jeff4912

That is a picture of the leading edge of my Sig 4 Star 60. I can't wrap my mind around how to cover over the dowels on the leading edge of the wing, and still keep the piece of covering symmetrical when it wraps around the leading and under to the bottom of the wing.

I'm sure there must be a simplistic work around, but I am not that creative.

Top of wing will be yellow and wrap under the leading edge about 2" and then underside will be blue.

Planning on using ultracote.

skylark-flier

Don't know if this will help but, my normal method of getting covering around dowels, etc is to do a 1-2" square of covering with a hole in the middle. Once the dowel is surrounded by that square the rest is usually easy to work with. Being that your covering will be the same color top & bottom, at least for a little bit, this should work decently.

AMA 74894

My Feedback: (1)

yup, I agree for nitro powered airplanes, I fuel proof that entire area with epoxy or epoxy paint first (since it's not seen with the airplane assembled)
add a couple of small pieces of covering as described, then cover the rest.
(I usually do tips/aileron cutouts/etc that same way as well.)

speedracerntrixie

My Feedback: (29)

Cut a 3/8" hole in the covering at the appropriate location and slip over the dowel. You are going to have a seam at the wing center so you only have to worry about one dowel at a time. Speaking of the wing center, I couldn't help but noticing the void in the glass at the wing center. Unfortunately that void eliminates any strength that the glass is supposed to provide. I also like to extend the glass out past the fuse sides so that the wing sheeting will not get dented by the fuse sides. Under vibration the wing sheeting tends to get eaten up.

Zor

Hi jeff4912,

The simplistic work around is simply to do like the control surfaces hinges; do not glue them in until the covering is done. Same with the installation of horns on control surfaces . . . install them then remove them for covering and reinstall them (usually screws in this case).

You already had ideas from others. Another way is to cut them at the leading edge, redrill the holes, do the covering and install new dowels.

Merry Christmas to you and your loved ones.

Zor

VincentJ

+1 on that Zor, I always wait to install the wing dowels until after the covering is completed.

jeff4912

Thank you for the responses. I will probably cover one at a time with a square and work around them. Next time, I will install them later after covering.

Speedracer, I will see if I can get more CA under that glass area that has air under it. I like the idea of extending the CA out to the wing mounting joint. I already have dents near the rear hold down bolts from test fitting.

Can I reinforce that wing mounting saddle area with only thin CA and no glass? Kind of like reinforcing a screw hole, or control horn with CA?

Just rub the CA on with a rubber gloved finger?

speedracerntrixie

My Feedback: (29)

Jeff, I have found that glass that has been applied with thin CA usually peels of pretty easy. What happens is that the cloth saturates with the CA hand keeps it from soaking into the wood much the same way a diaper works at keeping wetness away from skin. What I would do at this point is chop off the dowels, peel the glass off and apply new glass with epoxy resin. When applying the new glass, brush the epoxy resin onto the wood and then lay the cloth down. This will give some penetration into the wood and result in a much stronger bond. Re drill for the dowels, cover and install new dowels with brass sleeves so the dowels wont wear out the holes in the former.

Zor

As a couple of guys said recently _ _ _ I am the only one who does not understand.

I cannot figure out what CA has to do in this case. Glassing has the resin do the binding to the substrate.
The glass cloth has to have enough transparency for the resin to go through. I do not use resin; I use genuine aircraft dope and the application is identical. The material has about 80 threads per inch leaving lots of air space between the threads for the binding agent to go through to the frame.

CA has its use for tacking and is easy to take apart (weak joints) and also useful for ARF / RTF models.

I can see making the wood harder with impregnated CA if the required quantity is small (CA is very expensive). For strength I use wood glue and fillet the joints.

This looks like not enough resin was used in some areas or was not fluid enough to go through the glass. Applying CA as a repair may help; nothing to lose.

Zor

jeff4912

These were the instructions in the Sig 4 Star 60 kit:

[TABLE="align: center"]
[TR]
[TD="width: 4%"][/TD]
[TD="width: 32%"][/TD]
[TD="width: 32%"][/TD]
[TD="width: 32%"][/TD]
[/TR]
[TR]
[TD]
13.[/TD]
[TD="colspan: 3"]
2" wide fiberglass tape can be applied to the wing center joint (top and bottom) using the following method:

1. Cut the tape to length - one piece from trailing edge, around the leading edge and back to the trailing edge.
2. Lightly spray one side of the tape with a spray adhesive such as 3M "77".
3. Center the tape on the wing center joint and press in place all the way around the wing.
4. Flow THIN CA glue into the tape with a side-to-side motion. As the glass tape turns clear move down the tape until the complete length of the tape is glued. Remove any extra glue with a clean rag. Try not to flood the tape with excess glue as it will cure quickly, causing bumps and snags in the tape - bummer, more sanding.
5. When the CA has cured, sand the joint lightly to remove any rough spots. Try not to sand into the fiberglass tape itself.

I just followed the directions.[/TD]
[/TR]
[/TABLE]

Zor

You did not work on the wing saddle area which is on the fuselage. You worked on the wing joint.

A chain is only as strong as its weakest link; in this case the layer of 3M "77".

My previous posting is still applicable.
Perhaps some other fellow may help better than I.
I would have questioned these instructions.

Merry Christmas

Zor

VincentJ

That will teach you to follow directions! LOL

VincentJ

Jeff, I have seen those instructions on models that I have built as well. Any time I have to lay down some glass, my prefernce is to use Z-Poxy Finishing Resin. I apply it as Speed has suggested then using a cheap throw away china bristle brush, I work it in ensuring there is good contact between the cloth and wood structure. Once dry, I lightly sand and clean off any wax build-up with alcohol and then reapply a second coat of resin. (I do cut my resin with Denatured alcohol.) You will find that Z-poxy is a very good product and has very little odor unlike Poly resins...

http://www.supergluecorp.com/zap/z-p...inishing-resin

speedracerntrixie

My Feedback: (29)

Jeff, this is one of those cases where there are a few different ways to go. Going by the kit instructions would certainly work and as they say when all else fails follow the instructions. We could go around about the many reasons they went that way my guess would be so that you didn't need to go out and buy epoxy resin and the CA method is much faster. No matter what their reasoning was, using the epoxy will give you a stronger laminate, be easier to feather sand prior to covering and the covering will stick better. Again, you don't have to do it as I suggest but being that composites is what I do for a living when asked I feel compelled to offer advise on how to do it correctly.

jeff4912

Thanks for the input Speed and Vincent. I will check out that Z-Poxy next time.

sensei

I must agree a thin viscosity epoxy laminating resin would have been a great choice in this application.

Now I have a question for you Zor, you posted: CA has its use for tacking and is easy to take apart (weak joints) and also useful for ARF / RTF models. If CA is good for ARFs and RTF models generally manufactured from the same materials as found in our scratch built or kit built models then why would it not be a suitable adhesive for a complete scratch or kit built model of the same type of materials found in ARFs and RTFs? I only ask because I have been using thin and medium CA almost exclusively for the last 20 + years building entire wooden model airframes, and I have never experienced a model's glue joints coming apart in flight. Could you please elaborate on your statement?

Thanks in advance,

Bob

Zor

Hi Bob,

When fitting pieces to be glued and being as accurate as we can so the angles match (90 degrees or any angle) and putting the faces to be glued together there is contact at only a few places (often only one place) so some air space has to be filled by glue that has residual solids.

I experimented depositing some supposed to be the thick variety (crack filling) CA on a clean smooth metal surface where I think there is no penetration in the metal. I wanted to see what happens to the CA as it cures. How much change in volume occurs. What was left was very minimal. It appears to me that 80% to 90% of the volume is gone.

The CA being so fluid spreads out and penetrates any porous material. Whatever is left after curing may reinforce that material but does not contribute to a joint to another piece.

Manufacturers benefit by CA reducing considerably the production time (labor cost). That is good for them but not for us in terms of reducing damages in a bad landing. They are also concerned about replacement revenue. The model does not necessarily fail (break) in flight but does on a bad landing. Like I read before on a posting ... the fellow wanted to recover his ARF model and found out that the covering was the main thing holding the frame together.

A few words about clamping.
When applying the glue and clamping immediatly most of the glue is squeezed out of the surface being glued. Double gluing to create fillets does not only increase the binding area (up to five times) but also provides properly shaped binding surfaces. The clamping does not force the glue penetration; it pushes the glue out of the joint. The clamping main purpose is to prevent relative motions of the pieces while the glue cures. Relative motions might develop a gap between the surfaces being glued.

It is often advantageous to avoid clamping so the glue is not squeezed out. The pieces can be kept in position with simply pining with Tpins or any suitable pins. An example of such a case is when butting to sheets together lengthwise and it is not practical to clamp. I apply wood glue (Titebond, SigMent) for 3 or 4 inches separated by about a half inch. I put a drop of CA (tacking) in that half inch and gently press by hand the sheets against each other for a minute. If using pins then the glue can be continuous of course.

Above is my outlook on gluing and the use of CA. I hope it answers your question.

Zor

sensei

So let me get this straight, after the bond line has dried utilizing CA there is only between 10 and 20 percent of adhesive left in the joint due to the capillary nature of wood. A crashed landing will survive much better if glued with anything else besides CA because only the covering is holding the airframe together in reality.

Thank you for that informative information Zor I will use this to my advantage on my next build..

Bob

Zor

BLUE TEXT BY Zor

Bob,

You will soon see the gluing of the Kadet Senior that I am beginning to build the wings.

Zor

sensei

Thank you Zor, looking forward to your build thread...

Bob

Gray Beard

My Feedback: (-1)

Not many build threads of the Senior being posted so please start a build thread Zor so we can all see how it is done. I'm also looking forward to any mods you may make. Just learning how to do correct glue joints would be worth reading the thread.

overbuild

I have had excellent results bonding fiberglas cloth to wing center sections using water base Minwax clear. I use 3M77 to tack cloth than apply three coats of Minwax. Light sand and cover, no smell and clean up with clear water.

TomCrump

I just completed a Kadet Senior build thread, Gene. Here's the link. http://www.rcuniverse.com/forum/kit-...ior-sport.html

Gray Beard

My Feedback: (-1)

Tom, I watched you do the build but with Zor's well honed skills I would like to see and learn. Build threads are usually posted by the same people but lately I have been following some fellows I have never seen doing them before and have been very impressed with there skills and will be doing a few things differently myself.
Be nice to watch Zor instead of just watching Bob hack his way through another build. I didn't bother with posting a build on my latest, I went hit and miss in Ricks Up-Roar thread.
A Zor build would be exciting to watch!!

Zor

Here are a few modifications I am making _ _ _
1- Making the wings joined at their root with laminated joiners ... (drawing posted and pictures of the components).
2- Adding to the wing roots so in a bad landing they resist changing dimensions at the leading edge and trailing edge. IOW (In Other Words) crushing the fuselage sides inward or pulling them outward ...
3- Providing for the wing roots to be tied to the landing gear which goes across the fuselage bottom. This to resist the wing roots to be pulled upward out of their attachment to the fuselage.
4- Provision for quick switch over from trigear to tail dragger and vice versa ... (drawing and pictures posted).
5- Installation of flaps and ailerons without any gaps of importance while being activated to 40 degrees of rotation ... (drawing posted).
6- Exteniosn of the rudder top to increase effectiveness (authority as some say) due to the increase mass in the wings with the flaps, ailerons and servos. (drawing posted) ...
7- Tail assembly bolted instead of being cemented. This to provide adjustment of the decalage angle to optimize flying characteristics ...
8- Engine (OS MAX 55 AX) to be installed inverted for nicer looking fuselage front ...
9- Removable and re-installable tail wheel 1 1/2 inch diameter when converting trigear to tail dragger ...
10- Will be covered and finished with Ceconite light and genuine aircraft dope like full size airplanes.

11- Possible other modifications as I go along _ _ _

Some of the design modifications drawings and some pictures of preliminary construction were posted in the thread mentioned above. I am now not posting any of that stuff in that thread anymore. Apparently I misjudged the intentions of that thread. I thought it was for posting kit buildinng and in particular for Kadet kit building.

Many thanks Gray Beard for your encouragement. The present situation I have been put in are not favorable for me to initiate a build thread. I was brought in as a Brother wiithout my request and without being invited (that is the actual facts and the truth) and now was removed (#137 and #169).

Wishing you and your family and all your close friends . . . . .
A Happy, Healthy and Prosperous New Year.

Zor