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Old 10-23-2006, 12:56 PM
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40% Extra 260: Own-design build thread

It's obvious that the Giants love seeing a new bird being put together. Even more so, I can see that the group likes to see something built from scratch- truly from scratch, meaning you draw it up and build it yourself. Like most of you, I have been following Paul Sandys (paffy) Extra 300 build thread closely and I am just being blown away. The plane that I designed, built and flew during the 2004, 2005 and part of 2006 seasons was not nearly as impressive an engineering feat as what we see taking shape in Paul's shop. Nonetheless, it was for me quite an undertaking and I was very pleased with my efforts. What I hope to show you in this thread is that you don't have to be a smart guy like Paul to design your own- with some building experience under your belt anyone can do it. It is a very pleasing experience to fly something that you have built from the ground up. This plane has been flown competitively in the Unlimited class of IMAC.

Now, having said that, if you don't like building it might not be for you. And, yes, you can save some money- but not as much as you think. I estimate that, based on the retail prices I paid for the materials including the cowling, canopy, wheelpants, landing gear and foam wing cores, it cost me about $700+ to frame this plane up. In the grand scheme of things, the additional cost of a kit- even the most expensive one- is not all that much more - given that we probably have at least $5000 in a 40% plane I saved at the most $500- around 10%. That extra 10% gets you a kit or ARF that requires less work and has been proven to fly well. When designing your own, you are essentially building a prototype and you don't know what you'll get when you fly it!


One other thing- I have no intention of selling plans or kits. To me, this is a hobby and I enjoy it very much- I want to make sure I keep is that way!

I had taken a lot of pictures and wrote up a first draft for an article that was to go on the IMAC site. I never quite finished the article (lazy) and it has just sat partially completed. Along with the article I took about 150+ pictures. So, rather than let the effort go completely to waste I thought I would share the pictures and some thoughts with all of you.

I had designed and built a few planes in the past including, over the years, a 120 sized Sukhoi, a 33% Staudacher, and a 33% Extra 300L. With this experience, I started on my 40% Extra 260. Back in 2001 I drew up plans for what was to be my first 40% plane. At the time, there were not many Extra 260's out there on the market- I think that the Dalton 260 (at the time it was still the Troy Built/Von 260) might have been the only 40% 260 available. In designing my 260, I was influenced heavily by the Carden designs- Dennis's Extra 330 is, to me, the prettiest 40% Extra ever done. In addition, his construction methods are not difficult and allowed me to build a 40% size fuse using standard sized balsa and ply.

Step 1: Draw it!

In coming up with a design for the 260, I drew several different versions on 8.5" X 11" sheets of paper until I settled on one that I liked. Based on a wingspan of 120", I stretched the fuse every bit as much as I could while staying within the 10% max deviation. I don't remember what that measurement ended up being but I rolled out my plan paper, drew a line from left to right and made two marks to indicate the fuse length. Then, I took my small drawing and projected it up onto the plan paper that had been taped to the wall. After copying the fuse shape, I pulled it down and started drawing in how I wanted it to be built. The result is below. Please forgive me if you have difficulty seeing the plans. They are pencil drawn and don't show well in pictures.
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Old 10-23-2006, 01:05 PM
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Re: 40% Extra 260: Own-design build thread

GO DAVE!!!!!!!!!!!!

Joe
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Old 10-23-2006, 01:12 PM
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Re: 40% Extra 260: Own-design build thread

Yes...
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Old 10-23-2006, 01:13 PM
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Re: 40% Extra 260: Own-design build thread

Awesome stuff!! Lets see it! It's encouraging for me to see other guys who've been successful at scratch-building their own airframes.

I've got a 35% Sukhoi that I designed partially built. Over the winter I plan to finish it up for a friend of mine...hopefully I'll be starting a thread similar to this one..
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Old 10-23-2006, 01:23 PM
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Re: 40% Extra 260: Own-design build thread

Michael, is this the 260 that had built up foam wings?
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Old 10-23-2006, 01:24 PM
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Re: 40% Extra 260: Own-design build thread

Just so everybody knows - I first decided to design a plane from scratch after seeing Dave's finished 260 2 years ago....

P.
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Old 10-23-2006, 02:01 PM
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Re: 40% Extra 260: Own-design build thread

Its kinda cool knowing/seeing the finished product on the NE IMAC circuit, and seeing how it flies, then seeing how the entire thing came to be! Cool Dave! Thanks for sharing
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Old 10-23-2006, 02:09 PM
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Re: 40% Extra 260: Own-design build thread

I love this stuff....
Seeing threads like this motivates me to at least BUILD a kit....

Knowing that you guys designed and built them, makes building seem more achievable.

BRING IT!
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Old 10-23-2006, 03:21 PM
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Re: 40% Extra 260: Own-design build thread

Vic,

As you'll see later in the thread, it was in fact originally designed with foam ribbed wings. However, I didn't have any kind of decent foam cutting equipment and consequently was unsuccessful in cutting the long span on this wing (I was getting lots of sagging in the wire) so I ended up ordering the wings from FlyingFoam.com (very happy with them by the way). The tail surfaces are foam and I was able to cut them myself with the help of a friend who had a smaller bow and transformer that was of better quality.

I'll also mention that I started the build on this and worked on it off and on for several months- not steady but just when I wanted to and had some time. I was about 90% complete before I took a break from working on it- at the time Composite ARF was just coming out and all of a sudden I could get a 3m Extra for a lot less than I could from Fiberclassics. I flew the 3m Extra for almost two seasons until the somewhat infamous "Tree Point Roll" where I absolutely shredded it through a tree doing low, full throttle point rolls on the Friday before a contest up in New York. At that point I picked up construction on the 260 again.

Here's a pic of the wing jig I built when attempting to cut the foam ribbed wings. In the background is the 33% Extra 300L that I had designed and built prior to doing this 40% 260. It was 102" span and flew great. It's on its third owner now - belongs to a fellow out in Ohio.

Dave
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Old 10-23-2006, 03:34 PM
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Re: 40% Extra 260: Own-design build thread

Here are a couple more pictures of that Extra. I can't find any with the wings on right now. This one was done using the canopy and cowl from an Ohio R/C 33% 300L. Interestingly enough, it was done right around the time that Mike Hurley was doing his Hurley Extra. When Mike and his wife Candy lived in New Jersey we became friends from the various IMAC meets and events that we would attend. We had both developed an interest in designing and building IMAC planes and had had various discussions about the different planes we had build prior to this- I was building my Staudacher and Mike was working with Norm Casella to build his first Extra. Coincendentally, after Mike and Candy moved back to Colorado, we built very similar sized and looking Extras using the same cowls, canopies, gear and wheelpants.
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Old 10-23-2006, 04:45 PM
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Re: 40% Extra 260: Own-design build thread

Ok, on with the construction.

Started out with the main pieces of the engine box. Three pieces total included engine box sides that extended back into the fuse, the F2 former and the landing gear plate.
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Old 10-23-2006, 04:49 PM
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Re: 40% Extra 260: Own-design build thread

Install wing tube phenolic and make sure it's level.
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Old 10-23-2006, 04:52 PM
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Re: 40% Extra 260: Own-design build thread

Build the fuse sides.
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Old 10-23-2006, 05:01 PM
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Re: 40% Extra 260: Own-design build thread

Sheet sides with 3/8 balsa on outside and glue in plywood reinforcement plates on the inside to accept wing and tail tubes. The picture with the plate for the tail tubes is out of sequence but shows how/where glued. The other plates are for the wings before installation. I cut lightening holes in the bottom half before installation.

The overhanging sheeting is so that it will extend over the rudder post and provide additional gluing support when attached.
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Old 10-23-2006, 06:17 PM
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Re: 40% Extra 260: Own-design build thread

After sides are framed up and sheeted, install over plans, pulling together at tail.

Make sure that the wing tube is equidistant from the tail on both sides so the wing is straight.

Glue in F3 at rear of motor box including additional 3/8 square balsa to lock it in nice and tight.

Glue in cross bracing.
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Last edited by dmichael; 10-25-2006 at 08:17 AM.
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