8ft Zagi Sloper - DIY / Hot cutting / Fiberglass - MAIDENED!

thenated0g

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DKchris

Member
Nice job! And progressing with quite a nice tempo - keep up the good work! Bet you will enjoy flying it a lot - big planes just fly better!

A couple of local guys did a similar, slightly larger project, based loosely on the dreamflight weasel plank:

Figured the clips might add a little extra "itch" towards getting yours airworthy (not that it seems you need it) ;):D
 

thenated0g

Drinker of coffee, Maker of things
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speedsterden! Love his youtube and instagram. Hes many years ahead of me in the slope soaring hobby, i enjoy watching his stuff.
 

thenated0g

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Having never wrapped anything, I was somewhat intimidated coming into this part. It was super easy. Very easy to lift back up and stretch or reposition. Someone on Instagram suggested using the heat gun to lock it down to this fiberglass surface, that works great. Thanks @ramy_rc_ for showing me the idea of using vinyl on a rc plane, had not seen that before. Only added about 60g for the top.
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thenated0g

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As briefly shown in the last video, i got the top and bottoms covered with vinyl. Some trim tape made for a nice straight leading edge transition between the red and blue. When i did the second wing i took some better footage and made a lightly edited version of doing the process in real time if your interested. Also i hinged on the elevons with 10mil iron on laminate, which just seemed the simplest way to go.
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I also started installing the control hardware. This here is why i laminated that rectangle of carbon fiber. I wanted this to engage that section and make that whole area stiffer. But i ran into a problem i have had before. I put the servos so far forward, and flush, that the standard servo control arms are not long enough. The control rod is already contacting the top of the wing at neutral. So i ordered some longer arms and put the control setup to the side for now.
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For keeping the wings together i decided to order 2 different sizes of magnets and see if i felt any confidence in them. After playing with them a bit i totally feel that they will do the job. The ones pictured are 1" x 1/4" and have 10lb of force each, or 20 together. I also got the 1/2" ones and they are 28lb each! or almost 60 together. I pinched my palm on accident when they snapped together. ouchy. Way too much force. But 20 felt just right. I also grabbed one of aloft's wing separating wedges. These magnets will go into the epoxy/filler mix that will hold all the lead nose weight for CG. Ill sand them lightly and sink them into each side.
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Wing stores pretty nicely. I think ill probably make some "wing bags" to slide them into for storage and travel.
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Also before i can set the CG i need all the parts installed which means i need the wingtips on. For them i decided to try my first fiberglass vacuum bag job. It will be a sandwich of 4oz carbon in the center, followed by a layer of balsa on each side, and the outer layers will be 6oz s-glass. The finished look will be glassed balsa. I have thinner materials but i want it to have a little bit of thickness as these will be held onto the wing tips via nylon bolts into the balsa blocks i installed.
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Here's my longer form vinyl tape trim movie:

Heres a video of a guy making his own fiberglass plate i found on youtube:
 

thenated0g

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Got one wingtip under the vacuum bag this morning. Really no idea how much epoxy i need to have in it or how much that matters. I am somewhat worried about the balsa as that could soak up some epoxy and than not have enough on the outside to get that shiny look, but really i have no idea. But it will be one solid piece for sure, so that's all the really matters i guess. Its a first time IE it can suck and that's totally fine.

i mixed up about 48g of epoxy and i used maybe half of it? I will try and get some better measurements of what i didnt use when i do the other side.

I dropped vacuum to about 19 inches i think is how you read it. Over 15 minutes it drops down to about 16 inches and than the pump runs for 9.5 seconds to get it back to 19. I will leave that until late this evening, probably 15 ish hours under vacuum. And i will leave it in the mylars for another day or two. I have read that leaving it against the mylars will allow it to fully cure and give a better finish, so i figure why not. Once i get them cracked open i will do a video on the whole process.

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Recieved my aluminium control arms. $4 a piece but very nice and strong. I tested the control rod and the lower hole will probably be fine.
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thenated0g

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FYI this is my first time doing this, im no expert, so my calculations could be wrong. Having said that:
If you think about vacuum bagging from a clamping perspective it makes more sense. You want to clamp the material together. If you were going to apply weights on top, how would you do that so it was uniform? So that the same weight is being applied on all parts. Whatever weights you have, how are you going to stack them so it doesnt lean to one direction and apply more weight to one side? How are you going to make sure that the material in the middle is getting as much pressure as the outside?

In this case, at 19 inches of mercury, it is applying 1,343 lbs per square foot. Where are you going get close to 1,400 lbs of "stuff", a table that can hold that, and how are you going to, again, stack that in a way that can be uniform?
 

Piotrsko

Master member
Atmosphere is 13.7 psinch. Math is a bit off. I think Howard Hughes invented it on the HK1 wing laminations, We used sand or shot bags before Rutan improved this method and yes it was heavy. You can calculate the volume of epoxy you'll need to mix, but swag is way faster
 

thenated0g

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@Piotrsko Im at about 0.65 atmospheres. not 1 atmosphere. So one square foot (144 inches) X 0.65 atmospheres (9.55 lbs per square inch) comes out about 1,375 lbs per square foot.
 

Piotrsko

Master member
You're at +/- 9500 ft? And you did say 1343 lbs sq ft.

Just messing with you
 
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thenated0g

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Well i got a little impatient and cracked em open this morning. Looks pretty awesome. Nice and shiny. I could probably get away with less layers but this is pretty strong and it will have to take a beating from a 3.5-4kg beast hitting the ground hard repeatedly so maybe its just fine. Still need to sand the edges and weight it.
 

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thenated0g

Drinker of coffee, Maker of things
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Got the left side wingtip in the bag. Made sure to keep my area clean as last time i had a lot of pieces of carbon strand get under. I decided to also sign it with a sharpie but didnt let it dry and it bled all over as you can see. But i did wet out the fiberglass enough this time and its super shiny. Pretty happy with it. After sanding the excess i sealed the edge with thin ca glue.
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Using a line laser i marked the holes needed to meet up with the balsa blocks inside the wingtips.
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I CA glued in some carbon tubes. Its a pretty tight friction fit. Before flying i will apply some packing tape.
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