Slope Soaring PSS B-52 Project - page 2

Got the right wing "sparred". Three carbon fiber tubes glued into troughs. And in the case of the first joint (at the inboard engine nacelles) an aluminum bar and pywood box is added for insurance. This is proving to be rather tricky, as the tubes need to be aligned correctly to keep the wing straight, with no uninteneded wing twisting.

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Outboard and center panels sliding together.

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It makes for a stiff wing, and I have not even done the fiberglassing yet.

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Looking waaay ahead, I also did the artwork for the left side of the nose.

Small SAC Logo

Got the other wing all "sparred". Glad that is over. Lots of fussing around trying to glue those tubes in perfect alignment without gluing them together
Today I went over the dimensions, verifying the placement of the aileron cut and checking where I might mount servos. I also drew out the notches in the root for the bolt blocks and plywood short spar. I really want to get this in the bag.

I also dropped by the servocity website and checked around for what servos to order. I think it will be 6 of the HS-635HB for the ailerons and two of the HS-645MG for the elevators. Plus two receivers and crystals, charge jack/switches. Better not let the wife see the receipt for that order

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Center section of the wing has been joined. I just remembered, I never checked to see if it would fit in the vacuum bag material that I have... Oh well...

I added a 1/4 inch Birch Plywood spar across the wing joint and the balsa blocks to reinforce the area where the wing bolts will pass through. I have also been filling the holes in the epoxy around the spar. Don't want them to show through the carbon fiber skins when I am done.

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More boring wing pictures, but hey, there is composite material on them now!!!! Just lightly spray glued in place till the goopy stuff comes along. Kevlar leading edges and hinges. Carbon fiber over the spar and trailing edge.

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See that kind of ragged trailing edge?

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Started out nice an pretty and straight. But when the blue foam is this thin, it is like potato chips. All the handling takes it's toll. And these are not the worst dings. But the chips fill in and the carbon fiber keeps it stiff once the epoxy is on.

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Got new toys in the mail
6 HS-635 servos for the Flaperons
2 HS-645 servos for the Elevator
2 Supreme receivers
and two channel 52 crystals (what better channel to use? )
ServoCity.com delivers again, fast and cheap

This does not include the two batteries, two switches, servos for the rudder, bomb bay doors and bomb release. I suspect the rudder and bomb functions will not be finished by PSS Fest.

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I also did the left side nose art last night. 28th Bomb Wing. Strangely, the documentation photos I have of a restored B-52 on display, have the logo wrong compared to historical photos . I went with the historically correct logo.

This morning, the middle of the wing goes in the vaccum bag!!! It is going to be a tough layup. Doing the top and bottom, left and right sides in one shot One layer of fiberglass and two layers of carbon figer, top and bottom, both sides. That works out to 8 panels of Carbon Fiber, 4 of fiberglass. Plus all the misc bits.

28th Bomb Wing Logo and Stars
28th Bomb Wing Logo and Stars 2-small

It's in the bag. That was a JOB!!! My shirt is soaked with sweat. I am glad the outer panels will be easier than this. I took an hour and 15 min to get it done, but the working time is supposed to be 50-60 min. Good thing I made the epoxy in two batches. Once it it spread out on the carbon fiber, the curing slows. In the pot, the heat from the chemical reaction of curing, speeds the curing of the rest, so when it is spread out, the curing heat is not an issue. And I got it done in the morning while the ambient temperature is still in the 70-80 degree range. Higher ambient temps speed the cure as well, but it needs a min of 70 degrees.

I have it weighted down mostly to keep the trailing edge straight, and prevent any overall warping. The vaccum bag is what is really doing the squeezing.

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Fresh out of the bag with the major scrap cut and sanded away. Still need to adjust the leading and trailing edges back to spec. Kinda makes me want to do a B-2. The finish came out good, except where some blue tape somehow got on the wrong side of the mylar and tried to become a perment part of the wing surface.

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I thought I had the spar area sanded smooth with the foam, but a bump shows through. I wonder if it is caused by the foam "crushing" a bit.

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Time to do a bit of bench flying

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Uh oh... I calculated this all out a long time ago, and the top of the wing was supposed to be lower than the top of the fuselage . I guess I will have to cut the saddle lower, which means tearing out the plywood wing bolt platforms.

I also weighed the center wing section...6.5 lbs !!!!
6.5 wing center
6.0 fuselage
2.5 tail end of fuselage
2.5 rudder and elevators
-----------------------------------
17.5 lbs

and I still need to add the outer wing panels ( ? ), radio gear (2 lbs) and finishing materials (1-2 lbs). Probably heading to 25 lbs ready to fly.

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I put the whole wing together to measure and mark some things. This is the first time it has been assembled like this, before the center was not attached and it is easier to work on half a wing, anyways. For perspective, the white board of the worksurface is 8 ft long, the wing has an 11 ft span.

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The outer wings are prepped for bagging. Tommorow I cut the material and mylars and Friday, put in the bag.

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got the outer wings in the bag today. Starting work on the replacement tail section. Once those two items are done, the endless "prime and sand" can start.

Tail Section II, The Sequel
Things go pretty quick when it is something you have done before No tools to make, not techniques to learn, no figuring out how to do something. Just do it.
I only need to glue the extreme rear from the damaged tail section and I am ready to start glassing it.

While I was waiting for glue to dry, I did some sanding of the fuselage. Thank God for electic sanders and large flat surfaces It is going to help things a lot!

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Had to do some more bench flying Still alot of clean up to do on the wing edges, but it is great to see it all together.

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And my lovely assistant holds the wing up for perspective.

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I am going to run two receivers with separate batteries. One receiver will handle the right side, the other the left. Currently I am thinking of running one receiver's antenna forward toward the nose and the other receiver's antenna towards the tail, inside the fuselage (assuming the receivers wind up roughly in the middle of the plane). Rudder, bomb bay and bomb release will not be redundant (indeed, they may not even be present for the PSS fest ).

The batteries will be 4.8V, probably be in the 800 mah range, each. I figure there is not much need for increased servo speed by bringing up the voltage A plane this large is not going to be a snappy flyer. The selected servos should be plenty strong at 4.8V

Elevator - two servos
HS-645MG Torque 106 oz Speed .24 sec.

Flaperons - 6 servos
HS-635HB Torque 69 oz Speed .18 sec.

626 oz of torque. That is 39 lbs of puling power I should be able to pull out tree stumps with those servos

If I encounter an glitching issues, I will see about getting one of those servo isolators. But I have run long wires before in power planes (although not quite this long) and not had problems.

I did get the tail section in the vacuum bag last night. I tried to do it properly with the inside and outside bags, but it leaked so bad, I had to just zip it up with just the outside bag and hope it wouldn't implode. Once you have everything covered in epoxy, there is no turning back It made it through the night ok, so I reduced the vacuum this morning to about 10" to let it finish curing during the day, although the epoxy was already pretty hard (warm weather does have some benefits ). One more trip in the bag for the bottom of the tail section and I will be through with all the epoxy and bagging. Not counting the engine pods and external fuel tanks, but they can wait till later. That will be an interesting sub-project as I will need to make a plug and molds. I better start pestering Russ for ideas I am thinking of taking some wood and turning a "engine" plug on the lathe and sticking two of them together with a dowel, the gooping on filler to get the shape of a pair of engines and the fairing to the engine pylon. Cover that with something to make a hard smooth surface (epoxy or paint?) and use that for a plug. Then I get to lean how to make parting boards and build a mold on that. This project has been quite a composite boot camp for me

I have finally managed to get the "inside/outside" bagging process right! Instead of trying to make my own bags from plastic sheeting and various sealers, I just used the tubular bag that is made for wings. It is a bit wastefull, but if you take a bag three times longer than you need, put the part in the first third, and grab the bag at the 2/3 mark and stuff it inside, you get a seam free bag! Just the normal end clips, that work well.

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Here it is, out of the bag, mylar sheet removed. Ready to take my dremel cut-off wheel and cut along the blue tape so I can sperate the flashing.

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Here you can see the dremel cut made along the blue tape. You can also see some bits of blue tape from the first glassing and the overlap area between them.

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Once the cut is made, you can wrestle off the flashing

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Here you can see the edge left from the removal of the flashing. A bit of sanding the feather it into the previous layup and dissapears.

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Finally, completely glassed fuselage!

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Now it's time to measure stuff and get things aligned for mounting the rudder and elevators.

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All together now.

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Bondo - Sand - Prime - Sand - Repeat

I hate sanding At least I can do almost all of it with a powered sander.

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Got the wing saddle corrected and the to cover of the wing saddle cut to shape (not show). Next I had to drill the holes for the wing bolts, so I had to find a big flat surface to work on. The back patio was the closest thing to flat and level, so I toted all my measuring tools and the plane out there. After I got everything lined up and square, then drilled the holes. Eight - ľ nylon bolts and blind nuts will hold the wing in place (I hope). I was originally planing on gluing the wing down as well, but I am beginning to wonder if I should leave it removable. I donít think gluing the wing to the blue foam of the fuselage will add much, and the bolts should be strong enough. Of course, that would mean making the top wing cover removable to access the wing bolts, and I am not sure I want the seam to show.

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All primed and assembled

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I also did a trial CG to see how things were coming out. The plane balances about 6 inches aft of where it should. It took about 3 lbs on the nose to get it balanced! My last B-52 needed the batteries moved aft to get things ballanced. The culprit must be the tail feathers. I should have gone lighter on the fiberglass there. I guess I will buy some heavy duty batteries for this plane and stuff them in the nose.

Current weight of the airfram is 20.25 lbs Add a couple more pounds for the servos, another pound or two for the finishing paint and metal, and who knows how much for batteries and balancing lead...

Here is the wing saddle cover on. Still need to fill a couple of gaps, but it looks pretty. Got the wing to sit at just the right height to duplicate the way the wing sits in the fuselage of the real B-52. I only have 3 degrees of incidence (or decalage) as opposed to the 6 degrees the real plane has, but it reproduces the look well enough.

I still can't decide if I want to glue it down and seal the wing on permently or live with the gaps and be able to remove it.

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Here are the 8 nylon wing bolts. The front pair will need a slanted washer to keep the head of the bolt from getting bent/breaking when torqed down.

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