Longhshot 4 DLG - Buildthread

[xoration]

First of all nice build thread!

About your questions the airfoil depends on wether your building a right handed plane or not. For the other side you would have a different airfoil and you would also need to put the servo horn on the other side. From the pictures your building a right handed plane.
And yes this has to do with the force at launch. But some DLGs also have a symmetrical airfoil on the tailfin, that really depends...

About the wire don't use kevlar wires or something use metal. If your using kevlar or some other cord you need to be carefull when it comes out of the tail you have to add some plastic tubing or else the carbon is cutting it.

A lot of ppl are using fishing rope (metal) for the wires. I'm not sure how it would be called in the us in germany it's "Flexonit Stahlvorfach 7x7" just google for it and maybe you find out what I mean.

But you can also use guitar strings! Thats what I am currently doing 0.09 oder 0.10 etc. guitar strings they are perfect. They also already have a noose!

And you don't have to immensively retrim the plane what you have to do when you are using some kevlar or whatever cords. The metal from the fishing oder guiatar strings does not care about temperature or moist.

 

[xuzme720]

That's a great tip and a good point about the CF cutting into controls!

Except I think the kevlar/carbon he was using is for bracing/reinforcing the stabilizer mount to the boom, not as control rods.

 

[xoration]

Oh your right. Anyway then just use it as a tip.

Some are using cords for the rudders but I'd rather go with metal strings of sorts. They can't be cut by the CF and they don't need much maintenance.

But that are my 5ct.

 

[Fuchsi1411]

How many A do you need for these 4 servos?

 

[xuzme720]

Shouldn't need very much. 3 or 4A should be plenty unless you are using high draw digitals...

 

[xuzme720]

Oh your right. Anyway then just use it as a tip.

Some are using cords for the rudders but I'd rather go with metal strings of sorts. They can't be cut by the CF and they don't need much maintenance.

But that are my 5ct.

It's a really great tip since I think you're right about most people using either a pull/pull setup or a pull/spring setup. The CF would make short work of even kevlar control line...
I'm glad you brought it up!

 

[pgerts]

..The other point being that I live in Finland and we get some pretty intense winters sometimes. It can get really cold and lipo batteries are not know to handle cold weather as well as say NiMH...

I have a slightly different experience. I am normally using 2s small lipo to the receiver/servos in the winter without any problems. I have not heard of any problems with NiMh for receivers but my own experience is that they drop a lot in voltage when cold and under some load. Another fact is the rating of your LiPo. There is a really BIG difference when cold, but i have not had any problems using my "indoor" Lipos for receivers in the winter - and i live in a much warmer climate ;-)

 

[EraJomppa]

Back! I was in Hanover, Germany for the week and now I'm back and excited to get back to this build. I actually got a chance to fly on a REAL glider It was with one of our german friend at his flying club´s field. Plane was ASK21 for those who know it.



Also I just noticed that a RC event that I was last year is coming up at 25.4. so I want to get this thing finished before that! I made some progress today:


I decided to attach the wing properly, which meant tapping the M4 thread to the pod.
I started by fastening the wing with the metallic front screw and measured the distance from both wingtips to the tail. When it was aligned properly I drilled a 3,2 mm hole to the pod where the screw will come (correct position was directly on the small pre-drilled hole).


After that I used the tapping tool to make the thread.


I checked every now and then to make sure the threads were properly aligned.


First I used the tapping screw with the smaller threads (the one below the other), and afterwards with the one with bigger threads. I don't think this was actually necessary, since it is a procedure for metal threads, but better be sure I guess.


I think I might have been twisting the tool or something since the bolt can pivot. Nevertheless I tried it on and it feels solid with the wing, since the only force really is the pulling force. The aluminium tubing in the wing will make sure the bolt stays upright.


Wing is now attached. Tomorrow I will probably attach the boom to the pod and start working with the servos and pushrods.

PS: Thanks for all the tips! I used the kevlar to secure the horizontal stab mount on the boom, and I will be using metal wires inside teflon tubes for the pushrods, like it was pointed out before
Also I did order some 900 mAh round LiPos from Hobbyking´s european warehouse and I will try them out too. I will see which ones will be best suited for my needs. I might have to get a voltage booster for the servos sake?

 

[xoration]

If your using metal wires, you don't need the teflon tubes (they don't hurt tho)
Teflon tubes are mainly if your using kevlar strings or some kite strings for the rudders.

Not using the teflon tubes saves you some weight

If you are using them don't use them for the whole length. Just like 1cm or something where the wire comes out of the boom.

 

[EraJomppa]

I will run the wires outside of the boom. And if I didn't run them through the teflon tubes they would flex a lot when pushing I think. Those are very thin wires that came with the kit. I will run the wires out of the pod below the trailing edge as per instructions and then I will tun them on the boom all the way to the tail. Again following instructions. I don't feel like trying to run them through the boom, since I'g not going to use a pull-pull or pull string system, just a regular pushrod style, so the metal wire needs to be supported all the way and I can't glue/tape the teflon tube to the inside of the boom.

 

[xoration]

Ah ok. I'm not familiar with that particular build I thought it also has a spring setup where your only using one wire to pull the elevator/rudder.

But ok if you having such a setup go with it! Its best to go with the manual with your first ship anyway.

 

[EraJomppa]

A big gap between updated again, but I ran into some problems... I accidentally misread the instructions and I was not prepared for the CA to set so fast.. I put CA on the pod and started to insert it into the boom and adjust it to a correct angle when the CA set. I was horrified! This was the result:



Afterwards I asked around and tried CA debonder and other stuff, but I finally managed to get the boom free. I had to cut off the fuselage pod but at least I have the boom that I can reuse. Before I will order a new pod though I would like to hear your opinions on the matter. Can I reuse this boom:










I was thinking about using 30 minute epoxy this time to really make a strong joint with time to adjust it correctly. It would also strengthen the cracked area more than just CA would. I was also thinking about laminating a piece of carbon cloth over the cracked part to further strengthen it. At this point Im willing to sacrifice 50 grams of extra weight.

The crack reaches about 3-5 cm but the pod will reach even further inside the boom and I think it would give the cracked area a great support. I have faith that I can still use this boom! If you have any experience with these kinds of things then please advice me, should I or shouldn't I use this boom? I am willing to put extra weight on there in order to strengthen the area as best as I can.

PS: This has really been a disastrous error and was been feeling down for a couple days afterwards. I was worried that I might have made a 250€ mistake, but I hope that with spare parts from horejsi, I can still get this thing into the air without making huge budget holes.

 

[finnen]

I have seen a lot worse things repaired on bicycle framse, and those take a lot of abuse. I'm sure with epoxy and a layer or two of CF weave it'll be fine. Don't overdo the epoxy, the strength comes from the CF, the epoxy should just bind the fibers to each other. A nice way of compressing CF tubes while gluing is wrapping the epoxied part with black electricians tape, sticky side out, and pricked with a needle, so that superfluous epoxy will be pushed out from the holes.

 

[EraJomppa]

Well, I'm about to order a new pod. It will cost me 30€, which is a lot less than I was initially afraid this mock up would cost me. The guys from horejsi also promised to include some carbon rowing that I can wrap around the damaged area. Great customer service all together from them. In a bout a week or two I will be able to finish the pod and boom, maybe meanwhile I will finish the wing by assembling the servos.

 

[xoration]

I still don't understand how you did get it free? And actually you wouldn't have needed to buy new pod, boom what so ever.
Actually it is pretty "common" to even shorten the boom on high end DLGs.

My DLG is shortened as well. You cut off the boom remove as much in length as you want use second carbon pipe which can fit into both pieces sand it down till it fits perfect it just needs to be long enough to connect both parts.

And then you use carbon roving which you put around the connected booms with 24h epoxy and not much very small amount
and on the outer side when your using the epoxy with the roving you also use paper towels to suck away the epoxy so it gets light and strong.

 

[EraJomppa]

I still don't understand how you did get it free?

Well I didn't take pictures, so that's on me.. So, the pod goes inside the boom, but I hadn't pushed it all the way in yet when the glue set. I used a saw and cut the pod 5 mm before the boom, so I had something to grab with pliers so I was able to fish out all the pieces inside the boom. I used the pliers to crack the pod and pulled the pieces from inside the boom as best as I could, but the procedure was a bit violent and I ended up damaging the boom too.

About the boom length. I had it cut down on exact length that was recommended and I want to build as stock as I can. If I had cut the boom instead and removed the boom pieces from the pod I would have been left with too short boom with too narrow inside diameter and I wouldn't have been able to fit it around the pod. I already cut is so snug that I had to sand down the pod to make it fit.

But I think that is not what you mean. I think you mean that I would have used a separate carbon tube that goes snugly over both of the pieces and connects them together. Couple of reasons why I would not do it. Too complicated and with my skills it would be too heavy and easily breakable. Also it would be heavy I think? But mostly I dont think I could find a proper carbon tube anywhere. And if I did, it would most likely be more expensive than buying a new pod.


Rowing: I have laminating epoxy that should work like a charm. I'll keep the paper towel trick in mind. Also I think someone suggested using electrical tape and taping over it and poking holes to the tape to let the excess epoxy seep out through the holes.
But I'm really not too worried about extra weight right now. I lost the chance to make it extra light when I made the mistake with the CA..

PS. I received 900mAh 1s lipos from hobbyking. Anyone know any good voltage boosters to get the 1s lipo voltage up to 5V? Im not sure if I'm willing to risk brown outs by using just the 1s lipo voltage.

 

[xoration]

Well yes you would use another tube to put it in the inside and its not heavy at all. If your doing it right there is almost none additional weight as the inside tube does not need to be long either.

Thats also what your doing if you break your boom lateron thats how to fix it. Tube in the inside and roving around on the outside.
And yes you can use tape or kitchen foil but I would call that the last stepp after already using paper towels to suck away the epoxy.

The extra weight should not be much you said something about 50g, that would excessiv! You'll only get that if your using lead in the epoxy to make it thicker instead of cotton flocks.

About the Lipo what system are you using? RX/TX? I would use the 1S. I will do that on my next DLG, which I ordered some weeks ago. Its going to be the Snipe, maybe I'll make a buildthread.

But anyway most ppl are actually using or going to use 1S. No additional electronic which can faill. You can read the voltage via telemetry. Servos should be lasting longer.

 

[EraJomppa]

Hmm, yes telemetry. I probably need to get another telemetry receiver though, since the only one that I have laying around is a bigger 8ch one. I was planning on using a smaller 7ch receiver that I have, but no telemetry there. Also I got a small telemetry 4ch, but that is on a quad.

 

[EraJomppa]

Finally

Finally I got past the pod and boom attachment!



Now firmly epoxied together with plenty of 30 minute epoxy.



Now don't get me wrong, it isn't finished yet I will still have to get some carbon cloth and laminate that over the damaged parts of the boom in the base just to make sure it will not break easily. Then it's time to put the pushrods and servos and pretty much then it's done.
Wow, this has taken a long time! But finally I can see the light at the end of the tunnel and as the weather get better and better my itch to get this thing into the air just gets worse

 

[EraJomppa]

Oh, btw forgot to mention. I didn't take any pictures of the setup I had when gluing the pod-boom joint, since I was too worked up to get it done. Basically if you have already attached the throwing peg, you can't just put it on the floor upside down and use the wingtips to get it level, since the peg will lift the other wing higher. I almost fell into that, but noticed it early enough. I used couple of old VHS tapes, since they are all same size and stand sturdily. I put one under each wingtip, and a pair under the tips of the horizontal stab tips. Then I applied the epoxy and eyeballed it until when I gently lifted the tail, the both tips came up and down together. Then I used a 90 degree angle just to make sure I got it right and left it there for solid 2,5 h to cure.