Hi All


I wish to design a trainer plane with engine os .25 fx. I want to to know whether i can make the wings strong enough without sheeting ? i will be using hardwood spars ( 2-3 top spars ,2 bottom spars and le / te spars) .I am also thinking of sheer webs. If I use so many spars will it make the wing strong enough ? Or will it just add weight ?

I also wish to know what are the pros and cons of making steerable nose wheel and rudder control . I think I will never use it because I will take off straight and land straight down, and in air I will steer by using ailerons and elevator. Moreover I will save weight by reducing a servo in my aeromodel.

Please guide me

Thanks

OVERKILL... balsa spars ribs 3 or 4 inches apart (i dont recomend not sheeting LE and TE as wing will wrist in air and no amount of ribs or hardwood is gonna change that, physics of tention and compression...

erm.. tail dragers are in my oppinion easier to land but i dont particularly like making them... nose gear , harder to ream the engine into the dirt but easier to hit the tail on ground simple stuff... id recomend steering on a .25... y dont you buy a kit? y are you bent on making a wing?

For a .25 size plane, you may be able to sheet the center of the wing (over or under the fuse) and not use sheeting along the front edge of the wing. However you will need to use 3/32 balsa sheet between the ribs from the upper spar to the lower spar. This will make an I beam like structure in the wing. I have done it with smaller planes up to .15 and it has worked fine. However with a .25 or .25FX you may get some flex or twist. It all depends on what kind of plane your building. Is it a slow one or a hot fast combat? Hot and fast would require stiffer and stronger.

If you don't want sheeting, you don't need it, but you do need something to prevent wing twisting. If you look around, you might be able to find some of the older plans that show a wing with no sheeting but with 2-3 small spars between the main spar and the LE of the wing. If I recall, the origional PT-40 uses this construction. Also, the Golberg Eaglet is a .25 size trainer with no LE sheeting and only a LE, top, bottom, and TE if I recall. It does have a sheeted center section though. (I built one about 12yrs ago, so the design might have changed since then, I haven't seen one in a while). We flew that Eaglet pretty fast at times and never noticed a twisting problem. You'll want shearwebs, of course. You might consider doing the webs front and back rather than betweent he spars to create a "box spar" type thing. You get more glueing surface area compared to the edge of the sheeting.

As mentioned, you'll want sheeting on the center section, that's where the flight loads are highest.

As a side note, one advantage of LE sheeting is that it forms a more accurate airfoil compared to covering over an open structure. Depending on what kind of flying you're doing that might or might not be important. For a .25 size plane, you can use very light 1/16" LE sheeting to keep weight down.

I also agree that hardwood spars would be overkill. You'd be fine with balsa of a reasonable size, and lighter in the end. Just use fairly hard balsa for the spars.

You'll want a stearable nosewheel, but you can get away with out the rudder if you really want to. However, on the whole, I think you'll be happier in the long run with both rudder and nosewheel.

If you want to save weight, go with a tail dragger, a hitech HS-85 servo will work on a .25 size rudder (unless you are 3Ding), and will weigh less than a nose strut and wheel anyway.

Lots and lots of options. Have fun

still i ask why you dont want to sheet the LE and TE... also sheetign the middle kinda involves sheeting which is exactly what he/she doesnet want to do if i understand original post correctly, just read up on sheeting or pm me and sheet LE and TE youl be much happier when you have a hard landing and the wing is stiff enough not to snap if it nicks the runway.

-edit-

i personaly sheet the whole wing and fuse, makes for better airflow ill post pic of uncovered Kadet Mark II after i take some pics :-)

Why?
- Contruction time is less.
- Weighs slightly less.

Wing warp can be caused or controlled with cheep high-temp covering that you can really cook.

four star 60 doesnt have a sheeted LE and the TE only has a couple of inches of sheeting but it does have an upper and lower main spar with a piece glued between them making an I-beam, two upper and two lower LE spars then of course the leading edge it self and behind the main spar it has diagonal bracing, and center sheeting. the wing is very stiff. so sheeting is not needed if designed and built right but sheeting is easier and faster.

is any one here gonna argue that seeing the dip between the LE and the main spar and ribs ir pretty? sheeting isnt that hard (infact irs really easy) and it adds a lot of strength to the plane, also why would you want to have to do a micky mouse fix job on your plane to shrink the warp out of the wing when you can do it right the first time and be happy about how your plane looks and flies. also this is a trainer if im not mistaken, and a new pilot also correct? that planes gonna have its share of bumps and bruises as theyall do. not sheeting it is basicly asking for a wing failure at a critical time. the 4*60 was DESIGNED not to have the sheeting it wasnet stated that it needed to be there and you felt like leaving it off also, it still has sheeting defeating the whole point of the original question!!! i personaly think that adding 3/16 shear webbing everywhere would be harder than sheeting at least the LE.

clearly if your building your own plane, you want it to look as good as possible or am i the only one who does this??

btw ill take pics tomorrow and try to post em.

Thank you all for guiding me regarding sheeting. I will be making a relatively slow flyer, not speed devils sort. I will be using two main spars, le and te spars all these spars will be very strong I will also use more spars between main spar and le spar. I will also use Sheer web. I think it will do the job strong and sheeting will not be required ?


Thanks for guiding once again and any further information is welcome and thanks in advance

vikas

I will give try to a wing which is without sheeting and strong enough ! and one more surprise. I am not using BALSA at all and i will try all all to keep weight down
I am new in construction and it will be my first venture into aeromodel construction !! I will let you updated about construction along with pics and flying of this model

erm.... no balsa?? i see a plane not leaving the ground in your future...

I agree that complete wing sheeting is not necessary - it will only add weight. I would Spar the top and bottom of the wing to allow wing sheers and also a strong wing joining point (with a dihedral wing, eh). Sheet the leading edge of the wing to the main spar locations - keep light; build to fly. Use film on the wings. Tail dragger or tri-cycle gear? By default you'll have steering if you build a tail dragger, ie, rudder alone or wheel attached to rudder. Control linkage for tri-gear can be little more tight to install but having the extra weight up front usually makes the model easier to balance, ie, models have a tendency to build, tail heavy. IN any event - you need to be able to steer the model during takeoff and landing if for no other reason than to counter act engine torque. Use balsa planks for fuse and tail feathers. One final thought - CHECK BALANCE BEFORE FLYING!

what the hec kinda wood you gona use ply.........the plane will never get off the ground no matter how lite you build it........dude buy some plans.

well i was planning to use japonica which is not as light as balsa but surely within flyin range. I have seen very big aeromods without sheeting. actually it seems to me that spars are easier to fit than sheeting. I will post a pic of a big aeromodel without sheeting.

OK let me know the balsa type ( grain,width and size ) which i should order to construct this aeromodel ( just give approximate idea. no need for accurate one)

thanks

YOu can get away with not sheeting the wing. However I would take some of the advice given and sheet back to the main Spar and then drop on the T.E. and sheet about 2" back there. Plus I would sheet the middle. As far as looking good or not, that is a matter of opinion. Sheeting the whole wing on a trainer is something that I wouldnt do. There is NO need in it besides adding weight.
Plus the sheeting on the center is NOT the same as the sheeting on the rest of the wing. They both serve the purpose of strength but with proper wing construction you can get away with not sheeting the outer part of the wing where the middle sheeting is used for a different kind of strength. The middle is where the wing generally attaches to the airplane and it provides strength for attachment purposes (mainly).

P.S.

Use balsa you will thank yourself in the morning.

P.P.S.
If you dont use balsa use coroplast.

your gonna argue that a trainer with like 11 oz/sq' is gonna be weighed down by sheeting?? mesa thinks no...