Topic: Twin Wall Sloper

Wow Ade ,

    Thats cool m8, well done nice build and only a couple of days aswell ,

                         Congratulations , now i gotta make 1 out of egg boxes and coke bottles , hahahhahahaha   

                                   Bob

ps , nice vid Stu

Nice one Ade!

What was the wind speed? AUW etc?

Now if that had been a proper sectioned Sally she'd have been movin and a groovin like a goodun! 

Wow Ade ,

    Thats cool m8, well done nice build and only a couple of days aswell ,

                         Congratulations , now i gotta make 1 out of egg boxes and coke bottles , hahahhahahaha   

                                   Bob

ps , nice vid Stu

Do you want a sheet to make a bob creation?

Nice one Ade!

What was the wind speed? AUW etc?

Now if that had been a proper sectioned Sally she'd have been movin and a groovin like a goodun! 

Ades weighs about 220g now. Wind speed was I am guessing about 10mph Max often dropping to nothing. The wind shifted west though from the rquired north. While we waited to see if it was a temorary shift we watched the crops in one of the fields, you could see the wind nicely circling the crops. every field showed a different directio around it too. nice thermal, but it was too far away.

Inspired me to get the dslr out, hoping to do a time lapse video soon to see what it looks like sped up .

Stu

Lovely :-)

Saw one like this at the Nats one year, called a Dazi, was internally loaded with led's (at a time when night flying was a real rarety) - very impressive.

Decent correx is a wonderful material, but you do need to get the flutes the right way (and not leave the thing in a hot car either!).

Glass fibre tape (1" wide, parallel fibres) from Staples makes excellent external spars too, if you have enough section thickness to make it an effective stressed skin.

As for the battery, I'd consider the energy ...

I used to arrange Mugi flight packs so that, in the event of an arrival, they would go forward, straight out of the hatch, and not stay trapped in the model (and cause significant damage).

Perhaps use an extension lead to join the battery to the rx, anchor the extension lead socket well (and point it to the nose) so if you do eject the battery, the plugs just pull apart?
(Oh, if you do this, attach 2" of bright ribbon to the battery - you wouldn't believe how hard a pack can be to find in long grass!)

Regards the section, I did also use a length of epp, just to hold top and bottom skins apart, roughly where the spar would be.
Tapered, and only did the middle 50% of the wing's span, but seemed to help (you could bury your cf spar in it, might help survival after you "land"?).  For one I just used 2 small epp cubes, to make sure the skins didn't close up too much and interfere with the servo's.

All good fun.

Nige

Cheers Bob, it turned out ok, I ended up doing my usual trick of over engineering it! 

Pasty, as stu says it came out at 220g, the section is pretty much symmetrical with a tiny bit of reflex on the elevons.

It seemed to go ok in the light lift, I think it was probably a bit lighter than 10mph and the hill is small so I am hopefull it'll be good in light air on most slopes.

It does an odd bobbing thing when I fly it too slowley round the turns, is this a trait of the planform or a trait of my made up section??

Looking forward to building a proper one now! I'll go for blue foam cores with 80g kevlar skins. I may even make a mould for the fuselage pod! In fact I fancy making a mould for the whole thing

Cheers Pasty great little design (although its some way off your proper one!!)

It does an odd bobbing thing when I fly it too slowley round the turns, is this a trait of the planform or a trait of my made up section??

Looking forward to building a proper one now! I'll go for blue foam cores with 80g kevlar skins. I may even make a mould for the fuselage pod! In fact I fancy making a mould for the whole thing

Cheers Pasty great little design (although its some way off your proper one!!)

Odd bobbing? Sounds like hyper stalling, either the cofg is out, you got too much elevon movement or a combination of the two.... and who knows what that wing section is doing... it might have been purely stalling due to low air speed.

Its not a problem on the real deal Sally ... if you've got it set up right of course.

If you get a mould of sorts going, I might have to sweet talk you and get some bits of you , I hate doing lost foam pods... I should do my own mould really  

I managed to get my 180g glass Sally flat field thermaling yesterday (side arm launched), I had written it off for such things after a only a quick test and it seems I judge it way to early... well chuffed!  

The little girl seems to be getting a small fan base  

It does an odd bobbing thing when I fly it too slowley round the turns, is this a trait of the planform or a trait of my made up section??

Does sound like stalls and recoveries - wings can be very benign.

Try flying it slightly faster, may find it loses less height too!

Nige

Yeah I figured it was probably set up/too slow/hyperstall thingies. It was hard to figure out cg and all that stuff in marginal conditions, its blowing nicely now though so off to giver her another fly!!

Well, marginal again, but the bobbing was cg, I had it miles forward. I think I misread Pasties 30-35mm figure on the other forum. I am guessing thats not from the wing LE I was way back from there anyway and have just pulled clods of lead out of it, flies mich better now!

I have the curse of the cheapy servo though, double centering. Need to get that sorted before I can get it going properly!

Well, marginal again, but the bobbing was cg, I had it miles forward. I think I misread Pasties 30-35mm figure on the other forum. I am guessing thats not from the wing LE I was way back from there anyway and have just pulled clods of lead out of it, flies mich better now!

I have the curse of the cheapy servo though, double centering. Need to get that sorted before I can get it going properly!

Wicked! My Guts have settled a bit....but wasn't worth the risk  .

Can/have you reduced the elvator throws? If you can reduce it mechanically, it will help the double centreing, mine doesn't seem to suffer too bad with the elcheapos.

Stu

 Ade ,
                       If you swith the channels so unplug both servos swap them around in the reciever then reverse em , you may find that solves your double centering problem , worked on a few of the SG90's ive had m8,
                         May not work but worth a try

 
                    Bob  

    

Hi Guys,

Regarding the swept back original Correx wing of this posting, where's the CoG placed?  I've done a similar plan-form and want to know how's the best way to start?

Regards,
RH7 Flyer

Hi Guys,

Regarding the swept back original Correx wing of this posting, where's the CoG placed?  I've done a similar plan-form and want to know how's the best way to start?

Regards,
RH7 Flyer

Hi

It was actually quite nice learning something doing this. The way I did it was to use the method on this site http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/mean_aerodynamic_chord.htm

my numbers came out the same as here http://www.inlandsloperebels.com/Calc/cgcalc.html

I didn't included elevons though in my calcs, which was a mistake.

Its only an estimate, it will need tweaking when you fly, but its a start.
edit, Ade did say his way isnt that complicated, but the cg calc site is easy to use.


Stu

RH7 Flyer

As a general rule you want the C of G to be somewhere around 25-30% of the Mean Average Chord. It'll vary depending on layout etc but for this kind of thing its a good starting point.

To find the mean average chord you could do Stu's way or my simple easy way! This is for a wing with a simple single taper. Mark the mid span point on the wing panels (this is the average cord), measure the chord at this position and work out 25% from LE, mark this position on both panels, project a line between the two points, this is your cg position.

Adrian

I think I misread Pasties 30-35mm figure on the other forum.

On Sally its 33-34mm back from where the pod sides meet the wing LE, if you havent got the same size pod as the original you aint gonna get the same cofg

Glad you got it going better 

Ok so I did read it right! I am way way back from there..... Will keep you posted once I get round the servo centering problems....

My pod was just a guess and its around 30mm wide. I cant imagine yours is wide enough to account for the massive difference in position. I'll have a proper measure up tonight but i'd guess at around 45-50mm back from my pod side/LE point! 

Something is defo different as I fly it at around 35mm and its bledy pitch senstive (read tail heavy but thats the way I like it) with only a couple of mm elevotor movement.