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Author Topic: Comet Sparky for P-30  (Read 4471 times)
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Oldtime Flyer
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« Reply #50 on: April 19, 2011, 12:42:04 AM »

Z.I.

I mistakenly posted a copy of the wrong plan!...... Here is the correct plan L-10A and a copy of the rules as they were in the good old days. (1941 AMA Rules)......Until S.A.M. Messed with them.

http://i257.photobucket.com/albums/hh215/Fadedepi/scan0014.jpg http://i257.photobucket.com/albums/hh215/Fadedepi/scan0012.jpg
Hi Thom,
I recognized your mistake right away but knew you'd be back soon to correct it.

Hi Dave,

Thanks... (you know me too well) Hope all is good with you!!

All The Best to you & yours, Thom
Comet Sparky for P-30
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Zeiss Ikon
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« Reply #51 on: April 19, 2011, 07:07:18 AM »

I've got the left wing covered, top and bottom, at this point (sorry, no photo yet), and I'm finding a little problem; the trailing edge (1/16" x 3/8" strip -- plan calls for 3/32" thick) was bending downward (like a deployed flap) pretty badly by the time I got the top covering in place.

This flattened out by the time the tissue was dry, and didn't repeat when I doped the wing. All looks well now, photos will follow this evening.
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« Reply #52 on: April 19, 2011, 07:31:58 PM »

Here are the photos of the first wing half -- the dope is dry and, with the wing pinned to the board both when the wet tissue was drying/shrinking after application, and after doping (one coat 50/50, though it might have lost some thinner to evaporation; it's been eating the rubber gasket material inside the lid of the jar), the bottom surface is as close to dead flat as my eye can detect. If I need warps, or find I have one I didn't spot at this point, it should be easy to steam the tissue and pin the wing back down with shims.

Since these photos, I've covered the other wing half; it did work better to wet both pieces of tissue before starting the glue stick application for the bottom, though I had to lightly re-spray the top tissue (it dried a little too much while I was getting the bottom tissue applied, trimmed, and the edge stuck down). The wing is pinned down again while the tissue dries; once the dope (to be applied in an hour or two and the wing pinned again) has dried overnight, I'll be ready to lay down the fuselage section of the plan and start building the side frames.

I did notice, when I took the doped left wing off the board today, that there was a small hole beside the trailing end of rib 10 (counting out from the center, with the dihedral rib as 1). I'm guessing that the cat got onto the table and, though he's very good at not knocking stuff off, may have stepped on the wing. Not much of a hole; I used the old trick of applying celluloid glue over the hole, so that the shrinking glue will pull the edges together. If that fails, I'll have to patch that bay -- there's not enough of the yellow tissue left (from two sheets) to cover the fuselage (which is going to get orange instead), but there's plenty for lots of patches.
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« Reply #53 on: April 19, 2011, 09:51:09 PM »

And here's the completely covered wing, pinned to the board while the dope dries. Covered with four pieces of yellow Esaki, one try each piece. I'm happy with it. Smiley
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« Reply #54 on: April 19, 2011, 10:55:40 PM »

Great job there Zeiss!

Quite a confidence builder too.

Dave Andreski
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« Reply #55 on: April 20, 2011, 07:06:06 AM »

Great job there Zeiss!
Quite a confidence builder too.

Thanks -- and yes, this improves my confidence in being able to cover the fuselage wet with two pieces of tissue (we'll see how those "problem" panels under the trailing edge of the wing go, but I think it's possible). For tonight, though, I'll be putting the covered flying surfaces aside and laying down the fuselage plan to start building the side frames. This won't be my first time building one frame on top of the other, but the last couple times were with kit wood; this time, I've got some fairly light wood to work with.
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« Reply #56 on: April 21, 2011, 10:13:27 PM »

It's been a tough couple days for building; last night the blade came off the stripper I needed to make the longerons, cross pieces, and stringers for the Sparky fuselage (finally settled on 3/32" x 1/16" frame pieces, and 1/16" square is the original size for the stringers), and tonight I spent three hours in the local emergency room getting my girlfriend's abdominal pain diagnosed ("biliary colic" is what they printed out, same thing my mom used to call a gall bladder attack -- I'm just happy it isn't anything requiring immediate surgery or a hospital stay).

Even so, I managed to get the strips cut that I'll need for the fuselage, and get the first frame side laid out and glued up. Should be able to build the second side on top of this one tomorrow.

I have a couple pieces that were in the parts sheet that don't show on this plan -- they were identified as "cheek pieces", sheet inserts to go between the top and bottom longerons at the nose, holding everything in alignment and establishing the built-in down thrust angle. Problem is, they still don't show on the L-10 plan -- but the parts sheet images I extracted don't show a pair of window frames that would go inside the side frames (and likely greatly stiffen the cabane compared to the open framework, as well as contributing to the look of a 1930s high wing cabin airplane) that clearly are on the plan. Combine that with the very poor grain direction in the sub rudder parts (which look tacked on anyway) and I conclude that the parts sheet images in the L-10 PDF are actually from another version of the plan (probably the 3408), with the sub rudder parts pasted in. When I get time, I may try to extract the full plan, rebuild the parts sheets, and recreate the L-10 with better parts accuracy (along with improved notation on a few parts I found hard to identify, like #7, the stringer supports for the sides of the nose). That, however, won't be anything immediate; I may still have time to finish the Sparky before the fun fly on the 30th.
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« Reply #57 on: April 22, 2011, 07:04:16 AM »

That's nice progress Zeiss. If the fuselage comes out looking as good as your wing then it will be a very pretty model. Good to see that the wet tissue/glue stick approach works so well.

John
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« Reply #58 on: April 22, 2011, 10:10:39 AM »

... and tonight I spent three hours in the local emergency room getting my girlfriend's abdominal pain diagnosed ("biliary colic" is what they printed out, same thing my mom used to call a gall bladder attack -- I'm just happy it isn't anything requiring immediate surgery or a hospital stay)...

Glad to hear your SO is OK. I've had some random trips to the E-room and they consume an inordinate amount of time.
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« Reply #59 on: April 22, 2011, 08:59:39 PM »

Glad to hear your SO is OK. I've had some random trips to the E-room and they consume an inordinate amount of time.

With this trip, I've discovered that emergency care varies between organizations -- the last time I went to an ER on my own behalf, I sat for seven hours before I was even seen; this time, we were in and out in just over three hours. I know which ER I want to go to next time I need one...

That's nice progress Zeiss. If the fuselage comes out looking as good as your wing then it will be a very pretty model. Good to see that the wet tissue/glue stick approach works so well.

Thanks, John. I certainly hope it goes as well. I'm happy with the fuselage so far.

Tonight I built the second side frame. This is my first time building one frame directly over the other (hopefully I won't regret it when I try to separate them); I placed the pins with this method in mind when I laid down the first side frame, and was able to just sort of "weave" the longerons in between the pins when laying down the second frame. It took a little bit longer to frame the second side than the first, mostly because I was being extra careful to ensure I didn't push out the frame with an overlength cross piece, and taking extra time to line up the cross pieces. It should be worth the effort; with all the sticks stripped, one after the other, from the same 3/32" plank, and with this extra care to make the frame identical, I should get a straighter fuselage with less "compensation" than I'm used to. Next item is to build the "line-up former" and start joining the sides, mounting the formers, and then installing stringers; should be a total of two or three hours, with a couple glue drying breaks, until the fuselage is ready to sand, dope, and cover.
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« Reply #60 on: April 23, 2011, 06:01:00 PM »

These pictures make the project look so great and you are doing a wonderful job with the build. Glad you choose the Sparky for a P-30 project. Are you building the landing gear in or leaving it out ? The Sparky has always been one of my favorite old time rubber models for Flying Aces events . Cabin and Stick is possible.

Have a fun time building and flying. Put #1 on the first and each time you build another Sparky put the next number on it so people will know without asking. I once had a friend who built Sparky models and most of the time people were asking him how many this made. He could build one a week. He really liked the Sparky until he saw and fell in love with the Miss Canada Senior.
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« Reply #61 on: April 23, 2011, 09:23:46 PM »

I'm building this one without landing gear; though the option will remain to make a plug-in mount like the one I put on my Fat Lancer, the original mount location in the Sparky won't permit plugging in the wire unless one clips the bottom stringers at the gear mount (the plan shows them carried through to the line-up former).

Meantime, I'm starting to really dislike stringers -- if you've got a friend who can build a Sparky a week, he must have a lot more building time than I do, or a tame laser cutter. As noted some way back, it took me three hours just to cut the sheet parts for this one, and I've got about three hours of actual building time into the fuselage as you see it below (plus several glue drying breaks -- yes, I realize those could be eliminated by use of CA glue, but I don't like the stuff; it gives me a sore throat). Of course, if I were intentionally building a bunch of these, I'd make up a jig for the fuselage side frames and do various other things that save time -- but with the Sparky's high parts count and complex fuselage (compared to the simple contest models I've built previously -- at least in terms of successful fliers), I couldn't build one from a machine cut kit in a week, even with various jigs. Honestly, I'm not certain I could build a One Night 28 from a kit in under a week, though if the wood is precut I could likely do so with jigs for fuselage, stab, and rudder.

And why is the fuselage standing on end? It's pinned down while glue dries repairing a nose former (#2, with the stringer notches) that split when I attempted to use a too-tight rubber band to clamp the side frames into their notches for glue to dry. Since then, I've split all three top nose formers (3, 4, and 5) while handling the fuselage to install the size and bottom formers, cut apart and reassembled the tail end three times, finally installing a pair of rails in place of the #26 tail former, in order to get the tail straight (it's still not really straight, but it should at least fly straight -- all that effort to build the second side frame atop the first, and the strips I used in the second were thinner than those in the first, so it won't bend evenly).

Right now, the fuselage is sitting upside down while the glue dries on the bottom stringers, and shortly I'll go back, take off the rubber bands holding things together, repair the most recently split top nose former, and install the top stringers -- then it'll be time to take on the wing mount dowel and platform and razorback stringer. If I can get all of those done by bedtime, I can probably get the fuselage covered tomorrow, and likely have the DT built in time to take this to the fun fly next weekend for trimming flights (I still haven't found a local field big enough to trim this or my Fat Lancer with enough power to really see them climb). More likely, I'll have to cover Monday evening after work, but that should still leave time to build the DT timer, fabricate the DT itself, and rig it.

Sure hope someone is selling rubber at the fun fly -- I've got one and a partial bag of 1/16" Peck rubber that I bought around twenty-five years ago, and I'm pretty sure there isn't enough there to make both a 10 gram P-30 motor and a six- or eight-strand motor for the Fat Lancer. I'd order some, but there won't be money to buy rubber until I get paid on Friday the 29th (fun fly is the 30th).
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« Reply #62 on: April 23, 2011, 09:53:07 PM »

Zeiss,
PM me with a snail mail, street address, and I'll send you some TAN SS Rubber in three different widths.

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« Reply #63 on: April 24, 2011, 02:32:03 PM »

Thanks, Dave, that's a generous offer. Smiley I looked again, I probably do have enough 1/16" to make up both motors, but newer rubber is better.

I got the fuselage wood work finished up except for the side window frames last night just before bed (haven't got the photos processed yet, they'll be up later); I'm off right now to cut and install the side windows, then later I'll finish sanding and dope the frame and have time to cover tonight. Looks like I'll need at least three pieces -- one for the bottom, one for each side (meeting at the razorback aft, and the middle stringer forward). And, barring unforeseen problems, it looks like I'll have this ready for trim flights in time for the fun fly.
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« Reply #64 on: April 24, 2011, 03:28:52 PM »

Okay, as promised, here are last night's photos of the fuselage -- at the end of that session, all the woodwork was installed in the fuselage except the side window frames (one of those is installed now, the other is drying after repairing multiple wood splits from cutting out the window opening). BTW, I was right that a cotton swab works much better for solvent transfer of laser toner; more pressure and less solvent is indeed the answer.

First photo is my replacement for former #26, which was required to let me get the tail end reasonably straight. Should also save a fraction of a gram, I suppose, but I'm not at all sure it would have been worth the effort if the wood had been cooperative. Second, third, and fourth are installing stringers. The fifth and sixth show the wing saddle and front end of the razorback stringer, with the little shelf that provides clearance under the rear of the wing dowel (for which I used a piece of bamboo skewer) and its brace -- tiny little pieces that were annoying to cut out and difficult to handle (especially with glue on them). Pieces like these suggest why die-cut wood is usually so hard: to survive the cutting, packing, and removal from the sheet so as to deliver a kit that can be built, even if it doesn't fly as well as it might due to weight.

More photos following.
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« Reply #65 on: April 24, 2011, 03:34:39 PM »

Continued due to attachment limits -- first image here is the razorback stringer clamped in place as the glue dries, while the second is the fuselage essentially finished. The side windows aren't seen in all versions of the Sparky (just as the sub rudder isn't -- apparently the L-10A contest version had a single-wheel retracting landing gear and two sub fins near the tips of the stab instead of the single sub rudder), and aren't on any of the parts sheets I've seen, but I'm willing to add a fraction of a gram for the appearance.

The side window frame that's being repaired should be dry enough now to try to sand off the toner (silly me, I missed making one piece a mirror image, so the toner is on the outside on one side and would show through the tissue). Gently, gently, and once sanded, I'll glue it in. Covering will be after dinner, and more photos later once that's done...
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« Reply #66 on: April 24, 2011, 09:39:53 PM »

Well. I'll freely admit that the Sparky fuselage was, in spots, the most difficult piece I've successfully covered with tissue. Far from covering in two pieces, or even four (bottom, sides, and razorback), I wound up using ten. First, the tissue sheet wasn't long enough to cover the bottom or sides with a single piece, so I had to piece a few inches at the tail. Then, I found I wasn't yet good enough at covering, or there wasn't enough give in wet Esaki, or it was drying too quickly, to be able to cover a side to the razorback and center stringer, so I wound up covering the sides just up to the top of the side frame, then applying the top front and razorback as one piece each.

Then I concluded that Ed Lidgard and Carl Goldberg probably knew what they were talking about, seventy-some years ago, when they recommended applying the covering to the first transition panel behind the cabin on each side with the grain at an angle (which would imply covering that panel separately from the rest of the fuselage). There is flatly no way I can see that I could have covered those panels in one piece with either a side or the razorback, short of having a covering that would stretch like heated shrink film -- wet Esaki has some give, but nothing like that much. Done their way, though, those panels are merely difficult to cover, rather than impossible. And now it's covered, so I'm ready to mount the tail surfaces and build the nose block (I'll build the spinner last, I can fly without it if I have to), DT timer, and DT itself.

Oh, does anyone know what a Peck Polymers 9.5" propeller weighs? The parts that are currently finished (wing, stab, rudder, and fuselage, covered and doped) weigh in between 20 and 25 grams (my diet scale only reads in 5 g increments) -- I'll add five grams or so with the DT, but I'd be annoyed at having to add ballast just to get up to 40 grams on a design that originally built to 85 grams (even though I scaled to 94% and used thinner wood, this is a surprise).  Shocked
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« Reply #67 on: April 25, 2011, 07:19:49 AM »

Oh, does anyone know what a Peck Polymers 9.5" propeller weighs? The parts that are currently finished (wing, stab, rudder, and fuselage, covered and doped) weigh in between 20 and 25 grams (my diet scale only reads in 5 g increments) -- I'll add five grams or so with the DT, but I'd be annoyed at having to add ballast just to get up to 40 grams on a design that originally built to 85 grams (even though I scaled to 94% and used thinner wood, this is a surprise).

6.1 grams
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« Reply #68 on: April 25, 2011, 07:23:37 AM »

Oh, does anyone know what a Peck Polymers 9.5" propeller weighs? The parts that are currently finished (wing, stab, rudder, and fuselage, covered and doped) weigh in between 20 and 25 grams (my diet scale only reads in 5 g increments) -- I'll add five grams or so with the DT, but I'd be annoyed at having to add ballast just to get up to 40 grams on a design that originally built to 85 grams (even though I scaled to 94% and used thinner wood, this is a surprise).

6.1 grams

Hmm. Nose block, prop shaft, thrust button -- this is going to be close to minimum weight, I think.
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« Reply #69 on: April 25, 2011, 09:00:49 AM »

I had to use rubberbands on one one time to meet the weight. Extra bands went on the wing as hold down bands and worked just fine.

I will weigh a legal size pp prop tonight with my gram scale and let you know the weight. If you can wait till late tonight.

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« Reply #70 on: April 25, 2011, 11:28:50 AM »

Zeiss Ikon,

My Peck props are anywhere from 6-7 grams. Check that the pitch is the same on both blades. Often, they are not. Gizmo Geezer sells Peck props that have the pitch corrected to 1:1.25, or you can use an iron to heat near the hub and twist to fix it.

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« Reply #71 on: April 25, 2011, 04:44:10 PM »

Well, good agreement on the propeller weight, thanks guys. My real problem, if I come out underweight, is having to build an auxiliary tray for my reloading scale to get a weight better than 5 g increments -- OTOH, if the airplane will show "40 g" on my diet scale, I'll know it's between 40 and 45, which is close enough for jazz. I'm also concerned I might need tail weight with as light as this is and a plastic propeller up front, but the rubber's about 2/3 behind the wing, so there's effectively 3-4 grams of tail weight in the motor.
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« Reply #72 on: April 25, 2011, 07:55:09 PM »

My Peck prop weighs in at 7 grams.

In contrast the Czech prop of the same length tips the scale at 7.7 grams. I like the Czech better because the prop is built stronger. Especially when you look at the hub. Also no pitch changing is required. Hope this helps somebody. I am using the Czech prop on my King Harry project. It ought to really go since I know how well this prop carries a full size Sparky. Also a few others like Miss Canada Senior, Korda Victory, also a small Korda C stick.

Yall have fun ok ?
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« Reply #73 on: April 25, 2011, 09:50:53 PM »

Also no pitch changing is required.

Okay, I realize it's virtually unenforceable, but isn't it an illegal modification of the Peck propeller to change the pitch (even to make the two blades match)? I'm allowed to remove flash, balance by adding mass, and drill for a brass bushing to improve the freewheel ramp -- and that's it. Nothing about heating up the hub to twist the blades to match pitch (or bend them to correct tracking, come to that, both modifications that ought to cut vibration and improve propeller efficiency).

Well, perhaps there's a better forum for that kind of discussion -- meanwhile, I got the Sparky DT built tonight. This is the drag brake DT I was so mysterious about back up the thread; it's built now, I know I can stow and deploy it, and I'm pretty certain it'll produce enough drag to bring the Sparky down positively. Best of all, I made it from scraps, leftovers, and a little glue stick.

First photo shows the DT cover, cut to match the taper of the Sparky's fuselage and sized to fit just ahead of the crescent former in the bottom (which exists, I think, as a place to give access to the rear end of the motor). This was sanded to round the edges, so as not to produce too much drag when stowed. Second photo shows a scrap of yellow Esaki glue sticked to the edge of the cover. I missed an intermediate photo or two, showing the folding steps to produce a single bellows-like fold in the tissue, giving a broad wedge that fits under the cover, as well as another strip for gluing; the third photo shows the two tissue pieces glued in place and folded. Fourth is a step I should have done before putting on the side tissues -- covering the DT cover. I used the same orange Esaki that's on the fuselage, though a quick test showed it would be a bad idea to dope the tissue without a seal coat on the foam underneath (next time, I might brush thinned white glue onto the foam before covering it, to give an impermeable layer and allow doping). Still, the DT will be almost invisible in flight.

Photo 5 shows the hinge installed at the rear end of the cover -- very important, this goes over the glue flaps on the side tissue, but under the angled folds. The hinge is cut from plain copier type paper, a scrap I had left after transferring the window frame patterns. Photo 6 shows the DT "clamped" in place as the glue stick attaching it to the fuselage dries. Not shown is the little paper "tongue" I made to slip between layers, so I could put the glue stick on the hinge and top gluing flaps without getting it on the other layers of tissue.

Continued in next message -- attachment limit.
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« Reply #74 on: April 25, 2011, 09:57:02 PM »

The remaining three photos show the DT unit partially and completely deployed, from the front, and completely deployed from the side. Not yet made or installed are the attachments for the positive deployment tensioner (rubber band like the one that pulls a pop-up tail or wing) and for the timer restraint (to keep it tight against the fuselage bottom until it's needed). I could get away without positive deployment -- even with no airflow, this unit will deploy itself if I hold the fuselage up in the air for a few seconds, but why risk it?

In practice (tested by blowing gently into the open end) the tissue will bulge outward, rounding out the opening and maximizing the frontal area; the result should be similar to deploying a six or seven inch diameter parachute -- it won't (I don't think) bring the Sparky down like a shotgunned goose, but it should ensure it has too poor a glide ratio (hence, too high a sink rate) to continue climbing in any reasonable thermal.
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Re: Comet Sparky for P-30
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I'm here to have fun -- but winning isn't bad, either.
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