Nytrunner
Pop lugs, not drugs
That's a Lot of fin real estate to finish. Bondo and a rotary sander?
LOC Hawk 7.5'' Build Thread
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jmuck78
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I’ve actually set up a gofundme page to help pay for all of the bondo and sandpaper i will need to finish this: www.gofundme.com/bondo
Nytrunner
Pop lugs, not drugs
Lol
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I've been Rick Rolled... 
jmuck78
Well-Known Member
I've been Rick Rolled...
Thanks for donating to my Gofundme project!
Nytrunner
Pop lugs, not drugs
I very nearly posted here when my gmail gave me a preview and saved me from certain Ricking. But I figured I'd let the fun go on and just express my mirth to Muck in pm
jmuck78
Well-Known Member
I installed the 98 mm aeropack retainer to the aft most CR and updated post #5. The holes for the flanged aeropack retainer are almost 1/4'' diameter holes to allow for the inserts. The CR is a 5.38 in OD / 3.90 in ID ring, which doesn't leave a lot of room to drill the holes and still maintain the strength of the CR. I have ordered a 2nd CR of the same size and will laminate the two together for added strength. The Aeropack retainer should, however, add strength of its own to the CR since the retainer is substantially stiffer than the 1/4'' plywood CR, and the load is transferred up through the Motor Mount Tube to the rest of the airframe instead of the through the 5.38 in CR. Here's some additional pictures that show how tight the clearance is between the flanged Aeropack retainer and the CR.
I aligned the CR to the Aeropack retainer as closely as I could visually, but I'm running a small risk here as I don't have a 98 mm hardware set that would allow me to remove any alignment error.
I aligned the CR to the Aeropack retainer as closely as I could visually, but I'm running a small risk here as I don't have a 98 mm hardware set that would allow me to remove any alignment error.
Nytrunner
Pop lugs, not drugs
Use the mount tube. put strips of tape at 120 degrees till the retainer is centered. mark drill holes accordingly, when you've got a couple, you can use them to hold it in place for the others.
jmuck78
Well-Known Member
That's similar to what I did. The "slop" in my process here is drilling the marks accurately enough (or making the marks accurately in the first place.
jmuck78
Well-Known Member
Based on the discussion in the LOC VII build thread, I considering adding some reinforcement to the aft most centering ring. The centering aft most centering ring has a 98 mm Aeropack retainer installed and will be epoxied to the motor mount tube; but on the outside, the boat tail is epoxied to the centering ring, and will be carrying the load up to the airframe. Since the boat tail is a stiff coupler that has been sliced to allow the coupler to make a transition from a 5.5 inch to 7.5 inch air frame, it will be held together with epoxy ( see post #5) instead of a mechanical thrust ring. I may cut some pieces of plywood to transfer the load up to the next centering ring and provide a direct load path to the airframe. Thoughts? Is this overkill?
jmuck78
Well-Known Member
I glassed (or whatever you want to call it since I'm not using actual fiberglass cloth) the payload tube, which was substantially easier than the booster section since a) I don't have to cut any fin slots and b) I had enough Aeropoxy to complete the lamination in a single step. I ended up having some extra Aeropoxy in the cup, so I used it to coat the fins and body tube on a small Madcow mini cowabunga and a Fliskits ACME Spitfire I put together over the weekend. I think the Aeropoxy worked particularly well on the Spitfire since several major parts of it are cardstock.
See update to post #6.
I think I have worked out how to glass just the switch band on the avionics bay. I'm going to wrap the coupler portion immediately adjacent to the switch band with teflon tape, then apply the sock over the whole avionics bay. Carefully applying Aeropoxy to the switchband portion only and then trimming after should get me want I want here.
See update to post #6.
I think I have worked out how to glass just the switch band on the avionics bay. I'm going to wrap the coupler portion immediately adjacent to the switch band with teflon tape, then apply the sock over the whole avionics bay. Carefully applying Aeropoxy to the switchband portion only and then trimming after should get me want I want here.
jmuck78
Well-Known Member
Alternatively, I could eliminate the switch band altogether. If I have a coupler bonded inside the booster section that the avionics compartment can sit on, do I still need a switch band?
No. You can mount the switches in the forward end of the booster body tube, but where are your parachutes, ejection charges, etc?
jmuck78
Well-Known Member
Sorry, my post wasn’t clear. I would keep the avionics bay inside the coupler that joins the booster section to the payload section. The only change here is to remove the switch band from the avionics bay. To help compensate for the fact that the avionics bay no longer has the switchband to carry the launch load, i would bond in a short section of coupler into the booster section which would act as a stop for the avionics bay.
Thanks, that’s what confused me. I thought you said you would bond the entire coupler into the aft body tube.
That would work.
For future reference, I glass full length tubes and cut the switch band from the glassed length.
You could cut the switch band first and put it on a coupler, then put the coupler into the remaining length of body tube, glass the assembly, then cut the glass cloth where the band meets the rest of the body tube once the epoxy reaches leather, but it would be really tricky not to glue the coupler in place.
Last edited:
txeagle1
Member
I just saw that LOC added the Hawk to their inventory and I am so tempted to add a 98mm to my fleet. I have the PoleCat 7.5" 75 mm hawk which I have flown several times. The first flight resulted in a zipper so when repairing it, I adapted it to the "zipperless" design. The second an third flights..... this is something you may want to consider. The tailcone was a cut down nose cone and the tail centering right did not adhere to the tailcone, no big deal really, or so I thought. But after the third flight of an M2050, I found the cardboard motor tube had been compacted from about 5 inches to 2 inches up to the rear bulkhead, call it an accordion. For the repair I added 1/4" all-thread from the tailcone bulkhead into the rear bulkhead to transfer the energy to the airframe. The tailcone on the Loc looks to be cardboard and you probably will get good adhesion but the forces of several 98mm motors may collapse the tailcone section. I'd suggest considering reinforcing it with some segments of all-thread.
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jmuck78
Well-Known Member
The tailcone went in crooked and froze before I was able to completely straighten it out, so I ended up removing the tailcone and ordering a new one. Removal of the discrepant tailcone was a chore, as you might expect, as it was really well epoxied in place. The easiest way to remove it while protecting the main motor tube was to cut out the cardboard sections of the tailcone with a hobby knife and then use a dremel to remove the bits that were still epoxied in place. The centering ring that was previously epoxied directly to the tailcone was installed crooked by as much as half an inch, which was just unacceptable. I had to use a chisel to remove the centering ring and then dremel again to remove the cured epoxy and remaining cardboard bits of the old tailcone. The end result was pretty clean.
jmuck78
Well-Known Member
For the tailcone re-installation, I made two changes. First, the centering ring in the previous installation was sized to fit inside a standard LOC coupler, and the tailcone would then mate to the inside of the coupler and butt up against the centering ring, which had effect of pushing the tailcone out the aft end of the rocket by another 1/4 inch minimum. For tailcone 2.0, I used a centering ring sized to fit inside the stiffy coupler (which is what the tailcone is based on) instead of a standard coupler.
The second change I made (based on the discussion in the LOC VII build thread) is to include some additional supports for the aft most centering ring. Using 1/2 inch plywood (because there was a readily available scrap in that size), I cut four tapered pieces, where the taper matches the taper of the tailcone (about 8.5 deg). The supports are designed to butt up against the new centering ring, which then butts up against the portions of the fins that locked into the aft fin-lock ring. The goal was to transfer the load from the aft-most centering ring through these struts directly to the fins and airframe.
The short piece of standard coupler was epoxied in first. The tailcone went in immediately after the short coupler followed by the centering ring. I made sure the tailcone was correctly aligned and the centering ring was pushed in all the way to the edges of the fins. I then added the four struts so that they were aligned with the fins.
I then added some epoxy fillets to the centering ring around the motor tube and the tailcone.
I had previously attached the Aeropack retainer to the aft-most centering ring, but was unhappy with the alignment, so I started with a new centering ring and will re-attach the Aeropack assembly later.
I slathered a new batch of Rocketpoxy on the outside of the struts where the will attach to the tailcone and the aft centering ring and then slid the centering ring in to place.
I applied epoxy to the outside of the centering ring and inside each of the cuts of the tail cone. Once the assembly was sufficiently coated with epoxy, I started adding rubber bands to the outside of the tailcone to close the tailcone around the aft centering ring.
Once that assembly is cured, I can go back over the tailcone to fill in the gaps with more epoxy, and sand off the exposed edge of the motor mount tube so that it is flush with the centering ring, and finally add the Aeropack retainer.
The second change I made (based on the discussion in the LOC VII build thread) is to include some additional supports for the aft most centering ring. Using 1/2 inch plywood (because there was a readily available scrap in that size), I cut four tapered pieces, where the taper matches the taper of the tailcone (about 8.5 deg). The supports are designed to butt up against the new centering ring, which then butts up against the portions of the fins that locked into the aft fin-lock ring. The goal was to transfer the load from the aft-most centering ring through these struts directly to the fins and airframe.
The short piece of standard coupler was epoxied in first. The tailcone went in immediately after the short coupler followed by the centering ring. I made sure the tailcone was correctly aligned and the centering ring was pushed in all the way to the edges of the fins. I then added the four struts so that they were aligned with the fins.
I then added some epoxy fillets to the centering ring around the motor tube and the tailcone.
I had previously attached the Aeropack retainer to the aft-most centering ring, but was unhappy with the alignment, so I started with a new centering ring and will re-attach the Aeropack assembly later.
I slathered a new batch of Rocketpoxy on the outside of the struts where the will attach to the tailcone and the aft centering ring and then slid the centering ring in to place.
I applied epoxy to the outside of the centering ring and inside each of the cuts of the tail cone. Once the assembly was sufficiently coated with epoxy, I started adding rubber bands to the outside of the tailcone to close the tailcone around the aft centering ring.
Once that assembly is cured, I can go back over the tailcone to fill in the gaps with more epoxy, and sand off the exposed edge of the motor mount tube so that it is flush with the centering ring, and finally add the Aeropack retainer.
jmuck78
Well-Known Member
I drilled and installed the Aeropack Retainer (and then removed it until after painting). Since I don't have a 98 mm motor available for the alignment, I had to improvise. I happened to have a PML 4'' coupler laying around that is fairly stiff. It fits inside the motor mount tube snuggly, so I wrapped a layer of masking tape around one end to center it inside the aeropack retainer and then marked the holes around the perimeter. Drilled one of the mounting holes, and inserted the first insert, which of course stripped on its way in. I switched to a slightly larger bit for the remainder of the holes and filed off the protruding bit of the threaded inserted. You can clearly see the filed insert which is at about the 12 o'clock position in the picture. The small pilot hole next to it was the first pilot hole, and then I decided to reclock the retainer flange so that the inserts would clear the struts inside the tailcone, which are aligned with the fins.
jmuck78
Well-Known Member
jmuck78
Well-Known Member
I am contemplating adding another fiberglass layer to the tailcone. I used 3 oz fabric for the first layer, and it turned out pretty well, but it looks really thin. There are also some valleys I need to fill in to make the cone a bit more round, so the plan is to rough up the fiberglass layer a bit, fill in with bondo, then apply another fiberglass layer, probably with 10 oz fabric this time. Thoughts?
For the plywood fins, I'm sanding and filling with bondo, then when I'm satisfied there, I am going to seal the fins with laminating epoxy (have both West Systems and Aeropoxy now).
For the plywood fins, I'm sanding and filling with bondo, then when I'm satisfied there, I am going to seal the fins with laminating epoxy (have both West Systems and Aeropoxy now).
Nytrunner
Pop lugs, not drugs
Can fiberglass and epoxy adhere well over bondo? My intuition would lead me to do all my bonding and fiberglassing, then deal with filling in unevenness
jmuck78
Well-Known Member
I can do that - this is my first time fiberglassing a cardboard airframe, so I am open to suggestions here. Theoretically, I could just sand off all of the fiberglass layer I applied then apply multiple layers of cloth and epoxy in one sitting so that the epoxy adheres better, but given the tailcone shape, and the point of the fiberglass layer is to provide impact resistance from hard landings, I don't know that the layer to layer adhesion is as critical.
Either way, I can certainly apply the second fiberglass layer and then fill in with bondo - that makes more sense.
jmuck78
Well-Known Member
Side note, the pictures seem to be distorting the size and proportions of the tailcone - looks like considerable fish-eye effect in the pictures.
jmuck78
Well-Known Member
Thanks for the suggestion, Steve. I'm considering doing this with the glassed payload tube. My only hangup is that I normally use the miter saw to cut tubes, but the 7.5 inch tubes are too large for the saw to get all the way through in one cut. I could use the miter saw with two cuts and then use the odd discontinuity that inevitably results as an alignment key, but that may look funny. Is there a strength reason to laminate the switch band?
I would never put body filler between epoxy. If you put consecutive layers of epoxy and fiberglass down within 12-24 hours (West Systems says 24 hours, but that’s for their epoxy) the epoxy layers will crosslink, bonding permanently to each other.
Depending on the weave, heavier cloth, like 5.7 oz, drapes really well and conforms well to cones and compound curves without wrinkles. I would prefer to fill any irregularities with epoxy thickened with microballoons, but I have used body filler on large rockets to fill weave with good results.
You’re making great progress. We all sometimes have one step forward and two back, but don’t let it frustrate you.
I don’t know what kind of miter saw and stand you have, but you may be able to clamp a block to the stand or bench that the saw is bolted to, put one end of the tube against the block, then lower the blade, and turn the tube to feed into the running blade. That’s better done on a table saw and John Coker even did a project to do that with a diamond embedded tilesaw just to cut tubes straight.
https://www.jcrocket.com/tubesaw.shtml
No, it’s definitely not necessary to glass the switch-band.
I have cut tubes by hand using a wrap to mark the line and a hacksaw, followed by marking high spots and sanding with a sanding block or using a rasp. It actually goes very quickly and yields good results. Nobody can see it from the flight line anyway. [emoji6]
Let me know what your total ends up without motor. I saw a Rocksim weight of ~45.5 pounds loaded.
Not everyone has a table saw but this simple jig works real well. I cut any size tube that doesn't fit in the miter box. I hear different ways to cut FWFG tubing but I cut everything with fine tooth carbide blades. G10 fins on the table saw. When I cut the FG tubes I place 1 wrap of blue tape at the cut line, it hardly splinters at all if you feed real slow.
Here is how I use the tube cutter with a clamped stop.
Then I have several jigs to perfectly dress FG or glasses tubes. Smaller ones are sanding discs with arbor, the large one is a 10" disc to use on a table saw. Just find a universal arbor and some sanding discs. The picture is also jig to make switch bands. All were within .002" in length all around.
Then I have several jigs to perfectly dress FG or glasses tubes. Smaller ones are sanding discs with arbor, the large one is a 10" disc to use on a table saw. Just find a universal arbor and some sanding discs. The picture is also jig to make switch bands. All were within .002" in length all around.
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