Erik Johansson

Hi Mike!

Well it is a problem if the plane is meant to handle both electric and IC power. If one makes a plane purely for electric power, it can be lightened a lot because it doesn´t need to cope with all the vibrations from the IC motor. The german E-Factor is an all-wood electric 2x2m plane that weighs in at 7.5 lbs! If you´re interested in seeing how it´s built, there is a build thread going here: http://www.rcgroups.com/forums/showthread.php?t=295905

Really a beautiful design, but maybe a bit too fragile for my taste. But I just meant to show it as an example of what can be done with a pure electric construction. At least keeping one below 11 lbs should not be a problem.



Picture borrowed from: http://www.f3a-e-factor.de

/Erik

lfalsetto

My Feedback: (10)

Any idea if Gator is up with the cowls and canopies. If not I will have to start on another Giles for pattern next year.

wladkummer

My Feedback: (7)

Hi,

This is my first pattern design. I intend to use ZDZ 40 RE engine. The design philosophy was KISS. Wood and foam structure, hope to get it less than 11lbs.
Sigk...i´ll try to use the foam and paper method.... maybe I use white glue instead of epoxy....like papier marché

I was wondering....fuselage mounted gear vs wing mounted gear? which way would be lighter? (no retracts...remember the KISS)

Hope you enjoy

swlarcham

My Feedback: (1)

If you're gonna build foam cored wings then the Nat Penton Carbon Fibre Wing Struts are definetly the lightest, less than 3 ounces including the wheels/mounting blocks & etc.
His 2-M 8# all wood/foam plane handles well with his set-up.
Look for an article by Lance VonNostrand in the K-Factor in the near future
Eddie

sigk

Wladimir, so you are building your own design, that's great, keep us informed.
About the white glue, I have tried it and wouldn't use that on a pattern plane. It will only give you a soft finish. I know of nothing that gives better result than epoxy. I have tried polyurethane glue and I think that comes closest to epoxy. But the epoxy gives you so much better finish. If you don't like to use epoxy, there was a excellent article in Radio Control Model World august 2003 issue, about using polyurethane lacquer floor seal as an alternative to epoxy. It has very little odor, gives a very hard finish, is non toxic and impervious to glow fuel. Sounds almost too good !

Sig.

sigk

The fuselage bottom is made up from four pieces of foam. This is the one behind F1, covered inside and out with brown paper.
This one needs to be cut with the down and side thrust.

Sig

sigk

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sigk

To make things easy, the second and third pieces are cut for the pipe tunnel before gluing on to the fuselage.

sigk

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HuaChu

Hello,
I am planning to use 1/16 balsa covering all balsa structure wing of tempest. Eventually the wing will finish with 0.7 oz fiberglass.
Is it strong enough?

Thanks !!!

Mike

lfalsetto

My Feedback: (10)

sigk,

I don't think 1/16 sheeting over a balsa structure wing will be strong enough. Remember the wing tube area will be depending on the sheeting for strength. Just my opinion but if you purchase contest grade 3/32 that will be just as light and have the added strength.

MHester

My Feedback: (1)

You're both right. If you are going to paint the wings, then 1/16th covered with light glass is plenty strong. The down side is, it's difficult to keep the weight down with painted wings. It can be done, I've done it myself and Matt K has done it many times, and he is a master at this technique. I actually hit a tree with one that had 1/16 sheeting, laminated with glass and painted....the tree went all the way to the spar, then stopped cold and ripped the wing tube loose from the fuse...taking the fuse with it.....making a nice nose section and tail section, seperated right under the canopy. The wing however, from the spar back, was immaculate......and both panels intact with each other.

But if you're going to use monokote over a built up structure, 1/16 is borderline at best. I use 3/32 and sand the hell out of it.

All that being said, if you do those spars like I showed, 1/16 might be plenty even on a monokoted wing, and you'd save a couple of ounces. But I don't want to be the guinea pig

-Mike

HuaChu

Thanks Guys
I am crazy about spray paint my plane at this moment and I think I will go with the 1/16th and glass it.
It might end up overweight, but...it is ok as long as it looks good

Mike

lfalsetto

My Feedback: (10)

If you do decide to glass it go light on the epoxy. I have glassed several fuse, and what I do is mix west systems epoxy with the 206 (slow) harder. I then thin this mixture 100% with denatured alcahol and brush this over the glass I keep thinning the epoxy so basically I am brushing on verrrrrrry thin epoxy then I sand with 80 grit. the next day I brush more epoxy mixture over it, thinned again I do this for 3 coats and the finish is glass smooth when you are done. All with 1 layer of 1/2 oz cloth.

macro-RCU

My Feedback: (1)

sigk great pic's...

I'll be scratchbuilding a T2000 in a few months, so Mike I'll take your wing modifications too...

sigk

With the foam parts glued on the weight is now 274gr and it seams to have adequate strength.
But definitely not built to hit the ground.

sigk

The foam top is 66gr and is strong enough like it is and doesn't need any support only a former at the front. The rear of the fuselage is so much lighter than my previous T2k I just might have to move the wing a little forward otherwise it could be a little nose heavy.

macro-RCU

My Feedback: (1)

sigk, is there any problem for move the wing a little forward?

Let me explain: I think there are some rules about distances or moments, that is distance from engine to wing (CG), stab to CG, etc...

Is it true?

If there are not rules about, how these changes modify planes performance....

wladkummer

My Feedback: (7)

Hi Sigk,

How much thickness have you used for the foam? Seems about 4-5mm. Is that right?

sigk

macro-RCU I'm only thinking very little here and hardly enough to change the flying characteristics. The thing is, it can be very disappointing having to add weight later. This plane was designed with two servos in the stab and should balance right that way. I will be using one servo mounted in the fuselage. The stab, fin and rudder will be covered with paper which weights only 1/3 of the veneer I used on my previous T2K. Of course you are right about changing moments, CG, etc but I think it's best to leave that to designers.
In the 2 meter plans thread there was an excellent T2K built by Bokuda with the elevator servo mounted in the fuselage which needed weight in the tail. It would be best for my to contact him to know how much the CG changed.

Wladimir I'm using 7mm thick, on the bottom piece it did taper down to 5mm.

bokuda

My Feedback: (7)

Mike: You moved the wing 1/4" forward on the Tempest. Did you put the elevator servos in the stab?

I'm planning on putting the servos in the stab and wonder if I should NOT move the wing forward.

If the elevator servo(s) are put forward in the fuse, would it harm anything to move the wing forward another half inch as was done on some Typhoons that were built? (They were moved a total of 3/4".)

I'm getting worried about getting a cowl and canopy. Radio South is out and can't be sure when they'll get more. Gator has not answered my email recently...

MHester

My Feedback: (1)

Yes, I moved the wing tube forward, but that was more of a function of the CG of MAC on the new wing, not for balance. I also moved the stab forward slightly. I mounted servos in teh tail, but I think it's the last time I do it. It works, but after 500-600 flights, even the best servos develop slop and that's not a good thing for your elevator halves to be tracking slightly off. It can be easily remedied by simply refurbishing your elevator servos about every 400 or so flights, but I fly too much to make this practical. Most normal humans wouldn't even feel it or approach that many flights for quite some time. I have simply become very VERY anal and think I can feel every little thing (key word being THINK).

To address the relationship of the wing position (fore and aft) this most directly affects the longitudinal stability of the airplane. The relationship of the CG and AC of the wing and stab determines a great many things, most importantly the tracking vs manueverability of the plane in question. All designs are a balance, and pattern planes are the most balanced of all. If you tweak it to excel in one area, it WILL suffer in another. The schedules to some extent determine where that balance is most effective. If the schedules require a plane that tracks well at al cost, then you have a plane like a Prophecy. If it requires manueverability at all cost, you have a shorter coupled plane with a larger fuse. Ideally you want to find the perfect balance between the two and go with it.

This is an oversimplification, and believe me, if you have to move the wing forward 2" for balance purposes it won't give up TOO much manueverability, but at the same time if you want to keep your numbers close you have to down size the area of the stab, because again there is a direct relationship between area and the stuff earlier mentioned (I'm trying not to get too technical here).

The T2K had a short tail moment and made up for it with a larger stab. When I down sized the wing, I had to slightly downsize the stab as well. (And now it will snap and spin great).

So keep these things in mind if you want to change things without having to add lead and wonder why the plane is doing something great and then something else not so good.

-Mike

macro-RCU

My Feedback: (1)

sigk you are right....

Mike, great job with take in count moments and flight performance when modify plane... I'm learning too much

HuaChu

What servo extension and what length do you guys use for wing and elevator servos?

Thanks

Mike

MHester

My Feedback: (1)

I use 36" for the elevators, 2 of them.

12" inside the wing panels, 9" to the reciever inside the fuse.

24" for the rudder.

-Mike