Longhshot 4 DLG - Buildthread

[EraJomppa]

After flying couple of scratchbuilt gliders past year I decided I wanted a proper glider. DLG seemed the best way to go for me so I chose Longshot 4. Im more of a scratchbuilder guy and I like to go cheap so this is something way different than what Iv done before. Previously my most expensive airframe Iv actually bought was Tek Sumo at 20€. Longshot cost me 250€ for the airframe only, so it´s about 12 times more expensive

When it came to servos I decided to go to my LHS and see what the more experienced glider guys would recommend. I bought the Hyperion HP-DS09-SCD servos. They are 7,45g, carbon poly gears, digital servos. Price tag was 29,50€ per servo. The experienced guys referred to them as the "cheaper" stuff Then what do they call HXT900´s I wonder?!? Well since I already spent 250€ for the plane I might as well make it fly good. Bad servos can make a good plane fly bad, or so Iv heard.

Other electronics will consist of a FrSky V8R7-II 7ch receiver and 250mAh 2s LiPo. I might end up using different lipo (maybe 1s?) but those are the batteries that I have right now. Also I will use BEC or ESC to got 5V for the servos.

I bought the plane in December but Iv been swamped with other stuff, like a quadrocopter for school project etc, so I pushed the Longshot build farther and farther. To be honest at first I was intimidated by this. Its SO LIGHT! I felt like I might break it just by looking at it. But it turned out as Iv started building it that its made from quality stuff and its super rigid and strong. I can hold the whole wing from the wingtip and it wont show any signs of stress of deformation. Absolutely nice plane!

Anyhow this is as far as Iv progressed in couple of days. The setting time on the laminating epoxy is the number one thing that keeps me from building faster now (8 hours)

THE BUILD

I decided to start with the wing and then work the tail and the pod.

First I filed the hole locations to the winghalves (no pics of the sorry), making sure that the front hole is perpendicular to the bottom surface of the wing, since there is a premade 4mm metal threading on the pod for it.
The back hole should be perpendicular to the TOP surface of the wing so that the bolt will sit nice and flush on top of it. On the pod side there is no ready tapped hole so you can choose to tap your own 4mm thread to any angle you wish, I will go with perpendicular to the top surface of the wing (not done yet).

Next I epoxied the winghalves together with 30min epoxy (the instructions say 5min is enough but I wont risk it, only 30 min will be used on this plane). I didnt do any sanding, the wings sit together nice and snug already. I simply taped the bottom side with strong clear packing tape, opened the join and applied thin layers of epoxy to both surfaces. Then I just put the wing resting from its wingtips between 2 chairs and let the gravity do the work for me. I then wiped the excess epoxy that seeped from the join and let it sit there overnight. Wing came out perfect.



Before laminating the joint I drilled the holes for the screws to 5mm and cut and epoxied the provided aluminium tubing to the holes to support the screws. I also located the servolead channel and drilled a hole and tested that I was able to get the servowires through it.



Iv never used laminating epoxy, carbon or glass cloths so I dreaded the next step, which was laminating the wingjoint. It came out quite good and seems plenty strong. it aint the prettiest I know

I chose to put carbon cloth all over the wing joint. The instructions only show putting 4 pieces over the screwholes (top and bottom), but there was a mention that you can reinforce it further if you think you are flying in rough conditions. So I decided that I need the extra strenght and my friend sent me some carbon cloth so I was all set.
I cut a 5x40cm piece and I was meaning to use it as a one piece, but the tapes holding the ends intact were on the opposite sides so I had to cut it in two.



I first covered the wing where I didnt want the epoxy to go, I left about 6,5cm for the carbon cloth so it would not be too tight fit. I spread an even layer of the epoxy to the surface of the wing and some to the carbon cloth (under the tape especially since when the tape was on top, I couldnt add more epoxy to it) and lay it flat. after I got it properly fitted on one side I did the other one.
The leading edge was hard to make well, since the carbon was JUST long enough and its not really that elastic. so I was unable to get the fibers to go smoothly and meet up in the center from both sides unaided. I decided to use masking tape. I lay it so that it forced the leading edge fibers to lay flat agains the surface and then I just covered all the carbon eventually with masking tape to make it firmly flat against the wing. After 8 hours I removed the masking tapes without a problem and it turned out really nice. Its a bit thicker that I might want but the carbon cloth IS more heavier than the one included in the kit (see picture, you can see the difference in cloth pattern size).



After that I reopened the screw holes and the servo lead hole, used a bit of sanding paper to smooth some uneven spots.



Right now I just drilled the hole for the launching peg and laid carbon cloth pieces to the top and bottom and laminated them. 8h to wait until I can epoxy the launch peg in place.



Iv searched and there are not whole lot of Longshot buildthreads, which is a shame since Longshot is kins of an entry level DLG (even though the price is kinda high for me, apparently its very cheap for a DLG and it flies great, Iv heard).

I hope that this buildthread can be of assistance for those of you who might be searching for a entry plane for the DLG world. Especially since Im not experienced with any of this kind of stuff so if I can do it, you should not be intimidated by this either

More to come as soon as possible

 

[earthsciteach]

Thanks for sharing. You are right, there aren't many DLG build threads on here. Best of luck with the plane!

 

[EraJomppa]

Thanks man, the plane is starting to look ready when I put some screws on



But there is still a lot of stuff to do and not much time this week to do them. Gotta get back to building next week. Meanwhile, here´s whats been done so far:

I cut the boom to size, which is 650mm. There was about 5cm extra, so I started cutting from the wide end until the boom fit really snug on to the pod counterpart. I ended up going 5mm too far and its now REALLY snug, I had so sand down the black paint to get it fit correctly. Then I cut it to size from the tail side.



After that I made a slot into the vertical stab to accept the boom, but instead of going 28mm I decided to go 14mm and another 14mm slot on the boom. Some do the slot on the boom, some on the stab, I went the middle road Snug fit again!



Then I sought out the spot for the horizontal stab and used sanding paper on the boom to sand the mount to a correct shape. I sanded a bit too much from the back and now there is a slight gap. Im not sure is I will epoxy, laminate, CA or just leave it like that. We´ll see next week.



I decided that I will screw the stab on, no glue, so I can make it more transport-friendly.



After that I glued the horizontal stab to the boom, here you can see my marvelous straightening apparatus workstation



After that I took the screws out and put the rudder on and made sure it was straight with the plane forward axis. WHY IS THERE AN AIRFOIL ON THE RUDDER? how am I going to get this thing nice and straight when there is a non-symmetrical airfoil on it!? Well I think I eyeballed it close enough and its now as straight as it can be.



PS: The horizontal stab / elevator has symmetrical airfoil...... I dont get this

More next week!

 

[xuzme720]

The horizontal stab / elevator has symmetrical airfoil...... I dont get this

I don't either. Maybe something to do with launching? Sure seems like you'd want no airfoil on the stab, and symmetrical on the fin...

 

[airhawk]

thats wierd

 

[EraJomppa]

I don't either. Maybe something to do with launching? Sure seems like you'd want no airfoil on the stab, and symmetrical on the fin...

I think so too, maybe it will make the vertical stab perform better in a launch? But the problem is that you can make it either right or left handed lauching just by putting the launch peg to either wingtip... So which way is it better to launch? Also Iv seen pictures of longshot 4 that has the rudder airfoil on the opposite side compared to mine. Go figure.

 

[rcspaceflight]

I don't either. Maybe something to do with launching? Sure seems like you'd want no airfoil on the stab, and symmetrical on the fin...

I remember David saying that you know a DLG is in a thermal when the tail lifts up. Maybe it's so the tail and wings lift differently so you can more easily see what the DLG is doing in the air.

Or maybe it's just to streamline the plane more and you don't want the tail to be lifting up. If it had no airfoil, it would create more drag, I think. And if it had a flatbottom airfoil, it would lift up more than the wings, causing a nose dive.

Or maybe I'm just full of something.


Great build EraJomppa, by the way. There really aren't many DLG build threads on here. I like them for inspiration because I want to eventually get into DLGs.

 

[EraJomppa]

... I want to eventually get into DLGs.

Yeah me too

eventually...

I'm bummed out right now, since I'm super swamped with school work and school projects. I hope that I can get some tail strengthening done in the next few days, but that might be all I can manage this week. And that's being optimistic

 

[rcspaceflight]

Yeah me too

eventually...

Patience, young Padawan.

 

[EraJomppa]

Patience isn't my middle name, but nothing I can do about it I't too swamped with schoolwork...

Well some new development. I went and bought 4 pieces of 1/3 AA NiMH 180mAh batteries.



I wanted to try these out for a couple of reasons. I know I might end up tailheavy and these might carry some extra weight? maybe after I solder them and put a heatshrink over them. Actually right now they are just as heavy as my lipos are.
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. So despite these have less capacity, they might give better flight times than lipos during winter season.

But yeah, they weight total of 18 grams if memory serves, I had them weighted at the battery store, since my scale is a cheap one. The store keeper asked me if I was an "RC guy", I asked him how'd he know. He said that only RC guys want to know the weight of the batteries

They weren't that cheap though.. 4,5€ per cell.. That means I just bought my most expensive battery to date at 18€

 

[xuzme720]

Wow! That's over $25 US!
But at 18g total weight, that is pretty light...
For a bit of wait time you could have had these with tabs for ease of pack assembly and 300mAh...It's almost double the weight but it's a lot more capacity...
I guess on a DLG, unless you need ballast for penetration, the extra weight would be bad...

 

[EraJomppa]

Wow, same size, almost triple the capacity! I guess they didn't pack the ones that I bought so tight

Yeah, it was a "big" investment, but I just wanted to experiment with these. If I would buy more NiMH batteries (like some guys at my RC club, they like NiMH batteries on their big gas planes) I'd definitely buy more wallet-friendly packs

But yeah, I'll just try if these work well with the Longshot. I have like 5 or 6 of 250mAh 2s lipos that are also perfect size for this and I don't really use them for anything else since my micros went and broke on me NiMH has its pros with being easy to use (no BEC) and winter friendly. But if I fly too long and I run out of juice on the NiMH, I want to be able to switch it to a lipo on the go

These have some kind of tabs, not sure if they are what you're referring to. Some metal plates you can use to solder these together easier.

 

[EraJomppa]

Another thing that came into my mind when I was planning my next move was the plans tell you to use kevlar thread or similar to fasten the horizontal stabilizer mount firmly to the tailboom. But there is no thread included? Do they presume everybody as couple meters of extra kevlar thread in their drawer?


mucho importante


I think what I will do is use some of the carbon fiber that kept getting pulled out of the cloth when I man-handled it. There are few nice 10-15 cm long pieces that I might be able to wrap around the boom and the hole in the mount. I might have to use the laminating epoxy to make it stick and stay in place though. That might bring some weight to the tail and every 1 gram of weight in the tail needs 2-5 grams on the nose balance it...

Not sure yet, but I got some time to figure it out since I'm still too busy to start mixing epoxy :/

 

[rcspaceflight]

The only thing I can think of is fishing line. But that's more of a plastic and stretches when pulled. Maybe a thin steel or copper wire. Maybe see what electrical wires you have laying around, wrap it around two wooden sticks and try to rip them apart in order to test to see if that'll work.

 

[xuzme720]

Do they presume everybody as couple meters of extra kevlar thread in their drawer?

They don't?

The only thing I can think of is fishing line. But that's more of a plastic and stretches when pulled. Maybe a thin steel or copper wire. Maybe see what electrical wires you have laying around, wrap it around two wooden sticks and try to rip them apart in order to test to see if that'll work.

In this case, that's probably not the best idea. the copper will put a lot of pressure concentrated in one small area where the thread can flatten and spread the load across it's width.

The kevlar thread and carbon tow are fairly similar. Carbon tow is what they use to weave the cloth and is often used in the tow form for reinforcing areas just like this. Use the tow and a small amount of the resin. If possible, it's good to wrap it with a good stretchy film like cling wrap, but that area doesn't look like you can get that kind of wrap on it.

 

[EraJomppa]

The word I was looking for was just that, carbon tow. They sell that in a big quantities in my local hobbyshop.

http://prorc.fi/index.php?option=co...mart_product_id=479&virtuemart_category_id=41

But its way too excessive amount to buy for a single lightweight tail construction I think I can get away with using few of those carbon tows that ripped away from the cloth.

 

[xuzme720]

You should have no issues using it like that.

 

[EraJomppa]

Agh, still no time to get the project onward. But my better half is going to visit some friends of her's this weekend and I believe I can get some stuff done then, if I can't pull off any time during the school days.

After school I went to the hobby shop to get some carbon fiber spars for a hexacopter (school project) and talked a bit with a guy who had brought in a VERY nice looking pre-production DLG way off of my league! But yeah he said he uses 1S lipos on all of his DLGs and prefers the round ones from hobbyking. He said he usually put 600-900 mAh round 1S to the nose! Man that is a lot of capacity! He said that the new one will have 1200mAh! I got few of 250mAh 2s Lipos and the 180mAh NiMh. What a difference.

When I asked about it he said hes never had a plane that didn't need noseweight, so why not have extra capacity instead of lead in there. Makes sense, I think I will end up making the tail a tad too heavy so noseweight will be needed. Thus I got really interested in the idea of getting those big 1S lipos. Might add some to the cart next time I order from hobbyking.
Though I forgot to ask him if he used booster or just voltage straight from the 1s lipo.

The round lipos Im talking about:
http://www.hobbyking.com/hobbyking/store/__23317__Turnigy_nano_tech_650mAh_1S_15c_Round_Lipo.html
http://www.hobbyking.com/hobbyking/store/__23318__Turnigy_nano_tech_900mah_1S_15C_Round_Lipo.html
http://www.hobbyking.com/hobbyking/store/__23320__Turnigy_nano_tech_1200mah_1S_15C_Round_Lipo_.html

 

[EraJomppa]

Aww man, the time slipped by and I got so in love with the idea of a bush plane that I ended up cutting and gluing depron instead. I guess the intimidation is creeping in again if I don't get myself to continue this build soon! Next week is going to be a bit more relaxing school-wise so I think I can get some building done.

 

[EraJomppa]

Some preparations done before I can attach the pod to the boom.


A bit of thin CA to stiffen the ends of some various CF and glass fiber thread pieces. I went with the long glassfiber one. The carbon stuff kept snapping when you bent it too much.


I began with rolling it and forming some sort of knot so it wouldn't come loose and applied some thin CA. Afterwards I also applied laminating epoxy just to be sure (I had lots of it left so put some here too).


Cut some 25 x 30 mm pieces of the lightweight carbon cloth for the tail and cut them to shape. Put on with laminating epoxy and assisted with a lot of tape.


Drilled the hole again for the launching peg and put it on with 30 min epoxy. This time I made sure it would stay normal to the surface of the wing (my initial hole was a bit off 90 degrees).


Made sure there was some epoxy to form a fillet. It should hold on properly like this. I hope


Finally I put a patch of carbon cloth for the hold down wire for the canopy. I'v heard that it wont be enough to hold the canopy and I might need to use tape to hold it in place properly, but I wanted to make this one too.