doxilia

My Feedback: (3)

Glad to be of help. The first foam core wing one builds is always a thrill. Provided your building surface is flat, which I'm sure it is, you will be impressed with how straight and solid the wing turns out.

Further to Richards comments, a ply brace between halves is not needed, especially if the wing has a full airfoil joint at the root. When a brace or two is worth considering or is needed is when the wing center is sanded into a tunnel for use with tuned pipes in certain models with pipes slung under the wing on the fuse centerline (e.g., Prettner's Calypso). In this case, because the wing has half of it removed for 70% of the chord, there are two braces, one in front and one behind the tunnel. The tunnel is clearly also glassed as is the wing center joint overall but the braces insure that the wing is held together at a good 12" span or more. Otherwise, glass cloth and resin (whatever kind) takes care of the center joint.

There are different ways of going about the center joint glass work. My preference is to "glass up" in decremental layers of lighter cloth and wider spans. In other words, I start with 5-6 oz cloth about 2" wide. Then, when that is cured, I sand it smooth making sure not to cut into the cloth itself and lay up a wider band about 4" wide of 2 oz cloth. Sand again and finish off with a 6-8" wide band of 3/4 oz cloth. This last cloth fairs into the wing nicely allowing one to use plastic covering if desired without unsightly weave or otherwise provides a good surface to fill for paint. Of course, if the entire wing is to be painted, the final layer can cover the entire wing as it is "glassed".

As far as the glue used to do this, that is exactly what finishing (laminating) resin is for. It is thin so it will flow into the weave of the cloth and form a hard joint between the wood and the cloth. What you might know as "fiberglass resin" (from places such as Home Depot) is probably polyester resin which needs to be catalyzed. It is easier to sand than epoxy but it also smells awful - familiar with boat yards? That's the smell. I don't use it because it gives me headaches. If you are sensitive to solvents, stick with epoxy. Epoxy is of course also a catalyzed resin which is more commonly mixed 50/50 rather than 10/90 or similar like some epoxies or polyesters.

If you are planning to use water based paint, you might also like to try using water based varnishes to bed in the cloth (e.g., Minwax Polycrylic) although it can also be used if finishing with other types of paint. Granted, I'd use this for the 3/4 oz cloth for the entire wing but not for the real center joint glass (I'd stick to epoxy there). Polycrylic is not as hard as epoxy and requires more layers but it is lighter. I'd stay way from using regular "tough joint" 15 or 30 min epoxy with glass cloth. It is too quick to set and it is too viscous and will build up too much. The only way I'd consider using it is if I didn't have finishing resin and then I'd cut it down 50/50 with denatured (90% or higher) alcohol so that it flows. The epoxy is mixed first and then the alcohol is added until you have a semi liquid consistency. Finishing resin is much better and when it has begun to set, it can also be brushed with alcohol to reduce the amount of sanding required.

Regarding making cuts in foam core wings, with small openings like those needed for servo wells or HW landing gear blocks, I prefer to use a sharp blade in an X-Acto knife. A #11 is not long enough or of the right shape but a straight blade which is 1.5 to 2" long produces very sharp and clean cuts into the foam. Where the soldering gun/foam cutter is needed and comes into play is when one needs to cut horizontally in the plane of the wing. With servo wells it's not really needed. With LG blocks it is needed but it is also easy to remove the foam with pliers leaving a rough base and then sanding that base smooth with paper wrapped around the block itself.

I usually line the servo wells with balsa so that the HW servo rails have a tight and strong joint to hold the servo in place. Gluing in HW servo rails into foam is not great in my experience even if the cut is clean. Of course, with the LG blocks it's different as the joint between the block and the foam is sheeted and often glassed over top. Unless your wing is very thick, you can often open up the well to the top sheeting leaving a foam free cavity for your balsa lining work. When it comes to the tunnels in the wing for servo leads, soldering guns with loop tools are nice but one can also sand a groove into the top of the wing and then cap it with balsa before sheeting.

'nough said!

David.

kingaltair

My Feedback: (4)

So where do I get finishing, (laminating) resin, (Home Depot, Tower)? Sorry if this sounds like a simple question, but I haven't built that many planes, and I tend to do what "dear old Dad", or a couple modeling friends I've known have showed me back in the 60s, and I've stuck with that method.

Some of what I've learned has come from the "school of hard knocks", (or the "don't do that again" school...I taught myself photography basically the same way...one or two paperbacks, and a lot of bad pictures to learn from. Being a perfectionist helps. I try not to make the same mistake twice, and over time I get better.[8D]

I have never taken much of an interest in building threads on RCU up to this point, (unless I wanted to build that plane, which hasn't happened yet), but I can't help wondering if this isn't one of the most informative threads out there...largely because of the participation of all of you, and the time you take to detail out these techniques, (younger generation...take notice).

Duane

Sheeted the top of the King Altair right wing last evening with the plan to continue tonight. I used SIGMENT for the butt joints on the skins, and the L.E. I glued the skins to the ribs and spars with Titebond.

Duane

patternflyer76

Great idea. I used large ziplock baggies and filled them with fine play sand so that when I used them as weights they would conform to the shape of the wing or what every I need them to form to, plus it puts weight where I need it.

Kevin Clark

YellowBlueBird

Bird shot comes in 25 pound containers and is easer to deal with if the bag springs a leak. I use two zp lock baggies just in case.

edwarda10pilot

My Feedback: (3)

Bill:

Sorry, I did not see your question (post 426). Regarding glueing the sheets together, yes I was going to suggest taping the sheets together, then turn them over, apply glue to the joints. Once this is done, lay the shins on a flat surface (taped side down), wipe away any excess glue, place wax paper over the skins, place appropriate size piece of wood over the entire skin and then place weights (don't need a lot, perhaps 30 lbs evenly distributed) on them and let dry. When dry, the side that was taped becomes the side that I put on the outside. However, I use a "T" bar sander to sand both sides to try to ensre there are no ridges where the glue joints are. I ahve found that using an aliphatic resin works very well (Elmers glue or the "original" tite bond of Sig's white glue). The new Tite Bond II or 3 or some of the newer Elmers glue and gorilla glue are polyurethane and this as well as CA make a glue joint that is harder that the surrounding wood. If you use a CA or polyurethane for a glue then you will end up sanding the surrounding wood down and have a ridge where the glue joint is.

Duane:
There are a couple of sources for laminating resin. Z Poxy laminating resin is one but West Systems and System Three also make laminating resins. Personally, I have used System Three (www.systemthree.com) for about the last 10 years and about 25 builds. System Three (as does West System) have a full range of epoxies. I do not have any experience with West but I am sure they are just fine products. System Three have a structural epoxy called T-88 that I use for firewalls, landing gear plates and other high stress areas. They have a general epoxy that has a common resin and your choice of three different hardeners (each with a different cure time) and finally, they have a laminating resin called Clear Coat. the Clear Coat is mixed two parts resin to one part hardener. It has the consistency of Aero Gloss clear dope or very close. I use the clear coat to attach wing skins as well as to apply fiberglass cloth to the wing skins.

I agree with others that there are multiple approaches to grain orientation for wing skins. Long ago, I was taught that the grain for the skins should be parallel to the leading edge and to the trailing edge. What I do is to determine the rough widths required for the wing skins at the root and tip. I then run one sheet parallel to the leading edge and one parallel to the trailing edge. Once these are positioned, I then fill in the "triangular" shaped remainder with sheets to fill the balance of the skin. On my latest Black Magic VF 3 i glued a number of skins together (sufficient to make on top and bottom skin for a wing panel) and then cut it diagonally to make two skins for one wing panel. When I did this, I had the grain running parallel to the trailing edge of the wing and that left the graing running at an angle to the leading edge. I have to confess that I much prefer the grain running parallel to the leading and trailing edge. I have attached three photos. One photo is of my 2meter scratch built plane and if yo look at the wing you will notice the grain runs parallel to the trailing and leading edges (not the best photo but the only one I had that was close); one photo of my stab on the new Black Magic VF3 where the grain is parallel to the trailing edge but at an angle to the leading edge. The third photo is a better shot of this approach and is of the fuse on the Black MAgic (look at the vertical tail). I have found that if the grain runs parallel to the trailing and leading edges, it conforms to the radius of the foam much better and I get better results.

As for glueing wing skins to the foam cores, I again use the System Three clear coat (if you choose to use System Three clear cost DO NOT thin it). The amount I mix depends on the size of the wing panel. Most of my wings are about 450 sq. in. per panel (about 17' chord at root, 10" at tip and about 34" long). For skins for this size wing I mix about 30 -40 grams of glue. First thing I do is to apply two or three coats of balasrite to seal most of the wood and keep it from absorbing a lot of epoxy (this adds about 10 grams to a wing skin). I spread it evenly along the entire skin (always apply the epoxy to the balsa and never to the foam) using an inexpensive paint brush (the 1.5" wide units form Lowes for about $1 each works well) ensuring I get epoxy on all of the balsa. Once this is done I use an old credit card and gently squegee about 1/2 of the glue off. I then apply the skin to the foam core, set it in the shucks and then apply weights to the shucks. I went to Lowes and bought two pieces of 2 ft. x 4 ft. x 3/4" thick MDF. I put one piece of the MDF on the floor (need to find a very flat surface on the garage floor or some other place) On top of this piece of mDF I place the foam wing core with skins and the top and bottom shucks and then place the second piece of MDF on top of the wing. Once this is done I start to add weight continually checking to ensure that the foam wing core is still in alignment with the leading and trailing edge of the shucks as well as having the root and tip lined up with the end of the shucks. I use the "cinder blocks" from Lowes or Home Depot. If the wings are not honeycombed then I put about 250-300 lbs on the wings. This drives the shins into to contact with the foam. I once applied about 350-375 lbs of weight to a wing and when it came time to separate the shucks from the balsa skins, I had applied too much weight and managed to force some of the epoxy thru the grain of the balsa skins and glue the skins to the foam shucks, not good). If the wings are honeycombed, then you need to put less weight on the wings (perhaps 150 lbs). Honeycombed wings will crush with too much weight or if bagging too much vacuum.

I know this was a long winded reply and I hope I understodd the discussion about the direction of grain on sheeting wings and approach to skinning foam wings. If I misunderstood, I apologize.

Ed

doxilia

My Feedback: (3)

Duane,

I thought I answered this question in post #445.

David.

billberry189

My Feedback: (1)

Ed,

That's pretty much theway I do it too. I usually starton oneside ofthe sheet by cross taping the joint andgrain to get a tight fit and then flip it over and tape length wisedown the joint, flip it back over and remove the cross taping which gives me a piano hinge effect. After that ,it's just as you described.

Bill

kingaltair

My Feedback: (4)

So you did...I think I was hung up on the term "laminating resin" thinking it was somehow different. No disrespect intended..when it comes to new technologies, (to me), I'm not good at remembering details of posts. Before I'd actually buy something, I'd review the thread and the responses in more detail to refresh my memory, (which is sometimes porous).

somiss1

My Feedback: (5)

Guys, check the mags for foam cutters. Honeycombed wings are a extreme method for lighter weight, most folks don't use that method. As posted earlier, scraping most of the epoxy off, using a flat(true) surface and a ton of weight produce light wings. I use old model magazines to weight my wings. Vacuum bagging is the best way (from what I've read) to sheet wings. The weights press the sheeting tightly to the cores plus squeeze the excess epoxy out(if you didn't scrape the excess earlier).
I also never added a plywood joiner. Fiberglassing the center section is sufficent. I also scrape the excess off of the cloth.
8.25 lbs for the King Altair would make for a great flying airplane. My XLT weighed that amount and flew great! (A honking Rossi .60 on a pipe helped too!)
I have in mind to power my Simla with a DLE 20.
Frank

kingaltair

My Feedback: (4)

I fly the King Altair in SPA competition which has an engine restriction limit of .91 4-stroke or .61 2-stroke w/o tuned pipe. The "King" is a very large, graceful, (and beautiful IMO) plane...very easy to fly...I just like it, (see attachments for my former and current King, the current is the blue/yellow/white one, and that is the one I'm building the wing for. It is the prototype for Jeff's King Altair kit). The original wingspan is 80", (mine are modified to 70" and 74"). The love of this plane is why my RCU "handle" is Kingaltair.

Since I'm limited in engine selection, my main hope is to save weight. A couple of us are going to try to build the "ultimate" King Altair weight-wise this winter. It will be a (ugg [:'(] taildragger, as are most SPA planes to save weight), and we will try everything possible to lighten the plane to 7-1/2 lbs. As I said, it flies adequately at 8lbs 5oz, but we'd like to make it a bit more competitive to handle the verticals of EXPERT CLASS.

Duane

kingaltair

My Feedback: (4)

One additional note about the King Altair kit. Vic Husak was the designer of this plane back around 1965. It appeared in the April 1967 issue of Radio Control Modeler, (RCM). Because of its size, and rudder hinge line at an angle, a few mods to the fin and wingspan were made, (one wing rib on each side removed...original airfoil). I was corresponding with Vic Husak before and during the time the kit was being planned and engineered, and he was well aware of all the changes made. He looked at the same picture of my first scratch-built Altair posted above, and said he loved the color scheme, and approved of the mods for the situation of flying SPA. He sent me some photos of his King Altair models from back then, and I still have his correspondences.

Vic was going to buy one of the first kits to check Jeff's quality and wood, but passed away before the kit was ready. At least I got the chance to tell him how much I liked, (loved) the plane, and that there is still interest in it to this day. Everybody who has built a King, (that I know of), has raved about it.

Duane

doxilia

My Feedback: (3)

No disrespect read or offense taken Duane. I just wanted to make sure you had seen the post.

Laminating or Finishing resin are often used interchangeably. Basically it is thin epoxy designed to build up and cure slowly, be light and used for laminating materials together (foam/balsa) or for glassing models with FG cloth. It of course can also be used to produce FG parts when laying them up in molds such as a fuse or a cowl. When large amounts are needed (e.g., with a fuse), then one would typically move over to industrial volumes and brands such as those described by Ed above.

As a low cost starter and useful to have around in general, the Pacer Z-Poxy is good stuff. Try it, you'll like it.

David.

kingaltair

My Feedback: (4)

I will, thanks. One other thing. Typically I read these posts from work, and I usually stay late if necessary to make up for the time spent on the forum. After your last post, I actually took the time to click on the links...looks like just what I need for FG cloth and those future foam wings.

Thanks again.

Duane

kingaltair

My Feedback: (4)

While we're waiting for some progress on the Simla(s), I thought I'd post a few pictures from the shop showing the King Altair wing in progress. Notice in the background the #1 prototype Simla standing up next the Altair #2, which is hanging there waiting for a few pieces of Monokote trim to finish. It is way too heavy for SPA, built with Tower balsa before I became weight-conscious, (don't buy your balsa there).

Ed Kazmirski's original Taurus II wing, (semisymmetrical) at only 1.1lbs as you see it, (note the original FAI sticker...it was Ed's back-up in Belgium..this was Ed's super thick wing), with the present Taurus II wing below.

I never made any claims to be as neat as Kevin.

Duane

somiss1

My Feedback: (5)

Neat workshop? How do you do that????? I hate clutter but it always finds me!
Duane, that Sigment is the best for gluing wing sheeting. I wished it was carried by more hobby shops. I grew up using Ambroid. Testor's cement was also good for gluing sheeting. Your wing looks very good!
7.25 lbs for a King Altair? That would fly sweet. Please let us follow your build.
Frank

rg1911

My Feedback: (1)

Does anyone remember where the dihedral location braces are or were? I can't seem to find 4 of anything that might be them. I don't think I've thrown anything away. I've even kept all the scrap pieces.

If you have not yet installed them, perhaps someone could send me the measurements? I'm assuming there's a right-angle and that the top of the piece is a bit shorter than the bottom of the piece. If so, the height and the lengths of the two sides would put me back in business.

I realize they may not be critical since, as Bill mentioned a few pages ago, the dihedral is pretty much set by the wing tube.

Thank you,
Richard

MTK

There are many sources of laminating epoxy. The www lists most, but the problem is you have to know what to get

I've personal experience with ACP, CST Sales, Aircraft Spruce, John Greer (aeromarine epoxy). There are many others. Quantities are typically quarts.

The very best epoxy (also one of the most expensive) is Pro Set, by Gougeon Bros. I use their 70 minute pot life hardener for heavy duty stuff like landing gear and prop molding. Skin lamination is usually the lightest with this epoxy.....it's the thinnest I've found
West Systems also by Gougeon Bros is also excellent but the slowest hardener gives only about 40 minute pot life. 40 minutes will be enough time but you'll have to do things quickly
EZ Lam from ACP is very good product that gives adequate pot life for laminating skins to foam.
Aircraft Spruce has several epoxies inclusing West Systems.
Aeromarine epoxy from John Greer is a pretty good product, inexpensive, pot life around 50 minutes with terrific shelf life capability (hardener is not amine based). Very good as a skin laminating epoxy, except it takes a little longer to get full cure. With any of these epoxies, the wing panels should be left alone to cure 24 hours.

The key things to know about skinning foam, a good vacuuming of all surfaces before assembly will help the finished product stay laminated. One could use the foam husks and either weights, or a simple press to assemble panels. Two pieces of MDF coupled with long bolts around the perimeter. 6 bolts are plenty.

About 15 years ago, I used vacuum for the first time and it is by far the simplest and best method for applying even pressure over every square mm of skin. Best over solid foam, no honeycombing here. The epoxy sources above also have vacuum apparatus available. ACP's 30" wide bag and their sealing strips are very simple and effective way to a sealed bag. I do both panels at the same time in the same bag. Paper towels are the simplest and cheapest breather material. Anyone interested in this approach, contact me direct

kingaltair

My Feedback: (4)

The dihedral is set by the wing tube, but the braces, (or spacers which for some reason, ??? I never glued in place...just used them as spacers), help to set W-1 at the correct angle. We discussed an alternate method earlier in the thread where W-1 is kept loose (when the rest of the ribs are glued in), and is only fixed in place when the wing is mounted to the fuselage. It can be set flat against the fuselage side, then glued in place to assure there is no space between the wing and the fuelage.

Duane

rg1911

My Feedback: (1)

Duane,

That's exactly how I'm doing it. I was more interested in the braces as one more level of alignment and bracing.

Cheers,
Richard

kingaltair

My Feedback: (4)

Regarding post #459, and my reson for building a new wing for my King Altair prototype, (blue/yellow/white). The King Altair foam wing I originally bought with my first RTF "King" weighs in at whopping 2lbs 12.2oz complete. I also have a full-size 80", built up wing made out of the the very heavy Tower balsa with little thought given to weight savings at the time...that weighs almost exactly the same thing.....ALMOST THREE POUNDS just for the wing!![X(] I'm hoping I will be able to shave at least 8oz off the plane's wieght by being careful while building this wing, and by using contest balsa.

It is very early in the process, but right now, the basic structure of the "light" right wing half with the top sheeting and part of the bottom sheeting installed, (remember using the lighter pieces for the right wing), weighs 6.1oz...a good start.

Duane

doxilia

My Feedback: (3)

Duane,

I suppose those wing weights are a tad on the heavy side. I'm working on a 65" wing (so probably more than 80% of the mass of your 80" KA wing) and it came to 24 oz ready to finish. I added another 3 oz in the finish (monokote and trim basecoat/clearcoat paint) for a 27 oz wing. I'm using very heavy electric Multicon retracts with Kraft wheels which come to 11 oz assembled for the pair. Add another couple of oz for servos and that comes to an even 2.5 lbs or 40 oz. I suspect some striping tape and linkages will add another couple tops. The original designers retract built single servo wing came to 3 lbs with a 5.5 lb ready to fly fuse for a total model weight of 8.5 lbs.

Given you're not using retracts you should be able to save 9 oz easily on the LG for a 1.5 oz strut and wheel assembly per side. I'd imagine a good weight for a fixed gear dual servo KA wing would be in the sub 36 oz (2 lb 4 oz) weight range finished with a 2 lb max framed up unfinished wing with gear. The finish (paint or covering) will dictate the balance of weight.

Just some thoughts.

David.

kingaltair

My Feedback: (4)

Well we'll see...in the meantime I can at least "dream big". IF I could save 8oz I would be thrilled, (BTW...I suppose I could almost accomplish the same thing by filling the tank 1/2 full, which is about the length of flight I would have in a typical contest round).

Each practice flight is a full tank because I will run through the maneuvers, then spend the next 6 to 7 minutes working on "problem" maneuvers. For a contest...wouldn't it be great to do some of BOTH, by filling the tank 2/3 full (for "insurance"), AND carrying NO excess weight?

BTW...Some of you might be interested in following the Senior Pattern Association, (SPA) newsletter; it can be accessed online at www.seniorpattern.com , then going under the "DOWNLOAD" section under "newsletters". I am the SPA newsletter editor, and a new bi-monthly edition just came out over the weekend. There is an interesting picture of a guy, (John Nessler) with a big smile on his face carrying my King Altair at the Chattanooga, Tn contest. The caption is "why is this man smiling"? I think many of you would find the NL interesting whether or not you actually fly the earlier pattern planes or not. All pattern planes are similar in one way...they are all designed to fly neutrally and smoothly....these just don't have the retracts or pipe. Anyway, feel free to check it out...it might help some of you understand SPA better. [8D]

Duane

rg1911

My Feedback: (1)

Well, bother!

After all my fuss about screwing up the fuse, I got replacement parts and clarified a few directions with Jeff, and discovered I had done it right the first time.

Since there's a couple small things I'd do better, I'll go ahead and complete the new set.

Cheers,
Richard

kingaltair

My Feedback: (4)

billberry....how is it going with you? Haven't heard from you for several days. I hope it isn't already done and you're out at the field flying it.

Please report....we need an update.

Richard...I wonder how you did the fuselage right, but something was contrary to plan enough that you thought you did it wrong? Is the first fuselage finish-able?

In the meantime, I'm adding details to the King Altair wing halves, but I really don't feel in the mood to spend a lot of time down there working on it after working all day....I need to "push myself" a little or it will be too cold here to test the difference.

The 2X2X12 balsa blocks from National are much lighter than those supplied in the kit, and make nearly weightless "filler scrap" material to use near the front dowels and mounting bolts. That material weighed only 2grams after shaping to size.
Duane

billberry189

My Feedback: (1)

Duane et al,

Thanks for the interest . As things would have it, after I spent a day at a local swap meet and sold a couple of my airframes( a Sterling Fokker D-VII and a modified Taurus) I have been busy with several of the guys I met at the meet. That was Saturday Sept. 10. I have been side tracked since then . The gentleman who bought the Fokker lives in the Tampa, Fl. area andneeded me to send him the plans so he could set up the CG and finish trimming it out. The genlelman who bought the Taurus lives locally andI have been in contact with him several times sincethe swap meet trying to determine the best CG location since it was a swept wing long tailed version.We ultimately determined 63/4 to 7 inchesfrom the root leading edge. After moving the servo/receiver tray and battery around he established a 7" CG. Then he took itto his local field for a maiden flight. Keeping in mind that I began this model in 1975 and finished it in 2010 (How's that for a start to finish time?).I was very pleased when Clint called me Monday to thank me for presenting him with such a great model. He was hesitant to make the maiden so he had a club pattern hot shoe do it for him. It scored an A+ for flight and fit and finish. Needless to say, I was very proud. Add to all this the P-40 I picked up at the swap meet, which I finished up yesterday, and you can see that I have been fairly busy for the last 10-11 days. I know I stated earlier that the Simla was my first priority, but while I was waiting for payday to get here, I decided to see what I could getdone on the P-40 ARF. The P-40 is done except for a pilot figure and a ignition kill switch, so today I will be back on the Simla and I still have a week before payday.

Bill

PS- One of the advantages of selling two airframes is I now have radios and servos for the Simla and Taurus, as well as an engine for the Taurus. So I made some money and saved some money at the same time. Also,I finally made contact with members of several of the local clubs and received invitations to come out and get reintroduced to the joys of flying R/C.

Bye now