rtfm
Well-Known Member
Hi,
I'm considering a rather novel approach to building my fuse, and would like to ask for some feedback on this.
Essentially, because I don't have the usual bulkhead templates normally used to guide the builder in shaping the foam core, I have found a very simple and accurate way to get the fuse shape. I have tried the foam core method with disastrous results. Without many reference bulkhead templates to guid you, it's a bit like abeginner trying to cut hair. Too much off one side, so you correct by taking more off the other to balance it up. Oops... Too much. etc.
Since I can only work in 2-D CAD all I really have to work with is a profile view of the plane - the sort of thing you draw on the back of a napkin - except that the measurements are accurate.
I have translated the on-screen measurements to wood, and have cut the profile out of particle board. I fixed an 8" spinner plate to the front, and by trial and error (and the eyeball method) shaped two main bulkheads - one up front at the plane's widest point, and one backing the pilot's seat.
I then took thin pine strips, attached them to the spinner and bent them round the two bulkheads to the tail. I repeated this a number of times, and the results were wonderful. Smooth curves, completely consistent with no hollows. See photo of early stage attached.
But here I begin to run into some conceptual (and practical) difficulties:
My plan is to cut 3" strips of 1cm (about 1/2") square wire mesh, and attach these strips from top to bottom. I'm hoping that this will (1) produce a smooth curve from top to bottom over the longerons (2) provide a firm base over which I can apply plastic tape.
The reason for the tape is to act as a release film for the next stage.
The next stage is to apply 3" glass fibre tape vertically, laying each tape next to (not overlapping) the one alongside it. I can lay these tapes in many installments, making the process low-stress (on me). No crinkles, no large quantities of resin, no mess. The tapes, being only 3" wide, will easily conform to the complex curves of the fuse, and can easily be stretched reasonably firmly over the underlying framework.
Once these are in place, I'll repeat the process, but laying the tape at a 50% stagger (ie shifted half to the side). In this way, I'll get two layers of glassfibre, with plenty of overlap.
I can then fill and sand the surface till I'm happy with it. Finally, I remove the entire side of the fuse (hopefully the plastic tape will have done the job of acting as a good release agent) and I should have two sides of the fuse ready to attach to the "real" strongback waiting in the wings.
The important thing to remember here is that this two-layer skin bears no loads. All loads are carried by the internal strongback.
Comments welcome.
Regards,
Duncan
I'm considering a rather novel approach to building my fuse, and would like to ask for some feedback on this.
Essentially, because I don't have the usual bulkhead templates normally used to guide the builder in shaping the foam core, I have found a very simple and accurate way to get the fuse shape. I have tried the foam core method with disastrous results. Without many reference bulkhead templates to guid you, it's a bit like abeginner trying to cut hair. Too much off one side, so you correct by taking more off the other to balance it up. Oops... Too much. etc.
Since I can only work in 2-D CAD all I really have to work with is a profile view of the plane - the sort of thing you draw on the back of a napkin - except that the measurements are accurate.
I have translated the on-screen measurements to wood, and have cut the profile out of particle board. I fixed an 8" spinner plate to the front, and by trial and error (and the eyeball method) shaped two main bulkheads - one up front at the plane's widest point, and one backing the pilot's seat.
I then took thin pine strips, attached them to the spinner and bent them round the two bulkheads to the tail. I repeated this a number of times, and the results were wonderful. Smooth curves, completely consistent with no hollows. See photo of early stage attached.
But here I begin to run into some conceptual (and practical) difficulties:
My plan is to cut 3" strips of 1cm (about 1/2") square wire mesh, and attach these strips from top to bottom. I'm hoping that this will (1) produce a smooth curve from top to bottom over the longerons (2) provide a firm base over which I can apply plastic tape.
The reason for the tape is to act as a release film for the next stage.
The next stage is to apply 3" glass fibre tape vertically, laying each tape next to (not overlapping) the one alongside it. I can lay these tapes in many installments, making the process low-stress (on me). No crinkles, no large quantities of resin, no mess. The tapes, being only 3" wide, will easily conform to the complex curves of the fuse, and can easily be stretched reasonably firmly over the underlying framework.
Once these are in place, I'll repeat the process, but laying the tape at a 50% stagger (ie shifted half to the side). In this way, I'll get two layers of glassfibre, with plenty of overlap.
I can then fill and sand the surface till I'm happy with it. Finally, I remove the entire side of the fuse (hopefully the plastic tape will have done the job of acting as a good release agent) and I should have two sides of the fuse ready to attach to the "real" strongback waiting in the wings.
The important thing to remember here is that this two-layer skin bears no loads. All loads are carried by the internal strongback.
Comments welcome.
Regards,
Duncan
