Good target weight for a 1m balsa DLG

[cdfigueredo]

Thats a pretty looking DLG, I hope the build turns out well.
You can maybe find light weight balsa online, search for "competition balsa" for example... https://www.nationalbalsa.com/Aero_Light_Balsa_p/116348ct.htm, but depends where you live I suppose...
but in some strength critical areas you might still want to use heavier balsa or balsa ply anyway...
I've found balsa ply to be a very strong compromise between weight and strength.. just go really easy on the glue, 3 ply balsa, alternate the grains, and clamp it well. I used that for the bottom half of my rudder and the wing-tips).
Is that tail boom 100% balsa? is there a fiber-glass rod in there also? or are you going to glass the outside?
I think fiberglass rods can be too flexible, I have them in some kites, and they seem flexy... try to get hold of a wide diameter tube instead of rod. bigger diameter = less flexy.
I have 5mm carbon tube which I am not sure is enough... but the Pug's spar seems less than 5mm diameter tube and seems ok.

My last glider is a sloper with 3mm spar plus a coupe of balsa stringers for extra strength... it seems pretty stiff wing and is also about 1m span, I'll dig up some pics.

one thing can make a big difference in weight is to get the servos and electronics as far forward in the nose as possible, that minimizes how much extra nose weight you'll need to add later to balance it for the CG.
Also you can get away with small lipo battery but still a long flight time... my 220mah 1s lipo battery is only 6g but good for about 40 minutes or so.

I live in Cuba, so online shoping for me...
i am using a 2s 300mAh batetery and 9g servos with a 5V 2A BEC. this is the lighter eectronics i could find.

 

[CthulhuJon]

No, I whish I could have that fiberglass. What I h
it is not fiberglass, i mean this: https://es.aliexpress.com/item/4001214588311.html
View attachment 223638

Those look like they might be strong in tension, but very flexible. Tricky to make into a main spar? Thinking….

 

[CthulhuJon]

I live in Cuba, so online shoping for me...
i am using a 2s 300mAh batetery and 9g servos with a 5V 2A BEC. this is the lighter eectronics i could find.

That doesn’t seem too bad. Maybe in future you can find 5g servos but it seems ok for now

 

[CthulhuJon]

Here is slope glider I made with 3mm carbon spar and two balsa support stringer spars ( not sure of the proper name for them )
but I think you can still make strong wings without carbon. Maybe use more stringers, or sheet balsa to skin part of wing to make it strong/stiff. (3 servos, auw about 130g, 95cm span )

 

[cdfigueredo]

Those look like they might be strong in tension, but very flexible. Tricky to make into a main spar? Thinking….

Exactly, for the main spars i will use hard balsa like the conventional way.

 

[cdfigueredo]

That doesn’t seem too bad. Maybe in future you can find 5g servos but it seems ok for now

yes, it is a very good start point. it should be fine to obtain some nice flights.

 

[Piotrsko]

Everyone needs to "get over" the the idea that lighter is always better. It is, but only for low stall speeds which are not necessarily required. Higher speeds at low induced drag work as well except for those teensey tight thermals that you just can't stay inside of at low altitudes. @cdfigueredo knows his craft exceptionally well and should be able to build a main battle tank that would out perform most penny weight gliders here. Back in the day of 200 gram radio systems, I had a friend with a control line de-converted Junior Nobeler that won duration contests at the local thermal field.

 

[cdfigueredo]

Everyone needs to "get over" the the idea that lighter is always better. It is, but only for low stall speeds which are not necessarily required. Higher speeds at low induced drag work as well except for those teensey tight thermals that you just can't stay inside of at low altitudes. @cdfigueredo knows his craft exceptionally well and should be able to build a main battle tank that would out perform most penny weight gliders here. Back in the day of 200 gram radio systems, I had a friend with a control line de-converted Junior Nobeler that won duration contests at the local thermal field.

Sure man, lighter is not always better, i get that. Also i am doing the best i can with the materials i have. i will figure it out as always, maybe it wont be a contest class DLG but will be fun for me anyway.

 

[CthulhuJon]

Everyone needs to "get over" the the idea that lighter is always better. It is, but only for low stall speeds which are not necessarily required. Higher speeds at low induced drag work as well except for those teensey tight thermals that you just can't stay inside of at low altitudes. @cdfigueredo knows his craft exceptionally well and should be able to build a main battle tank that would out perform most penny weight gliders here. Back in the day of 200 gram radio systems, I had a friend with a control line de-converted Junior Nobeler that won duration contests at the local thermal field.

Thanks Piotrsko, I do agree with you, I know about different gliders and weights for different situations... affecting launch heights, wind penetration, ballasting etc... For me personally, I'm a bit of a noob pilot, and built my first couple of gliders way too heavy for me... flew like bricks. Then I built a decently light one, and it flew much better, and works on a light wind at slope, and importantly for me, flies more slowly while I practice. I enjoy the engineering challenge of trying to get them light yet strong enough.... and the light ones seem to survive the crashes better ( also good for noob). kinetic energy in crash is mass x V^2 so both mass and velocity factor much lower in a lighter plane. So when I ask for good target weight... it comes from my nooby point of view... I could have phrased the question better... more like... i.e. how heavy would be too heavy to be flyable... and what is a good target to aim for, so its fly-ability is decent. based on 1m wingspan.
Seems like the fly-ability question has been somewhat answered in the form of wing-cube-loading, so I'm using that as a guide of sorts.

 

[cdfigueredo]

Thanks Piotrsko, I do agree with you, I know about different gliders and weights for different situations... affecting launch heights, wind penetration, ballasting etc... For me personally, I'm a bit of a noob pilot, and built my first couple of gliders way too heavy for me... flew like bricks. Then I built a decently light one, and it flew much better, and works on a light wind at slope, and importantly for me, flies more slowly while I practice. I enjoy the engineering challenge of trying to get them light yet strong enough.... and the light ones seem to survive the crashes better ( also good for noob). kinetic energy in crash is mass x V^2 so both mass and velocity factor much lower in a lighter plane. So when I ask for good target weight... it comes from my nooby point of view... I could have phrased the question better... more like... i.e. how heavy would be too heavy to be flyable... and what is a good target to aim for, so its fly-ability is decent. based on 1m wingspan.
Seems like the fly-ability question has been somewhat answered in the form of wing-cube-loading, so I'm using that as a guide of sorts.

Very correct explanation. I think a good idea is to replicate the weight of the original model and try to stay in that range. The Falke should be weighing a little under 150g, maybe 200g is too much weight. I will try to lighten it as much as I can. The truth is that my wood is heavier but also stronger so instead of using 5mm x 5mm spars I could use 3mm x 3mm without losing structural strength and saving some weight.

 

[Piotrsko]

Had a diatribe going on but said, naaah. You all can figure it out for yourselves.

 

[cdfigueredo]

Based on the pictures of the construction threads I tried to make a mechanism to disassemble the horizontal stabilizer using a metal screw in the absence of plastic screws.


This is the weight of the fuselage and tail unit + electronics. 128g but i am planing to reduce it to 100g, not sure how but i will.


I have already finished a semi wing with a weight of 23g and I am already working on the next one. I'm not sure how much weight I added the ultracote but I think the final weight of the wing should be around 60g.

 

[Piotrsko]

Great starting point. Learning how to build that light takes time and experience and is something I will probably never learn since I suffer from "That needs to be stronger" syndrome. How does it fly?

 

[CthulhuJon]

Nice idea and execution with the removable tail. Mine is glued on, but after I spent time making the wings as two-part, I should maybe have done something similar with the tail in hindsight. Maybe a future modification if all else goes well...

 

[cdfigueredo]

Mine is done and ready for maiden flight.

223g. Pretty heavy.

 

[CthulhuJon]

Congrats on completed build. looks great. Hope maiden flight goes well.
I'm still working on things.... I just got my tail end pull strings/springs sorted out last night, my first time using spring wire.
I wonder.. is it ok to store them in tension or should the string be removed when not in use?
I have yet to finalize transmitter setup, and do covering.

 

[CthulhuJon]

I didn't make my target weight either, currently 157 all finished with electronics, but without covering or nose weight yet, so will go a bit higher, but I'm still pretty happy with that.
Did you maiden yours yet ?

 

[cdfigueredo]

I maiden mine last saturday and went pretty well. The nose and one od the left wing spars ended broken but i already repair it. it performed well, a bit heavy but at least it flew.
i don´t remove the springs when not using it, 9g servos do the jb pretty well and don´t seem like they are under stress by the force of the spring.
Will try to make a video compiation and upload it later

here is a picture taken from one of the videos

 

[Piotrsko]

The only possible effect of storing springs under tension is that eventually they take a "set" based on the stored position. Worse for home made springs because you don't heat treat in this position. However this is a long term condition after a long time and can be fixed by rebending.

I was hoping for duration times, but suspect it isn't optimized for that, yet. @cdfigueredo : have you ever flown thermal?

 

[CthulhuJon]

Thats a very nice still image taken from the video. . glad it flew ok, and minimal damage
I see you have a throwing blade now. Did you make one or buy one ?