Sig Twister - to lengthen or not?

It flies better with the mods.

Joe, the tank setup in the picture was a slight overkill in creating an adjustable tank mount for a plastic clunk tank and although there is nothing wrong with the set up it isn't what is on it now. Originally I had put a GMA reworked OS 35-S on the nose but had major vibration problems. Even though the plane has longer motor mounts (bottom one all the way to the wing), Aircraft ply doublers and a much deeper nose I was getting a resonate vibration with the 35-S that created all kinds of engine run problems. In the process of trying to solve the engine problems I put a GRW 41/4 oz Chicken Hopper mounted with Brodak brass adjustable tank mounts. The final fix was to replace the 35-S with an FP-40 and just left the Chicken Hopper on as it was working fine.

What you are seeing in the picture is a piece of the kit light ply large enough to engulf the tank with two spruce rails epoxied to the top and bottom to fit the tank. I then fashioned the hooks for the rubber bands out of 1/16 music wire and inserted them into the spruce bent over and epoxied on the back into a relief channel. The light ply has four elongated mounting holes for up/down adjustment and is mounted to the fuselage with four sheet metal screws and washers. I still have the mount but the Chicken Hopper has worked so well I have not gone back.

Ed,

One word of caution here.....if you go with a 3" fuselage extension, be very WEIGHT CONSCIOUS with the tail end of your plane.

I did do a full "Fancherizing" of my Twister, and ran into a major problem of coming out tail heavy....it required 4 OUNCES of lead in the nose to balance.

The problem was an accumulation of several problems...I didn't over sand the rear of the fuselage to minimize twisting of the stab, too large a canopy and turtle deck, too much paint, and I was using the OS 25 engine. I didn't want to got to the OS 40 because that would defeat the purpose of the whole program, besides that would only add 2 additional ounces of weight. I think I have found a solution....I just bought an OS Surpass 40, and I think this might make a good match.

I did speak to Ted about the problem, and he suggested that a 2" extension of the fuselage might be better.

What every you do, be sure and exercise all of your best weight saving techniques on everything behind the CG, i.e. wood selection, sanding, and painting.

Cheers,

The CG would probably have came out about perfect with an FP-25 but the FP-40 fit the holes for the 35-S and didn't want to plug and re-drill. The next one will have an FP-25 on the nose and I am going to cover the fuselage with .02oz carbon fiber matt instead of using the spruce stiffener. I expect it to end up well under 35 oz.

I liked the spruce stiffener when you showed me the plan but I wondered about a carbon fibre arrow shaft instead. We can get arrow shafts that are supposed to be outside the straightness tolerance. I checked some out by rolling them across a glass shop counter, but I couldn't find any wobbles.

Price is 25 South Pacific Pesos for 12. US$1 for you guys if you can find them.

Also, has anyone tried a white foam plastic rear fuselage clad with balsa or ply? Tom Morris wrote about the technique in Stunt News several issues ago. Also, Phil Cartier used it in a model published in Flying Models some years ago. 2 pound per cubic foot foam is a lot cheaper than 6 pound balsa.

Here is my rendition of a Fancherized Twister. It weights 39 oz with a McCoy 35. Recently I upgraded it with a Big Art Tower 40FP and added a 1/4 oz to the tail to adjust the CG. It won a 1st and 2nd in two events at the recent Huntersville CL Stunt contest with Clayton Berry flying it. The secret is to use contest grade balsa and build light.

Lt Col Tom McClain

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I know that yellow airplane well now...(!) Clayton beat me by three points for first down there. Did he mention that he bounced it off the ground in Friday's practice?? You build pretty strong as well as light!

Steve

And, Clayton won those placements with no appearance points since he didn't build the plane.

Yes, Clayton told me of his crash on the first practice flight on Friday before the contest. He smashed the Dubro spinner, the prop and knocked off a 4 x 1/2 inch piece of the rudder. He made some temporary repairs and then proceeded to get almost 30 flights on it over the weekend. I understand he did quite well at the Metrolina contest on Saturday and Sunday. Several of the club members here told him to buy the ship from me, but he wants to finish a Brodak Profile Cardinal and besides I like the ship and am unwilling to sell. I have repaired the damage and have tried some different props on it since he brought it back. Right now I have a Grish Tornado Magnum 3 blade 10x6 on it and it is humming right along. I like it better than the Rev-UP 11x6 EW that I had on it. It flies well with an APC 10.5x4.5 too. Go figure. Ted Fancher truly modified the Twister into a world class stunt ship.

I flew this one (my first 'stunt' airplane) 97-99. Basically stuck with the kit, with additional built up wing tips and adjustable leadouts (solid, with whatever bellcrank comes with the kit). Began with an Enya 35 and a round clunk tank, then a Fox 35 with a metal uniflow (no muffler). Things got better when I discovered RevUp 10-6 EW props (bought 30 of them for $2.25 each). Line tension. How nice. Flew that set up at Norfolk in the fall of 97. Always windy there, and while I say I had line tension with the Fox and the 10/6 RevUp, I had a hard time with the wind on that particular weekend. Steve Fitton may recall me crashing my original stunter due to the wind that weekend. Anyone need a broken ST 46?

A non-flying friend at the local field backed away from the circle as his son took off, and crushed the tail with his size 10 Nike. In repairing it, I enlarged the stab/elevator about 20%, and added 1 7/8 inches to the length of the fuse. I also added adjustment facilities to the rudder. Recovered entire airplane with a single roll of monocoat (light blue, this time). I say a single roll, because if you're real careful, you can do it and end up with a single piece about four by six inches. For patches. When you hit a tree. I mounted a new K&B 40 ABC with a metal uniflow. The Fox and Enya were both leftovers from the days when I flew with my dad in the 60s. The real reason for the lengthening was that the K&B is significantly heavier than the Fox or the Enya and I knew it would be nose heavy if'n I didn't. That others were lengthening theirs just reinforced my thoughts. I still maintain that the biggest improvement you can make to a Twister is adding wingtips. Airplanes are supposed to have wingtips. You don't want anyone laughing at you for flying a butt ugly airplane, do you? Add wingtips.

Discovered the 10.5/4.5 APC when Tom Hampshire of New Jersey insisted that I try one at the 98 Brodak meet. It is a thin and small prop that spins really fast. I was trying an 11/6 RevUp, and the engine wouldn't run with a break. Either slobbering rich, or full song runaway. It worked great. I used that set up to fly Intermediate thru 98. I also occasionally used an 11/4 Top Flite Power Point, but there isn't that thrill of flipping a nice sharp APC. I have a chicken stick, but I usually use it as a spindle for winding up my lines.

I returned from Brodak 98 to fly thru an Ash tree in my front yard(I've since trimmed it up a bit). I also laid a square of slate in the center of my circle, lest I ever wander from that spot again. 17 holes in the wing. I patched it, but got tired of folks commenting on my weird covering technique. Every other rib bay had this ugly seam in the plastic where the patches met. Another roll of monocoat (green), and I flew it some more.

I ended up with a Tower 40 that I really liked, and being lighter than the ball bearing K&B, gave me what I wanted. A slight movement rearward of the CG, and a friendly engine run. Same APC that I was using on the K&B.

I was now flying on 64 foot lines, and doing okay. Don't recall lap times, but I was very comfortable with the set up. Then I flew at a field where the two circles were designed with the idea of 60 foot lines being the longest anyone would ever contemplate.

The Twister flew off into the woods. One hole in the plastic, and a broken prop. Glen Daggs' full fuse warbird wasn't so fortunate. As in, a write off. A month later, a miscommunication ensued, and someone took off whilst I was flying. He hadn't been made aware of my additional inches (no, I didn't feel funny typing that at all), and I clobbered a Veco Chief. This time, there were two write offs. The guy's brother mentioned that there had only been two collisions that he knew of, and that I was involved in both of them. I'm still welcome there (Goddard Space Flight Center, Greenbelt, MD), but with trepidation, no doubt. And it motivated him to finish a Nobler he'd had hanging in the shop for some twenty years. So, what's not to like?

That's my story, and I'm sticking with it. I didn't own a decent scale back then, so I never weighed it. But I'm a decent builder and monocoat is relatively light, so I'd guess around 40 ounces or so. It did have an aluminum gear, for what that's worth.

I actually built a nice one last winter (from a kit, mostly), but it met it's demise on the second flight due to a line breaking. I'll never add heat shrink tubing to the ends again. It hides the fact that the little tiny wires are fraying and this is important information one needs to know. It had half ribs and trusses in an X pattern between the ribs on the spars (again, because they're easy and maybe they stiffen things a bit). Stiff is always good, right? A wire landing gear, two inches on the fuse, and larger empennage of my own shape. It was 37 1/2 ounces ready to fly, with a Tower 40 and a tongue muffler. I gave the pieces to someone. Maybe it'll get rebuilt. It wasn't like it was all fuel soaked or anything. Did I mention that it was the second flight?

As to flying Tom's Twister, it flew just like mine. His set up was different than mine with the big prop, and after I broke his on the first flight (my cowboy hat came off in the overhead 8, and I tripped on it while whipping it so I could land near the pit area), I slipped on the APC. Was a little fast on his lines, so I whipped out the 64 footers. The weather was perfect, the company was good, and I was showing off my new little flying partner (Clayton II). And I proceeded to do the best flying I've ever done. Took a second in combined Profile behind Curtis Comer of Huntsville, AL. He's beaten me there before (he flies Expert), but I still felt pretty good. Dale Barry (winner of Advanced at this year's Nats) would have put me in third, but he ran out of fuel early in both rounds with a new engine set up. I didn't look at his scores, but he's a better flier than me. More flying until darkness, as the weather was absolutey perfect. Sunday's first round flight was probably the best flight I've ever made. And it held first place.

Was a great weekend, what can I say? I broke Mister Happy (my only real stunter) back in June, so I had nothing to fly. I would have gone just to show off my little guy and spousal unit, Marlene. Maybe do a little judging, converse with some fine folks... But it just so happened my pal Tom had this Twister that he felt brave enough to lend me. A great way to end the season.

Thanks again, Tom.

LAST EDITED ON Oct-24-01 AT 09:28 PM (CDT)

Geoffgg said "I liked the spruce stiffener when you showed me the plan but I wondered about a carbon fibre arrow shaft instead."

How were you going to install the carbon tubes? Unless you split the fuselage, carefully groove each half for the tube and re-glue (epoxy seems logical, tho Urethane glue might work too), you will use a lot of epoxy or something to fill around the tube. Besides all that, the best approach would be to just glue a piece of CF uni-directional tape down each side...cut a recess if you must. Prather, ACE R/C and others sell it, along with the usual CF sources. Putting the strong stuff on the extreme surfaces of the structure is ALWAYS the best for stiffness vs. weight. Steve

Edit: Geoff, I was referring to the .009" to .020" thick bands of CF pre-preg that come already hardened in a roll at the local R/C store. 1/64" plywood is a close substitute. I covered the sides of a Foxberg racer with it, and the fuselage was stiff as a plank of pine...no blurred tailsurfaces at all. I like the foam aft core idea, which has been used by more than a few. Experiment, then send the knowledge to Stunt News, so we can all learn from eachother.

I was just going to cut a tight-fitting slot and fill the voids with Aeropoxy or similar. I have not been able to find a source of the really lightweight CF veils in Oz and, with the Aus dollar (aka South Pacific Peso) running around US$0.50 at present, inporting from any of the usual sources is very expensive.

Tom Morris has been using 1/2" pink foam planks for the aft portion of profile planes. He sheets them with 1/64 plywood. Not quite as light as sheeting with balsa, but then you don't run into warping problems that the balsa can cause. I have a plank of the 1/2" inch pink foam he gave me and I plan to use it on a profile plane sometime in the future.

I was not sure of the foam that Tom used but Steve Cartier used white Polystyrene foam with balsa skins for a semi scale Zlin profile stunter that he had published some years ago--I can't remember when. I just scanned the article from the mag and can't find a date or magazine title on the scans.

There is a lot of good information and advice in the above posts about the Twister. The one thing I wish to add is the Twister is a really good flying model in stock form. Yes it will fly better with the mods but it really depends on your ability to build and properly trim the model. I had the bad luck of loosing my Twister just a few weeks ago when the engine quit in the vertical leg of the four-leaf clover. This Twister was built from the kit without substituting any wood. The only mods that I made were the adjustable leadouts, tip weight box, and a Sig 4” bellcrank. It was powered by an OS .25FP (stock) that provided plenty of power even at 5000’ here in Colorado. It wasn’t Super light at 38 ounces but I was really impressed with the ability of this model to fly a very decent pattern. I flew it in a number of P-40 contests and did quite well with it.

The important things to remember is to build it straight and reasonably light and add the adjustable features that allow you to trim the model to its full potential.

Mike