Another Sagitta XC

[Miraj]

Hi guys, another Sagitta XC up for a build log. What a beauty of a machine, i've been asking around on different aspects and which option to choose. I'll be updating my private pages and also this thread.
Sagitta Pages: http://www.silentwings.com.au/index.php?option=com_content&view=category&layout=blog&id=3&Itemid=4 (http://silentwings.portfoxdesign.com/sagitta-xc/)

Modifications:
I collected a tone of mods for this model, but have come to the decision below;
1. Change the counter balanced rudder to a normal one and extend it.
2. Thicken the stab
3. Move the spoiler out one bay
4. Carbon wrap the joiner box
5. Use circuit board on the stab tubing to make it rigid
6. Carbon along the inside of the fuse
7. Spolierons (but thats more RX option)

Started out using Tracfoil to draw out the airfoil, neat little application, I think there are other that are better and have more functions. But I just printed out the plans and grabbed the ruler and went for it.

Cut out the main section of airfoils, 30 in total. (image below) Tips to be done.

Grabbed some hardware yesterday, 1.5mm and 3.0mm ply, It does call for 2mm on the some parts, but i will just use either the 1.5 or 3 depending on the situation when i come to it.

Tailplane is on the menu for tonight, more to come.....

[soarluck]

i have the sagitta 900 and i made the same mods but please explain the circuit board mod ,,,thats new to me
thks

[Miraj]

All that is, just around the back part of the stab inside the fuse the sagitta's get the stab wobble. So rather than soaking the ply in cyno/superglue i use circuit board. The board doesnt wear like ply and therefore keeps the rigidity of the stab.
My Eclipse has it in there, works nice!

[soarluck]

also ,,i have heard that many have used basswood instead of ply for the fuze and claim its stronger and lighter

[Curare]

ahh the beginnings... from little things , big things grow!


Miraj, you've totally lost me on the circuit board, are you fitting this to the areas around the stab bearing tube?

[Miraj]

Curare, yes, that was my method, my Southern Sailplane Eclipse does the same thing, its as stable as a rock.
Also i did forget to mention on the outside of the fuse I was also going to build up some housing, similar to what they do with fibreglass all moving stabs (like the aquila glass fuzz)

[rogerflies]

Is "stab wobble" the same as bellcrank?

If so, I thinks it's a good idea to use circuit board. If not, I don't have a clue what you're talking about.

Roger

[PizzaHunter]

Miraj, have you ever thought about using templates for ribs cutting?
just two aluminium or steel ribs - the first one and the last one(these are templates). each has 2 holes, they are connected with studs. you take balsa plates little larger then ribs and drill them through the template. and then you assemble balsa plates and templates using 2 studs and after that you can make all ribs at the same time. this method is not good for very thin ribs, where a hole in a rib can make is very weak.
I made all ribs in my life using such templates, except BD (laser-cutting)

[rdwoebke]

Best of luck Miraj. I have been in a Sagitta XC build since 2003 (not really working on it currently).

Ryan

[soarluck]

yep ,i get the stab mod now ,,,the width of the vertical fin is thin [1/4 inch] and the metal rod is not very tight threw the brass on my 900 and i get a floppy stab ,,,i did i similair mod by just notching the stabs and put a pc of 1/16 ply on ether side ,,,also i stuck the rod in a orange overnight and the rust that forms on the rod increased the dia a bit to tighten the union

[Libelle201B]

yep ,i get the stab mod now ,,,the width of the vertical fin is thin [1/4 inch] and the metal rod is not very tight threw the brass on my 900 and i get a floppy stab ,,,i did i similair mod by just notching the stabs and put a pc of 1/16 ply on ether side ,,,also i stuck the rod in a orange overnight and the rust that forms on the rod increased the dia a bit to tighten the union
soarluck, rubbing a candle (candle wax) on the rod/pins does the same thing without corroding the metal :)

[Miraj]

Miraj, have you ever thought about using templates for ribs cutting?
Yes, i have had a go at this system before, I must have no done the templates correct and ended up with a mess.
I should give it a go next time around.

[soarluck]

soarluck, rubbing a candle (candle wax) on the rod/pins does the same thing without corroding the metal :)
thks for that ,,,sounds great because the wax likely adds a bit of lube too

[Miraj]

Talking to another rc grouper and the joiner system may need a bit of attention from the standard. With wings this big and anyone bent the steel joiner bar?

It was suggested and I'm all for this as it sounds a stronger system. Rather than have the brass tubing flush with the wing root, have it hang out a 1/4 to 1/2 inch. Ditch the brass tubing in the fuzz and have the steel joiner free floating.

M

[soarluck]

i shouldnt comment because i have the 100 wing but i know that some have also used a hollow carbon rod with a wood core which is stronger than the steel and lighter ,,,read it hear a few yrs ago search username ollie he wrote it and i think it was just called ;;;;steel/carbon rod?????

[Miraj]

Interesting, you get the strength of carbon with the timber flex. mmmmmm thats food for thought.

[Ercoupe Ed]

Good luck with your Sagitta XC Mirag.
I may just set my Gran Esprit aside awhile, and build another XC ship.
I enlarged and drew up a set of what I call "SUPER BIRD" plans.
I built a 13 foot span Bird of Time about 15 years ago.
Flew like a homesick angel.
Unfortunately it got into a HORRENDOUSLY STRONG thermal one afternoon under a huge thunderhead, and spoilers and full down elevator, attempts at spinning it all failed, and it went UP,UP, and AWAY!!!!
Never saw it again!
The top of that thunderhead was probably 30 plus thousand feet
You could have thermalled a BULL DOZER in it

The spoliers on my BOT were big too, spanned 7 wing bays on both wings

Ed

[Miraj]

Wing joiner system, really couldn't decide on which system to use, so ask everyone in RCG. Some good options, but the 5'16 or 8.5mm just didn't look strong enough.
I spoke to friend of mine Peter from RC headquarters, and he has suggested that i go with the square tubing option.
The strength is exactly what is needed and the weight should be ok as well. Plus this system will give me a good look at what is needed for my blanik. It asks for the same setup.
Hurry up Mr Postman!!

[Miraj]

A bit more, the fuse and tail done. Next onto the wings.

[rogerflies]

I'm not a big fan of rectangular wing joiners because they only have strength in one direction. They'll end up getting bent forward on a hard landing. Also, they leave little room for the spar caps if they're centered on the spar.

I was happy with the joiners I made for my XC out of 4130 tubing. I filled the center joiner with a shorter solid rod, but I left the outer joiner as tubes.

That's a mighty nice looking fuselage and tailfeathers!!

Roger

[Curare]

*swoon*

nice work man:)

[Miraj]

Roger
I did think of that and looked at carbon, steel and a mixture, i'm going to use a free floating spar system in it. So if the hard landing ever happens i can just replace the steel it in.
M

[John Walter]

Does anyone know where I could buy that sort of joiner blade in the US?

[atmosteve]

She is looking real nice Steve. Like the idea of you experimenting with the rectangular section Cf joiner, I briefly looked into using some i got from RCHQ on a polyhedral joiner system recently but reneged due to time constraints. I'm a huge Sag fan, I would still like to build one again in the future.
Good weather to your build.

[Miraj]

Just an update, inner right hand wing about 85%
build log: http://www.silentwings.com.au/index.php?option=com_content&view=category&layout=blog&id=3&Itemid=4

[lincoln]

Roger
I did think of that and looked at carbon, steel and a mixture, i'm going to use a free floating spar system in it. So if the hard landing ever happens i can just replace the steel it in.
M
Suggest it may help if you reinforce the fuse where the leading edge will push in on hard landing, then maybe put strong wing retention system to reduce bending of the steel. If you've got full sheeting of the inner bays, maybe put a strong spring holding the wing together near t.e. That way, even if the spring is not SUPER strong, you've got nearly the full chord as "spar" depth. Of course, you don't want that spring to be strong enough to bust the wing. Bending the joiner would be better.

Carbon rod sounds like invitation to disaster if not well taken care of and overbuilt. I've heard, and it makes sense, that the carbon is vulnerable because it has little strength across the fibers. The wood inside would only prevent buckling or collapse, not change the structural behavior otherwise.

[Miraj]

lincoln
that makes sense, the reinforcement in the front is a must with the flat bar. But I didnt think of the rear spring. I'll have a look this evening.
M