can allow flutter to tear/break it off. This occurred on an upsized 2/60 version of this same plan a couple seasons ago.
Mike.

For some history on the plane here's a quote from William Robison in a previous Duelist MkII thread:

"Some history. Dave Platt designed the Duellist 2/40, and in 1976 when he owned Dave Platt Models he produced a kit for the plane.

I don’t know the details, but he and Morton Tanger had a fight about one thing or another, Platt was forced out of DPM and Tanger took over. The Duellist stayed in production, Dave Platt Models became Pica, and the later kit plan for the Duellist showed Morton Tanger as the designer. This was a lie, but Tanger’s name stayed on the plan until the end of production.

After leaving DPM/Pica Dave Platt then redid the Duellist 2/40, made a lot of improvements, and RCM published the improved plane as the Duellist 2/40 Mk II. But it was plans only, no kit. A better airplane, but you had to gather up your own materials. The plan is still available. Pica never incorporated the improvements in the kit version.

Estes has now bought Cox, and the Cox division of Ests has bought the kit line of Pica from Morton Tanger. They have plans to produce the Duellist 2/40 as an ARF. According to the early information given, it should already have been on the market. I do not know the reason for the delay. When I spoke to Mike Fritz at Cox, he said their version was the exact design Pica had kitted, so it must be the early model, which we now call the “Mark I� plane.

At the same time Platt was doing the 2/40 Mk II he was thinking about a larger plane for 60 engines. He did build a single prototype, but never published plans.

A few years ago several of us on RCU, who also happened to be Duellist lovers, got together and decided to do the larger 60 size version for ourselves.

We had an open discussion in a thread on RCU about the design, and then started another thread inviting subscriptions to defray the development costs.

We started with the Duellist 2/40 Mk II, enlarged it by 25%, and made a very few other changes. The biggest alteration was converting to a two-piece wing. We retained all the proportions of the Mk II 2/40. We called it the “Super Duellist 2/60 Mk II.�

And yes, we paid a royalty to Dave Platt.

We packaged a total of 50 kits, there was also one set of the laser cut parts used as a proof of the drawings, Ernest Fleming, as far as I know, still has this set. Forty-nine were sold, kit serial number one was given to Dave Platt in appreciation.

At the end of our production all rights were assigned to Northeast Aerodynamics, they are close to the release of the Duellist 2/60. Originally they had intended to sell it as a kit, but with the market as it is they have decided to sell it as an ARF only.

If you want either version as a kit, there are still some 2/40 kits that come up on one of the auction sites now and then, and some 2/60 kits are still not built. Once in a while you will see one for sale.

So. Three other options. Buy the plan and build from that, or wait a while and pick either the 2/40 ARF from Estes/Cox or the 2/60 Mk II from NEAero."

I thought that was a pretty good summary!
Mike.

Blade47 documented an excellent build thread of the 2/60 kit but on the maiden flight the stabilizer broke off in-flight. He miraculously saved the plane but one nacelle separated with a clean break when it crash-landed. Although this is a larger plane than the 2/40 it helps illustrate a couple of potential weak spots in the design. Substituting spruce for the trailing edge of the stabilizer might be wise insurance!

Mike

Ulf,

Nice job so far, keep up the good work ! Unfortunately, back to work next week , hey ?? !! [&o]

Mike, thanks for the information and history about the Duelist, very interesting...


I'm glad you mentioned about the tail being a possible weak spot, I'll have to see what I'm going to do to beef it up a little, I have the same concern after building my CG Extra 300 that is now just about completed, it seems flimsy and is only sheeted with 1/16" balsa (very soft balsa sheeting used), I kind of regret not beefing it up more, but it is too late now...

I just finished the testing of Titebond glue, I soaked the test piece for about 35 minutes in warm water with amonia and none of the glue disolved when rubbing my finger on the glue joints so that is good.
But I'm afraid my test wasn't very sientific, I started to bend the wood and it held up good enough to follow the contour of fuselage but the Titebond 3 did snap the glue joint first, but that part of the wood was definetly harder wood than the glue joint of Titebond 2, it felt much more flexiable but it also snapped after bending it some more.

I do like Tiebond 3 best for building, but I did not test with CA Glue so I am still undecided which way to go.....


Thanks Juan, yes I'm going back to work so my building is going to slow down some, I hope to have the fuselage skinned this coming week if I can decide what type of glue to use.

Hey,
How is the build coming along? Haven't heard anything in a while. Busy with summer??

I finally got a [link=http://www.rcuvideos.com/item/FTFPQS39JNNNMHTG]video[/link] of the Duelist in a flat spin. Not my best and it was the first flight at a field I have never flow at before but I think you'll get the gist. It really flattens out nice!

TCBLightning,

My building is at a standstill for now, have too many other things to do. I will start up this fall with the Duellist, right now I'm enjoying summer.............


Thanks for sharing the video of your Duellist, nice flat spins........

Hi I have had a duellist (one of the old kits) for about 15 years and it flys great with 2 40 FP OS moters even on one moter I hope these new are as good cause I may need one some day.Have fun cause it is a good plane.

Hey CrateCruncher, how did the rest of the build go if you finished it? I've got two YS 45 rear exhaust's laying around and I'm thinking about building the Duellist MKII off of the plans. I'm interested in making it fast and find the Profili idea a great one to thin out the airfoil a little. I'm somewhta worried about the tail strength as the fuse gets pretty skinny in the back. I'm sure other Duellist fans would like to see some pics of the advanced stages of the build. Thanks!