Twin edf SU-27

[Flitedesign 3d]

So do you first model the outer shape as surface model , and then the internal structure?

The two main options are either first make a surface model and thicken it into 3d solid or make a 3d solid and hollow it out. I feel like it is more a personal preference which one to favor. I use both, the latter one more often perhaps. Hollowing out a lofted solid has the advantage that the ends of the loft are actually planar. So the workflow might look something like: make two profile sketches using splines or arcs -> loft a solid between them -> hollow it out -> using the same profiles extrude out formers/bulkheads -> offset their outer surface inwards by the thickness of the foam. There are many ways to do it and trial and error is the best way to find ones own method

 

[Karthik1130]

The two main options are either first make a surface model and thicken it into 3d solid or make a 3d solid and hollow it out. I feel like it is more a personal preference which one to favor. I use both, the latter one more often perhaps. Hollowing out a lofted solid has the advantage that the ends of the loft are actually planar. So the workflow might look something like: make two profile sketches using splines or arcs -> loft a solid between them -> hollow it out -> using the same profiles extrude out formers/bulkheads -> offset their outer surface inwards by the thickness of the foam. There are many ways to do it and trial and error is the best way to find ones own method

1. How do you comeup with various internal structures design? what specific process do you carryout?it would be really helpful if you could share.
2. How do you CAD model these nose cones? it has lot of intricate bevel-cuts inside.
3. What CAD program do you use?
4. How to know the bendradius, k-factor, bendallowance for applying to the foamboard parts?

 

[Karthik1130]

1. How do you comeup with various internal structures design? what specific process do you carryout?it would be really helpful if you could share.
2. How do you CAD model these nose cones? it has lot of intricate bevel-cuts inside.
3. What CAD program do you use?
4. How to know the bendradius, k-factor, bendallowance for applying to the foamboard parts?

@Flitedesign 3d could you reply to the above question, and also can this Su-27 be built with 7.25mm thickness foamboard?Could you share some tips to a beginner on how to learn designing foamboard airplanes?

 

[Flitedesign 3d]

@Flitedesign 3d could you reply to the above question, and also can this Su-27 be built with 7.25mm thickness foamboard?Could you share some tips to a beginner on how to learn designing foamboard airplanes?

Hi, regarding the questions above: I don't have a specific process to carry out, It's more a trial-and-error process. Model something, realize how it could be improved, improve it and repeat. For cones and parts with non-uniform bevels, I unwrap both the outer and inner surface and merge them in LibreCAD, the software I use for drawing the 2d plans. I use Fusion360 for 3d modelling, you can get a personal license for free though it's somewhat restricted now days. I wouldn't be so concerned about which cad-software to begin with, once you understand how cad works jumping from one software to another is quite effortless. I suggest pick the software that's accessible to you and you find the best tutorials for regarding modeling of airplanes. For the fourth question, I don't use sheet metal modeling for foam board although I suppose you could. Given the neutral axis, that is the surface that stays dimensionally unchanged in bending, of foam board is basically the outer paper skin, the k-factor is presumably very close to 1. Bend radius parameter is for applying minimum radius in sharp corners an you shouldn't worry about it if you draw your lofting profiles correctly and bend allowance is, as far as I'm concerned, computed automatically from k-factor and bend radius?

I wouldn't recommend going beyond 5 mm in the foam thickness as the bending of plates becomes drastically more difficult as thickness increases. If you do want to try foam of a different thickness, please read the posts #81 and #87 in this thread to avoid a known issue. For you last question: as cliche as it sounds, the best tip I can give is just get started with it. Follow tutorials, such as those Mr Man suggested in post #96 and simultaneously build a model yourself. Get familiar with your tools and the rest will follow.

 

[Karthik1130]

i

Hi, regarding the questions above: I don't have a specific process to carry out, It's more a trial-and-error process. Model something, realize how it could be improved, improve it and repeat. For cones and parts with non-uniform bevels, I unwrap both the outer and inner surface and merge them in LibreCAD, the software I use for drawing the 2d plans. I use Fusion360 for 3d modelling, you can get a personal license for free though it's somewhat restricted now days. I wouldn't be so concerned about which cad-software to begin with, once you understand how cad works jumping from one software to another is quite effortless. I suggest pick the software that's accessible to you and you find the best tutorials for regarding modeling of airplanes. For the fourth question, I don't use sheet metal modeling for foam board although I suppose you could. Given the neutral axis, that is the surface that stays dimensionally unchanged in bending, of foam board is basically the outer paper skin, the k-factor is presumably very close to 1. Bend radius parameter is for applying minimum radius in sharp corners an you shouldn't worry about it if you draw your lofting profiles correctly and bend allowance is, as far as I'm concerned, computed automatically from k-factor and bend radius?

I wouldn't recommend going beyond 5 mm in the foam thickness as the bending of plates becomes drastically more difficult as thickness increases. If you do want to try foam of a different thickness, please read the posts #81 and #87 in this thread to avoid a known issue. For you last question: as cliche as it sounds, the best tip I can give is just get started with it. Follow tutorials, such as those Mr Man suggested in post #96 and simultaneously build a model yourself. Get familiar with your tools and the rest will follow.

thanks for all the information which you have provided, and its really helpful.I have queries for the following:
1) Why both the outer and inner surface has to be unwrapped and merged? Can't the outer surface alone be used to create the flat-pattern?
2)do you use any other glue apart from hot glue?

 

[Flitedesign 3d]

i

thanks for all the information which you have provided, and its really helpful.I have queries for the following:
1) Why both the outer and inner surface has to be unwrapped and merged? Can't the outer surface alone be used to create the flat-pattern?
2)do you use any other glue apart from hot glue?

For one, it's my solution for otherwise hard to draw intricate bewels, wasn't that what you asked? And for two, rarely, perhaps some 30 min epoxy for some really large and risky seams