moggyman64

Hi All,

Can somebody please point me in the direction for information of how to join/bond the two halves of a composite fuselage,and composite wings etc.
Regards

Keith

wyowindworks

Are you talking in the mold our out of the mold?

There are 4 primary techniques that are used for in mold seaming for fuses: 1) Bog joint, 2) Tape Joint, 3) Joggle gasket using joggle tools, 4) and the wet seam (co-cured). These are also put in order according to their toughness. If you are seaming out of the mold you can use a tape joing or a joggle gasket seam...although both are easier to do in the mold.

Most model wings are joined with a bog joint. Some larger ones may use a jogglle gasket joint on the LE and a bog joint at the TE.

moggyman64

Hi wyowindworks,

I suppose it would bebetter to do in the mold as this would keep the everything in alignment, excuse my ignorance but could you expanda little more on the 4 types of joint you have listed, I have not done this before.

Keith

wyowindworks

Bog Seam
When making a bog seam the layup is trimmed flush with mold flange on both halves. Typically you wait until the layup gels and then run a sharp razor blade long the flange. A bead of bog, a mixture of resin + thickener + chopped fiber, is run around the edge and the molds are closed. This is the easiest seam to make cosmetically but it is the weakest in respect to fuses. It works well for wings because the surface area at the bond is larger.

Tape Seam
The fabric is trimmed flush just like the bog seam but a strip of fiberglass tape/fabric is positioned so it spans the joint. You can also use a little bog as well. The seam is stronger than a bog seam but typically heavier and not as strong a wet seam. This technique requires openings in the mold so the tape can be pressed into place.

Joggle Gasket
This seam is made by using some additional molds/tools that are clamped/bolted to the mold flange. These joggle tools create a step in the layup. The layup is allowed to fully cure, the tools are removed, and the joint is made with some bonding resin/bog on the joggle flaps. This is the most common technique if the fuselage is going to vacuum bagged. This technique does not require any mold openings.

Wet Seam
See the attached illustrations. This is typically the strongest and lightest seam. It is the most difficult to make cosmetically. This technique requires mold opening to press the flap into position unless a bladder is going to be used. This is the most common technique for bladder molding.

Here is a short video clip that breifly shows these seams being constructed

Here is another video that may be of some help. & Part 2

wyowindworks

Here are some illustration for using joggle tools.

moggyman64

Thanks wyowindworks,

Very helpful details, as they say "a picture paints a thousand words". Have you completed the beginners videos as mentioned in the link you provided. I have registered on the Vimeo site and just need to activate my email.

I think I have got my head round the different methods of joining the fuse but will they work on wings especially the rear stabs because there would be less material to create a joggle at the leading and trailing edges. I was also thinking of using fibreglass to make formers and wingribs etc. obviously as light as structure needs would allow.

Really appreciate your info.

keith

wyowindworks

Keith, almost all model wings are joined via a bog seam at the LE and the TE.

If you send an email to [email protected] I'll add your email to a list.  When the videos are ready I'll send an email letting you know.  I'm closing down the kit fabrication portion of my business.  I'll work on the videos again when I get the kit stuff wrapped up.

SCALECRAFT

My Feedback: (13)

As pointed out by wyo, the bog at the TE will work and has worked for our models since 1991 without failure. As it is squeezed buy the molds, the bonding material will move forward in the wing and cover more area.

On our LE seam, we choose to use the Joggle gasket. Although on some of our early wing molds without the wing tip in place, we used a seam tape on the joint.

Ours are all warbirds with retracts and a hard landing can split the LE without additional support.

Steve

SCALECRAFT

My Feedback: (13)

This pic is one of the models. And a 54" span corsair wing.

Steve

wyowindworks

I should amend my statement: Most glider wings use a bog joint on the LE and TE. This works well because the wings are very thin compared to power wings. The bog gets a lot of bite on the LE because of this. Often twisted lengths of carbon tow or glass roving are also used in the LE to increase their strength. The "blunt" leading edge of thicker power sport wings makes the bog seam much weaker. A joggle like SCALECRAFT is using would be the way to go on the LE of thicker wings.

wyowindworks

Here is an example of the internal construction of a hollow molded glider wing.

moggyman64

Thanks scalecraft and Wyowindworks for your input which is extremely helpful.

AsI said earlier I have built and flownplanesusing traditional methods but I am new to working with composite, and really looking forward to getting started in the next few weeks, however beforeI steam straight in and probably make lots of mistakes and waste money etc. I want to gather all the information I can regarding all the little tricky bits like the topics covered in this post. I know that sometimes you might be saying to yourself that the answer to that is common sense and I do use it to arrive at what I think will be the correct answers but there is no better way to learn than to get the opinion from people with experience.

I have a few more questions,

1) The models I will be building will generally be sport types and havequite adeep aerofiles so I will use the joggled gasket joint to the fuse and the leading and trailing edges on the wings, my question is on the control surfaces wherethe jointswill bealot smallerwith acute angles, as recommended I would use the Bog seem joint but would this joint be sufficient to fit say robart pin hinges into or would I have to put in some wood blocks to fix the hinges to. The reason I ask is because looking at Wyowindworks wing section, and is a great joint for that type of wingbut it looks like theremay not be anything significant or consistant to fit say a25mm pin through. This would be highlighted in the instance of the control surface leading edges where the is usually a double chamfer to allow for clearanceand movement up and down or side to side. What do you think?

2) I am planning on fabricating composite "I beam" type ribs to accept and support the wing tubes and using foam infill between the ribs to support thecomposite wing sheet, do you think this is a good idea or would it be best to just use these ribs without any need for foam. Would a set of composite ribs be lighter that ribs and foam? What do you think?

3) When using the bog and joggle methods of jointing in the mold, It has been mention by Wyowindworks to wait til the layup gels and then trim away the excess material and then carry out the joint procedure, my question is do I polish the mold flanges and if any adhesive oozes out of the joint when the mold is clamped shut do I trim this off after parting the mold of should there not be any adhesive leaking out of the joint.

Kind regards

keith

wyowindworks

Most people use kevlar to make the hinge. This create a a continious hinge and seal. Here is a really old video that I did that shows how a kevlar hinge is made: https://vimeo.com/2368007 Just jump ahead to minute 18:00 to see how to cut the hinge free. Although this hinge in the video isn't for a control surface the technique still applies.

Most people just tie the joiner receiver into the shear web of the spar. This way the force is directy tied to the spar rather than the wing skin.

Typically the wings are vacuumed bagged into the mold with peel-ply. This isn't necessary if you are just using a composite laminate for the skin, but if you are creating a sandwhich structure (lighter, stiffer, and stronger) then vacuum will be required. The peel-ply leaves a nice bonding surface for the bog.

A polished mold flange makes for a better release and the mold clean-up goes much better between mold cycles.

You will have some bog squeeze out between the flanges. This "flashing" gets trimmed off the parts after they are demolded.

Here is a great video showing the process for a molded wing: https://vimeo.com/1737393

SCALECRAFT

My Feedback: (13)

Wyos' methods are are a bit more advanced than the methods we use for our application.. Both methods can and do work.

Our concept is essentially a glass skin of a certain weight, and layers, along with balsa/plywood framing, spars, ribs, plates, and bulkheads. All ours are scale warbirds and now scale jets. For our own use at this point. Models range form 40" span Me 163 Komet to a 69" span Spitfire Mk. The glass weights depend on the parts configuration and role it will play in the air frame.

Also taking into consideration is CG during lay up and "grab areas". All the while taking finished weight into consideration

We, for our application do not vac bag or sandwich wood/foam between the glass. Although the glass tends to oilcan, none of our all composite models have ever failed in the flight since 1991. Our wings have one big advantage over balsa/foam sandwich, glass skins do not dent. They just rebound if impacted while in transport, stored, ect...

Our ailerons are razor cut from the wing, then a balsa radius cap is glued to the aileron, then robart pin hinged to an internal balsa support. If done right, the aileron to wing joint looks scale and rotates scale.

However, the kevlar hinge eliminates the headache of all that. Our jets will go that route.

Foam in the wing will just add weight. The framing is the trick in our configuration. Composite ribs and such. Cool, but you may burn out making small parts. I have. Making Composite prop blades, a good investment.
Steve

moggyman64

Hi Steve,

I am having a little difficulty in understanding some of the terminology that is being used for example - grab areas andoilcan -maybe you could shed some light on those please.

At this point I dont want to get into sandwich type construction, what I meant was to insert foam to fill in the spaces between the ribs, as If I had a foam core and just cut out and inserted ply formers at relative points.

Your concept wing type that you have describedsound exactly the same asthe type I want to adopt, I just want to keep it simple with minimun internal framing (composite or wood) and skin the wing in glass instead ofa film type covering.

With regards to making small parts well that is something I would enjoydoing because I like being challenged hence why I want to get into composite construction.IfI do get fed up making small parts the there is always balsa and ply to fall back on but I would have tried.

I have done the traditional builds from plans and kits but never really questioned anything just followed instructions, now I want to understand what makes a plane fly or not.

Do you have any photo's/video's of the internal structure of one of your wings being built,using the methods weare discussing. The wing shown in Wyo's video is quite flat and the wings I will be doing havelargecurved aerofiles edges so there is only an edge the thickness of the layup to bond together.so will the "bog" seam stay inthe right place when the mold is clamped or just run to the low side?

Regards

keith

SCALECRAFT

My Feedback: (13)

Hi.

"Oilcan". When one grabs the fuse for instance, and it is squeezed a bit inward and back out.... not really a problem at certain locations on the fuse, but some modelers use this as a gauge on fuse integrity. Looking for reliability and durability. Over engineering just adds weight. Nothing will survive a good crash.

"Grab area". Area of the model you will grab. For us, it's the area around the back of the cowling that we grab when starting a glow engine. But still forward of the CG.

The wing shown is a 54" span Corsair wing (Jemco). The pic is around 15 years and many models were pulled. The glass used is plain weave "E" (electrical) glass. "E" glass conforms easier in a hand lay up with no vac forming than "S"(structural) glass and is enough for what we did with it. The entire wood frame is glued using epoxy and cabosil as a paste. An economical very good bond.

USE A RESPIRATOR AND RUBBER GLOVES WHEN CUTTING COMPOSITES AND USING CABOSIL (FLUFFED SILICA). AVOID VAPORS WHILE EPOXY CURES.

One of the ways to get the correct combination for what you need on your wing configuration is to experiment. Long flat span on your wing may need support, but not every sq. mm.

The glass used at first was 5.75oz with two layers, and removing residual epoxy. Later down to one 5.74oz and a 4oz. The entire composite model ready for flight (dry), with rotating retracts, was around 7.75lbs and was very forgiving at landings.

The original wood/foam Corsair was 8lbs.

Steve

moggyman64

Thanks Steve for taking the time to answer my questions, I think that I now have enough information to get things underway. One area I may struggle with is which glass and resin to use an where to use it. Obviously I will need use different layups for the fuse and wings.

When I have made the plugs and molds I may need to post some queries on here again for some help or if I may PM you that would be great?

Regards

Keith

SCALECRAFT

My Feedback: (13)

Of course. PM or here. Your choice.

I use West Systems, it a Marine resin, ( UV qualities) but I have a few pumps for it and it's a local pick up for me. There are others that may cost less that also work just as well or better. Wyo has mentioned a few on other posts. I may try those as well later.

Steve

moggyman64

Thank you All for your help with this thread

Regards

keith

yankee samurai

My Feedback: (175)

Wyo, what is you mold made of?

wyowindworks

Which mold are you referring to?

yankee samurai

My Feedback: (175)

The one in your video, where you make the glider fuse!

wyowindworks

The mold for the DLG fuse is made from carbon fiber, MDF, and a partial casting of epoxy and sand. You can see the mold construction in this thread on RC Groups: http://www.rcgroups.com/forums/showthread.php?t=1514414

yankee samurai

My Feedback: (175)

Thanks!!!