As promised, here is the next installment on the foam wing processes that I use. I left off in my last thread with the molded leading edge caps accurately attached to the foam core. The next step is to trim and edge sand the sheeting that will be joined up into skins and eventually grafted to the rear edge of the balsa L.E. caps. So… here we go.

Balsa edge trimming and sanding:

The balsa sheets that you have chosen for your skins need to have both edges trued perfectly. I start this procedure by trimming the edges with a straightedge and a sharp #11 blade knife (See Photo #1).




Most balsa stock is cut from raw blocks that have not had their edges trued, and so it is not uncommon to have to trim off as much as 1/8 inch on either side to make the edges of each sheet straight and true.
After the trimming process is complete I edge sand each balsa sheet using a 24 inch long Permagrit sanding bar that is laid on its side. The Permagrit sanding bars are made from extruded aluminum and the sides are perfectly perpendicular to the sanding surfaces. There are two different grits on each Permagrit sanding bar. For this operation I use the side that has the finer grit of the two. I position the Permagrit sanding bar at the edge of a piece of 5/8 to ¾-inch thick particle board and then lay a balsa sheet in against it. I use a Great Planes extruded aluminum sanding bar fitted with #80 grit sandpaper as a gripping tool, and that allows me to slide the balsa sheet fore and aft against the Permagrit sanding bar and true the edge (See photos 2 and 3).






Skin layout:

Once all the balsa sheets have been trimmed and sanded, it is time to layout the skins. I like to lay the sheeting out to size right on the core surface to which it will eventually be attached. I lay one piece of trimmed and sanded balsa up against the rear edge of the installed balsa L.E. cap piece and tape it in two or three places to hold it secure (See photo #4).



Next I trim the ends about a ¼ inch past each end of the foam core (See photo #5).



Lay the next piece of balsa skin stock against the first and tape as before to hold it in place, and again trim each end ¼ inch past the end of the core (See photo 6).



Lay in the third piece of balsa against the back edge of the second sheet and again repeat the end trimming process. Note that there may be a small triangular shaped section of core that is not yet covered with balsa (See photo 7).



Now turn the core over, being careful to not let the taped up balsa skin “flop,” and trim the rear edge of the rear-most piece of balsa so that there is 1/8 to 3/16-inch of balsa sticking out past the trailing edge (See photo #8).



Place the core top side up in its cradle and tape a section of the piece that you just trimmed off of the trailing edge onto the rear of the third piece of balsa. Turn the assembly over once more and trim this piece to achieve complete but unglued skin (See photos #9, 10 & 11).







Tape up and trim all of the remaining skins for the two core halves in the same manner.

Skin joining:

Now it’s time to join the balsa sheets into a skin that is ready to be attached to the core. Remove the pieces of tape that is holding the unglued skin to the L.E. Cap piece (See photo 12).



For the joining process you will need the following: The taped together skins, a masking tape dispenser, some building weights, a 2-ounce bottle of medium cure CA glue, some waxed paper and a flat and clean building board (Se photo 13).



The building weights that I use are scrap pieces of cold rolled steel that I made up while working in my father’s machine shop many years ago. Many have commented on them and have asked how to find such weights. You can try looking in the phone book for a local machine shop and ask them if they would make up a set of similar weights in various sizes. Failing that, try purchasing some small concrete bricks from a home improvement store; they will work just as well for this application. If you do opt for the concrete bricks, try cleaning one side thoroughly and then glue some #80 grit sandpaper to it. The sandpaper is clean and it will grip the balsa better!

Remove the tape from one skin assembly and lay the pieces onto a piece of waxed paper in their proper orientation. (See photo #14).



Now position weights back about 3/32-inch from the edge of the second balsa skin piece (See photo #15).



Next run a bead of the medium cure CA glue along the front edge of the second balsa skin piece, being careful to not let any glue get on the upper surface of the balsa (See photo #16).



I find that a piece of Teflon tubing fit into the end of the CA glue bottle makes this an easy task. Next lay the first piece of balsa in against the second piece, edge to edge, and then rotate the weights across the seam between the two pieces being glued. Quickly stretch several pieces of masking tape across the joint to pull the two pieces tightly together (See photo #17).



Now repeat this procedure to glue the remaining pieces of balsa together (See photos 18, 19 & 20).







Let the CA glue cure thoroughly (usually about 5 minutes) and then remove the weights and peal the completed skin from atop the waxed paper (See photo #21).



Foam wing sheeting:

I recommend that you sand the outer surface of each glued skin assembly to remove any slight high or low spots at the seams (See photo #22).



I prefer to use an aluminum sanding block, fitted with #220 (or finer) grit sandpaper, for this operation. If you did the gluing properly, there will not be any excess glue on the outer surface of the skins, and only a few swipes with the block will be required. Don’t remove too much material, as you will be doing a finish sanding after the skins are glued onto the core.

Before gluing the skins to the wing core it is suggested that you seal the skin’s surface that will actually contact the core. I recommend sealing the wood grain with a thin application of an inexpensive, unscented hair spray (such as Suave or Aqua Net brands) (See photo #23).



Hair spray is actually a type of lacquer and it is much lighter than the epoxy with which we will eventually attach the skins to the core. The hair spray will soak into the grain and when it dries it will form a barrier that will prevent the epoxy finishing resin from soaking too deeply into the wood. Don’t worry; there will still be plenty of grain for the epoxy to grab into to insure a permanent bond between the balsa skins and the foam core!

Hold the can of hair spray about 8 to 10 inches from the inner surface of the balsa skin and apply a light to moderate coat (See photo #24).



Let the hair spray dry for at least 20 minutes before proceeding.
For the next step you will need the following items: A box of fresh Z-Poxy Finishing Resin, some old newspaper, a mixing cup, a mixing stick (a Popsicle stick is good) and an epoxy spreader that is made from a piece of 1/32 inch thick birch plywood (See photo #25).



This spreader should be about 3 inches long and all the edges should be rounded with sandpaper to prevent it from digging in during use and marring the balsa skin. Use a three-corner needle file to make several small grooves in the edge of the spreader tool. These grooves should be spaced about ¼ to 5/16-inch apart and be no deeper than 1/64-inch. If you make the grooves too deep, too much epoxy will be left on the skin after the spreading process.
You will need to mix up enough finishing resin to ensure that you can cover two skins with a bit to spare. It’s better to mix up a bit too much than to mix up too little! Only experimentation will tell you how much to mix in the future. Place a lower balsa skin for one of the core halves, inner face up, onto a piece of newspaper and then pour a moderate stream of resin lengthwise down the center of the skin (See photo #26).



Use the plywood spreader tool to move the epoxy resin around and try to get all of the skin coated (See photo #27).



After the resin is evenly spread around the skin, place the spreader at the trailing edge at the tip end of the skin and pull it forward until it runs off the leading edge of the skin. Repeat this process and move down the skin towards the root end. Tiny “rivulets” of resin will be left on the skin (See photos #28 & 29).





Note: Once the skin is fully prepared with the resin as described above, use an acid brush to apply a small amount of resin to the forward edge of the skin where it will butt up against the molded balsa L.E. Cap piece (See photo #30).



For extra strength, use the acid brush to apply a very light coat of resin to the spar area and also along the length of the balsa trailing edge piece (if you have chosen to install one…). See photo #31.



Carefully place the resin coated lower balsa skin onto the corresponding core section, (See photo # 32)



which should be setting on an absolutely flat table in its upper cradle half (I like a piece of ¾ inch thick ground granite for this). Once in place, stretch a few pieces of masking tape across the seam between the skin and the LE. Cap (See photo #33).



The idea here is to draw the seam as tight as possible. Now place the lower cradle half onto the flat table and repeat the gluing process on the inside face of the corresponding top balsa skin piece.
Place the top cradle piece in place atop the core and carefully align the sandwich of lower cradle, core with skins attached and upper cradle. Place a flat board atop this sandwich and weight it down with 150 to 200 pounds of weight (See photo #34).



Double check everything for accuracy once the weight is in place.
Cut the nose off of several spring-type clothes pins. The nose should be flat when you are done. This will allow the pins to be used as clamps. You will also need several Popsicle sticks (See photo #35).



Place a Popsicle stick on top of the trailing edge piece that will be sticking out in the back of the weighted sandwich. Hold another Popsicle stick below the trailing edge and in line with the upper Popsicle stick. Clamp these tightly against the skin that is on the trailing edge piece (See photo #36).



Now repeat this process all along the trailing edge (See photo #37).



This process will insure that the top and bottom skins are tightly glued to the trailing edge piece along its entire length.
Let the sandwich of parts cure overnight! See photo #38.



Repeat this entire process to glue the skins to the other core half.
In the next installment we’ll discuss in detail how to trim and sand the ends of the skins to match the core, and how to final sand the wing halves.

Hope this has been useful. I’d like to thank Bob Kruger who took the time to help me post this long piece to the forum. Without his assistance I’d never have gotten it online!

Yours for better modeling

Bob Hunt

Awesome post, Bob. I love all the detail photos, and always learn something from your material. Thanks!



"Those who do not want to imitate anything produce nothing." -Salvador Dali

Thanks, Larry!

It is fun to be able to have enough time to do this now. I've wanted to post a few How-To things for quite a while, but there never seems to be enough time!

To be honest here, I took all of these photos (and a bunch more...) to be used in my new Robin's View Productions Foam Wing Core Sheeting Manual that will be included in CD format with each foam core that we will sell from now on (Actually it will be about a month before the entire manual is completed...). I just thought this would make a logical second piece to follow up on the molded LE Cap piece I recently posted.

I'll try to to post one of these on various subjects every couple of weeks if possible.

Later - Bob Hunt

Bob Hunt

Thank you, very much, Bob. This is an excellent *How To*. I appreciate all the help you give us!

Big Bear <><
Character: It's what you do when no one else is watching.

Thanks, Bill!

I look at it as "paying forward."

Bob Hunt

Bob Hunt

Thanks Bob this is great, you did a wonderful job.

Ed Migon
New Orleans Ringmasters
AMA 4635

Bob,

While I've only been involved with control line for a short period of time I've been building planes for well over 35 years. Thus, many of the topics you are presenting are not new to me ... BUT .... I still find it amazing at just how many new things I learn from you posts even on a topic that I THOUGHT I knew. You and Mr Kruger have done a wonderful job and thank you very much for taking the time to share. This is publication quality work.

Very Appreciated
John

"Often Wrong" .... wife

>new to me ... BUT .... I still find it amazing at just how
>many new things I learn from you posts even on a topic that I
>THOUGHT I knew. You and Mr Kruger have done a wonderful job
>and thank you very much for taking the time to share. This is
>publication quality work.

John;

While Bob Hunt is generous with his credit, this is his work. My effort consisted of some file upload, placement and establishing hyperlinks. My work was the equivalant of a lab tech cleaning the petri dishes for Dr. Jonas Salk....

I first saw a Bob Hunt foam wing in 1972 at the old Bristol, Conn. meet (when we were both just a little younger...). The level of workmanship was first rate, even to a kid like me, but until now I never actually saw how he did it.

I look forward to seeing more of Bob's articles on line.

V/r

Bob Kruger

Thats a totally awesome article!

I've done loads of wings with the partial sheeting ala some of Tom Dixon's articles, but I need to master fully sheeted foam, and this sort of information is a huge help.


Steve

This is a wonderful tutorial, Bob. What a generous way to spend your "retirement". I hope that you enjoyed doing them as much as I enjoyed reading your posts.

I have never built a foam wing. I always thought it was some sort of black art that I could never handle. It will probably be a while before I do try a foam wing, but after reading your posts on the subject I will certainly view it as a viable option for me. Thank you.

I do have a question, however. The technique you show in your posts for joining the pieces of the wing sheeting is different from that which you demonstrate in your Lost-Foam DVDs for joining the pieces that make up the molded leading edge for a built-up wing. In those DVDs you butt the pieces on a flat surface, put the CA on top of the seam, and rub the CA into the joint using two fingers well wrapped with masking tape. Are these alternate techniques that could be used for either purpose or are they specific to the different tasks?

I can't wait for whatever it is you might have in mind for your next contribution.

Peter Hess
Canton, CT

Hi Peter:

I use both methods for joining the skins, and both of them work fine. The one described and shown in the photos on the Sheeting How-To I just posted allows the use of the medium grade CA, which I believe has a bit more strength when used for this purpose. The thin CA method described in the DVD set is also a bit messy, and requires that you wrap your fingers with tape before gluing the skins into one piece. I suggest trying both methods and then choose the one that works best for you.

There is a third method that is more traditional in nature, but still produces excellent results, albeit reults that require a drying time. That method is as follows: Trim and sand the balsa sheets as in the How-To. Layout the sheets right on the core as in the How-To. After the skins are taped together, lay the skin on a flat board and remove the tape that is stretched across the seam and holding the pieces together - again, no difference so far from the How-To. Next hold two pieces together tightly and run a strip of masking tape down the length of the seam. Join all the pieces with the lengthwise strips of tape. Now fold the balsa apart at the seam, just like a hinge. Run a bead of Ambroid or Sigment down the resulting groove between the balsa sheets and then set the sheets down flat on the bench. The excess glue will be forced from the joint, and be on the side of the skin that will eventually be glued down to the foam core. Scrape the excess glue from the bottom of the sheets and then draw pieces of masking tape across the seam to hold it together tightly until the glue dries. Works great, but in this age of CA, why bother?

You know, this is fun! Thanks for the kudos...

Later - Bob Hunt

I do believe Bob wrote the book on how to give step by step, clear and concise "how to" information on nearly any aspect of our hobby.
Lots of good info out there....but none so well layed out as yours.

It is such an honor to include you as one of my mentors, competitors and friends. Telling you to keep up the good work seems silly...you dont know how to do anything half hearted. Your passion inspires all in our SIG as well as several others I am sure.

I have been reading your stuff, and following your ideals since before I could vote ...over 30 years now! I could never have enjoyed this hobby so much nor had the successe I have enjoyed over the years without you.

John Sunderland

Wow, John, I'm blushing... and believe me, that ain't a pretty sight.

Seriously, thanks from the heart. You and I have always seen eye to eye on much of this stunt adventure. We are both passionate builders and have much the same outlook on the event's history and how its many heros have positively affected our lives.

My only hope at this stage is to pass on as much as possible of what I've learned from others, and on my own, to and for the next generation. I received so much help from so many, and they never expected anything in return. I think the best way to honor them is to, again, "Pay it Forward" to the next generation. That seems more important now than ever before as many have stopped building, or those who are new to the sport don't see the need to learn to build. You and I both know that more than half the fun of this endeavour is the creativity that the designing and building process provides/allows. I don't believe in compelling people in this sport to build by rules making, rather I'd like to help make it so attractive that they will want to build just for the fun and satisfaction it provides.

I refuse to let this aspect of the sport go away without a fight.

Bob Hunt

Hello Mr Hunt, I'm an isolated guy in the far north of Alberta Canada. I never get to commiserate with flying buddies because there aren't any here I just wanted to say that your tutorial is very inspiring and comes at a very fortuitouse period. I will be starting to finish the wing on my Sig P-51 in less than a month. I will have to do exactly what you show and I was a little afraid of it, because I have never used a foam wing before. Your tutorial has taken all the fear away. Reading your tutorial was like being in your shop, watching over your shoulder. If only you could have handed me a coffe as all good hosts do Thank you very very much.

“I have never crashed, but I have proven the theory that gravity sucks!”
Glenn Reach
Westlock, Alberta. Canada
gtreach @ hotmail . com

Hi Glenn:

I'd bring a cup of coffee up to you, but I'm afraid it would get cold enroute... If you are ever in the neighborhood of Stockertown I'll brew you up a fresh pot and then we can build awhile.

If you have any specific questions in the midst of sheeting the Mustang wing, please feel free to give me a call. My number is 610-746-0106 and I'm usually in the shop from 7:00 AM to at least 10:00 or 11:00 PM. I'll be glad to help and each of us can drink our own coffee while we chat!

Bob Hunt

Glenn,

You may want to consider some of Bob's videos, especially the "Stunt Flyer Video Magazine" series. LOTS of information.

Bob also interviews many of the flyers you have "heard about" over the years as well as current flyers in his Vintage Stunt Championship videos.

And of course, he has videos available for specific tasks presented by the experts.

I dig one out every once in awhile and watch it. Mine are in VHS format but now they are available as DVDs...what a space saver.

If this piques your interest, contact Bob for what is available now.

George

>next generation. That seems more important now than ever
>before as many have stopped building, or those who are new to
>the sport don't see the need to learn to build. You are I both
>know that more than half the fun of this endeavour is the
>creativity that the designing and building process
>provides/allows. I don't believe in compelling people in this
>sport to build by rules making, rather I'd like to help make
>it so attractive that they will want to build just for the fun
>and satisfaction it provides.
>
>I refuse to let this aspect of the sport go away without a
>fight.

Bob,

Please include me in the ranks to support your philosophy on the satisfactioy of building what you fly. Thanks for putting into words what I have a hard time expressing.

Terrific posts by the way. But of course that is expected from you...your posts and videos have been an inspiration and modeling education to me for years. "When Bob speaks, I listen".

Cheers.

Warren Wagner

Hi Warren:

I think that there are many who feel the way we do about building. Those who have come into this sport via ARFs may eventually feel that way too. I think it's great that new fliers can have a positive flying experience right away, but I'm hoping that most of them delve deeper into the sport and discover the joy and educative process that building affords.

Us old timers had to learn to build. That was the only avenue to flying in the old days (You know way back in the 1950s, '60s, '70s, '80s and '90s...). If we broke something we couldn't just send away for another part. We had to learn to repair so we could continue flying. Today's "instant modeler" has that part easier. The fact that he or she can pick up a phone, call a distributor, reel off a few CC numbers and then wait only a couple of days for a new, finished component simply means that it is less painful to learn the difficult aspects of flying.

Let's all remember that anything that gets new blood into the sport is a GOOD THING! We can subvert them and make builders out of them in short order if we but make the information on how to build available and then make ourselves available to fill in the voids. "Each One Teach One" really works, but it means that each of us has to teach someone else. We can't wait for the next person to do it. It is a program that we can start on our own and not have to wait for a club or organization to do it.

Uh oh, I'm off on a rant again... The next post from me will be a step-by-step How-To on building a soap box...

Later - Bob

Bob Hunt

Bob and the rest of the gang,

Just as an aside....the man who is generally credited with development of the hot wire technique of cutting foam cores for models, was an engineer working for General Electric company in Syracuse, New York. He published his technique for cutting foam wings in an early issue of Model Airplane News (sorry, I don't have the issue ID handy).

Hi name was Ed Izzo.

Ed was a fellow member of the Aero Radio Club of Syracuse (ARCS) and also, at one time, Ed was my boss at GE.

Ed campaigned in controline speed for many years before settling on RC pattern competition, where he was a nationally know competitor. He flew his own design which was called a "Skyhawk". Ed was a very innovative fellow, hence his engineering career and his exceptional creativity in modeling. Ed passed away several years ago after retiring here to Florida.

He was quite a guy, and I thank him every time I build a foam wing.

Cheers,

Warren Wagner

Hi Warren:

The article you are referring to was published in the June 1964 issue of Model Airplane News and it was co-authored by Ed Izzo and Ray Olson. Technically they were not the first to cut foam with a hot wire, but they were among the first to use the technique to cut model airplane wings using it. Certainly they pioneered many of the procedures that are still used to this day.

I wore out that issue of MAN reading that article and in 1968 I started cutting foam wings myself. Much of the first equipment I used was gleaned directly from Ed and Ray's article.

Around 1976 I was conducting a foam wing demonstration in upstate New York. I was showing how to do precision internal coring, spar inletting, landing gear rib installation and many other things that I'd developed after having learned basic lessons of foam wing cutting from that article. In the corner of the room a man stood smiling throughout the entire demonstration. He never said a word or asked a question, but I just knew from his look that he was right on top of what I was saying as he kept nodding his head in approval. I thought he looked familiar, but I just could not place him. After the demo he came up and told me how much he had enjoyed the presentation and that he'd learned a few new things from it. He told me that he'd cut some foam as well. I asked him his name and almost fell over backwards in amazement when he introduced himself. It was Ed Izzo. Well, I just fairly gushed with hero worship for the man who was at least half responsible for getting me interested enough in cutting foam to give it a try. We chatted for almost an hour and exchanged many ideas and laughed over foam cutting mistakes that we'd both made in common. He was a truly gifted and gracious man. We hit it off instantly as friends, and I was devastated when his wife sent me a card with the news of his passing. A loss of heroic proportions. He was a pioneer and a craftsman, but above all a great and gentle man.

I think I'll go read that article again...

Bob Hunt

Bob Hunt

>
>I have never built a foam wing. I always thought it was some
>sort of black art that I could never handle. It will probably
>be a while before I do try a foam wing, but after reading your
>posts on the subject I will certainly view it as a viable
>option for me. Thank you.

Peter,

Don't be scared off by the thought of building a foam core wing....it's not that it's difficult...it's just different. One you have built a few foam wings you may never want to go back to a built up one.

Probably the best way to get started on learning to build foam wings, is to build a "Kept-Foam" technique that was popularized by Tom Dixon. Instead of a fully sheeting wings, this system uses a leading edge sheeting, and trailing edge sheeting, and cap strips in between. When covered, the cap strips make it look like a built up wing.

The "Kept-Foam" system builds very fast and is really fun to do. Aside from joining the two wing halves, I can build an entire wing in one day. Once you start, you never have to stop. Tom has a write up on his web page.

Just do it.

Cheers.

Warren Wagner

Thanks, Warren, for your encouragement and reference to Tom Dixon's "kept foam" technique. I have, actually, read the how-to on his website and found it very interesting. With a molded leading edge - - which I am about to try for the first time using a beautiful buck acquired from Bob Hunt - - I am sure it would make a great wing. I guess I really will have to give a foamer a try once my current built-up wing projects are finished. Unfortunately, given the way I build, that is likely to be some time.

Peter Hess
Canton, CT

I have another question, Bob. You suggest using between 150 and 200 pounds to weight down the core and shuck sandwich. The wing you are using for the demonstration is cored only in front of the "spar". If the wing were cored behind the "spar" as well would the sandwich be sufficiently strong to hold the weight without deforming or crushing? Using 200 pounds on a 600 square inch wing is only 5.3 ounces per square inch, but that still sounds like an awful lot of weight. If that's what is required, I guess I better get myself to the gym. Thanks.

Peter Hess
Canton, CT

Hi Peter:

The reason the front section on the wing used in the How-To is cored is because the landing gear system is in that bay. There would be no way to core it out after the plywood landing gear ribs, or "clips" as they are commonly known, are installed. I prefer to leave the wing halves un-cored out until after the sheeting has been applied because it prevents the possibility of any flat spotting of the airfoil. I have covered fully cored wings with great success, and yes, I did use a bit less weight on the "sandwich."

As you indicated, the actual amount of weight per square inch is not a lot, and it should not be anywhere near enough to crush the wing.

Bob Hunt

Bob,

Any suggestions on the brand of hair spray?

oops

Just saw the suggestion. I was thinking that there is an old can of Aqua Net below the sink in the bathroom (it having, I assume, gone out of style or whatever). I wondered if this could be used (if it still has propellant).

Hi Randy:

I use whatever is on sale! The Suave in the photos was on closeout at $2.00 a can. I bought a bunch of them! I can coat several wing's worth of skins with one can. I don't apply too much; just enough to slightly wet the skin. When it dries it leaves plenty of grain for the resin to grip to.

I stay away from the scented variety because I don't want my planes to have an aroma about them that will make me the target for more abuse from my "friends." They are brutal enough as it is since I switched to electric power. The ribbing and taunting (Good natured of course) is amazing. Just imagine how bad it would be if my model smelled like a... well you get the idea. I can't understand why they do this. After all, I never bust anyone else's chops about such things... (Yeah, right)

By the way, the trim sheme on your new ship looks great!

Later - Bob

Thanks, Bob. It will be a spectacular "5 foot finish".

I learned a new rule: never finish a plane when the humidity is consistently above 75%. It's just not a bright idea. Who knew high humidity would cause adhesion problems? Don't be shy, raise your hands. Sheesh!

See you at VSC!

Wow Bob (Bubba)

I used to think I was pretty good at technical writing, but I just sat at the Masters feet when I read your last two posts.

Your thoughts on teaching to build were also eye opening to me.

Well done my friend.

I'm wondering why everything is spinning around?

John Miller

I learned how to prepare sheeting from a Bob Hunt Video years ago. It was like a giant light bulb went on over my head.

One of the most important steps is sanding the sheeting in a flat surface prior to installation. This goes for foamers or Molded LE that have more than one piece. This cuts finish time by about 50%. Plus the surface you start fininshing on is free of seems and flat, you just final prep and cover and or fill as normal. That one step has certainly changed the finish on my wings from pretty good to excellent on the sheeted areas.

Thanks Bob.

Doug Moon

I totally agree with Doug on this, and perhaps in the How-To above I didn't really take the time and space to properly emphasize just how important pre-sand the skins. Like Doug, for years I first attached the skins and then sanded them. Same holds true for the molded L.E. Shells for built-up wings; I would mold them first and then sand them on the mold buck.

Sanding them while they are still flat enables you to get 99 percent of the imperfections out in a short amount of time. After the skins are attached, there is still a little sanding required, especially where the skin is glued to the L.E. Cap piece. This sanding is reduced from 15 to 20 minutes of hard work to just a couple of minutes of detail work if you pre-sand the skins!

Just one more thought on this: I don't pre-sand the L.E. Cap piece on its mold buck prior to attaching it to the leading edge (Although I do pre-sand the piece of wood from which it will be made, prior to molding). I want some material left there for sanding it into the skin. I do, however detail sand the leading edge sheets for built-up wings on the buck prior to installation. In fact, once the shells are installed on a built-up (Typically Lost-Foam) wing they are hardly even touched with sandpaper, except to blend in the front edge of the capstrips.

The sanding operations and sequencing of those operations is really the secret to a perfect wing. Thanks, Doug, for pointing this out!

Bob Hunt

Just a note here about glue:

I just received a sample package of the new Mercury CA adhesives and I'm extremely impressed. Not only does this stuff appear to be incredibly fresh and "active," but it also has a unique new spout that virtually eliminates clogging. They also have a set of Teflon applicator tips that snap onto the snout of the bottle and make it easy to pin-point glue with this stuff. I'd recommend trying it for the sheet joining procedure outlined above. I'd use the medium for this operation and I'd also use the Teflon applicator tip.

The new line of Mercury CA adhesives is very extensive, and I'd suggest visiting their website for more information on all the products they are now offering. Take a look at: www.mercuryadhesives.com

They sent along a brand new formula of there CA glue that is not yet on the market and asked me to test it a bit and give them some feedback. I'm not at liberty to divulge just what makes this particular formulation so attractive for our use, but I can say that I think you will all like it very much.

I'll write more on this when I am allowed.

Later - Bob