..or control line flying.
So when I don't fly well enough to place well in F2B, I can allways build a Banshee and go beat some juniors. L

The building surface is the "poor man's," or in my case, the "lazy man's" fuselage jig. I'll admit it; I should make a jig.

It allows for really light carbon skin, the ones that we use in our wings now have have just one layer of about 1oz/sq.yd spread tow at +/-45 degrees. And then a good spar to take care of bending.

Is spread tow something you buy, or do you buy regular old tow and spread it?

I was wondering why you were posting skiing pictures, until I got the expanded view and saw what you were really holding.

Larry Cunningham and Ted Fancher took profile fuselages seriously.

Mike

Maybe, but who says that they got it right?

Anyway, it's not me in the pic but my friend Pelle.
We buy spread tow fabric, either from Texreme or Gavrilka. L

Maybe, but who says that they got it right?

Anyway, it's not me in the pic but my friend Pelle.
We buy spread tow fabric, either from Texreme or Gavrilka. L

I don't care much for arrogance Lauri.

Mike

One good source for Nomex is R&G in Germany. Other than that, they have everything you need fot this kind of construction.
It is quite amazing but Nomex honeycomb can be sanded to shape. I mean to shape like airfoil. Robert Leško has won the last World- and European champs in F1A with a model with spreadtow carbon skin molded around sanded Nomex core. He made an interesting article about it, it can be found at least ifrom "F1A Flappers" group in facebook.
If you want to make it stiffer and perhaps lighter, you really must pay attention to the core material. Using balsa in the usual way (but hollowed to reduce weight) or styrofoam you can only improve stiffness/weight ratio but not really improve stiffness. compression resistance is the key.
Perhaps easier to work with than honeycomb, and nearly as good in use would be Rohacell foam. The lightest Rohacell is about 30kg/m2. It resembles roofmate foam but compression resistance is better.
It allows for really light carbon skin, the ones that we use in our wings now have have just one layer of about 1oz/sq.yd spread tow at +/-45 degrees. And then a good spar to take care of bending.

A good source for Nomex or Rohacell is my basement.  I got them from the late (boo, hoo) Boeing surplus store.  The Rohacell was a particularly good deal.  There was a pallet of thin Rohacell sheets outside the store, and the guys there hated it, because it kept blowing away.  They were happy when I bought it all.  I think it was 50 cents / lb.  I haven't used either for awhile.  Thanks for the tip on sanding Nomex.  I never tried that.  I am way behind on composite technology.  I'll have to spread my toes, too.

OK Lauri.   LOL

Howard I use a fuselage jig to build full body fuselages, I was referring to a jig for a profile fuselage.

Mike

Its a foldable work table called Work Mate.   Harbor Freight has them for less money than the original.   Put your wing in the fuselage and set it in the Work Mate and clamp it.   Once the glue joint has cured move it in the Work Mate enough to align the stab/elevator.   

Tim,
I'm sorry if you find arrogance in my writings. They are certainly not ment to be so. English is not my first language, not even second or third so maybe the friendly small talk is not my specialty.

No no no!  You're doing great, keep it up.  I was making a joke myself.  I just hate smiley faces -- if you have to point out that it's a joke, then by definition it isn't funny.

Please don't get me wrong, also because of my work I really like when stuff is made in a traditional way. That's why I love F2B. But I also hate it for very same reason. In free flight the mentality is completely different. I am quite sure that modern FF models are about finest that composite technology can offer.
But as I don't have much to give in theoretical side, all I can do is to try to improve the structural things.
But our engine instead, that's another story. It will be the best I'll try to behave.

From cold Moscow,

Lauri

I am both attracted to and dread modern composite construction -- attracted to, because it looks like the way to go for light, accurate, rigid structures.  Dread, because it uses a bunch of skills that I don't possess (car fenders out of fiberglass -- yes, I can build those.  Light, strong wings for stunt -- not yet), and because I've seen it drive the price of airframes up in other areas of modeling.  A friend of mine competes in RC sailplanes, where serious competitors have stopped building their own models because you just can't do as well as factory-built and stay competitive, unless you (essentially) build your own factory.

Serge my FULL FUSELAGE jig is as follows:

I have 10 "L" shaped plywood brackets.  The bottom leg that goes against the building board has a screw hole it it that I screw down to the building board.  I cut the top view of the fuselage out of the plan and tape it to my building board.  I usuall use a 4' piece of melamine coated shelving board for the building board.  Once I have taped the top view of the plan to the board. I screw down a bracket each side of the former locations and then I start building.  It isn't fancy but works real well and the thing I like about it is that you can screw the brackets down at the former locations.  It works for me

Mike

I am both attracted to and dread modern composite construction...

I went nuts with then-modern composite construction in 1990.  It gave me a great appreciation for balsa. 

Thanks, Mike. I may make one this season.

SK

Is spread tow something you buy, or do you buy regular old tow and spread it?

I was wondering why you were posting skiing pictures, until I got the expanded view and saw what you were really holding.

It is called Carboweave website here,  http://www.carbontow.com/
This is spread tow Carbon fiber depending on the type you buy you can get 2 or 3 layer of tow.
CW 30, CW40 is 2 layers +-45 degrees CW60 is 3 layers +-45 and 0 degrees.
Also there is Textreme which is a lot more expensive where the material is a fabric make of spread tow and the width of the weave is about 1in square (kind of like weaving 1in wide peace of paper in a cloth) and they make starting in the 50g and up range.
On ebay you can find spread tow carbon too. Here you go https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.Xspread+tow+.TRS0&_nkw=spread+tow+&_sacat=0
For a fuselage I would use CW60 which is best by far as it provides stiffening in torsion and flex. If you ask me if I care if the fuse is flexing the anwser is no i do not care, do I care if it is having torsion in flight the answer is absolutely yes.

Stiffening for torsion is done with the weave at +-45 degrees
Stiffening for flex is done at 0 degrees (nose to tail direction)

Honestly I would make a foam fuse 3/4in wide when finished taper towards the tail,  plate it with balsa 1/32 and CW60 Carboweave on top.

Steve don't misrepresent what i said. I am aware of the 3/4 rule thus that is why I said "3/4in wide when finished". There are a couple of words you missed in my post and those are "when finished" which means after you add all the doubles etc and after you apply the finish. 

Hi.

If I had to do it, I would do something like in the scetch below:

-Against bending 2 horizontal "I" beams with about 1/64x3/8" UD carbon strips (1) glued to cross grain balsa shear webs (2). In highly stressed areas the beams can be wrapped tightly together with kevlar thread but I doubt if it is necessary. You can also compress +/-45 degr. glass or carbon to sides of balsa shear web, with vacuum or between glass plates. The beams should taper towards tail, both in height and in width.

-The space between top- and bottom beams (3) should be something light with enough compression strenght. For example lightest Rohacell foam or honeycomb. Perhaps also some sort of hollow zigzag structure would be enough, with 1/32..1/20" balsa skins.

-For torsional stiffness the fuselage sides between top- and bottom beams (4) should be a thin laminate with fibers oriented in +/-45 degrees, for example made from Carboweave or similar. There are several good carbon products available in about 40...60g/m2 range.
Ideally, the sides could be slightly curved (6) for better form stability but I don't know what your rules say about it.

-Done like this, you should end up with a very light and stiff "closed box" structure.

-Then at last to make it pretty, light balsa top & bottom blocks (5) are added.

But still I don't get it, my idea of a profile model is something you can build quickly untill your flying is safe enough fo moving to better and more complex models.

Lauri

Then there is a person who does not care if it flexes.

Do you still complete your goals with the profile?  Pattern?  Fun? 

Will the fuselage fail?  If so, then I doubt anybody would fly them.

Anybody notice that real airplanes flex a lot?

But still I don't get it, my idea of a profile model is something you can build quickly untill your flying is safe enough fo moving to better and more complex models.

Lauri

Do they have profile-only contests where you are?  We have 'em in the US, to attract people who want a more casual event than stunt, or who want to have another event in each contest in which to fly.  But there are some people who see a set of rules and think "how can I make my design the best it can be, and still be within the rules?" -- and so, you have people scheming on the World's Best Profile Fuselage.

At least in the US Pacific Northwest (and Canada Pacific Southwest), there's also a phenomenon that if you're really good, but not national-class, then when you move up to expert you kiss your last trophy from Advanced goodby, and set it on the shelf, because you're either going to get almost as good as Paul Walker and start getting third-place trophies, or you're going to never get a trophy in stunt ever again.  As a consolation prize, we have Expert Profile, where if you want to distract yourself from getting better with a real plane, you can have a profile plane and compete with the other folks who generally put in 550 point flights, and have a chance at a trophy from time to time.

One "advantage" that profile planes have over full fuses is that the control system is pretty much available for service or adjustment easily.
Accessibilty to engine, tank, linkages makes things easier to all, but especially beginners.
Just my observation.