24' glider spar....

[FairlyFaded]

hello everyone!
Im building a massive foam wing (24') and i need some advice on the spar. Im doing a D box structure as you can see, i plan on having two spars. one being the back of the D which will be most of the strength and another a foot or so behind the first one. The ribs are each 4' long. The entire thing is made out of white eps foam. The wing needs to beable to hold around 140 lbs ish. Most of the load will hopefully be on the spar/dbox. I did put the spar a little far forwards but hey theres no going back now! My mats are- 4yards of 1' 4ish oz uni directional carbon, and 4yards of 4oz glass. My original plan was to put a few layers of the uni directional stuff on the top and bottome of the 1 1/2" foam spar with glass underneath and above going a few inches over the edges of the spar, but i dont think this will be stronge enough.... I am now thinking of using some very nice light wood i have seen at the hardware store. It is 1 1/2" wide by around 1/4". It feels veryyy light and very rigid. Im not sure what kind of wood it is but i think it would make a great spar "cap". So now im thinking i will do one layer of glass, then the wood spar, then ontop of the wood 1,2 maby 3 layers if the unidir. carbon, then another layer of glass all over that. I think that would make for an increadibly strong and light spar. what do you guys think? thanks!

michael

[Phoebusflyer]

Why not go to Wicks Aircraft supply or Aircraft Spruce and order some aircraft grade spruce for the spar caps. It's good wood, light, strong and very close grained.

[FairlyFaded]

picture sais it all.... and by spar to spar i mean rib to rib....

[FairlyFaded]

thx for the link! i could use that stuff, it would probably be the best stuff to use. but shipping would be a huge pain for a 10' long section, or even a bunch of 7' sections. I think i may go with the stuff at the store, its cheap and looked really nice, if i get it ill post some pictures of it. What kind of grain should i look for? thanks!

[lorenkb]

The wood would help to distribute any buckling loads across the foam, but won't do as well as carbon will as far as resisting bending loads. I personally would replace the foam spare cores with endgrain balsa (which will hold up to a lot more compression to resist buckling) and then stick with several layers of carbon for spar caps.

If you go with the wood caps ditch the fibergalss between the wood and foam; it's not going to do anything for you that the wood isn't already doing. Keep the fiberglass wrap though, that will help prevent the spar caps from buckling outwards during bending. Kevlar would be a much better choice for this than fiberglass though. Keep in mind that the entire length should be wrapped, and if you only wrap between the ribs (leaving gaps evenly distributed) the wing will fail at these unwrapped sections near the root of the wing.

Oh, and that is a HUGE wing! :eek:

Loren

[FairlyFaded]

I agree completely that there would be better ways of making the wing spar, such as end grain balsa and kevlar. but im doing this on somwhat of a budget so that knocks alot of ideas out. So if i understand right you think the spar will lift off were it crosses over the rib because theres not cloth over that right? I agree so i will remidy that by putting a 2" strip running cross wise over the spar cap and then down the side of the guset. It is true that carbon is technicly stronger then wood, but i find when combined together then can be reallly strong, much stronger then either one of them alown, so i think my wood/carbon/glass spar cap will be plenty strong. One thing that comes to my mind with the spar is the fact that my foam will be much more enclined to depress then to have the spar cap lift off. For this reason i dont think i will really need much glass- or kevlar holding the spar down, unless i put it weblets and up the load greatly. I will run the glass all the way around the spar though as you sugested. I think i may want to add some weblets... agreed? or do you think this setup will beable to stand up to 150lbs? thanks!
michael

P.S. any ideas on cool inexpesive ways of making some weblets?
Also i need an idea for the trailing edge.... Right now i just have the spars going down to about 1/4" on eacn end. I also added the middle spar a bit ago and it is all drieing right now. Do you think i could maby do a trailing edge just made out of a rod of carbon or glass. Iv seen this on some hlg's. It seems like it would be preaty flimsy. I could amagine after the shrink covering goes on it may get warped... but it has worked for some people...Anyong have any ideas?!

[Ollie]

"The entire thing is made out of white eps foam. The wing needs to beable to hold around 140 lbs ish."

The shear load is carried thru the foam rib. So the spar design is the very bad because of weak foam at the rib is part of the spar. You must split the ribs so that shear web is not from root to tip so that the shear load is not interupted.

I don't think the wing is strong enough for is size. Why do you think the wing strength is to carry 140 pounds? Do mean 140 pounds of lift? If lift is 140 pounds, what red line air speed to generate lift? The wing will fold at very, very low air speed in my opinion.

[flystoolow]

I think the opposite, I feel you will have more strength than you can imagine with two thin spar caps of spruce. Just think, a 16' 2X4 supported only at the ends can easily hold a 140lb person even on the 4" side. Sure it will bend, but it won't break. 2X4's are made of poor wood.

If you use spruce, and have spar caps of 1.5" X 3/4" dimension epoxied to the foam and wrapped as is with thick carbon tow (or similar), it will support 140lbs with ease.

When you load a wing with 140lbs, the center area of the wing supports the majority of the load, the tips do less than their share of work. Therefore, if your spar can hold 100 lbs while spanning only 16 feet, you will be all set.

Here is another option:

Skip all this complicated and time comsuming spar work, make a simple spruce cap spar wrapped with cheap flat strand cord, and add two 1/16" stainless cable flying wires below the wing.......similar to a hang glider.

Very strong, cheap, quick, and probably 20 lbs lighter.

Here is an ancient photo of an early hang-glider, but it is a great shot of the flying wires I'm talking about. (The assistant is holding one of them). Note, the hang-glider's span is about 24', and the "spar" (3" alumimum tube) is very weak compared to even the simplest spruce spar for your wing.

http://open-site.org/newsletter/batboy/images/aviation/hanggliding.jpg

Good luck

[miniphase]

140lbs !!!, is this being built to carry you Fairlyfaded?

[FairlyFaded]

So what if it is : D.... 140lbs is a bit light, i think the wing should beable to suport 160lbs of lift, so around 150lbs of dead wieght. I agree with flystoolow that the spar will be pleanty strong- for example the 2x4. Olie you do have a good point that it may have been good to split the rib not split the spar, but i think both ways have their adv. With my set up when the spar goes into the rib the foam around it widens because of the gusets. So instead of the spar being 1 1/2" wide it goes to being 2" and then 48"s wide. Why i think this design will be good is also because the but joint wont be suporting any of the load. All of the load will be ontop and on bottom of the spar in the wood/carbon which will be continues across the wing. The foam isnt suposted to be stronge its just suposed to make there be a gap between the to spar caps- the larger the gap the stronger it is. Of course the foam needs to resist buckling which it does but the wood/possible weblets will increase the buckling resistance.
-fly, i think im going to use my original method. Im fairly compitent when it comes to composites and iv allready spent the money on them : D. I think the spar will come out being very light, id guess the wood was about 2lbs each so around 5lbs, then maby 1lb of carbon/glass.
michael
p.s. can you imagine how strong a piece of 1/4" wood with a bunch of unicarbon ontop of it is interms of tension and compresion!! probably a few tons....

[FairlyFaded]

Here is the second spar in place, put little foam booties on the trailing edges to keep them warm (safe). The wing wieghs 1 1/2 lbs right now! :D
So do you think i should put one layer of glass on the second smaller spar just to give it some rigidity? Also do you think i should put glass on the tops and bottoms of the ribs? it wouldnt add much wieght but would make them alot stiffer, the covering will add a ton of stifness to the structure behind the d box.
One last thing, any ideas on light clear inexpensive covering? i heard you can use laminating sheets??? thanks!

[rdwoebke]

So is this going to be for some kind of "Red Bull" human flying thing?

[miniphase]

So is this going to be for some kind of "Red Bull" human flying thing?


my thoughts exactly
come..... on fess up

probing minds want the full story



oh, and by the way...are the olds on holiday or something? not sure if I'd have won any favours doing that
on the dining room floor when I lived at home!

[rdwoebke]

I also think you are going about this all the wrong way...

You should have titled the thread something obscure like "here goes nothing II"

The photos are way too clear. We can clearly see that you are quite the crafstman.

Your posts don't have near enough spelling mistakes.

Because of the above, you are missing out on free parts/advice from highly frustrated posters. Of course, you also have a lot less chaff (except this post) in this thread...

http://www.rcgroups.com/forums/showthread.php?t=372482

Good luck with your project...

Ryan

[FairlyFaded]

lol the "olds" are at work.... I have this week off from school. Iv been building planes for 10years all over the house so they have gotten used to it : D. Im not to sure what a red bull human flying thing is, maby one of thouse events were people jump off a dock and try to fly? If so no thats not what it is : D It occured to me a few weeks ago that electric human flight is not only doable but also could be doen quite cheaply. I have found a nice sourse of li-ion 18650 cells (2.2ah). At only 1.75$ a cell i can put together a 1.6kwh pack for only 325ish$$$'s. With the price of chinese brushless stuff at its alltime low i can put together a very efective motor system for another cupple hundred. With that set up i could have bursts of 120lbs of thrust at 30mph pitch speed from a 25lb set up.
Yes it is true that this should be in the electric forums, but i think if i put it there theyd say to make it out of one huge piece of depron.... O.o
Also another thing that spured on my building of this plane is the fact that airplanes are really veryyy simple. I have found that i can make a plane from scratch in 2 hours and it works, all you really need is a decent SG/wing loading and some resonable control surfaces. Ill try and get over to the local ACE to get the spar cap wood so i can start building the spar, ill post pictures if you like, hahah who am i kidding who WOULDNT want to see pictures : D.
Anyone have any ideas for a trailing edge? thanks guys!
michael
p.s. dont get to thinking "oh this guys young and foolish itll never work", cuz back a many years ago when i went to get a "fire bird" as my first rc plane the guy behind the counter said i was too young, boy was he wrong. Iv built alot of nice things like my composite dl50 and my cnc cutter so dont prejuduce me, not that anyone has been : D

[FairlyFaded]

lol rdwoebke i just saw your post, hilarious man! maybe i am doing this the wrong way!!!! better start hackin up the wing : /

[Wing-span]

Is this thing going to carry a human? If so you better make sure the spar is made properly with vertical grain webbing between the top and bottom of the spar. Proceed with care, you don't want anybody to get hurt. Try 12mm dowel for the trailing edge.

[lorenkb]

Couple more thoughts...

I'm not sure if the foam will be able to take the required shear loading (as Ollie pointed out). Some balsa siding on the foam spar would hel pa lot, and shouldn't break the bank! (it does have to be continuous though, calling for surgery to cut the ribs free of the spars...)

More importantly, if the spars do survive the load, I think you will have very bad flutter problems. With non-structural foam ribs being the only thing connecting your spars together there is nothing keeping them from bending independently. I would either bond some thin wood to the rib sides that had a good bond to the spar caps as well, replace some ribs with plywood, cap the ribs with carbon, or perhaps some combination of all three (not sure just how well carbon caps alone would fair being bonded to just foam). Anything you can do to tie the two spars together in a stiff fashion to resist torsion will help.

Loren

[FairlyFaded]

lol i wasnt planing on making the spar properly, good thinking! : D hehe just kiding. this things going to be light (under 200lbs easly) so i really dont know if the spar is going to need to be "proper" Ie. full scale strenght. Dowel may work for the trailing edge but im worried it wont be rigid enough, im going to be covering the aft section with some sort of shrinking material so i fear if i use dowl it will warp. I actualy dont think i will need much on the spar to keep it from folding though i would prefer to over build it then under : D, i was thinking i could implant peaces of iether fiberglass rod or dowel going verticly every 4"s, this would help even more with keeping the spar cap from depressing by dispersing the load from just the top of the foam to inside the spar.thanks
michael

[rdwoebke]

This thread has a TON of potential. I'm glad I got in early on this one. I feel I joined into Rip the Bring too late... I predict we are in for a FANTASTIC ride here....

Anyhow, it seems obvious to me you are quite the craftsman. Those ribs and that wing look pretty sweet.... I'd concur on the suggestion of facing the spar front and back with vert balsa (or perhaps even light ply. Looks like you plan to D tube this thing, right (looking at how you have the ribs cut).

Ryan

[FairlyFaded]

lorenkb im going to have the glass wrap around the spar which will do the job of the balsa siding. Im still considering wether im going to put glass on the ribs and if so were, i think it would be a good idea, maby just two strips one running on the top and the other on the bottom of the rib. im not sure if you saw my latest round of pictures, i installed a second spar farther back that will be lightly glassed, this should get rid of any fluter along with the trailing edge. Come to think of it i think just a strip of glass on the bottom and top will do very well. The farthest distance from spar to spar will only be a bit more then a foot. within that distance i dont think there will be much twisting, ill illustrate my idea later, thanks guys!
michael

[flystoolow]

TE can just be a hollow 1/2" tube of aluminium, just like on ultralights. If it sucks in a bit between ribs, it will look good. 7075 tubing is stout and very light.

[lorenkb]

I did see your latest photos. The second spar will not prevent flutter by itself. The rear spar will not be as strong as the main, and will bend at a different rate. This will cause torsion throughout the wing, and can/will lead to flutter at a high enough speed. With the relatively light construction of the wing, that speed will be pretty low.

You need to create torsional stiffness between the two spars, and with only foam ribs connecting the spars you won't have any.

Finally, the fiberglass wrap will not hold a lot of shear, its primary purpose is in tension to keep the spar caps from buckling outwards. If you got fancy and laid the fiberglass weave at a 45 degree angle to the spar then it would take up shear, but be worthless in resisting the buckling loads...

Loren

[Crashaholic]

When this thing is ready to go, make sure to take and post video of the maiden!!

[FairlyFaded]

haha will do. good point loren, so if i understand right your saying that because the aft section of the wing will be less stiff it will curve up earlier then the front will. I could see this happening, but keep in mind, there will be covering back there. From what i remember from my balsa plane days the covering adds a TON of rigidaty in all directions. I could use some guy wires to stop flutter perhaps? I honestly dont think flutter will be an issue considering the max airpeed will probably only be 20mph. of course if i was doing flips....... : D thanks for the support ryan. i think ill put one layer of 90/90 FG on the spar face and another of 45/45, this will remidy both problems you and loren proposed. Hopefully ill have the spar by tonight. one question, the foam spars are not perfectly aligned with one another, meaning some are slightly lower (1/16") or at a slight angle, i have filled in most of the gap with light wieght spakling but i dont think ill get the spar cap face perfecly flush. Im thinking of just using gorilla glue to fill in any gaps, i really like the stuff-its strong as hell, and also it'll fill in any gaps well, anyone have a problem with that? : D thanks guys,
michael
p.s. im off to ACE.

[rdwoebke]

lorenkb im going to have the glass wrap around the spar which will do the job of the balsa siding.


I don't think this will work, because you have the ribs that go through the spar. On the Drela foam core wings (Supra, Aegea), he has a drop in spar that has a foam core and the entire thing is wrapped in glass. But you can just glass wrap between the ribs, and that area of where the ribs are will be weak, so the glass won't do its job here. Now if you instead had a drop in spar, then the glass would do its job as you wrap the entire thing.


i installed a second spar farther back that will be lightly glassed, this should get rid of any fluter along with the trailing

I like the guy above's suggestion of aluminum tubing. How about having the rear spar be a straight piece of metal that goes through the ribs?


P.S, please promise if you try to fly this thing and hurt yourself, your folks won't be trying to sue us for giving suggestions....

Ryan

[DavidB.]

You must tell us where you're getting your cells for $1.75. Is this an ebay special? Are they name brand? Keep up the good work :D

[FairlyFaded]

david-there sony and seem to be nice, the seller sais there good for 5c, ill tell you were im getting them if you dont figure out once iv gotten my lot : D... heheheh.... anyways, im a bit unclear on what you think the problem will be with the spar not going all the way through, if i understand conrectly you think it will be weak were it goes over the rib? maby i could remady this by putting in a peace of fiberglass rod from top to bottom on each rib like so.... remember its going to be light and its not going to be doing flips! :cool:

[waltbald]

Check out the Sky Pup (Google will find it), a rudder/elevator ultralight design from twenty something years ago. It has a cantilever (no wires or struts) wing built with fir caps, styrofoam shear webs and ribs and a light birch ply D tube. Looks like a real airplane and everything engineered by a real live airplane engineer. Fascinating stuff if you have any interest in this thread.

[FairlyFaded]

thats cool! i like it : D, i was looking at the specs, it says wing area-130ft2. Now lets see... my wing will be 10x4 + 2(7x3.5) = 90ft2... hummm smaller then i thought.... :p anyways. The skypups gross wieght is sayed to be around 400lbs, mine should be around 150, so 150/400=.375. The criuse speed is sayed to be 55mph, so if lift is linear (which it isnt) then my cruise speed would be 29mph, thats kindof fast! we will see! so i got my spare caps, they look nice if you ask me, 3 of the 6 have a slight warp length wise of about 1/2" bow in the center. Should i wet them and let them dry clamped down straight? Anyways here are some pics.
I got the spackling sanded down and it looks really nice and flat : D... finaly.
On to glueing them in!
michael

[FairlyFaded]

well because im going to be going to bed soon and i want the glue to be dry by the time i wake up i went ahead and glued in the spar. I went with my intuition's and didnt put in any weblets... (this better not screw me over later). I started out by putting a long bead of glue down the spars top, then i spread it out evenly. then i lay the spar down ontop, i started from one root and put two pieces of tap down under alot of tension in between every rib. I went on like this till i riched the last rib, then i staked one book ontop of the spar cap in between each rib, next i went through the house looking for heavy objects. I found 3 SLA batteries, 1 750watt dc motor, 1 2gallon jug of washing stuffs, 2-5lb dumbell wieghts and.... : D you get the point. i hope it turns out well in the morning!
By the way i weighed all the spar caps for the entire wing, they came out at around 2lbs. So it looks like my wing all up should be a good bit less then 10lbs :D. Onwards and upwards!
michael
p.s. iv been pondering the idea of making the wing a 5 seciton one. The middle being 10' then two slightly angled up 7' secions then two 3' secions at the tips, this would give me more surface area that i think i will need to keep a nice slow criuse speed. More to come on that!

[FairlyFaded]

Loren/Ollie- i reread your post and it is becoming increasingly unclear to me,
you said
I'm not sure if the foam will be able to take the required shear loading (as Ollie pointed out). Some balsa siding on the foam spar would hel pa lot, and shouldn't break the bank
So i take it you think the spar will have problems bending forwards and backwards not up and down? this wont happen because the d box will be very strong in that sense. my original thoughts were that you thought the spar would break verticly, i dont see how balsa sidding would be any better the glass siding for that.... could somone fill me in? : ) thanks
michael

[FairlyFaded]

Lol i hope somone appriciates my humar, but seriusly hows it look? :D

[Wing-span]

I went with my intuition's and didnt put in any weblets... (this better not screw me over later)


I think it will screw you over. You should have designed the wing around a strong spar and not your ribs.

You need an element that is strong in compression as a shear web. Normally vertical grain wood in model AC wing building. And also the spar will need binding to stop expansion.

When a wing spar bends with lift a number of things will happen. The lower spar cap will be in tension and the upper will be in compression. This will tend to try to force the two elements together. Thats why you need the vertical grain wood there. Ply would probably do. Also you may get some local buckling. This is where binding the spar with thread comes into its own, holding the unit together and stopping it from bursting. Look at the following:

D-Box Technology. Lesson 101. Please read. (http://www.airplane-model.com/tech-built-up-d-box.html)

[FairlyFaded]

I apreciate your respons, but i dont think you have completely read this thread,
"And also the spar will need binding to stop expansion."
it was allready stated that I am wrapping fiber glass at 90/90 and 45/45 over the spar cap and down the sides of the spar till it reaches the other side, and the same on the bottom spar. I agree that in a heafty wing one needs to have weblets and the works but this thing is light and dosnt need to cary much wieght at all! also
"You should have designed the wing around a strong spar and not your ribs"
just isnt very valid. The spar is just as strong as if i built it any other way exept when it goes into the rib, the but joint at the rib is very reinforced with gusets and glass runing along them. the spar dosnt have to do with the ribs at all exept that it crosses over them. i may put in the weblets after all though as i too am not sure wether or not the foam will beable to take the compresion load. again my intusion says it will beable to, this is mostly because the wood spar cap im using is VERY rigid, it would take alot of wieght to make it buckle espcialy with carbon on it.
I think to sum my thoughts up, this plane isnt a DLG, it dosnt need to take any large forces what so ever, its not even going to by bungy lounched! iv gotten away with a flat piece of foam for a wing thats was flimsier then a ball of yarn, the reason why i could is because all it needed to do was take off from the ground a criuse around, unlike dlgs and 3d's.

[FairlyFaded]

Everyone who thinks i should put in weblets Say aye, everyone who dosnt say nay.
i hope to see some aye's and nay's by the morning! : D

[Wing-span]

Good luck then. On your head be it.

I was only trying to save your neck. :rolleyes:

[Curare]

aye.

It may sound kind of stupid but there's something to think about. If you're gonna put a person in there, then you're building something that has to be able to carry the loads associated with it, including a factor of safety. If you mess this up you could very possibly kill someone, probably yourself.

Ask yourself if the extra time fitting weblets and making sure that spar will support flying loads and whether you trust it with your life.

TBH I think you're trivialising the amount of effort it takes todesign build an airworthy craft, it's not just "oh, we'll throw the tail there and a wing here, THERE! it's done." As an engineer this scares the living hell out me that you're even considering this without having any sort of design apart from foam and particular wing area.

MS paint does not an aircraft make.

[Wing-span]

My last offer of help.

Spar construction techniques (http://www.badger.rchomepage.com/spar.html)

[Resurgam]

I've been following this thread with a kind of fascinated horror. This is an extremely risky undertaking. Just three thoughts if you insist on going ahead:

1. Yes to the weblets
2. Static test the wing to at least 2.5x your intended load - say 350lbs
3. Put a radio and 100lbs of sandbags in the thing for the first flights and keep your feet on the ground.

I'm not joking.

[rdwoebke]

anyways, im a bit unclear on what you think the problem will be with the spar not going all the way through, if i understand conrectly you think it will be weak were it goes over the rib?

That would be my concern. See, the spars can bend in flight. That is OK, most planes have the wings bend/bow in flight. But if that foam is just white EPS, it might crumble in the bending. Now, you are going to glass wrap it, and hopefully that will keep the foam in the "spar" area from crumbeling (once again, I'm not qualified to really know what will happen with something this size, I'm just trying to explain the theory to you). But at the rib area, you don't have such extra strength. Will it crumble/tear, I don't know. Testing should help you find out though.

BTW, I'd skip the pod on your plane. Just make it open frame out of tubing like an ultralight.

I better not end up testifying in court over this thread...

Ryan

[flystoolow]

Don't tell your mother when you are going to 'test' it for the first time, but give her a hug in the morning , tell her you love her.

[FairlyFaded]

lol well maby this is just my young age but i really dont think this is going to be very risky. My plans are to yes use a 110lb sand bag and make it rc for the first flights. Then i would hop into it and have two people tow it on bikes so i could get maby 5 feet of the ground and test the controls, then if all goes well id start up the motors and take off, of course staying bellow maby 10 feet. im not about to go jump of a cliff! Also if i started testing it at higher alt. i may put in a shoot, i like my life, i dont want to loose it : D
Wing span- i really do appriciate your help, i just think your over desigining the thing is all, the only thing that bugged me was that you hadnt read what i was planning on doing before posting saying my design was doomed to fail :D, please dont leave! lol, so i think i will put in some virticle weblets consisting of fiberglass tube running from top to bottom. this awta help alot. thanks guys!
michael
p.s. why should i tes it to 350 lbs, just curius? if all im going to be doing is taking of and landing at least with a "weak" wing then wouldnt say 200 be fine? i think this spar will be way stronger then it needs to be : D.

[FairlyFaded]

anyways enough of this saftey stuff, on with the design. For power my original plan was to gear 4 motors together to spin a large prop (45" ?) but now i think i have a better idea, Split the four motors up, gear them nice and low to spin a prop at 30mph pitch speedish, then make them some foam pods to live in, Glue the foam pods to the wing and glass em up. This would make it so i couldnt break a prop and also i wouldnt need some big goofy lookin landing gear. Also gearing 4 motors to handle that much tourque could be a nightmare, how do you guys like it? 4 pods 30lbs of thrust each. sounds good to me.... : D

Also im going to go with a 30' wing going from tip to tip 2.5x3---3.5x7---4x10----3.5x7-----2.5x3, this would give me a bit more wing area (15 ft) and also a more stable wing. So with a wing this big how long should the body be, im sure 20' would be fine but what would happen if i made it shorter? id loose alot of stabilaty correct? thanks guys!
michael

[DavidB.]

You really can just scale up or down any known design and you'll be safe. I would look at some the HPV (human powered) designs for inspiration. Of course you'll have WAY more power and be flying about twice as fast so you're wing area can be 3-4x less I would say. Just make sure you wear a helmet and fly when there are no gusts :)

Also, are you going to use several RC systems for redundancy? If it were me, I would have 2-4 DX-7 systems scattered around the aircraft with 1-2 servos per control surface with maybe a split rudder in case one system failed you would still have rudder control. It would also be smart to split the batteries up, but maybe still run wires out to the individual system packs to maintain charge. This would be absolutely bullet proof. The only weak link would be the transmitter, I'm not sure how to add redundancy to that?!

P.S. I can't find your source for the batteries, ugh.

P.P.S If you're successful, this may well start a new hobby of building ultra cheap aircraft.

[georgebinns]

I've just found this thread and I've been in stitches reading it from the start! At first I thought it was a wind up but now I'm rooting for you! :D

I've been as aircraft engineer for 32 years and a model aircraft pilot for over 37 - You are trying to do what most modellers only dream of so I hope you succeed - good luck!

In my experience full size aircraft are generally massively over-engineered with a huge safety factor built in. Don't get me wrong, when I'm flying on holiday (vacation to you guys) I'm glad of that fact, but the truth is they could be much more simple and still fly without any problems. There are lots of reasons why the aircraft industry over engineer their craft but mostly it’s to increase profit! ;)
Look at the Russian aircraft industry - for years they were telling us that their fighter aircraft were rubbish because they used basic construction methods - things like welding items instead of casting etc. etc but when the Iron Curtain came down we realised that they were every bit as good as ours if not better and MUCH, MUCH, MUCH cheaper to produce.

How long do you think it will be before you are ready to test fly your machine?

[FairlyFaded]

Hehe, another protagonist! I was looking a bit at some pedal powerd stuff, there awsome! i wonder if there spars have weblets? LOL, my guess is yes. So i have started putting in the weblets and it is a total pain but what must be doen must be doen. I have doen 10 of the 30, here are some pics, i think these will beable to stand a ton of presure. i was thinking of using RC stuff just for when its RC, then when i hope in it ill probably switch to control line pull pull set up. I have a few new ideas in the works, heres one for some small alerons to help level the wings out.
David-i agree that one can just scale up an allready working design, but come to think of it, look at what we have in rc foamies, i think just about anything can fly made out of foam, theres no way this wont work! : D

[FairlyFaded]

hey george, im glad you have faith! lol well these damn weblets are slowing me down but im sure ill be doen with the middle wing if not the whole wing by the end of this break, i may see if some of my friends want to help in the nonskilled labor department, such as sanding... :D i can amagine what you say is correct about production planes, i mean if 1 out of 1000 of theirs fails thats going to be a big stain on their company, i dont think ill have to build my plane to such high standards : D, oh yeah and does anyone know what the FAA would say if they knew i was doing this. It really bugs me that in the us the gov. seems to be against the production of any home made vehicle. One cant make an electric go kart and drive it on the streets, isnt the lame?!?! i guess its to protect the non practical people in this world... well im off to go put in more weblets, : /. More to come!

[rdwoebke]

I have no idea what you are doing with those rods in your ribs...

Anyhow, if you are going to go with ailerons on servos, I'd just stick a battery, receiver, and servo in each wing tip control the ailerons. You won't want to run wiring for 10+ feet to power an aileron servo anyway, and this would be simple.

[lorenkb]

Now that its' comfirmed that you are thinking of getting in this thing, I have mixed thoughts. On the one hand I really like the way you are actually following through with the idea, and on the other hand I can't help but think some more knowledge would prevent possible disaster.

You have a light density foam with low strength as your spar cores. On small RC aircraft this alone is fine. As the aircraft sees more load, you can see that proven models use higher strength methods (balsa, high density foam, augmenting foam with structure such as weblets, etc.) Now you are talking about the loads required to loft a human, which are much, much higher.

My comments on balsa siding to help shear loading are not in reference to the spars bending for/aft. You have an upper spar cap in compression, and a lower spar cap in tension. This effectively creats a large shear loading in the spar core (travelling in the direction of the spar's length). Your only resistance to this load at the moment is a light density foam that has very poor shear resistance for the load you will be applying. The balsa siding comment was a "quick fix". The ideal would be to use balsa cores or add weblets, or possibly higher desnity foam. I honestly can't make a suggestion that you should base your life on... I haven't dealt with the loads that you will be encountering, nor have I gone thorugh and calculated the loads you will be seeing.

Also, I mean this in the nicest possible way, but you need to do more research. Instead of guessing at the speed required for flight, calculate it! I assume you are using an airfoil of known performance; find out what speed it will require to fly with your given wing area at any particular angle of attack. Find out exactly how much you think the plane will weigh ready to fly with you in it, and build a seperate set of spars (mock-ups) and test them to destruction. If the spars alone will hold up to the weight of your aircraft + a safety factor, then you know you aren't going to have a failure in flight.

Your comment of "enough of this saftey stuff, on with the design" is contradictory. Design IS Safety. It's the entire reason why there are degrees in aircraft design. I don't mean to sound like a snob or anything, but I've seen what a spill at 30 mph on asphalt will do to a human, and it's not pretty. Add to that sharp bits of carbon and wood, and safety should be the first and last thing you think about while building this plane. Keep in mind that a lot of the great pioneers in aviation lost their lives in realtively low speed crashes... learn from their mistakes and use the knowledge that they hepled to develop.

Relating to design, your question about fuse length: specifically, what distance to put the horizontal stab at. This is determined by the need for stability, which includes how big your horizontal stab is, and how much moment your wing is creating due to lift. This should be calculated, not guessed at. At the very least, choose an aircraft that resembles the one you are building (make sure it was a good plane!) and use similar proportions.

Lastly, on your comment about the covering adding torsional strength: Yes, it does add a fair amount. However, it alone won't be enough.

OK.. I think I've rambled long enough for now...

Loren

[lorenkb]

As far as I understand weblets, what you have done aint them...

Weblets run full length down the spar, but do not penetrate all the way from top to bottom spar cap... they aid in keeping the composite spar caps from buckling.

What you have added will help a tad, but will also create stress concentrations...


Oh yeah... i worked on a HPA for several years as a volunteer (the Raven, based in WA). Spar cores were full depth honeycomb, capable of withstanding tremendous amounts of compression. Spar caps were very thick pure carbon. Spar failures were always a problem, as the plane was built right on the edge of not being strong enough to fly.

Loren

[FrogChief]

Oh boy...this IS getting good! :D

Be sure to test the plane on a soft grass field, wear a helmet and be safe.

[Crashaholic]

wear a helmet

Wear a helmet cam ;)

[hohensej]

one of the biggest reasons (besides just having a margin) for testing to 300+ is that your load factor increases with bank angle. So in other words, If you plan on turning your wing is no longer making just 150lbs of lift. Now start adding gusts and things to your weight and you will see that there is alot more to this then just planning on 1g level flight. I agree you need to run some numbers before you continue...

[georgebinns]

I wouldn't bother with any conventional control systems, they will just add un-necessary weight - be the first to actually fly in a radio controlled aircraft!!!! :p
Just use your normal radio gear - you won't have any range problems during flight! :D

[webguyjv]

MANY people have posted in this thread now, imploring you to think about safety ONLY -- I'm concerned that you're not taking this seriously :confused: :confused: :confused: :confused:

I know that you really want to move on this project and get this plane in the air. That said, a good friend of mine has flown on the slope with you and he enjoyed your company. For that reason, I feel it's kind of important to once again implore you to be totally comitted to safety on this project.

I wish I were your parent because I would insist that you make this plane a very large RC airplane, and load it up with a crash test dummy, and fly it MANY MANY times before you ever even consider setting foot inside of it.

I don't want to be harsh, but this thing could very easily kill you.

Please do as so many others have said and be extremely careful with this project.

John

[FairlyFaded]

I think this awta do for saftey
http://cgi.ebay.com/Antique-Willson-motorcycle-or-aviation-goggles_W0QQitemZ170082669044QQihZ007QQcategoryZ12 QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
and
http://cgi.ebay.com/Vintage-Aviation-Motorcycle-Helmet-Cap-with-Goggles_W0QQitemZ110093137452QQihZ001QQcategoryZ36 076QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
lol, anyways, my weblets are not conventional by any means, but i think they will work. The pieces of glass i have stuck in there alown seem to beable to withstand a huge amount of compression, at least with foam supporting it on the sides, I think one must feal the wood spar caps to understand my design, these things are really great. There increadibly rigid and this will be even more so once they have carbon on them. The glass rods should keep the spar caps from buckling inwards quite well....

I finally got all of these weblets in, it was quite a bore....
I do plan on flying it on a nice grassy field :D with frawliking dears and squirrels! :)
Loren-I hate to say this but i still dont really understand what you are saying, well i get that you think the spar needs to be stronger but why?.... just from what i understand 2 pieces of glass is alot stronger then balsa is..... maby im missing somthing? Im going to be honest with you, i am smart, but im only 15, so i havnt taken any physics classes yet, my mother is a physics teacher at stanford so im sure she could help in running numbers, but i pearonly havnt been trained.
What kind of "numbers" should i run? :)

well im off to build instead of ponder! lol im just kidding, but really im going with my intuition which has proven itself time after time :), if anyone wants to run some numbers for me i will sertenly incorporate your findings into my design. Thanks guys/and gal?
michael

p.s. uhhh what was i going to write...... Oh yes, should i put carbon ontop and on bottom of the top spar, i think this would help keep it from buckling. yeah, naye?

[FairlyFaded]

another thing, dont you think it would be more productive to tell me how i should go about making it safer, then to just tell me its unsafe! :D kidding, but not. :)

[rdwoebke]

My only question is when do we get to see pictures where you have branded yourself?

:-)

Sorry, another "here goes nothing" reference...

:-)

[FairlyFaded]

lol, im not into that kindof stuff :cool:
just for fun, 30lbs on a nude spar, did fine... probably couldof put 40.
not that this really proves much, just thought id show yall.
my hands are just taping it to keep it from falling btw.

[rdwoebke]

Wow, what kind of foam is that? Just regular white foam?

What kind of wing joiner system are you thinking of going with?

[FairlyFaded]

yup thats just regular eps, i havent desided on a wing joiner yet! : / im going to have the wing seperate into 3 10' sections, so ill need two joiners. im thinking somthing simple like this.
well actualy come to think of it, i bet i could get away with just using a wooden dowel instead of the carbon inner tube.
michael

[dawg]

This is probably obvious to you, but the spar needs to be strongest in the center and not nearly so strong at the tips. So regarding all this talk of yes/no to webs and caps etc, well you could make the center sections really strong and go simpler at the tips.

What control functions do you plan? Rudder, Elevator, Throttle only?

I predict you’ll be very successful and safe with strait ahead flight. Turning is where it could get ... interesting :eek: .

[FairlyFaded]

Lol, yes interesting... i think i am going to use rudder elevator for most turning etc. I plan on instaling a pair of small alerons on the second wing panels. These wont really serve as a means of stearing but more of a way to flatten out the wing after a turn, or incase of a small gust. I agree about making the tips simpler. i plan on basicly finishing the center section, seeing how strong it is and building the tips based on that, of course if its not strong enough then i guess ill start over! im now waiting for the glue to dry on the bottom spar cap.....

[FrogChief]

We should encourage the boy...yet offer as much advice and support as possible. Who knows, he may end up being a great aeronautical engineer one day! :D

I also feel that anyone who is an expert RC guy and / or aeronautical engineer on this board living in California should visit this young man to check everything out. Especially before and during the test flights.

Who will volunteer to help him?

As long as he doesn't exceed 10 feet in altitude during tests, he should be ok. I'm very proud of this kid because today too many are content to sit on the couch and play video games all day. Where as this kid is really willing to make his own airplane.


Stress safety and stay at low altitudes.

Cause I mean lets face it. The Wright Brothers didn't exactly have "safe" gliders by modern standards.

[FairlyFaded]

lol i am now the "boy" and the "kid"... how diminutive : ( haha just kidding, thanks for the support frog, my thoughts are much like yours if i keep it below 10' then nothing to terrible should happen to me! =) The second spar caps glue is hard but not cured yet. I went with gorilla glue this time, ill post pictures in a little once i have it all sanded etc.
michael
p.s. today has consisted of me laying up a part, leting it dry while searching rc groups. laying up another part etc... very productive.

[FrogChief]

lol i am now the "boy" and the "kid"... how diminutive : ( haha just kidding, thanks for the support frog, my thoughts are much like yours if i keep it below 10' then nothing to terrible should happen to me! =) The second spar caps glue is hard but not cured yet. I went with gorilla glue this time, ill post pictures in a little once i have it all sanded etc.
michael
p.s. today has consisted of me laying up a part, leting it dry while searching rc groups. laying up another part etc... very productive.


No offense. To me just about any teenage person is a 'Kid."

Just be very careful and good luck.

-Sean

[Kirkgh]

Michael...Michael...Michael, my friend...it has been awhile. I see you are as busy as ever. Sorry for the delay in chiming in here...The last time we flew together at Coyote Hills you told me you were going to work on something bigger...I had no idea, I am impressed!!!

Let me say to everyone following this thead...if anyone can do this, Michael is the one. That said....

Michael, we have a little group over here in the East Bay, the "East Bay DLG Brain Trust". We get together about every two weeks to build planes and help others finish projects. I am sure that if you needed any help or wanted to pick a few brains any of our very generous members would be there for you. Just say the word.

Oh, and by the way...please, put me on the guest list for any and all test flights. I would be honored to help document the testing with photos and/or video.

Kirk :cool:

[FairlyFaded]

Hey there, thanks for offering your help, and for the compliments! i will put you at the top of the soon to be made list for the test flight : D, if i ever need any help other then rcg (which allown is a huge help) i will call on you and the "east bay dlg brain trust" : D.

The wooden spar caps are in place and glued down, now its time to carbon them, this is gona be fun!

all up wing weight ATM: 3lbs!
pictures soon to come!

michael

[waltbald]

You want to run some numbers? Let's get started. First number, Gross Weight.
Fill in the blanks and add them up.

prop _________
motor _________
motor mount_________
motor controller ________
batteries _________
fuselage ________
tail section ________
landing gear _________
wing ___________
pilot or other payload __________

total __________

This will tell us a lot.

[singlestick]

What you are doing is definitely not structurally sound. The spar webbing needs to be continuous and un-interrupted by the ribs. A spar must take bending AND SHEAR. If the shear webs are not continuous then the spar might as well not have any. Your ribs make discontinuities in the spar that no amount of reinforcement will fix. Remember the weakest link theory. A beam can't take bending if it can't simultaneously take shear. The shear forces in an aircraft wing are significant. With your construction technique wherever you have a rib you can't have a continuous shear web. No shear web means no bending strength at that point. This one is a certain widowmaker.

I suggest you take-up smoking and drinking and get a motorcycle... You will live longer.

Consider contacting the local Experimental Aircraft Association chapter. You'll get a lot of good advice that you won't get here. One of their members is bound to help you learn the basics by letting you help them build an airworthy aircraft. You are also bound to get several free plane rides.


http://www.eaa.org/chapter/chapter_locator.html

http://www.eaa62.org/

[sekollera]

Your design looks a lot like a Goat air-chair so why not build that documented design? It has a 36' span and larger chord, ie, a much lower wingloading...

http://home.att.net/~m-sandlin/goat.htm

/Adam

[hohensej]

This is a really good idea, those guys build their own planes and many have years of experience. also they can help preflight your plane, may RC people dont have experience with this size plane but the EAA guys would be a good judge of flight worthiness

[FairlyFaded]

Lol, i realy cant stop laughing at some of you guys, its like you seem to think if i hop into my plane a giant knife will come and decapitate me before i even get off the ground! im sorry but i really think your underestimating me and my spar :D Im going to be taking saftey precontions dont you worry about me, worry about if my plane will work or not. Anyways i carboned the spar tonight, is it just me or is the combonation of carbon and wood really beautiful in a strange way? anyways, all went as planned, i maid a nice little roller for the spar strips, its the perfect size. enough talk on with the pictures....

michael

p.s. that goat plane looks awsome. very much like my plane but mine will be much lighter, keep in mind im not a very big pay load : ) 110lbs.

p.s.s. If this thing works (which of course it will :D) there is going to be such a huge "i told you so" list! :p

p.s.s.s. we had some guests over so i had to pick up shop and move to the living room :eek: :D

p.s.s.s.s. the wing is upside down in 2 of the pics, its not a really weird airfoil.... :D

[FairlyFaded]

Here are some numbers.
Props: 4(20ish")
motors: iether large outrunners or large inrunners: around 5lbs
esc: cheap chinese things on united: less then 1 lb
motor mount: ply/glass nothing fansy just butting up against a foam pod. less then a pound
Fuse: carbon/glass 3" tube, probably only a few lbs
Tail: conventional tail nothing fansy, probably built like my wing. less then 1 pound
landing gear: single wheel- round a pound
wing.... less then 10lbs
batteries: 200 18650 lion cells 20 lbs
all up wieght 50lbs, with me 160lbs.
Go run some numbers : D thanks!
michael

[reylf_gnijieB]

Michael,

I wish you the best of luck, however, it seems you have neither the design background nor propper attitude towards safety to make this a successful project.

1) You don't see any need to design for greater than 100% load! A static structure such as a bridge usually has a minimum of 30% safety factor in the design. In addition, you do not even have a clear idea of what gross weight will even be:
"Fuse: carbon/glass 3" tube, probably only a few lbs
Tail: conventional tail nothing fansy, probably built like my wing. less then 1 pound"
These are just wild guesses.

2) You don't understand the function or importance of shear webs. What you have added are definately NOT shear webs.

3) You put a piece of foam in a vise and pushed on it with less than a 12" moment (physics term, ask your mom) and take that as proof of strength. Try doing the same from 12', or even 4' and see what happens. The load of a spar is much greater at the root. Good designs usually have a tapered spar so that weight can be saved at the tip, and added at the root where needed.

4) Your ideas on wing joiners are totally inadequate. At the least, stay with a one piece wing.

5) You believe that by staying close to the ground you will be safe. My 5 years as a hangglider pilot, and life-long interest in aircraft have taught me better. Altitude is safety. You can only get hurt when you contact the ground. Otto Lillienthal died making very low gliding flights.

I have 40 years experience in modeling, 35 in R/C. I studied engineering in college. I have done professional fabrication in wood, metal, and composites (bicycle and motorcycle frames, racing cars, boats from 8' to 900', etc.). Do not scoff at my,and others, well intended advice to keep you safe.

Richard

[Resurgam]

We aren't worried that "a giant knife will come and decapitate me before i even get off the ground!" - we're worried that you will get off the ground, get 50 feet high, hit a gust, fold the wings and break your neck.

[DavidB.]

all up wieght 50lbs, with me 160lbs.


You must be joking right? 50lbs all up weight is impossible. I hope you have success, but that's not even close to a legitimate weight. Just the motors/wiring/controls/battery will weigh that much if not much more. For reference, the electricppg weighs over 50lb I believe, and that's just the backpack..... Oh, and he's using lithium polymer cells.

[Ollie]

FairlyFaded,

For this project, you don't have enough smarts and you have way too much ego. You will hurt yourself and your mom, in my opinion.

[webguyjv]

The previous four posts have all been ones that focus on safety. I hope FairlyFaded will take these to heart.

Further, I hope he'll invite his parents to read this entire thread. I'm pretty sure if his parents knew that he was designing a go-cart with a jet engine, that he intended to drive on Highway 280, his parents would get strongly involved. :eek: :eek: :eek: :eek:

He needs everyone here to uniformly state that he needs to think about safety ONLY. Everything else is just a pile of foam, carbon fiber, wood and glue -- it doesn't have any value in his life!

Personally, I have no idea why he completely scoffed at my suggestion that he design this plane any way that he wants, and then use it ONLY as an RC plane, loaded with a 150 lb crash test dummy, and fly it as many times as he can, for as long as he can. I think time will tell if his design works. If his design fails, only the crash test dummy will die :)

Happy (safe) flying ;-)

John

[FairlyFaded]

man this is getting interesting. Can you please stop worrying about me, im my wings arnt strong enough im not going to take it to any high altitudes, comon its that simple.

Anyways im starting to feel i should just stop posting pictures of my build even though i think they would be fun to look at, it seems no one pays any attention to them but just goes on to post how crummy my design is and how its doomed to fail...

Again *if* this thing works, oh lord there will be such a huge i told you so list.

Heres the latest round of pics, got up this morning, glue was dried on the carbon it looks very very nice, But who cares if your so sure that my wing is going to fold in right?!?! btw i went with two layers of carbon on the top.

Could somone please explain with a diagram the shear load idea on the spar, im not saying you guys i wrong i just dont undestand the consept. thanks.

here are the pics.
well as it turns out you cant see the little squre of presure i was talking about in one of the pictures, oh well, point was i shoulda glued the carbon on befor i put the wood on, whydidnt i think of that?!? it turned out fine though so not to worry.

[FairlyFaded]

hey webguy, i value your opinion on testing it with rc stuff, once this bad boy is doen ill probably do that, But Can somone explain to me how rideing in a plane 5' off the ground with people towing it at less then 20mph is so dangerus, or maby it isnt?!?!? : D
michael

[Resurgam]

Ah, in post 75 you were talking about an electric power system. Now it's a hand tow at low altitude. That does seem relatively safer (and a lot cheaper), but have you really thought through all this?

[Fouto]

Hi Michael!

I'm ending my MSc in Aerospace Engineering and have been in some SAE AeroDesign type of events.
First of all, you should value what older people are saying here, specially the ones with an engineering background. You know, I'm young too, I have promissed myself I will build a "flying machine". However, you cannot, i repeat, you CANNOT expect to do something like this and fly it safely.
It's not a question of "If it works...". Engineering is not that. Learn, learn, learn then learn some more and then you will KNOW if it works, instead of wondering.

Second, regarding safety, I can guarantee you one thing: image you're hit by a car at 20~25 mph. Do you think you'll be ok?? Having a plane crash at 20 mph and 10' or so high may not sound like a harsh thing, but it'll be way worse than being hit by a car at that speed.

Oh and remember, having a "few pounds" fuselage (which is ridiculous, add another zero to the right and even then it'll be light) will only avoid you from getting a cold from the breeze, because during a crash, it can shatter to pieces and pierce your body in nasty places.

Not trying to scare you. I'm just giving you an idea of why a plane can take years to be design and built, instead of a few weeks. There's just a lot to think about.

But may this experience give more joy to actually study things on planes, learning about them, and then designing a great plane for you recreation ;)

Cheers!

[Crashaholic]

He has been warned many times. I say back off with all the safety warnings and let's enjoy the ride :D Remember... lots of video of the flights ;)

[rdwoebke]

Could somone please explain with a diagram the shear load idea on the spar, im not saying you guys i wrong i just dont undestand the consept. thanks.


http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/rc_aircraft_design/shear_webs_in_model_aircraft_wings.htm

You do have shear webs in your spar (the ribs themselves and then the foam between them. The question is if this material is strong enough to serve thier purpose. I suspect with the glass wrap that you are planning on doing might be. But then you have the area of the ribs themselves, and I'm not sure the foam there will be strong enough or perhaps the spar could buckle. The Supra has a foam core spar too, but it has a fully wrapped in glass (on a 45 degree bias) aka no ribs where there is not wrapping.

Perhaps as a test of strength, you could support the spar at both ends, then hang from the middle. I mean, you would not hesitate to put your planes on thier wings and then hold the thing by the middle of the wings, right? Or heck, you even hold a DLG by one of its wing tips.

Ryan

[FairlyFaded]

What is still unclear to me is why people think my spar is bad,
I see one good reason and that is what ryan just mentioned about the area were the spar enteres the rib, i cannot put glass on the sides of the spar here which could make them weaker, then again they do have foam and glue on all sides....

So maby instead of saying my design sucks (ryan you and others are exempt because you are explaining the problem) you could think of some clever ways of fixing it, Im sorry if im sounding condisending here, i know i know alot less then alot of people about physics, but i wish thouse people who knew more then me would pipe in more.

So so far i only see one fault in my spar and that is were it enters the rib and that being a possible weak spot. anyone have any ideas for fixxing this? maby some cleverly positioned glass rods.

Anyways, my plan is to have it be electric, but for the first bit of testing i will be probably towing it not using its own power.

On the fuse. im thinking of making the body all out of large carbon tubes sortof shaped in a very curved spoon. I will sit in the spoon and if i crash (which indeed would be bad and probably wont happen) i could sortof "hop" out of the spoon or more get forced out. this would make me just go flying forwards onto the grass i was flying on, and comon, i have suffered far worse mnt biking accadents then that.

Another thing, do you guys not get the idea of the fiberglass rods? i think they are very clever, and make the spar much stronger against buckling. They also help to prevent the top layer of the spar from shearing off from the bottom layer.

So how do you guys all think im gonig to hurt myself, i want to hear and it might even be a bit funny!
1. wing fold?
2. maby to sharp a turn at to low alt.?
3. hmmmmmmmmm

[rdwoebke]

So so far i only see one fault in my spar and that is were it enters the rib and that being a possible weak spot. anyone have any ideas for fixxing this? maby some cleverly positioned glass rods.

After you do your glass wrap, how about cutting into the ribs on the back side of the spar, and inserting a piece of say aircraft plywood. This plywood would be as tall as the spar (aka flush with the very top and very bottom) and extend out on both sides of the rib. You could attach the spar there and then do glass wraps on the areas it extends out past the rib. You would have to be careful not to mess the alignment of your ribs up that much, but I don't think it would be terribly difficult.

This is just an idea. I don't know if that would help a lot or not. At least with a wing like the Bubble Dancer (where the ribs go through the spar like your setup) the ribs and spar core are balsa, so they are relativly strong considering the plane is just a model that weighs ~40 ounces (of course, it is designed for 150 pound load on the tow).

Ryan

[lorenkb]

Can you please stop worrying about me, im my wings arnt strong enough im not going to take it to any high altitudes, comon its that simple.
...
it seems no one pays any attention to them but just goes on to post how crummy my design is and how its doomed to fail...

Again *if* this thing works, oh lord there will be such a huge i told you so list.


No, the worry is well founded, and is BASED on your pictures and descriptions. You have multiple aeronautical engineers and engineers in general advising you of your wing's shortcomings for a very good reason.

The last thing you should be thinking about is an "I told you so" situation. This isn't some contest with a prize, this is you gambling with your life. Don't believe me? Go do some research on how many poeple died in the early days of aviation. They were guessing a lot too, and they payed with their life. There are excellent books and orginizations that you could consult and learn from instead of relying on your intuition.

You are callously ignoring people with a lot of experience who are only concerned for your safety.

Oh, and a reality check... you say that it can't be that dangerous at low altitude and low speeds. Would you be comfortable jumping off a two storey building? You're "only" going 25 mph when you hit the ground from a fall of that distance. Now add in the fact that there is an aircraft worth of mass and sharp pointing crap (from stuff breaking) hitting the ground along with you.

I am all for you building this plane, and applaud your efforts, but when you ignore the warnings and advise of many people who know a lot about structures and flight in general, you need to to realize that you your ego is getting in the way.

Loren

[FairlyFaded]

Im not ignoring the tens of posts saying im going to die, also, im quite sure it wont be going 25mph, less then 20 i think is more lickly, i have jumped off 1 story roofs, so if 1 story is more like 15mph then it shouldnt be to big of a deal, again my spoon structure should save me from pointy carbon spears.

I HAVE been listening to what people are saying, this is what i have heard.
1) im going to die
2) my spar is to weak for no reason
3) the reason my spar is to weak is because it is based around foam and (even though i have glass inside of it), and the spar rib delema.
4) nice project!

3) is the only really usefull post im getting here, there are only like 3 people here telling me WHY my spar may be faulty, thats you ollie and ryan, I dont fully agree with any of you because i think the foam and glass will be up to the job, we will see.

So everyone whos coming in here posting your going to die, lay off it, i get the point.
See if i were you i would have the same reaction that this is just some crazy kid, but the people who actualy know me in pearson mostly think it is reasonable. You have to meet me to relize im not some moronic fool who is going to hop into a plane that wont fly.

That said can we have less talk about the fact that my planes going to be unsafe, because there is no way you are making me stop building this, even if it may cost me a few bones. Why not use your years of experience that you say you have which makes you so much wiser then me and tell me how to build the thing right? :D

On the i told you so thing, if i were you i think i would be saying that itll never work in part becaue of my ego, so i think the i told you so situation is quite valid... if you know what i mean?

So anyways, i have the bottom carbon glueing atm, next step will be cutting out the 30 or so glass patches for the spar.... ill keep you all posted.

michael

[FairlyFaded]

ryan- so if i get you right this is what your thinking? It seems really invasive, i would like to find a less invasive way of doing it..... hummmmmmmmmmm,
oh yeah and to the pearson who told me my wing joiner was highly insufficient and that i would be better off making it solid, i cant do that cuse how would i transport a 30' wing, do you have any ideas about how i should do the wing joiners? (i think my idea would work personaly : ), thanks
michael

[rdwoebke]

That is exactly what I was talking about. Yes, a bit invasive. Although on the flip side, might be better than having the wing fail in testing and then all that nice work you put into this would be gone...

So far as joiners go, how about doing an upsized version of the Drela end grain basswood joiner? You'll need access to a drill press. The end grain basswood needs to be the FULL height of the spar. Perhaps rather than using basswood, you could take 2 by 4rs and make the end grain blocks? http://www.charlesriverrc.org/articles/supra/all%20PDFs/joiner_build.pdf

Please keep in mind that these suggestions I post come from a person that is not an aeronotical engineer. I'm an electrical engineer, and a poor one at that! :-)

Ryan

[rdwoebke]

I keep toying with the idea of building one of these some day:

http://www.continuo.com/marske/monarch.htm

In a few month's I'll have a basement large enough to build one. Of course, I would get actual flight instruction first (even though technically, this is an ultralight and that is not required). Having a place to fly it would be a concern for me, there are not a lot of flat areas where I could auto tow here.

But dreaming about building one is fun!

Ryan

[FairlyFaded]

lol from what i see aeronotical engineers spend to much time pondering and to little time doing! Lol just kidding, anyways i do have a drill press, im not really sure what that idea is just from the picture, is it sortof like 5 of my idea stacked ontop of one another?

good point that it would be better to have the wing stay strong...
but you know i really think its going to be pleanty strong, with the D box, the spar, the second smaller spar, the covering, and guy wires, i really cant see it folding. IMHO...

[rdwoebke]

They end up looking like this. The vertical grain basswood goes between the spars. The holes are sort of cut at an angle, or like in my case I used a belt sander to sand the angles, and that gives you the dihedral. These photos are from a 2 meter Aegea I built (a kind of mini Supra).

I have no idea what size would be appropriate for a plane like you are building though.... That might be where an engineer with background in determining loads would come in helpful.

Perhaps this link will help explain it better:

http://www.charlesriverrc.org/articles/bubbledancer/PDFs/joiner_V2.pdf

Ryan

[FairlyFaded]

mmmmmmmm i see so basicly instead of using an alu tube id use wood, and one must make the wood piece in segments because you cant make a 1' long whole? i will consider this... the wood would help desperse the load onto the foam and glass.... interesting....
michael

[Wing-span]

FairlyFaded.

You must consider bracing the wing. The spar design is unconventional as it is and I must recommend you brace the wing.

Try Dyneema string from a kite supplier. Two 300lb breaking strain strand either side will really improve the chance if the wing not folding.

To fly with the surface area of the wing I am of the feeling your airspeed will be higher than you expect. The Gossamer Albatross which had much more wing area flew aroung 20 mph.

Albatross (http://www.answers.com/topic/gossamer-albatross)

[rdwoebke]

mmmmmmmm i see so basicly instead of using an alu tube id use wood, and one must make the wood piece in segments because you cant make a 1' long whole? i will consider this... the wood would help desperse the load onto the foam and glass.... interesting....
michael

Well, I'd say you'd have to piece the wood together because you can't find a piece of 10 inch by say 2 feet by 2 inches wide vertical grain hardwood....

I'd then suggest perhaps aluminum rod for the joiners? Perhaps 2 inches in diameter? This is a guess. A few feet long perhaps? Also a guess. Why not look at the plans for a light plane (like an ultralight) and then try to find out what size joiners those use?

The vert grain wood is what carries the loads to the spar caps. You don't want the foam to be involved in the joiner, there is just too much load there, it would surely fail.

Ryan

[FairlyFaded]

wing-span, glad to see you havnt lost hope, lol, yeah im going to use some sort of guy wires, im not sure what type though. the kite string would probably work but i could amgine it has some stretch to it. ill tests some i have. True the albatross went a max of 18mph, but strangly the goat plane only goes about 25, my wing loading with the new 30' wing will be much less with an area of 100'2 then that of the goat, so i can amgine it would fly a bit slower, thus my estimate of <20mph. man is waiting for glue to dry boringor what! also what sort of covering should i use, i know the QF dlg uses this stuff
http://www.mcps.k12.md.us/departments/procurement/MCPSBids/4089.pdf
third down doculam stuff, maby ill just get a roll of that. at 25"'s wide it would be wide enough to span from one spar to the next which is all i really need.

Somthing interesting to consider, the seeker, and then they swyft built by master craftsman scobie putchler both employ the same idea as mine, The combo of a carbon tube and alu outer tube with some sort of lateral belt ontop and botom of the join turn out to be VERY strong. Ill snoop around some more looking for ideas.....

Anyways, what do you guys think about the fact that my wings only 3lbs right now!?!?? to light to work!? lol we will see... Thanks for the input guys!
michael

[rdwoebke]

Somthing interesting to consider, the seeker, and then they swyft built by master craftsman scobie putchler both employ the same idea as mine, The combo of a carbon tube and alu outer tube with some sort of lateral belt ontop and botom of the join turn out to be VERY strong. Ill snoop around some more looking for ideas.....


The Seeker's joiner is exactly like the Bubble Dancer one I posted above, except on the Seeker it uses balsa (and not vertical grain) with plywood facing and the Bubble Dancer uses hardwood (stronger) and even stronger yet being vertical grain. The Bubble Dancer of course has to take more loads than the Seeker.

I suggested aluminum rod rather than carbon rod due to the price. What diameter were you thinking of going with? 1 or two inch in diameter? That would be a pretty expensive carbon rod.

Ryan