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Comet Sailplane

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Old 03-10-2005, 08:37 PM
  #1
50%plane
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Default Comet Sailplane

I am a young stupid modeler that is building a short kit of the Comet Sailplane. If any of you modelers know from the origional kit the specs of door formers D1, D2, and D3; how to make the cowling; the specs of C1,C2, and C3; how the landing gear works; and the specs of L1, L2, and L3, I would be grateful.
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Old 03-10-2005, 10:11 PM
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Default RE: Comet Sailplane

I don't remember there ever being a landing gear shown on the orighinal instructions for the Sailplane by Goldberg. The cowling was made up from wrapping paper.

The outlines for parts which Pond traced and sold did not match those as needed on the model. If you copy the rudder assembly, then trim to the edges, and place over the sideview on teh plan, you will see that too did not fit.

With all the ill fitting parts, no wonder the performance for the Sailplane could not be duplicated, even by another one.

Wm.
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Old 03-11-2005, 06:59 AM
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Default RE: Comet Sailplane

The plans show a retractable gear near the nose. I am building the short kit from Bob Holman Plans (CRAP). A lot of the parts don't match the plans very well, but I am continuing to build it.
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Old 03-11-2005, 10:15 AM
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Default RE: Comet Sailplane

If You can find the plans from a Comet kit of the sailplane, They were drawn by Carl Goldberg.
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Old 03-11-2005, 12:53 PM
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Default RE: Comet Sailplane

Bob Holman Plans sells the plans for $15.
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Old 03-11-2005, 05:52 PM
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Default RE: Comet Sailplane

My original Sailplane plans show a single retractable landing gear that used a suction cup to hold it extended, then leaked down to allow it to be pulled up by rubber or a spring. The two original Sailplanes still residing in my dad's basement have a conventional two wheel gear, and I'm told that most were built that way for more reliable takeoffs.
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Old 03-11-2005, 08:15 PM
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Default RE: Comet Sailplane

strat2003,
thats what my plans show, but it looks to me that the suction cup releases to let the gear fall.
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Old 03-12-2005, 02:09 AM
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Default RE: Comet Sailplane

In the old days the models had to ROG (Rise Off Ground). So the gear is intended to stay down until airborne and then snap up to the retracted position. Single wheel takeoffs can be a matter of stark panic as often as not so it's highly recomended that you convert over to a two wheel fixed landing gear setup for your Sailplane.

Woops, I assume you're making this for RC? If so don't be surprised if you find you do not need much rudder throw if the rudder is the usual 50% of the fin area. All that dihedral will ensure a snappy response.

A positive note for you. The Sailplane is a thing of beauty in the air and floats like nothing else. Carl got the airfoil JUST right on this one. However it does have one serious fault, it won't like to fly fast so don't expect a penetrating glide to help fight back upwind. Calmer conditions are it's forte. But when it's right it'll bring a grin to your face. And the best part is that it looks just as good close up with all those curves.
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Old 03-12-2005, 06:47 AM
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Default RE: Comet Sailplane

BMatthews,

I know what your talking about. The reason that I am doing this project is because I love old-timers and have flown my grandfathers heavely modified for RC version. The Sailplane that I am building right now is going to be built almost all original but it will be converted to RC. I am making it as original as possible with a cowled O/R .60, covered in silk, and the retractible landing gear.

After I get this one flying, I will build a more 'pilot friendly' model with two wheels, Monokote(R), a .25-.40 size glow engine, and probably without a cowl.

You are right about how it flies, my grandfather will usualy over shoot the small runway that he flies at because of the grear glide ratio. This is probably one of Carl Goldbergs best planes.
There is a reason that is called 'The Caddillac of Model Aviation'.
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Old 03-12-2005, 09:52 AM
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Default RE: Comet Sailplane

Bruce...

I think you have that backwards.

Landing gear in the old days was just for that, LANDING.

Most model aircraft were hand launched. The landing gear was meant to protect the propeller. There were very few model propeller makers during the 1930's when the Sailplane was first designed. Most builders fabricated theirown. Thus a great amount of time and effort was expended. The often reason for extended landing gear like on the Quaker was to protect the propeller. The extended landing gear on models like the Quaker was not for "Anti-tipover" reasons as has been noted earlier, although this was a side benefit.

The Sailplane was designed to suck up the gear, and once the engine quit, the landing gear extended, (and if without a dethermalizer), it then glided into a touch down. And, did not damage the propeller.


Wm.
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Old 03-13-2005, 08:09 AM
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Default RE: Comet Sailplane

Guys:

Not to get into a p*****g match over an old landing gear arrangement, but....

While I understand the logic of saving precious hand carved propellors, I just checked the plan and it shows a rather complicated (possibly more Rube- than Carl Goldberg, lol) mechanism to hold the gear extended til a suction cup gives up the ghost and lets a spring pull a cross-shaft out of the way to permit another spring to pivot ANOTHER shaft, pulling the main strut up into the fuselage. The "timer" is in a location that can only hold the whole arrangement extended. It's kinda neat, as it pulls the gear straight (okay, daigonally) up , rather than pivoting the landing gear leg like we would do it today.

I wonder how many of these were actually brought to working condition?
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Old 03-14-2005, 09:27 AM
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Default RE: Comet Sailplane

Would someone who has built or seen an origional sailplane with the retract please post.[8D]
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Old 03-21-2005, 04:27 PM
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Default RE: Comet Sailplane

Saw one a long time ago, have drooled over many photos since. The Sailplane is on my "To Do" list, and I have devoted some study to the LG situation. From my study of several sets of plans and Carl Goldberg's construction article it seems that the gear was designed to extend for take off-amatter of inches, then retrace. Aproximately half of the (balsa) wheel then protruded from the bottom of the fuselage for protection upon landing.

That being said I have also read of a RC assist version that was notabale for having the wheel pop out moments before touchdown. If I can figure out the engeneering I may attempt that, but I am still a bit nervous about 1 wheel takeoffs, though with ample power it should be ok.

Disclaimer: I ain't done none of this-just speculation and wishfull thinking.

jess

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Old 03-21-2005, 05:53 PM
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Default RE: Comet Sailplane

Regarding single-wheel takeoffs:
I've flown several low wing sport planes with a single retract and they handle surprisingly well. My experience with old timers is that no matter how many wheels you have you pretty much have to take off directly into the wind. None of them are worth a darn in a crosswind! I think the Sailplane idea of landing on the semi-exposed wheel might even help reduce blow-overs on landing, but it might be a good idea to try it out on something less labor intensive than a Sailplane.
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Old 03-21-2005, 06:58 PM
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Default RE: Comet Sailplane

Thank ya'll for the great input. I will definately not be using the origional engineering on this one part of the plane if possible. I am trying to figure out a way to make the wheel either drop, or raise up using a servo and a spring.

The sailplane is the best flying sunday afternoon flyer it doesn't do aerobatics and needs extra wing reinforcement if you use monokote(R). Bob Holman Plans sells a laser cut short kit for $85 and plans for $15, but some of the wing tip parts don't fit right.
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Old 03-23-2005, 11:03 PM
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Default RE: Comet Sailplane

Woops, et al,

I bought a Sailplane partial kit by Bob Holman at the model show at Ontario this January.

The plans are the original Goldberg from Holman...I have not yet opened the plastic bags the Homan partial kit parts come in, so I have no comment on the fidelity to the original plans...nothing would surprise me! Work around it, we are lucky it's there at all.

I have been in love with this design for some time, and am trying to figure out how to build it...old sparker?...old sparker radio assist?...likely!...electric with radio assist....very likely, but only because it's the most practicle.

The solution...trace all parts, and build TWO!!!!

Lets keep in touch on this.

I have a Red Zephyr I thought I would build first to get further along on building skills...have just finished a Ken Willard CAVU by Lidberg...it is three channel electric...too heavy to be a good flyer...I fly control line, not r/c...thank god for my "test Pilot" Tony Nacarrato from T&A Hobby Lobby in Burbank...he has bailed me out a few times.

Just caught this thread, will try to keep up on the Sailplane thread...

Pete Munroe, Los Angeles
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Old 03-26-2005, 08:59 PM
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Default RE: Comet Sailplane

I have confirmed that the landing gear pulls up after take-off. [sm=RAINFRO.gif]
Does anyone have any patterns for formers C1, C2, C3, D1, D2, D3, L1, L2, and L3. If you do please post them.[sm=idea.gif]


Ifr2lax,
Bob holmans short kit is very good for the money. I can't imagine how much time it has saved me. The only problem with it is some of the parts don't fit the plans. The ribs appear to be correct(thats what counts)[sm=lol.gif]. The main problem is the wing tips which don't fit the plans.[sm=angry.gif] But for $85.00 you save about 10 hours.[8D]
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Old 07-13-2005, 06:50 PM
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Default RE: Comet Sailplane

Okay I thought ya'll might want an update. I have glued a couple more pieces on it. I'm cutting out some of the spars to the center wing section also. Does anyone know where to mount the pylon?
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Old 07-14-2005, 04:49 AM
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Default RE: Comet Sailplane

Let's see some pictures! I've been working on mine for some time now off and on. Got the wing Monokoted and the fuselage and tail feathers are done, just need covering. I'm making mine RC with the two wheels in front, no single retract because I need room for a fuel tank.

I don't have the original instruction book, but I believe that the wing support or pylon was left off until the very last so that it could be adjusted for best glide, maybe tacked on and then toss the plane in some tall grass? I don't know?

I have an original pattern parts sheet, is your kit an original or modified?

Dion


Quote:
ORIGINAL: woops

Okay I thought ya'll might want an update. I have glued a couple more pieces on it. I'm cutting out some of the spars to the center wing section also. Does anyone know where to mount the pylon?
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Old 07-14-2005, 07:25 AM
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Default RE: Comet Sailplane

The original plan recommends not locating the pylon until most everything is done to get the balance point right. That would mean having a covered fin/stab assembly, pushrods in place, engine and landing gear mounted, and some idea of where the radio is going.
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Old 08-14-2005, 06:18 AM
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Default RE: Comet Sailplane

Has anyone else built the Bob holman short kit? Did you reinforce the spars?
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Old 11-16-2005, 12:17 AM
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Default RE: Comet Sailplane

Woopster,

How is your Comet Sailplane, aka Carl Goldberg Sailplane coming along?

I can not say any modeling progress at all has gone on in my "shop"...nothing but deferred home maintenance.

The Sailplane thread, and other vintage/old time model topics seem to get folks pumped up to posting interesting things!

I suspect many of us are reading web pages more than building...not good, but we are still here!

Pete
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Old 11-16-2005, 01:21 AM
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Default RE: Comet Sailplane

Looking for an engine for my Sailplane. What would you all recommend? I'd like a 4 stroke, would a .30 4 stroke be a good choice?

Thanks,

Dion

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Old 11-16-2005, 01:35 AM
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Default RE: Comet Sailplane

Man oh man have to love the wood work and red covering. It makes me want to drag out my short kit of the Lanzo Bomber I have downstairs, the 1/2-A one.[&:]
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Old 11-16-2005, 02:43 AM
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Default RE: Comet Sailplane

Quote:
ORIGINAL: dionysusbacchus

Looking for an engine for my Sailplane. What would you all recommend? I'd like a 4 stroke, would a .30 4 stroke be a good choice?

Thanks,

Dion

A .30 four stroke would provide an uphill powered glide. If that's your desire then go for it. To achieve a strong climb to altitude and then cut the throttle for the glide more or less as per the performance of the original spark engines you'll want something like an OS48 to Saito .56 or similar up to about a .60 size 4 stroke. Or if you stick to a 2 stroke then a .35 to .40.

Back at the '91 SAM Champs that I went to there was a guy with a free flight Sailplane with a Dooling .61 on spark in the nose. That thing was GROSSLY overpowered and took off like a modern AMA power FF model. He was even using the single leg takeoff gear but left it in the down position to provide some spring action for the harsh dethermilzer landings. You have not seen anything impressive until you see a Dooling .61 at full revs ripping across the ground for a free flight horizontal takeoff.
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