Well the HSA's got me down to the wire, with a J180T sitting in the club magazine, and nothing to fly it in. I was gonna sell it, but with last weekend's launch canceled, I figured there's little chance. So I'm just gonna have to get off my butt and build CRUISIN' FOR BURGERS, a 3" 54mm bird that's been on the drawing table for at least a year. It's actually a two stage design (Called CRUSIN' FOR DOUBLE BURGERS in the 2 stage config), but I'll only build the sustainer, but still make it staging capable, because I've got SIX days to build it...
Step 1) Fin stock: The original idea was to go way light, so I've got some 2mm (I think) Rohacell 71 and some 5.8 oz Twill and some other loose plain weave I bought off ebay a long time ago. It's probably 5.7 oz. I've used John Coker's method to laminate carbon tissue and balsa before and it works great. I build 2 4"x24" sandwiches of Twill/Plain/Rhoacell/Plain/Twill on a glass plate w/ butcher and wax paper, then bag 'em in an 8" Foodsaver bag and pull the vacuum. It leaks all over and the glass is a goner, but after I pull the plates in the morning they look pretty good. A little gooey still, so I slam 'em between wax paper and more glass and clamp the crap out of 'em. Overall all thickness is .155, and it's stiff and LIGHT for being that fat....
Step 2) Tubes. I've got 3 3"x34 LOC tubes already peeled, but I'll only need two for the sustainer. I wrap a full length PML coupler in paper and wax as a core to keep the tube from collapsing and insert it in a tube. I wrap one in 5.8 oz twill (glass this time), epoxy and wrap it in wax an butcher papers and bag it up. THe vacuum doesn't seem to pull as well, and I'm worried about a seam... We'll see...
Step 3) Couplers. I roll some 5.8 Twill into two LOC couplers (one for ebay, one for zipperless mount) and wet 'em down. I blow up a balloon in one, and leave the other be. I'm interested to see the difference, as I've always ballooned before....
Step 4) Bad News. The tube came out crappy. Big long glue seams, not just extra glue, but the glass is bunched up.
Step 5) Tubes Take 2. When in doubt, KISS. I spend four hours laying up the other two tubes by hand...They look a lot better and I seem to have controlled the epoxy uptake a bit..
Step 6) I go into RockSim and fiddle the fin shape so that I can get three out of each single sheet I've laid up. I may have to add a touch of weight, but I'm planning on lengthening a bit and thing look pretty good up to a pair of K250s ( a quick Sim sez 29.7K when staged with a 12 sec delay.. heh heh) so away we go. I'm thinking I'll have to fire up the band saw, but the fin stock cuts pretty nicely with a razor saw, so I do 'em by hand, then finish 'em off on the disk sander. The mount is TTW, but the tabs are TINY, not much room between the MMT and BT.
Step 7) I knock a 54mm MMT tube down from 34"->24" figuring that it should support a Hammerhead J should Big Brother completely lock down AP in the future. 'Course that's gonna make staging REAL interesting....
pictures @ https://home.mindspring.com/~wildbill14/index.htm
More to come...
-bill
Step 1) Fin stock: The original idea was to go way light, so I've got some 2mm (I think) Rohacell 71 and some 5.8 oz Twill and some other loose plain weave I bought off ebay a long time ago. It's probably 5.7 oz. I've used John Coker's method to laminate carbon tissue and balsa before and it works great. I build 2 4"x24" sandwiches of Twill/Plain/Rhoacell/Plain/Twill on a glass plate w/ butcher and wax paper, then bag 'em in an 8" Foodsaver bag and pull the vacuum. It leaks all over and the glass is a goner, but after I pull the plates in the morning they look pretty good. A little gooey still, so I slam 'em between wax paper and more glass and clamp the crap out of 'em. Overall all thickness is .155, and it's stiff and LIGHT for being that fat....
Step 2) Tubes. I've got 3 3"x34 LOC tubes already peeled, but I'll only need two for the sustainer. I wrap a full length PML coupler in paper and wax as a core to keep the tube from collapsing and insert it in a tube. I wrap one in 5.8 oz twill (glass this time), epoxy and wrap it in wax an butcher papers and bag it up. THe vacuum doesn't seem to pull as well, and I'm worried about a seam... We'll see...
Step 3) Couplers. I roll some 5.8 Twill into two LOC couplers (one for ebay, one for zipperless mount) and wet 'em down. I blow up a balloon in one, and leave the other be. I'm interested to see the difference, as I've always ballooned before....
Step 4) Bad News. The tube came out crappy. Big long glue seams, not just extra glue, but the glass is bunched up.
Step 5) Tubes Take 2. When in doubt, KISS. I spend four hours laying up the other two tubes by hand...They look a lot better and I seem to have controlled the epoxy uptake a bit..
Step 6) I go into RockSim and fiddle the fin shape so that I can get three out of each single sheet I've laid up. I may have to add a touch of weight, but I'm planning on lengthening a bit and thing look pretty good up to a pair of K250s ( a quick Sim sez 29.7K when staged with a 12 sec delay.. heh heh) so away we go. I'm thinking I'll have to fire up the band saw, but the fin stock cuts pretty nicely with a razor saw, so I do 'em by hand, then finish 'em off on the disk sander. The mount is TTW, but the tabs are TINY, not much room between the MMT and BT.
Step 7) I knock a 54mm MMT tube down from 34"->24" figuring that it should support a Hammerhead J should Big Brother completely lock down AP in the future. 'Course that's gonna make staging REAL interesting....
pictures @ https://home.mindspring.com/~wildbill14/index.htm
More to come...
-bill
