radioflyer9

Bryan,

Hope all is well.

Do you mind commenting on why you went from a smaller wing on the Shark to the larger wing on the Alferma. What do you think are the advantages, and do you notice the larger wing getting bounced around a lot in the wind compared to the smaller wing bipe? Or was the larger wing designed specifically for the high altitude in SA?

Thanks,

Caglia

flyncajun

Hi Mike

I modified my Alferma wings so I could use my new Bipe trimming methods developed on the Shark and the first Alferma Bipe,and to take advantage of the YS185 power!
The wind is a little tougher on a bipe so, power and prop selection is way more critical as well.
The new unknowns are what any F3A plane should be designed around. Unlimited Power, and Lift is king for these new demands.

Brett also has a Style we were trying to match with the design ..it`s all one big package for us and 3 years of developement.
this is not to say other ways won`t work I just follow my own path.
Bryan

serious power

Hi Tuny,
I agree completely - they need to be stiff and durable.
Nice work on your own build. I have been following your progress.
One question;
Do you have, or know, what weight your wing panels were for the foam cores and or for the panel just after sheeting with no other work done ??

Brian

Edit; Tuny, I see what seem to be the 'just sheeted' panel weights in your thread OP.
Thanks

Dsnow

Brian just for reference I have some built-up bipe panels for my attempt at a biplane, plug-in wings, that weigh about 166 grams no finish or servo but expect them to weigh about 8.5 oz (240 grams) per panel ready to fly. The total wing area, not counting area within the fuse, will be 1300 sq.in. with each panel 325 sq.in. So far they look to be strong and stiff, currently trying to nail down the wing location in the fuse but it's based on the fuse from this years mono plane that I was flying.

Dave Snow

serious power

Hi Dave,
They sound like great weights.
Just so we are on the same page;
240 RTF ; 240 -30(servo and linkage) = 210.
210 x 2 = 420g per wing with no radio !?

Brian

PS ; Bryan, sorry for diverging your thread - but this may be good data for us all.

Dsnow

Brian the weights I gave are panel weights for a plug-in, for a one-piece wing you would add the center area inside the fuse and glass center section, for plug-in you need to add the wing tube and I would assume about 50 grams or so at this time,

Dave Snow

serious power

Dave,
Thanks.
They sound pretty good.
As you know heavy DOES NOT = strong.
I would advise that you pay particular attention to the fit of the struts.
They should set and maintain the outboard panel incidence.

Brian

tuny

On my builds each panel weights about 180g after sheeting. This includes all the internal carbon/wood reinforcements

serious power

Tuny,
Thanks. All info,, is much needed and appreciated.

When I get some work done I will return the complement to you guys.

Brian

flyncajun

Everybodys #`s are in the ball park ,My Buddy Torbin Parsburg has been building very light composite wings for his Bipe design.
This may be the solution But the effort it takes to do this is Great , Building Molds ect. I still think we can reduce weight with a Hybrid solution
Balsa -Glass, molded But I have not had the time to prove it yet.

However ,on Average getting a model flying and being able to make running changes for improvements you can`t beat built up, or foam wings.

There are quite a few new bipes coming out and I think this will advance thinking and improvement. There was a nice Bipe Called the"Dagger " from Turkey in S.A. Not sure who built it, but it was a nice platform And one of the larger Electric platforms I`ve seen. witch is a step in the right direction.
Jason, Andrew,Chip all have new Bipes coming out so , I think we will see some creative thinking and different approaches next year.
I still think Glow is the wave of the Future for Bipes though, and this will be proven with the new sequences. In my oppinion A small bipe is like a 120 sized pattern plane you lose impact and presentation. as well as performance.
SO, if your thinking of building one, do your research.And build it as big as possible to make weight, it will pay off in the end.


Bryan

Bryan

MTK

Dave, are guys using standard (for a mono) 7/8" tubes? Seems to me a little smaller, lighter will work just the same. What percent thickness are you using?

Are these weights with wrinkle kote or paint?

I think that if guys played more with lightweight painted finishes (I've been using and discussing for 2 decades) a stronger product will result at no weight penalty. One other thing to consider, the smaller wings of a bipe don't require 1/16" balsa unless it is built up. I'd use foam and cover it with 1/32" (with carbon veil under), Jap tissue on top of the skins but I'm not going into bipe building any time soon. It's much more work of course.

Dsnow

Hi Matt,
1) using 3/4" wing tube each wing, no adjusters but carbon pins front and back
2) monokote finish, I have no place to paint - fuse is built-up and monokote too
3) varies but averages 12% airfoil

Dave Snow

flyncajun

Matt,
I worked this out some what over the last five years.
There are many things to consider when designing a Bipe wing , "where to get the wing strength from" is the most important , and to make it durable for the snaps in FAI. the reverse KNife snap has sent many to the promiss land alreadybuilt by master modelers!
I have built 5 sets of bipe wings, only 3, by by refining the same methods, was I able to reduce weight and increase size,Built up and film covered.
I think I may come close with a paper/silk paint method, I`m still not Certain. I know you have done a lot of testing and finishing in this area so you may have numbers of comparison that will help us with the finishing methods. film will add 80grams to the wing Thats hard to compete with.
The majority of the strength is attained with the sheeting. The majority of the weight reduction is attained through selecting the sheeting.so this is our problem.

The problem is when you get thin, you have to increase the sheeting thickness and rib cound for the strength thereby adding the weight back in. 1/16 is not viable on a built up Bipe wing they will fail in FAI. unless structure is added back into the ribs and wing design .
1/32 skins over foam does not acheive the weight saving you would think, because the Glue adds the weight back to the sheeting without adding strength. I even tried 1 pound density foam.(as did Oxai for a time on the Euphoria) still, small painted wings were 5oog.

When you add a tube for adjustability, you have way too much weakness in span and problems twisting changing inc during manuvers.
The center is where the load is and carbon tubes just are not able to distribute it ,ot handle it as well as a center structure like the wing ,glassed over the sheeting.

This is why a Hybrid approach is needed Maybe Torbin can give us his composit wing weights for comparrison
Bryan

serious power

' I think that if guys played more with lightweight painted finishes (I've been using and discussing for 2 decades) a stronger product will result at no weight penalty. One other thing to consider, the smaller wings of a bipe don't require 1/16" balsa unless it is built up. I'd use foam and cover it with 1/32" (with carbon veil under), Jap tissue on top of the skins but I'm not going into bipe building any time soon. It's much more work of course. '

Matt,
With your guidance I have worked out a modification to the approach which I took 20+ years ago.
I think that with this method I will get a strong enough/stronger result that will also be lighter.
This I have yet to prove but based on your reports and my previous experience I can't see why not. ( might be setting myself up for a fall )
The funny thing is that, in conjunction with some modern stuff, I am back to the traditional stuff; dope etc.
Though the preformed composite skins approach we discussed already is probably the optimum for weight and strength - short of going with full blown moulds etc. Moulded is doable but is very difficult to justify ,as Bryan has said, while experimenting/developing and or for one off's.
However if we went moulded the glider guys have it all worked out for us.

Brian

Doug Cronkhite

My Feedback: (34)

Molded wings are more repeatable for certain once all the engineering is done, but it takes time to develop the proper materials schedule to achieve the weight and strength you're looking for. They're also infinitely less affected by handling rash. I've cracked sheeting on my BiSide wings in a couple places just from moving them around my shop! Nothing structural affected but I have to remind myself to handle them with kid gloves. A composite wing would be much better in this regard. The other big thing composites CAN give you if done properly is incredible torsional rigidity.

As for finishing methods.. Silk and Dope is still the preferred method for the control-line stunt guys, and they have some of the most beautiful finishes in modeling. But like anything, it takes a lot of work to achieve those results, and many people simply aren't willing to invest the time to learn/perfect those skills.

MTK

Brian, when I see that you can get a 35 gram foam core of appropriate size (center removed), lightness with excellent strength becomes much more likely. A scant 70-75 grams (<3 ozs) for a whole wing of around 800 squares. 1/16" sheeting should weigh around 4 ounces for that size wing. 1/32" sheeting will weigh less than 3 ounces and probably 2 1/2 ounces. With veil/epoxy on the inside, I don't see the whole wing weighing much more than 7 ounces unfinished. Jap tissue and dope plus paint shouldn't add more than 4 ounces. I still see an 11 ounce wing excluding servos (top) and maybe 12 ounce bottom (retract mounts and no servos). RTF, top maybe around 14 ounces (400 grams) and bottom 18 ounces (520 grams)?

I haven't yet done it myself but have thought of a technique by which a full cavity mold is not necessary for a full composite wing. I'll throw it out here for consumption and if anyone tries it and has success, I'll take a lowly 5% contribution to our World team (aha, didn't say contribution of what exactly?? Bovine Skat excluded of course, hehehehe)

Anyway, the idea requires some 2-4 lb density foam cut the regular way, and a release agent (sticky backed teflon or PE tape) be applied to the core. The husk will require something like 0.010" mylar since this will be the finish side of the composite panels.

One would set the balsa or lighter composite sheets (airex) up with 2 oz glass on the inside and 0.2-0.3 oz carbon veil first topped with 3/4 oz glass on outside. A sandwich is made and bagged directly on the foam. Certainly requires a learning curve but I think it would build a nice light wing in the end for monos, bipes, tripes whatever

flyncajun

MAtt
I produced My" entire" SHark Bipe this way THE fuse( built two male plug halves bagged the skin around them) , did the wings this way as well, Except I monocoated the outside of the skins on the wings. My proto Patriot 3d decks fin rudder , were also done this way Except I made molds and bagged them with carbon,balsa .5 glass super strong But 6 months worth of work just for those parts. I shared this Method with Dean Pappas and Bob hunt in 08
My Proto shinden wings were produced this way as well and completely painted 1150sq wings were 15 oz ready to fly
The Bipe wing is a different animal as Tuny will attest for and will require much more labor with foam, and no gain.

The Shark proto wing was hybrid composite skin over a traditional built up structure , without a true mold there is no way to make it light just bagging then painting the outside after silking is not going to acheive any real quality results


The only way weight savings is achieved is through a strong well engineered substructure, and good skins there is no other way to do it. Unless you build molds from plugs and make Hybrid composite skins Veil, glass balsa

Bryan

Doug Cronkhite

My Feedback: (34)

Realistically, is weight even an issue anymore? Mayr had a friggen TriPlane at 4600g! My BiSide is 4780 and I'm not even trying to shed weight anywhere. I used heavy batteries, with an aluminum spinner and a heavy prop. Seems like the goal now should be increasing stiffness, not area really.

serious power

Hi Doug,
You are correct.
Stiffness is the goal.
So ,from my point of view anyway, this 'weight' discussion is one of building these relatively skinny bipe wings strong enough in span and 'stiff' in chord so as not to twist under the more extreme loads, and to do so without a weight penalty.
Quite a lot of the E bipes, purpose built, have to use smaller batteries. That's a compromise straight away and stiffness may still be in question with these.

Brian

tuny

As Bryan said and I can give you my word, bipe wings are very different. BE VERY CAREFUL, they will fail if not. 1/32 sheeting in my oppinion is too thin. (As Matt said it would be great to make an experiment and test it. Is the only way to get innovations in our sport). But trust Bryan. I have also builded my set of wings from scratch an even on foam wings it takes an internal structure to really hold up in FAI.

so like I said before I dont think that even 550-600 wings rtf without servos are a bad thing. Even Naruke's wings weight as much as 650 with servos. This is because yo NEED them to be very strong.

TUNY

MTK

Bryan, I will never know if these are more pain or less pain. I don't plan to develop a bipe for Pattern in the near future. I'm thinking tho, that based on the foam work I do with 1150 square wings, an 800 squares wing can be built light and strong, lighter than some of the weights I saw thrown into this thread.

As far as molding balsa over a male plug alone, this has been kicked around for quite a few years in this neck of the woods, well at least the 9 years I've been up here in freezing Joisey. Bob mentioned to me that he was building fuses for CL back in the 90's using the technique. Maybe he wasn't who knows

The idea I presented goes beyond that and is not for fuses...as always however, there are more ideas than time to try them all. I've given up even attempting some of the stuff. It's a hobby afterall, not a job.

Doug, try carbon veil under the skins next time, the lighter of the three offered. It might surprise you. Suggest you apply to the inside face of the skin first, with nitrate.

flyncajun

Yea I know Matt The control line guys do this, But they normally wet the balsa and mold the balsa with bandage wrap on a male buck.
and just recently they are using Molds and bagging balsa skins. lots of work making molds!
I`m talking molding wing skins inner and outer at the same time with carbon and glass /epoxie. over male plugs
you only need .5 cloth .3veil 12 grams each side of epoxie on 50grams of balsa But the primer and paint weighs more than the skins in the end.

My first set of foam wings 700 square each honeycomed finished with film the traditional way( poly glue )was 500 grams this is with the wing strut mounts in place that adds 20-30g
like I said I would have agreed with you about building light foam bipe wings ,till I actually did it never again.

Designing and building a bipe is three times the work and twice the dissapointment when you get something wrong lol
those grams sneak up fast
The Electric Guys can build the airplanes lighter than the glow guys tho. they have too
Bryan

kochj

I am guessing the work involved isn't worth the time...but I will ask a very basic question...
Is there any benifit to using a C.F Ribs? not good for testing, but what about a finished product?
Or do balsa do just as well, come in as light, and w/o all the health risks?

Thanks...

flyncajun

The average weight of a balsa rib is about 1 gram the average weight of each half wing structure is about 50 grams
It would be impossible to save enough weight to justify using carbon ribs plus the weight of the glue to assemble it would send it through the roof.
Thats not to say there is not room for some carbon in there ,some of my ribs have carbon Veil laminates in the root area for compression.
80% of The gains are in the Skin ,Stregnth or Weights. the other 20% is in the finish

ALso,The life of the average design is about 3 years and you sell few airplanes to justify a complete set of carbon ribs and the work involved to produce them. the average life of a set of bipe wings will be much less than that! LOL
Not a bad Idea ,But Balsa with the right grain is plenty good enough for the task.


Bryan

flyncajun

the weights I`m talking about are on wings that are much larger than the normal sized F3A bipes
so some of the smaller wings may be able to be built 2-30 g a panel less but these wings are 1600sq
Bryan