Graupner Cirrus build

[John Cole]

Call it regression, dopey nostalgia, whatever... but I've got this nagging desire to build a Graupner Cirrus! ;)
The build will be somewhat abbreviated since I'll be using an old set of wings built in 1983 for a Graupner 'Cirrus 75'. This model used a different fuselage and tailgroup, but the wings were nearly identical. These wings are in need of restoration. I'll be adding tip extensions just for the heck of it, and recovering of course.
The kit I'm using is complete, but really trashed, from a collector's perspective. It had been stored for quite a few years in a humid place, and it shows.

I'll try to keep this thread going as time permits. Comments and suggestions are always welcome!

John

[John Cole]

This is what the Cirrus 75 looked like. It flew pretty well, but was heavy. Eventually, I may restore this fuselage and build a new set of wings for it.

[John Cole]

I built the wings per plan, but added blade-type spoilers. They worked well, and unlike pop-up type spoilers, the nose did not pitch when deployed.

[Curare]

oh man you know how to make me weep.

I'd kill for that kit.

Love them cirruses. (or is it cirrii?)

[John Walter]

oh man you know how to make me weep.

I'd kill for that kit.

Love them cirruses. (or is it cirrii?)

You mean like the kit sitting on the floor behind me as I type this? :D

[bobthenuke]

What John failed to mention is that he built the spoilers from scratch. These, in themselves, are a minor work of art.

...bob

[John Cole]

Curare,
Too bad they are getting so scarce. I'd usually not build an older collectable model such as this, but this particular kit was pretty rough. Some of the wood had gotten wet, but the damage is not permanent. I was hoping to use the decals, but they may be wrecked, won't know until I try them. I'll try to do the model justice. Glad you're following along!

John

[John Cole]

Thanks Bob! :o

It will be a fun project, it was the first time around!

J

[Curare]

You mean like the kit sitting on the floor behind me as I type this? :D


:eek: :( if only I could find another in australia

[John Cole]

The main difference with the wings of the Cirrus 75 and the original Cirrus was the aileron controls. Both versions could be built with them as shown on the plans, but the 75 used a very thin steel cable and plastic sheath which was included in the kit. The original design considered them optional, and parts were supplied by the builder.

[John Cole]

I got the covering removed from one of the wing panels, tedious but necessary. The wood and glue joints look sound and secure considering they're nearly 25 years old. :)

[John Cole]

Graupner produced a very comprehensive kit for it's time, and would be considered well above the average than many kit makers even today.
The plans were well done, and Graupner was careful to translate all of the building text so the model could be sucessfully completed by a large, international market of glider enthusiasts.

[John Cole]

Included within the instruction booklet were these terrific drawings to aid the modeler. They could almost be used alone to build the kit!

[John Cole]

Beautifully drawn plans!!

[bobthenuke]

Those really are great plans. Only one other kit manufacturer I'm aware of that does anything like those - Proctor. Too bad so few kit manufactuers are willing to (or can perhaps afford) supply plans with such detail.

...bob

[Curare]

beautiful

I have a set of plans for the kyosho one. not nearly as nice I've got to say.

[John Cole]

The plan set includes a seperate sheet showing radio installation details, a good idea in 1969 as many folks simply didn't know how. It was printed on a semi-transparent paper that could be overlayed on the main plan.

Another novel feature of Graupner plans of this era is that the part numbers for each subassembly are unique; they correspond to construction sequence. Good idea.

[John Cole]

The spoilers were originally set up using a cable to pull them up, and a small spring pulling them back. The servo was located in the fuselage.
With new servo technology, I'll place all the servos in the wing, including the aileron controls.

[John Cole]

I finished one of the tip extensions, and I'm sure they will add little to the overall performance of the model. Actually, I'm hoping they don't take too much away from it.. :rolleyes:

Span will be 136.5" vice 118".

[MarkusN]

Actually, I'm hoping they don't take too much away from it.. :rolleyes:

Span will be 136.5" vice 118".
Did the same thing to an Amigo II once. Boy, did I ever regret it. Rudder authority was nowhere near sufficient. But you got ailerons there. Should be a different story.

[Thermaln2]

I have been flying a Graupner Cirrus for over 7 years. I added a CF to the spars and webbed the wing all the way to the tips. I originally flew my fist Cirrus back in the mid 70's for my LSF V 8 hour slope flight. I have plugs for the Cirrus fuse parts in the works and a freind is pushing me to finish it. If it were of fiberglass now, the parts would be alot lighter than the plastic fuse.

Here is a link to a picture: http://www.spieltek.com/Chris1Visalia2005s.jpg

I like flying the plane. Everyone says the wings are going to fold on the 12 volt winches. Then on the ping, the wings flatten out. The original kit wingpins are great.

Good luck with your build.

Chris

[John Cole]

Chris,
Good insight on the wing pins, thanks for that. Yes, the plastic fuselage is pretty hefty alright. This ship won't be a light air floater.

Hey, get that glass fuse done!! :D

[Curare]

you'd be suprised how good they are in light air!

wow, look at that, a pristine fuse.

[Ray Hayes]

Chris,

Looking good, you and the Cirrus ..... I have to figure a way to have you and Ken Bates in the same pic, you would pass for brothers.

Keep us informed on your RES design.

Ray
Sky Bench.com
Home of Wood Crafters

[seanpcola]

What John failed to mention is that he built the spoilers from scratch. These, in themselves, are a minor work of art.

...bob


True dat, Bob!

John, do you have any more pics of your spoiler build, drawings or such that shows details? I have been squirreling away every Multiplex/Graupner spoiler set I can find in both lengths. They work great but so easy to bend or twist out of alignment and hard to ever get working right again. I would love to make a wood set like yours.

Sean

[John Cole]

Sean,
Yes, I'll be sure to post more pictures and details of the spoilers. They are easy to do. When I stripped the wings, I didn't take a lot of pictures. But I'll make a point of showing them better as the wings are prepared for the new covering.

John

[John Cole]

Well, I have a few fleeting moments to do some glider stuff, so away we go!

The fuselage parts are laid out and prepared for joining.

[John Cole]

The moment(s) of truth.. Bonding the front fuselage halves while trying not to screw it up. ;) Thanks for the help Bob!

Came out fine, glue used was UHU-Hart. This is interesting glue, feels like Duco, but surely is a different compound. Makes sound bonds between plastic and wood. No wonder Graupner recommends it for this model..

[John Cole]

Once the halves are joined, the assembly gets REALLY stiff, more so than fiberglass. And, heavier.

More to come...

[G.P.]

I have plugs for the Cirrus fuse parts in the works and a freind is pushing me to finish it. If it were of fiberglass now, the parts would be alot lighter than the plastic fuse.Chris, are you just teasing us or would be willing to sell a few? I bought a Cirrus off a guy at work and it is one of my favorite gliders. The fuse has a few repairs though and it needs alot of weight in the nose to balance now. I would love to get a new fuse for it. My other option is to throw an electric motor in the nose. It's carrying the weight anyways and would probably allow me to fly it even more.

Thanks for doing the build. The plane that I have is older than I am, so it's neat to see that people are still building them. It actually amazes me how much interest there is in the Cirrus still. -Greg

[Thermaln2]

To answer a few questions RE the FG fuse. I expect it to be in pieces just liek the original, I have the canopy molded also for a clear canopy. The goal, as givien me by a local friend is to make this available. This is a winter project which is continuing and now that I have a new building area, I can get back to it. when completed, I will make it available.

For those I see building the fuselages with original plastic parts, I have a required suggestion. I am using the original wingpins. If you look at the plans, you will note that the pins slide into brass tubes whihc are embedded in the plastic of the fuselage bulkhead. The pins join at the center, and that is the biggest weakness of the design. Nowadays with stronger winches than we had in the 70's, the wings flex, the tubes flex and fatigue, the plastic bukhead breaks and the wings assume a greater v-shape on launch and may break. So the failure mode is not wing failure, but fuselage failure.

To stop this, you need to laminate plywood on either side of the bulkheads, and then make sure the front and of the reinforcement are glued together. Essentially you make a box around the plastic bukhead and tube. The ship I have pictured , had this done on both sides of both bulkheads and is extremely stronger. So Strong, it makes the winch guys flinch, expecting the plane to be destroyed on launch. That will not be the case, little do they know!

This is just a suggestion. Most launches, like at Visalia, pull up heavy lines and winch retriever lines, so there is alot of pull on the wings and fuse.

As for other modifications, the CF laminates on the spars, and full webbing of the spars front and aft are the only wing changes. I did add 3/4 " of moveable rudder area to the back. I fly only RE. I have spoilers built in and ready, but have never cut them out. I fly with alot of washout in the wing.

I'll keep the post updated as it goes.

Chris Adams

[John Cole]

Chris,
Thanks for the tip. I will find a way to box the cross tubes in. This may be a little tricky now that the fuselage shells are joined, but I'll figure something out.
Question; My wings are already built. Would you suggest I glass the 'D' box prior to covering? Would the weight gain be worthwhile?

I'll be in line for one of your glass fuselages when they become available.

John

[rrdiaz30]

<< I'll be in line for one of your glass fuselages when they become available. >>

Count me in for one as well! I still have a wing set and canopy with no where to go.

Rick

[G.P.]

when completed, I will make it available.Thanks Chris, that would be sweet! I have been trying to find a replacement fuse for some time, so count me in! -Greg

[John Cole]

The floor is prepared for the tow hook mount. A small strip of ply helps level the seam.

[John Cole]

The boom needed a little attention to get the fit as close as possible.

More soon!

John

[John Cole]

Progress is slow but that's just the way it is while I'm working a lot. The fuselage is glued together, most of the internals completed, wings ready for glass (D-box).

Will post pictures soon.

John

[Curare]

I've replaced the wing joiners with two hardened steel rods.

It's not easy to thread them into the fuselage but it is possible if you spend some time.

I made the bend as shallow as I could (big and round) and then filed out the holes as best I could to get them through the fuseleage.

I should point out that the way that I did it, ended up making the wing sit about 0.5mm above the wing fairing, but what I lose in aerodynamic efficiency I make up for in launch hieght. But be warned.

If you do this modification, you do run the risk of splitting the fuselage pretty badly in a crash. the rods make mincemeat of the plastic in a crash.

[John Cole]

Sounds like an interesting mod on the joiners. I'll be using all of the kit's original wing hardware. I realize it won't be nearly as rigid as the current designs use. I don't anticipate standing on the winch pedal, and maximum launch height won't be necessary since this model will be used for leisure sport flying. Yeah, I'm affraid I'll be pampering the old girl.. ;)

I may have some time off this weekend, will post progress!

John

[John Cole]

I forgot to post this picture before... showing the tip extension. This mod will accomplish one useful thing; provide a little more aileron. :rolleyes:

[John Cole]

This elevator pushrod support was added before glueing the fuselage together.

[John Cole]

Up to this point, the fuselage has been glued together, laquer putty applied to level the really bad spots, rough-sanded, and elev pushrod and horn installed.

[John Cole]

My big plan is to keep the flight gear out of sight, below the canopy frame. Easy to do (especially once you've built a couple of discus gliders..) but still required a little planning. The elev pushrod is just a straight carbon tube with fittings bonded to each end. The rudder will be pull-pull.

[John Cole]

Here's the rudder pull-pull arm. Made with a servo arm, two nylon bushes, bolt, washers, etc..

[John Cole]

The fin is built-up, and is really strong. Since I'm painting the fuselage anyway, I'll be glassing this fin. It will get primed and painted together with the fuselage.

[Bill Ervin]

In 1977 my dad took me to a local airshow in Minnesota (Anoka MN to be exact). Among all the full-scale acts was a demonstration by the RC glider club. They launched three Graupner Cirruses and floated around for a while. At 14 I knew exactly what they were, it was the highlight of the show for me.

keep up the good work John, like many here I have fond memories of these sailplanes.

Bill

[John Cole]

One of the small changes I'll make to the kit is eliminating the rudder/ fin gap. The kit includes a neat synthetic cloth hinge, but the resulting gap is bugging me. ;)

The following technique works on all types of models. The strips will get glued into the recesses, providing a smooth joint. The ply will overhang the fin by about 1/4", creating a pocket for the rudder to set in.

What one will do to eliminate those embarrassing gaps! :D

[John Cole]

Hi Bill,
Glad you're following along. It's a fun model to build.

John

[rrdiaz30]

There is a Graupner Cirrus on EBay...this one will be fun to watch!

http://cgi.ebay.com/Graupner-Cirrus-RC-scale-sailplane-glider-model-kit_W0QQitemZ140189540281QQihZ004QQcategoryZ2563QQ ssPageNameZWDVWQQrdZ1QQcmdZViewItem

[John Cole]

Yeah, I saw that. I bought my Cirrus on eBay, and as a point of reference, I paid $225 for mine, and the kit is rough. :o Taking inflation (since 1969) into account, $250-$300 really isn't such a bad price.

Isn't it funny how guys will roll their eyes at this, but so willing to spend 3X-4X(or more) for molded ARF's, and then again when an improved model is developed?? *sigh* Same dynamics in hang gliding and full scale soaring... Creates a great 'used' market!

John

[John Cole]

Oh man... I was SURE one of you guys would bite on my last comment. :p

Dang, this crowd isn't as easy as I thought.. ;)

Ok, well, the rudder/ fin is progressing along, more pictures soon. The gapless hinge joint is shaping up. It's a lot of fussing around for such a small detail, but fun to do.

John

[Curare]

Indeed

I've gone completely off the "cyborgs" I thought they were cool, once, now they're just discarded after a year because something better is around, when for me, soaring is all about the float, man.

[ka7cse]

I sure would like a copy of those plans for my collection.....

[Mike Taylor]

Speaking of which, so would I. I still have my original Cirrus, but not the KP-2B that went into it, and a second fuselage with no wings or elevator...

[schrederman]

OK... I'll bite... I bought my PIK for $13,900- and sold it for 17,500-. I could afford a moldie after that. I could actually afford a moldie before that, but I couldn't justify it, even to myself. However, to be competitive in full-scale, the initial layout is about $120,000- and you'll easily spend $3000- going to a 10-day contest. Makes buying a $1,200- moldie and $400- worth of servos seem to be sort of a bargain.

Jack

OBTW - There's a good used market for molded models, too...

[John Cole]

Good point Jack. Once you've participated in full scale aviation, ALL facets of modeling seem cheap!
Also, I will never put down moldies OR ARF's, the technology and science applied to our soaring sport these days is incredible. We live in a great time.

Do I have a molded model now? Nope. But I can assure you I will someday. ;)

John

[Miraj]

Curare, why not get one of the lads in the states to copy the plans for you. The lost foam fuse method should be ok to do on that fuse.
I have the plans to the Aquila Grande that i'm going to do that way. mmmmm aquila.
S

[Curare]

I'm still chasing a set of plans for a sagitta, but I'm too lazy and cheap to deal with RCM on that one.

ANyone got the time to scan some plans?

[John Cole]

Tired, pooped out, whiney, sick of work, but ALWAYS time for models! ;)

Here's a few shots of the 'gapless' rudder fix.

[seanpcola]

Excellent job.

[John Cole]

Here's some rudder stuff. The hinge method is not my idea, it's commonly used in some of the Multiplex models, and is similar to the Cirrus 75 setup.

Two small pieces of brass tube will be bonded to the fin post, wire will pass up from the bottom of the rudder to create the hinge. Way simpler than I'm making it sound. :rolleyes:

[John Cole]

And more rudder stuff..

[John Cole]

Next step will be to glass the fin and rudder with 1oz cloth and thinned epoxy resin. Once these parts are finished, the brass hinge tubes will be bonded to the fin post.

More soon!

John

[John Cole]

Thanks Sean. Glad others are up late too... (late for me, anyway)

[adodad]

John:
Thanks for the interesting thread. Would you be so kind to give me some more detail re. the material you used to fill gaps and nits in the fuselag?

[schrederman]

Nicely done!

Jack

[John Cole]

Thanks Jack. Wish I had more free time to work on it. :(

adodad, the filler I use is 3M acrylic laquer body putty, available at most auto parts stores. 'Bondo' has their own version too. No mixing, just squeeze it out and smooth it on. It shouldn't be used to fill big holes or deep areas, because of shrinkage, but is good for leveling seams and filling scratches. It bonds well to wood and plastic. R/C scale guys buy this stuff by the case. ;)

John

[adodad]

John, Thx for feedback re. lacquer filler. I too am about to embark on a Cirrus build from an old kit. I built two of these as a teen in the early 70's (I worked at a hobby shop so I got a discount on the kit). If you are interested I can post a picture of my last Cirrus in 1973 (it has a "V" tail mod that worked out quite well). Anyway, I plan to build mine relatively stock, with ailerons and reduced dihedral. I'll add spoilers and a modern airfoil. I expect to use the stock airfoil at the root and blend it to a S3021 about 8"-10" out from the root and keep the 3021 out to the tip. The 3021 isn't too sexy but will fit the performance envelope of this old gal just fine. I like your "gapless" rudder treatment and will folow in your footsteps. I am hopelessly stuck in the 70's as far as sailplanes are concerned. I built and fly a Grand Esprit (kit) and Aquila Grande (scratch). Again, if anyone is interested I'll post some pics. Like your work...keep it coming.

[John Cole]

Ado, YES! Please post your pictures, I'd be very interested in seeing them. Sounds like a cool mod to the wing, I hope you start a build thread.

I'm flying a Grand Esprit from a kit also, that's one cool glider. Built it in '77, it's my oldest flying model. I restored it a while back and have it flying again.

John

[adodad]

O.K., here is the Grand Esprit and Aquila Grande. The Aquila is a scratch build so the fuselage is wood. The fuselage for the Aquila Grande and standard Aquila were identical in planform but the Grande was fiberglass. The rest of the Grande is as per the original Airtronics plan. The Esprit was built from an old kit and is stock except the airfoil has been updated to the S3021 and the spar system has been updated also. I fly from a high-start so I don't add any composite material. The Cirrus pic is scanned from an old photo so I apologize for the quality. The kid holding the bird is me at age 18. The V tail is all moving and worked well. I can't say the performance was drastically changed but it sure looked cool. If you squint real hard while looking at this pic I'll bet you think you are looking at a modern moldie...imagine that, a 30 year old Cirrus leads the way!

[rcsoar4fun]

Man, never thought I would see another V-tailed Cirrus. I have an original vtailed cirrus from about 1972, very interesting flying airplane, heck of an l/d but weird to turn. Funny thing is its the exact same color scheme. You guys have some sort of agreement or something?

[adodad]

rcsoarforfun: It may well be the same machine. I notice you are from Tulsa. If you look veerrrry close at the pic you can see the Tulsa skyline in the background. I built the plane in the pic and sold it in the '73-'74 time frame just as I entered The University of Tulsa. I think I sold it radio and all...can't quite remember. The radio I installed was an EK Logictrol 'Brick" (receiver and two servos all together in a brick). Also, the "pilot" was a small plastic figure of "Grover" from Sesame Street. It would be very cool if you have my old plane.

[adodad]

rcsoar4fun: Sorry for the last post. I got ahead of myself. How did you acquire your v-tail Cirrus? Did you build it? My first Cirrus was completly stock and the 2nd one received the v-tail mod. If I remember, initiating a turn was tricky but once you got it into a turn it grooved real well and I don't recall any nasty habits. I grew up in Tulsa and began sailplanes sometime around '68 or '69. At that time we flew from the field just south of the Mabee center at Oral Roberts University. The field disappeared when they built the hospital and "praying hands" that stand there now. I was most fortunate to receive some help, training and sailplane mentoring from Dale Nutter. Dale has some notoriety within rc sailplane circles as a highly successful rc sailplane competitor. Enough of this trip down memory lane. Please let me know the origin of your v-tail Cirrus.

[rcsoar4fun]

IIRC Dale moved to Arizona. I purchased the Cirrus along with a Aquila and Super Questor. I cannot remember the name of the guy here in town I bought them from. The Cirrus came with the same radio mentioned, but without the white writing on the right wingtip.

[adodad]

rcsoar4fun: Sounds like the same bird. I am pleased to see it has survived the cruelty of time. The white markings on the wing are my AMA numbers which were required for contest flying. The definitive mark of this plane is how the all moving tail was actuated. The pushrods exit on the top of the fuselage and slip into plywood control horns attached to the tail. The pushrods were goldenrod and the "springyness" of the pushrod held tension on the tail pieces to keep them on the pivot pin. I think you have the only vtailed Graupner Cirrus on the planet (must be worth a mint!). I have never seen nor heard of another.

[rcsoar4fun]

Pics of the old girl, look familiar? No grover pilot though. :)

[John Cole]

How cool is that!!! :)

John

[adodad]

rcsoar4fun: That is definitely her! Looks like she has been well taken care of...kind of make me misty eyed. This plane was built to compete in the soaring nationals of 1974 to be held in/near Chicago. It never made it because my traveling buddy crashed his plane so we canceled the trip.

[John Cole]

With a little push from Bob (thx Bob!) I though I'd post pics of my Esprit.

Ado, there are some similarities in our glider stories. I was seperated from this old girl for about 6 years and aparently several owners, and it suddenly and unexpectedly presented itself to me again 1200 miles from where I built it. Blew me away when I saw it again. Repairs, restoration, tlc.
Anyway, it's home now...

[John Cole]

Oh yeah, more Cirrus stuff soon... And, MERRY CHRISTMAS!!!

John

[adodad]

John: A few questions as I prepare for my Cirrus build: Are the stock ailerons large enough? How well does the Cirrus handle a winch launch on a modern hot winch and stock wing pins? Any suggestions on a launch hook? Anyone figure out what servos will fit in the wing for ailerons? My old Cirrus had spoilers ala the Airtronics designs (Aquila, Sagitta) and I ran a sub spar out from the stock diagonal secondary spar to form the spoiler bay. Why not run the secondary spoiler bay spar all the way to the root and forego the diagonal spar...any thoughts?

[John Cole]

Hello Ado. I will try to address your questions with some factual based answers, sprinkled with a little opinion. ;^)

The stock ailerons are weak in providing enough roll authority. You might consider adding 1/4" of chord. I believe that would help alot.
The Cirrus will launch on any winch, the trick being not to overdo it on the pedal. Earlier in this thread, Chris mentions the pins, and a slight fuselage mod for strengthening the brass sockets.
I'm changing out my hook to a heavier one, available from ArtHobby. Nice hook. For wing servos, I'm installing Hitec HS-81mg's for the ailerons (one per wing) and HS55's for the spoilers (one per). I was going to mount the ail servos right to the removable ply plates. Will show this when the time comes. Lots of room for them, plenty of torque for the application.

Your sub-spar idea will require some thought (ouch, my brain..). The original design has the sub spar crossing the rear wing pin intentionally, forcing the rear pin loads to the main spar. You can probably route a second spar however you want, as long as it somehow 'captures' the rear wing joiner tube. You might consider the blade-type spoilers like I made for my Cirrus. They are not hard to make, and the glider pitches very little when they are deployed.
Hope you are having a warm and happy holiday!

John

[adodad]

John: Thx for the feedback. The add'l 1/4" of aileron chord fits my guess...I suspected the stock ailerons were too narrow. Any input on making the ailerons gapless? Seen there any good threads on this? The alternative is to simply use some mylar "gap tape" on the bottom surface but this does not seem a very elegant solution. I also suspect the rear wing rod carries very little of the load and acts as an alignment pin. If this is true, the rear joiner pin can be radically reduced in size. I am contemplating up-sizing the spars to 1/8 x 3/8 and I could then use a 5/16 joiner rod for the front rod. I agree with the earlier comment re. placing ply doublers on the main rod former. However, I am curious how many winch launches have been thrown at my old 1972 Cirrus...it seems to be holding up well and I did not reinforce this area at that time. Yes I like your blade spoiler but must confess I can't glean enough information from your pics to fully understand their construction / operation. Can you shed some more light on this portion of your build? I can get my hands on some Graupner aluminum blade spoilers as well.

[John Cole]

I've been giving the aileron hinge line some though as well. Since my wings are already built, I will probably just use tape, hinged at the top. If/ when I build another set of wings, I would likely treat them similar to how I did the rudder. This would be a good place to use Robart type hinges.
I like your wing rod idea! Might make things a little complicated in the fuselage, maybe? I'll be very interested in seeing how your wings come together.
I should be, God willing, able to spend some time on my glider in another week or so :rolleyes: . I'll make a point of showing the spoiler/ air brake installation and include as much detail as I can while I proceed with the wings.

John

[bobthenuke]

I've been giving the aileron hinge line some though as well. Since my wings are already built, I will probably just use tape, hinged at the top. If/ when I build another set of wings, I would likely treat them similar to how I did the rudder. This would be a good place to use Robart type hinges.

John

John,

If you're willing to have servos mounted in the wings (I'm not familiar with the configuration but think you mentioned to me yesterday that the Cirrus aileron mod involves pushrods and bellcranks) the moveable surface enclosed LE would be an *excellent* setup for RDS control. I dare ya... :p

-bob

[adodad]

John: Can you shoot a pic of the vertical stab post side of your gapless rudder hinge? I think I understand the set-up but I am not completly clear on what hardware hangs on the stab side.

[John Cole]

Bob, servos (4 ea) WILL be in the wings. Pushrods and bellcranks are the stock setup, but with micro stuff available today, will be running servo extensions instead of pushrods. (I was going to use pushrods in the Alpina, tho)
RDS; good design concept, but perhaps excessive $$ and fiddling for this baggy old thing. ;) Something to consider on a new build though. You know my mantra; simplicity.

Ado, I don't have any pics yet of the hinge parts that get glued into the fin post, but will as soon as I make them. Description-wise, they are 1/2" pieces of 3/32" OD brass tube, flattened on one end. The flat end gets drilled for the wire to pass through, the other end will get glued into the fin post. I'll use two of these for this size rudder, or you could install three if you wanted to. Will be clear once I get pictures up.

John

[rcsoar4fun]

Not to hijack the thread, but if anyone is interested I will probably be listing my Cirrus for sale soon. PM me if interested, pics a few posts back.

[John Cole]

Rcsoar, hope you do well with the Cirrus!

I'm still working a lot of hours, not by choice. Guess my Cirrus will get done when it gets done. :rolleyes:

John

[John Cole]

Here are some details of the rudder hinge.

Someday, I may actually get this model done...

[John Cole]

The hinge tubes will get glued into the fin post AFTER the parts are glassed. This will insure a good fit with proper clearance.

[John Cole]

On to glassing!!

I'm using 1.0 oz. 'S' glass, and Z-poxy finishing resin.

[John Cole]

Here, the rudder gets glassed. Weight build-up must be closely watched!

[John Cole]

The fin and rudder are glassed!

Next, the glass will be sanded, then primed. One step at a time... ;)


More soon. (I hope)

[adodad]

John: I assume the Z-Poxy is compatible with the Graupner plastic fuselage? Thx for the xtra detail re. rudder hinge, that explains your system well. Why did you choose to hinge the rudder this way as opposed to a robart style pin hinge? Not a critique...just a question.

[John Cole]

Ado; Yes, the Z-poxy sticks pretty well to the plastic. No problems with the plastic reacting. Good idea to first hit it with some 220 grit paper or so.

I actually WAS going to use Robart hinge points, as their design would accomplish exactly the same thing. But I got to thinking about how inaccessable the hinges would be if I ever needed to remove the rudder. Normally, you would just cut a hinge point and drill out the old hinge, but this type of hinge line allows no access. I could imagine tearing up the rudder/ fin: a mess... Anyway, that was my train of thought. Robarts or equiv would work fine, just have to hope you would never need to service the parts involved.
At the rate I'm going, you can start your Cirrus next month, and still get it done first. :o

John
p.s. glass sanded, ready for primer, pics soon

[John Cole]

I was able to get most of the glassing completed, I decided to do the wing 'D' boxes as well. Small triumph. With the fin and rudder sanded after a coat of high-build primer, it's time to set the hinges! :)

[John Cole]

Rudder control lines will be made of 65# Spider Wire. A small plastic conduit will be glued into these holes later for the line to pass through.

John

[John Cole]

Here's some wing stuff.

Since the dihedral will be a few degrees less than the two channel version, wood root ribs are fitted and shaped to compensate.

[John Cole]

I decided to glass the wing sheeting, mostly because it was soft in some areas. Also, there were other places that were uncomfortably thin, thanks to my construction abilities 25 years ago. Of course it added weight, but I hope the benefits outweigh the, um.. You know. :rolleyes:

More soon.
John