Richard,

I'm sure Matt will be able to offer you some good suggestions. However, you just inquired about glass! Where is the carbon veil actually going? Are you using CV on top of the wings and stab or on the fuse?

I wouldn't use both, use one or the other. If you are going to use glass, I'd go with 3/4 oz cloth - the weave is a little tighter and it will require less to fill it.

David.

Richard,

I hope you have the 0.2 oz carbon veil from ACP. I've tried using the thicker material but it definitely requires more filling. It's fluffier and unless you bag it the results will not be satisfactory.

But the 0.2 oz material is worth a closer look. First off I have not used PolyU to bed this stuff, only dope. I've found that nitrate dope will loosen the binder if you let it soak for a bit as you are bedding it on the wood, making the veil much easier to negotiate around compound curves. Wing tips are not difficult. BUT, you may also slit the material if you don't want to smooth it down with a finger, and allow the slit stock to fully flash. Carbon feathers exceedingly well, better than anything else I have ever used, so covering slit sections is no big deal. Glass is easier to work with in this regard though. Carbon takes more patience and care and is not for the timid.

I use nitrate for the initial bedding because it adds almost no weight and makes bedding a cinch. Two coats of nitrate and I am ready for epoxy clear to finish the bedding, or, in your case, coats of PolyU. Of course not every one tolerates dope so if you can't, this material may be best relegated as undercoating of wing sheeting over foam.

I'll assume that you tolerate nitrate fumes long enough to bed it. Come back with the PolyU clear for a couple more coats but use care and blot the paint with toilet tissue. Sand and smooth after the bedding as usual. Weigh everything every step of the way to measure your progress. As a gauge, my panels are 510 square inches each. Primered and ready for paint the weight was 320 grams each. If your wing is smaller than 1000 squares, judge the weight in proportion.

Carbon veil in not bullet proof. It is a very thin material, thinner than medium silkspan, and is not tough, as you already have found out. However the stifness it imparts has to be experienced to be understood. Of course, as far as stifness goes, you accomplish the task just as easily by applying the veil inside skins. BTW- I'll assume you are not covering an open bay structure. It is far too fragile to cover open bays. BUT it will impart lots of stifness to open bay wings also especially if you silk and dope the panels after the carbon. The Control Line Stunt guys are sold on this stuff.

It will stiffen fuses but you probably won't be able to tell the difference. Classic fuses were terribly overbuilt with thick balsa..... stifness was their strong suit. For fuses, it is easier to do one side at a time and overlap the edges. You will probably need to use your fingers to rub the carbon down onto the wood, until the dope flashes and holds. Glass shines in this area comparatively speaking since you possibly could use a single piece of glass all around. As far as the fill coat difference between glass and carbon, I've found it takes about the same amount of material and time. Carbon finishes thinner meaning lighter, and stiffer but not necessarily stronger, and you must be very careful. Because of the thin section, hanger rash is a real issue, but it would be no matter what.

Anyway, the fill coat for me is typically Klass Kote clear filled with talcum (Johnsons original baby powder is fine in a pinch; don't use the stuff with starch in it) or calcium stearate. Brodak carries Ca-St. It is applied fairly thick and sanded nearly off after a few hours of cure. Then comes Klass Kote primer. Highly recommend this epoxy paint system. I have had a small problem with yellow coverage but the guys are KK fixed me up. Call them and talk with them. Good people especially Nate Dickerson

Hope this helps get you started. I've found the material a bit more challenging than glass at first. Once I figured some things out such as how to handle compound curves, it became much easier. Also, I had to figure out that I didn't need to be heavy handed with the dope for great results

Good luck

Matt,

That certainly is a wealth of information!

I have the .3-ounce veil. I didn't do enough research to learn that the light veil is used for stiffness, not strength or ding resistance. It also sounds as though I should get nitrate dope to apply the veil before filling it with the urethane. Or possibly hitting it with a high-bulk sandable primer as filler and finishing with the urethane.

Your other idea, to use it *under* the skin for stiffness, is a real possibility. (Although it sounds as though I'd need to let the nitrate or epoxy cure with the sheeting tacked and formed to plastic wrap-covered ribs.) That would impart the stiffness with, I would hope, little added weight, and then use glass on the top surface.

I had planned to use carbon rods glued into the rib alignment holes until I weighed the 5/16 rod. It came to 3.2 ounces and there would be two for each wing panel, or real close to a pound of weight.

Or I may be seriously over-engineering this build.

Again, many thanks for your time and detailed information.

Cheers,
Richard

I received my balsa from National* the other day. I ordered 24 sheets of 3/32X4X36 for three projects I have in mind, the first one being the built-up wing for the King Altair prototype. (After about four years, It's about time I built the wing...don't you think Jeff)?
Then comes a new King Altair, and finally a foam wing for Ed Kazmirski's Taurus II, (Ed had built the fuselage and stab...it is ready for paint), but it needs a Bosch airfoil wing...just like the wing on Ed's original Taurus II.

Anyway, I have these 24 pieces of...some of it is the "bargain" contest balsa sheeting, and the rest is the "clear" premium quality. They are BOTH supposed to weigh the same, the "bargain" is supposed to have more staning, and imperfections...that's supposed to be the ONLY difference.

When the wood arrived, it came as one big stack...the "bargain" wasn't separated for the "non-bargain" expensive stuff. I couldn't tell much difference between them...yes, a few of the sheets have a few more flaws, and color associated with them, but only a handful, (less than the number of "bargain" or "stained" sheets I received).

I had 5 sheets that weighed in at 16 gms, 3 sheets that weighed 18gms, one sheet at 20gms, 13 sheets at 22gms, and 2 sheets at 24gms. The two 24gm sheets I'll probably use for the Taurus, so the wood used for my "super-light projects" will be built from 22gm or less balsa, (22gms is approx 0.8 oz).

Duane

Richard,

I usedfour 5/16 CF tubes in the wings and it only came to a total of 5.6 ozs. Did you plan on using CF tubes or rods? Since I don't have a wing without CF tubes in it I have nothing to compare my wing to. All I can say is that the completed wing is extremely stiff. Perhaps the best part about using them was the ease with which they were installed. It only took a few minutes to install each one with fast CA. The use of the tubes also allowed me to use the tubes as the alignment pins.

Bill

Duane,

I had similar results from National Balsa with 20 sheets of the 3/32X3X48" premium grade balsa.

Bill

That may be OK for those with a 120 2-stroke engine, however, for somebody with a .90, (or especially a .61), that 5.6oz is still 5.6 extra oz. You took your wing off the board before sheeting was added, so I can see you might want to add CF tubes to have a more rigid wing while "messing" with it. The question is whether you really NEED the tubes. Most of us leave the wing on the board until the top sheeting is installed. When you do that, of course it is much more rigid. If you make the "standards" or wood pieces the rods go into at the size I gave earlier, you can even flip over the wing with the rods still in place until the underside is nearly ready to sheet. (BTW...leaving the STEEL rods in place is not recommended, and may adversely affect the weight of the final project, and subsequent vertical performance, (maybe even horizontal performance), of your Simla...your wing will be very strong however).

(Of course I'm just kidding here about the last past regarding the steel rods...couldn't resist).[8D]

The point is, the extra 5.6 oz, while a nice experiment, is certainly NOT required for a strong wing.
Duane

Bill,

I hadn't seen 5/16 CF tubes. Of course, I hadn't been looking for them.

Did you get the .312 O.D. or the .315 O.D.?

Thanks!

Richard

Duane,

I agree with you about the 5/16" CF tubes in the wing. As a matter of fact I plan on foregoing their use in my next Simla project. Once again, I'd like to do somethingin the 96" wing span with all contest balsa, a 60 size engine, and any other techniques to make it as light as possible without altering the overall Simla appearence. This second projectwill require a great deal more planning and research. I am looking forward to it .

Bill

PS- I was considering making use of the steel rods as stiffiners, but decided that I would need them for any futrue Simla builds.

PPS- I didn't run into the diminishing wing tip problem. Not sure why, but it just didn't rear it's ugly head.

PPPS- Yes, I did remove my wing panels from the build board, butonly after I installed the CF tubes. As it turned out, when I placed the wing sections back on the build board they were as flat as when I removed them. But then I already knew that they would be. Now that they have been covered they are really rigid and about 740gm. each with servo and landing gear.

Hmmmm....3.2 ozs for a carbon rod seems heavy to me. Carbon tubing, thin walled should weigh no more than about 15-20 grams per piece. With the large panels planned (I think they are around 50" each, right?) you should use some form of spars in the built up wing. For even better strength you might consider forgoing the carbon install in the alignment holes and relocate the carbon tubes into the spar holes in place of the wood spars. Lighter and stronger and stiffer. Just an idea.

Total weight shouldn't be, what, 10 lbs? I mean for the whole plane, how much weight does the wing really need to support?

My foam wings are generally skinned with 1/32" or taper sanded 1/16" contest grade, with carbon veil inside. Each panel has a span of 37" in a typical example, and an area between 500 and 550 squares. Full skins weigh 40 grams each, top and bottom. The panels are joined with a joiner tube, usually carbon thin walled 7/8" x 040. It's a different arrangement for certain and is without retracts. Actually, with a socket installed, the wing design would be adequately strong for retracts too but that's not in my plans right now. The outside is either carbon veiled or silkspanned. Power is typically 4 HP, 30-35cc gas engines on pipe.

I am so confident of their strength that for my new plane design the same wing design will fly using a 6 HP 55 cc engine. Total flying weight will be around 12 lbs. Just a couple numbers to gauge by. Good luck with your builds and if I can assist in some way, don't hesitate to contact me

That's good to hear...it wasn't a MAJOR problem, but my tips turned out a slightly different shape, (the curve at the rear of the tip), than shown on the plan. That being said, I was happy with the overall look of the wingtips. The Simla has a distinctive wingtip and "stabtip" pattern compared to the average plane of the period...it helps give the plane its unique look.

Duane

Richard,

The .315 tubes were nearly a perfect fit.

Bill

Speaking of sheeting ...

If I understood several earlier posts, some people use the "standard" method of applying the leading and trailing edges and then carefully trimming the sheeting to fit in the space before trimming the LE and TE to be level with the top of the skin.

Others add the LE and TE, trim them to be level with the edges of the ribs, and then apply the sheeting *over* the LE and TE before sanding the LE contour to a paper thinness.

With the ribs aligned by rods and feet, what would be the downside of sheeting and trimming to the front and tail of the ribs *before* adding the LE and TE ? It would seem to solve the problem of trimming the sheeting to fit between the LE and TE without having to sand the LE contour so thin.

Cheers,
Richard

That's great to hear...it wasn't a huge problem, but the rear of my tips in the curve are not EXACTLY the same as the plan, still I'm happy with them overall.

The tip shape, (both wing and stab), is unusual for the time period, and is one of the features that give the Simla it's distinctive and unique look.

BTW...Your plane should be starting to look something like this. Yours should have LESS of a Taurus-like appearance than the prototype. After these pictures were taken, I sanded the heck out of the top and bottom nose area of the fuselage, and it helped to a certain extent, but yours should have a more slender nose section, and a slightly taller vertical fin. I basically wanted the slope of the nose to naturally follow that of the top of the spinner.

Looking for pictures.[8D]

Duane

Richard,

Perhaps because of the airfoil shape the sheeting does not need to be sanded paper thin when it is placed "over" the LE and TE. Only a slight amount of sanding of the leading edge gave a really nice contour and the trailing edge required no sanding at all. The best part of it,as Duane stated earlier, is that it is much stronger than the butt joint. Also, if you use the butt joint method, when you sand down the LE and TE you run the risk of sanding the sheeting at the joint very thin. IMHOthe overlap method is far superior in many critical ways.

Bill

PS- Take a look at photo #4 in post 380. It's not completely finished, but it will give you an idea of what I,m saying.

I was looking at your post #380. Looks like you decided to use CF rods INSTEAD of the wooden dowels...nothing wrong, just different. Did you plug the ends with wood?

Even though we are building the same wing, it's amazing how many little "micro-differences" there are in building methods. It looks like you could sand the sheeting over the L.E. almost down to a point right at the L.E. if you chose to...did you leave the L.E. that way?I'll have to look at mine from the side to see what I did. Hopefully it is still visible even after painting. Chances are I sanded off more than you did. I'll post a picture.

The way Jeff finished your ribs makes your root rib appear different...again, interesting.

Duane

Duane.

I really haven't finished sanding the leading edge. So far I have only sanded the excess sheeting off the front of the LE. I started by sanding the laminated leading edge down to the rib pattern, which basically left a sharp pointed LE. Then when I sheeted the wing it left a LE of 3/16". At this point I could either leave it relatively sharp or I could round it some. What would you suggest?

I suggest you do it just like Ed. For my King Altair wing, I'm going to experiment with a sharp L.E. in an attempt to handle the wind a bit better, (the KA has drag to burn, and literally "whistles" as it goes by).

When I post that L.E. picture, it should show the L.E. pretty well. My goal throughout was to try to make the prototype look as much like Ed's Simla as humanly possible. It looks to me like Ed went more toward a "normal" or even blunt L.E.

Hello everyone,
Just checked in on the thread the other night and was very surprised to see how much it has grown. The last time I looked at it you were just getting started on the 2nd page. You guys make a kit manufacturer proud!!

I have deliberately stayed away from the thread because of my schedule. Besides Classic RC Hobby, I have a full time job where I am a plant engineer, I am on the board of directors of two non-profit organizations, and I recently started an RC club here in Lancaster County, SC. Add to that the never-ending projects here at the house (the current one is replacing all of the windows) and perhaps you will agree I'm a bit busy. It seems to have slowed down here a bit in the last week or two so maybe I can spend more time on the hobby and participating in this thread.

I have other Simla builders contacting me for info. I am entertaining the thought of sending out an email to all of the current Simla owners and letting them know about this thread. I also plan to link to it from my web site. It might get a bit busier in here Duane!

Thanks for the compliments on the kit guys, very much appreciated.

Duane,

I was just on the Classic R/C sight and I noticed something that I had not seen before. In the gallery at the Simla sale sight , the third photo(the first black and white) the rib pattern is showing through the wing covering. I was just wondering what you wouldmake of that? Was the sheeting he used very thin or maybe the covering material he used shrank so much that it left the imprint of the ribs?

Bill

Although we elected not to, it is quite possible that Ed used 1/16" sheeting for the wing. For example, I know that Don Lowe called for 1/16" sheeting on his original Phoenix 1, (see pictures of Don's and my Phoenix 1). In a situation like that, you have to be very careful sanding the wing skins.

I just went downstairs and checked the TWO KNOWN Kazmirski wings that I have to see what Ed did on those. The Taurus-II uses 3/32" sheeting. The other wing I have was the ORIGINAL wing for that Taurus, and made the trip to Belgium as Ed's back-up plane, (it still has the FAI sticker on it). This wing is no longer used because it has a semi-symmetrical airfoil...it was replaced with the Bosch airfoil in the 1964 season. Another distinguishing feature of this wing is its extreme thickness, (see attached of the original Taurus II before the wing was switched out, and comparison pictures of this wing).

Anyway, this wing is also extraordinary because of its unusual construction and its lightness...it is a 71" span wing that weighs only 1.1 lb including landing gear. On this wing, Ed used 1/16" sheeting. When you hold this wing, it reminds you of an eggshell, and you tend to hold it as you would a hollow egg.

I also looked at the Simla, and if you hold it to the light just right, you can see a hint of sheeting ripple, but you don't normally see it in pictures of the Simla, (see a couple examples). For all these reasons, I believe that in the original Simla, Ed used 1/16" sheeting because the ripple is so pronounced, (see the B&W photo). I wouldn't be surprised if it had a "superformed" L.E. like the Taurus, but maybe not because the L.E. is much more "sharp". Ed was VERY conscious of how to choose and use balsa for different functions. For a plane this large, it makes complete sense that he would opt for the more delicate, but much lighter 1/16" contest balsa. One more thing...I believe good quality lightweight contest balsa was much more available than it is now. Models were not competing with wind turbines.

Duane

Both of my Taurus have the sagged wing skins, both use 3/32 skins, no dope and plastic covering. OK, I build light and select wood 'fit for task' but the point remains, this sagging is not unusual. With doped and silked surfaces it would be an expected result, and the older the airframe...As far as 1/16 wood is concerned, I use it for most of my wing skinning, 3/32 is pretty heavy stuff, compared, and my scale models tend to be a bit bigger, 90 to 120 " stuff, so I need to save weight where I can. You can limit the rippling thing by sanding skins before attaching them to the wing, if you pre-curve damp before gluing, then allow days to dry before attaching, and using non-shrink dope (Banana Oil) to seal and attach the covering if you are not using films. Banana oil does not sand well, so you have to use not much, and sand carefully before priming. As to what skinning Ed used, well I cannot tell, but given the weight of the finished Simla, it would have been light, so the rippling is not in any way strange.
Evan.

Question: If you wanted to avoid the sagging, but wanted to save weight, would there be any benefit in laminating .2 or .3 ounce carbon veil to the underside of 1/16 sheeting? I'm *guessing* (since I don't have any weights available) that there would not be a weight savings. That is, the weight of the veil plus the dope or resin would equal or exceed the weight of the extra 1/32 of sheet thickness if you used 3/32 sheet.

From my perspective, since I am not a competition flyer, there comes a point where a little more durability outweighs saving a bit of weight. My main interest in using carbon veil and composites is how it will increase durability with the least weight penalty. Thus, the veil looks like it's out since it imparts rigidity but not strength or ding resistance. Although it *might* replace the stiffeners added to the sides of the fuse, especially if you also removed some weight from the doublers. Just some musings on my part.

Cheers,
Richard

Define what you mean by 'durability'. Adding carbon and epoxy to 1/16" sheet will weigh far more than selecting light 3/32". What do you intend to use the wing for? Whacking it into the garage door? Flying it through the local vegetation? Or do you want the model to last for some time? If the latter then keeping the oil out of the airframe is much more important, along with intelligent flying. If you want to keep the wings pristine then make up some wing bags, corrugated cardboard makes good, cheap bags, wrapped and taped around the panels. Use them to store and transport the wings and your model will last pretty well, Ed's have, and he didn't need glass or carbon, just a good finish.
Evan.

Evan,

Yes.

Richard