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Jan 14, 2020, 08:43 AM
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Thread OP
Crash:

Exactly.

Ya' know what I really need? A good photographer.

Greg
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Jan 14, 2020, 12:40 PM
volare est vivere
ray foley's Avatar
hi there from Toledo!

Hey Greg;

Actually this will be my first attempt at a Vtail airplane of any sort. I have been sort of interested in Vtail and have read a lot about them in the magazines and here on RCG but never got "a round tuit" as it were. Well that will change shortly as parts and pieces arrive from Corky over the next few weeks. Until then I will follow your lead. Lead on!

Ciao, rjf.
Jan 14, 2020, 02:46 PM
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Thread OP

Mounting the Tail (and getting it RIGHT!)


The first step is to make sure the tail posts wil actually fit in the carbon tubes. Trust me on this: they won't - at first. I never found out where the German builders got their carbon rods and tubes for tail mounts, but a 2mm rod fit comfortably into a 3mm carbon tube. Corky chose 3mm rods, and the corresponding tube has an "official" 3mm inside diameter, but.... Corky knows this, he warned me, and now I'm warning you. Do NOT repeat NOT try to force the 3mm rod into the carbon tube you just glued into the tail surface.

Instead, do what I did.

I started with a new, sharp 3mm twist drill. Any brand will do. Use it to ream out the tube. Just like the rod, it will not go in at first, but I twisted it with pliers and finally got it inserted all the way. Snickering may now commence. Keep working at it with the pliers until you can push it all the way in and pull it out again.

Next, cut four pieces of the 3mm carbon rod, each 1 5/8" long. Kind of sharpen one end and sand the other end flat. They still won't go into the carbon tube, so if you try it, don't push very hard. Take any of your personal favorite abrasive devices (including a strip of fine sand paper) and start to work on a rod. Hold it by the blunt end, and always work from you fingers to the tip. Sand a bit, then try it. LIGHT PRESSURE ONLY! Keep at it until you can insert the rod all the way in (and still get it out again!). It should fit without slop, but still be finger-tight. I used petroleum jelly as a lubricant. They are ready to glue into the boom.

Make sure you know which holes to use and from what direction. I used toothpicks, and marked with a dot the top of the boom. The angle between tails is NOT ninety degrees, but more: 100 degrees. Insert each rod from the bottom. If you haven't played around with the boom much, they should fit snugly and remain in place. Fix them in place with small (really! SMALL) drops of thin CA where each post penetrates the boom, top and bottom.

Trial fit the tails. I used some more petroleum jelly, and they finally seated home.

Now for proper alignment.

Bolt the wing center section on. I used two machinists blocks to support the airplane upside down on my wife's level kitchen counter. Let the boom rotate until the two tail tips rest naturally on the counter top. The wing and tail are now properly aligned.

Notice the complete and utter lack of protractors, rulers, carpenter's squares, bubble levels and other precision instruments.

I fixed the boom in place with a drop of thin CA (holding my breath!) at former F4, which is exposed from this angle. That is all it takes. Turn the airplane over, and use more CA to actually and firmly attach the boom. I followed up with a fillet of medium CA, but epoxy is also fine.

Done and done.

Next, I will finish the fuselage. I want to do wings, but still need another day away from any meaningful CA.
Jan 14, 2020, 02:56 PM
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Thread OP
Ray:

About V-tails.

For a variety of reasons, I have had a lot of experience with V-tails. As far as I am concerned, a designer pays his money, and takes his choice. For every supposed advantage/disadvantage of a V-tail, there is an opposing disadvantage/advantage for a conventional tail. If I were presented with flight test data of two airplanes, one with conventional tail, the other with V-tail, and never saw the airplanes, I could never tell you which data set came from which airplane.

I built my share of Slites, and they were unique in offering either V-tail or conventional tail as a buyer's option. Building both options side by side, finished weights came out identical, within a gram or two. Performance was indistinguishable to me. I have heard many, many rationals for one (either one; pick one) is better, but my experience has shown me no inherent advantage.

A good designer can design either a V-tail or a conventional tail, and deliver exactly the same handling, performance and weight with either setup.

But (and here it comes!): My trusty Slite, with it's too-small polyhedral, and its too-draggy under camber, and its too-silly V-tail, when it swoops into a gaggle of conventional sailplanes I always think of a hawk coming to harvest pigeons.

Greg
Jan 14, 2020, 07:15 PM
Balsa breaks better
Thermaler's Avatar
Quote:
Originally Posted by glidermang
when it swoops into a gaggle of conventional sailplanes I always think of a hawk coming to harvest pigeons.

Greg

+1


Joe

Osprey 2M, Super and Grand Esprit, Weston's Magic and Merlin, last but not least Gordy Stahl's Graphite. All "V" tails.


Balsa Breaks Better
Woodies Forever
Jan 14, 2020, 07:25 PM
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sunnybreeze's Avatar
Nice job on alignment. Super simple way to do it.
Keep it coming

Steve.
Jan 15, 2020, 10:11 AM
volare est vivere
ray foley's Avatar
Hi there from Toledo!

Hey Greg;

I used a similar technique when installing the boom and tail feathers on my YJ3Me.

I also attached the wing center panel to the pod but set them on two 2 x 4 scrap pieces on my building table. I used sand bags on top too keep everything from sliding around.

I also supported the fully flying Hstab, Vmount, and boom on more 2 x 4 scraps with a lighter sand bag on top.

Then I put a thin coat of epoxy in the ID of the boom's mating surface and on the pod's OD mating surface and slid them together.

Clean up inside and outside with rubbing alcohol and paper towels.

Easy peasy.

Ciao, rjf
Last edited by ray foley; Jan 15, 2020 at 10:23 AM.
Jan 15, 2020, 04:55 PM
Registered User
Thread OP
Ray:

I wish I'd invented the technique, but I didn't. It was taught to me by Oleg Golovodov, who sold me my Taboo DLGs.

Yours, Greg
Jan 15, 2020, 05:13 PM
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Thread OP

Prepping the Fuselage for Final Shaping.


This is an easy step, and necessary for achieving a smooth finish. Also, proper and studious sanding reduces both drag and weight. I've developed a technique that minimizes time as well. I don't like to wait a lot for an airplane to be completed, do you?

Corky includes several pieces of 5/16" balsa sheet, and it turns out they fit pretty much between formers F3 and the aft end of the fuselage. It takes only the most minor sanding or trimming to get each one to fit. Once I got each piece to fit closely, I used Titebond on the sides and ends, and pushed them in. Except for the long one that fits under the wing trailing edge, I did not try for anything like a flush fit, but just let each one stick up. The excess will be easily trimmed.

Next, I got some of the light-weight spackle compound from Lowe's, and mixed a large tablespoon of that with roughly a quarter teaspoon of water. I mixed it up well, until all the lumps were gone. Then I applied it to the fuselage, where ever there was either (1) a hole or depression; or (2) something sticking up. I apply this very, very liberally, and let it really pile up. It will stick tenaciously, but is till soft and easily sanded. When I do sand the fuselage, literally 99.5% of this filler will disappear and be gone forever.

Later, when the nose block is sanded to shape, if the block surface is rough, I will mix more of this spackle and use it as a sanding sealer for a smooth appearance and good adhesion of the covering.

Slop the stuff on. Filling is more important than any supposedly "saved" weight, and you won't save any in any case. When it sands, it sands clean, without any clogging of the paper, to a glassy finish. If you really must smooth it out now, use an old motel door card as a squeegee.

Now, we wait until tomorrow, when we can begin sanding.
Jan 16, 2020, 07:20 AM
FlyLikeAnEagle-LandLikeADove
u2builder's Avatar
Hobbico Balsa Lite is also a good filler. https://www.amazon.com/Hobbico-Hobby.../dp/B0015H4EB8 It is probably pretty much the same stuff, but comes premixed, and tends to match the color of balsa and maybe even less likely to show through light coverings. I usually use several thin layers, often applied with a scrap of thin balsa, mostly because I think several thin layers dry quicker.

This is a great thread. The only thing that is holding me back, aside from having too many planes, is the dreaded CA allergy, that may, I think, be combined with a wood dust allergy. I have been sick for 2 weeks with cold like symptoms (working on an old BOT kit build) and have taken to wearing a 3M respirator every time I enter my shop, and taking your lead to try to do sanding and CA ing outdoors with the respirator in winter weather. I use Titebond for most gluing, which would not be possible for the YJ. Still, I'd like to build the YJ and so I am following closely!
Jan 16, 2020, 08:11 AM
Registered User
Crashbound's Avatar
Quote:
Originally Posted by u2builder
Hobbico Balsa Lite is also a good filler. https://www.amazon.com/Hobbico-Hobby.../dp/B0015H4EB8 It is probably pretty much the same stuff, but comes premixed, and tends to match the color of balsa and maybe even less likely to show through light coverings. I usually use several thin layers, often applied with a scrap of thin balsa, mostly because I think several thin layers dry quicker.

This is a great thread. The only thing that is holding me back, aside from having too many planes, is the dreaded CA allergy, that may, I think, be combined with a wood dust allergy. I have been sick for 2 weeks with cold like symptoms (working on an old BOT kit build) and have taken to wearing a 3M respirator every time I enter my shop, and taking your lead to try to do sanding and CA ing outdoors with the respirator in winter weather. I use Titebond for most gluing, which would not be possible for the YJ. Still, I'd like to build the YJ and so I am following closely!
I have developed a terrible allergy to balsa dust, and to a lesser extent, CA fumes. Simply knocking off the laser char on one rib without protection can mess me up for a week, with symptoms that mirror an upper respiratory/sinus infection.
Much as I hate it, when doing anything that may involve the least small amount of sanding balsa, I wear a 3m respirator all the time. The one with replaceable filters.

My shop has woodworking tools and I have an overhead homemade airfilter I turn on that constantly pulls the air through a dust filter. If I do any amount of sanding, like tapering the TE or sanding the whole wing, I use a shop vacuum hose suspended beneath the surface where I sanding and constantly sweep the dust into the vacuum. And yes, weather permitting, when sanding a whole wing I prefer to go outside.
Jan 16, 2020, 01:41 PM
Registered User
Thread OP
u2builder and Crash:

You certainly know what I'm talking about.

There is also an allergy to epoxy, so if you're doing more than mixing a small bit of 30-minute stuff, use those gloves! The allergy comes from long-term exposure.

Greg.
Jan 16, 2020, 02:26 PM
Registered User
Thread OP

Shaping and sanding the fuselage.


This stage is what I personally find the most obnoxious part of building a wood sailplane. The balsa dust is just the pits, even without an allergy. However, I find that being methodical and setting realistic goals gets me through it OK, and it takes about two hours total for me to get a fuselage to my personal standards. When covered with opaque Ultracote/Oracover, it will look pretty seamless and cool (using a squint, and standing about 2 meters away, of course!).

Making the Hatch: This is a typical hatch, and my way is NOT repeat NOT the only way. If you have a way you prefer, I say go for it. It will probably work just as well as anything I present here.

There is a plank in your kit, 3/16" thick and about 1 1/2" wide. That is your hatch. I cut off an arbitrary 1" piece from one end, just as square as I can manage with a razor saw. Glue that piece to the top of the fuselage at the front, butted up against the nose block. I face the laser-cut end aft, to match what becomes the hatch. I used a small scrap of plywood for a tongue, to fit under this piece. I tapered it to fit the forward fuselage and glued that under the hatch itself, exactly centered. Oh, and I used the laser-cut end for the front of the hatch. I took another scrap of balsa and tapered that to fit as exactly as I could manage across the fuselage just in front of the wing lead edge. That I glued, centered, under the hatch itself. The hatch now goes on centered, and the friction fit at the aft end holds it in place (I will use an additional trick to secure the hatch in flight, when I cover the airplane). Finally, I applied two, small drops of Titebond on the fuselage sides, and temporarily glued the hatch in place.

On my fuselage, the sides extended about a quarter inch beyond the filler blocks. So, I just cut them off.

The fuselage is ready for sanding.

Initial shaping:

I use a razor plane first, and then a really aggressive sanding block. The goal is to make the profile smooth when viewed from either the sides or top. We are knocking down all those rough and square ends of things that make the fuselage (at this point) look the streamlining appears to be blunt force trauma. Nothing is made round that is not already round. I even use a square to true things up, using the base of the fuselage as a reference.

Next, I go to the plane once more, and start knocking down the corners. We want to leave no sharp corners anywhere at all. Did you read your Dave Thornburg? Remember the Old Buzzard? The fuselage will be round eventually, but right now we start by making it octagonal - which is also a way of making sure it is symmetrical. Do NOT repeat NOT be afraid of removing too much. That is very difficult. The razor plane will work on the top, forward of the wing. On the bottom, the razor plane will work until it starts cutting the plywood sides. Once you are at that point, switch to your most aggressive sanding block. Aft of the wing, the balsa is pretty soft, so just use a moderate sanding block, and work gently.

Did I mention the spackle? No, I did not. Just go to work.

Rounding.

The Big Boys, who really produce good-flying airplanes, will sand the corners at the bottom until they can discern the basswood longerons just showing. There is no loss of strength until those longerons are reached. Your takeaway: keep sanding those corners!

Now, having exposed a face of at least 1/4" (no less!) at each corner face, you can start the rounding process. I started with my aggressive block, and worked first one side, then the other side, and finally the bottom and top (hatch). I sanded each surface until the corner lines were no longer discernable. I worked aft of the wing trailing edge as well, and sanded the tail cone to a roughly circular shape. When I was done, the fuselage would still stand up flat on the table, but tip over easily if pushed. I also angled the nose block at each side at a 45-degree angle. As I rounded the corners, these flat angles transitioned naturally to a nice, round nose.

Polishing.

Finally, I took a sanding block of fine paper and polished everything. There is no shaping now - that is all done. Just polish. Every time I think I'm done, I hold the thing under strong light, and find more scratch marks, so back to polishing! Any scratch marks yo do not polish out, will be apparent later under the covering. Be sure to wipe the dust off with a soft cloth before inspecting.

Done?

OK, if you think you are done, you can remove the hatch with a razor blade. Lift the back end, insert the blade and move it forward. Typically, when you hit the glue blob (it was small, right?) the hatch will lift right off on both sides.

Now, look things over once more. Where, I may ask, did all that spackle go? The answer: right where it belongs!

By the way, all the pictures pretty much show the fuselage on my wife's kitchen counter. I did NO SANDING WHATSOEVER in the kitchen. It is a winter's day, the sunroom is dark, and all the sanding went on out in the breezeway: cold, yes; workable, also yes. My wife is out earning money teaching Red Cross classes.
Jan 17, 2020, 03:44 PM
Registered User
Thread OP

Outer Wing Panels


Here we go, the outer wing panels.

For starters, I need a show of hands: is there anyone out there who would not believe me if I told you that the left and right wings are mirror images, but other wise part-for-part identical? Is there anyone out there who can see the right wing being built, and from that not be able to build a left wing as well? No? Great!

My plan is to do first the right wing (both outer panels) then the left. So I started by taping down the right wing outline on my board. Just like the center panel, I cut close to the trailing edge so I can clamp the actual trailing edge to the plans.

Now, here is a CRITICAL STEP: making the wing washout shim. I went overboard, here, but a simple piece of 1/16" balsa sheet will suffice. It goes under the outboard tip of the intermediate panel, and results in some twist being built in. This really is critical. Without washout, your airplane will be a doggy performer, seeming without the ability to run at all. Furthermore, it will stall abruptly, and you will never know it it breaks right or left. Properly twisted, the airplane is lively and quick. Properly twisted, stalls (when they occur) will be straight ahead. Think: How would I know this?

Now I laid out all the ribs. Corky is very helpful. There are two carbon tubes for the intermediate panels, and almost the correct length, just slightly longer than required. So no cutting or measuring. In order to expedite matters, I set out all the ribs on my kitchen counter. I started by making sure ribs B1 and B2 fit over the appropriate spar, then made a sandwich: make darn sure you make a left and a right! Once they were glued together and on the bench, under weights, I reamed all the holes in the remaining ribs.

Taping down the right wing plan, I covered it in wax paper, with the trailing edge near the edge of my bench. I clamped the actual trailing edge to the bench (it almost exactly matches the plan) and proceeded to thread ribs onto the spar. I clamped the plywood ribs to the trailing edge, and the whole assembly stayed secure. I made sure the 1/16" shim was under the trailing edge at the outboard end.

Finally, all the ribs in place and pretty close, I used more weights to hold it down. I started at the center, and used thin CA (holding my breath!) and glued each full rib to the spar. One drop is all it takes, by the way. I made sure each rib lined up exactly, and put in a drop. For the outboard rib B18, you have to use the 6-degree template to tilt the rib. This requires three hands, which I don't have (do you?) but do your best. If it's not right, I will show you how to correct it easily, when we join the two panels.

The full ribs glued to the spar, I moved the weights near the trailing edge, and glued in the 3mm tube leading edge, only to the full ribs. I start at one end and work across. Once the leading edge is attached, you can go back and make sure each half-rib is properly aligned, then glue them to the spar and leading edge. (While I was doing this, I had the overhead fan running and held my breath whenever I was actually applying CA. Then. I left the room for a bit.)

Coming back in, I moved the weights once more to the spar, and lifted each full rib i turn, and glued it with wood glue to the trailing edge. I gave the wood glue about 20 minutes to cure, then removed the panel from the bench. I used my Dremel with a cut-off wheel to remove the excess spar and leading edge, and it is done for now.

The right wing outer panel went exactly the same. Just fewer, smaller parts, but exactly the same. There is no shim required. If your center panel was straight, your two right-hand outer panels should be fine as well. I did not attach the fancy outer tip at this time - that will be part of finish sanding later.
Jan 18, 2020, 12:34 AM
Registered User
I am OK with only seeing pictures and description of the Right outer wing panels - as long as you follow through and build the remaining set of identical parts into Left outer panels. Don't get all dyslexic and end up with two Rights!
Great thread, you build fantastically fast and get first class results.


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