FTFC'25 MS Design Bristol M1c designed by Spitfire76

[Spitfire76]

I actually designed and built this plane back in early 2022 for another challenge but have been looking for an excuse to make some major improvements so thanks for allowing me to enter this challenge. The judges should take into consideration that I will have a major head start over someone that is starting from scratch.

This is the link to my original build log.

1:9 Scale Bristol M1C - The HangarRC 2022 Build off Challenge

My build log for the following challenge https://www.thehangarrc.com/buildoff/ Although I’ve scratch built and flown several FT planes I have never designed a plane before so this will be a first for me. The "HangerRC Build off"challenge ruled out multiple wing and multiple motor designs and so...

forum.flitetest.com

Link back to main challenge thread

FTFC’25 MS Design And Build

I am thinking the Komet so far…….

forum.flitetest.com

 

[Spitfire76]

The scale I used for the original design was 1/9th but I felt it could be a bit larger so I plan on going with a 1/8th if that is acceptable for this challenge (i see that 1/10th scale is encouraged)

Full scale wingspan = 30ft 9in
1/10th scale = 36.9in
1/9th scale = 41in
1/8the scale = 46.125in

I did not make the wings removable in the original design and don't plan on changing that in version 2. This would make it slightly shorter than the master series Spitfire (48in) that also has the wing glued to the fuselage.

 

[Mr Man]

The scale I used for the original design was 1/9th but I felt it could be a bit larger so I plan on going with a 1/8th if that is acceptable for this challenge (i see that 1/10th scale is encouraged)

Full scale wingspan = 30ft 9in
1/10th scale = 36.9in
1/9th scale = 41in
1/8the scale = 46.125in

I did not make the wings removable in the original design and don't plan on changing that in version 2. This would make it slightly shorter than the master series Spitfire (48in) that also has the wing glued to the fuselage.

Any scale is acceptable. Those are just the encouraged scales.👍

 

[Spitfire76]

I did not use Autodesk Fusion to create the plans for the 2022 version but will be attempting to do so with this 1/8th scale version.

The 3 views are copies of the original full scale drawings, dated 1917, that were kindly provided to me by the Shuttleworth Collection in the UK that had built and flown a full scale replica.

I am using a lot of the methods from the following series of YT videos.

 

[Spitfire76]

The most challenging part of designing a model of this plane is the rear part of the fuselage.

Above, full size replica - Shuttleworth Collection UK

I have managed to create it this time in Autodesk Fusion using the loft feature and rails to follow the contours of the top and side views.

For the 2022 version I used card stock around a foam board box core but was never really happy with it. For this version the intent is to make it "Master Series" style and use foam board with the paper removed from one side.

 

[Mr Man]

The most challenging part of designing a model of this plane is the rear part of the fuselage.

View attachment 249541
Above, full size replica - Shuttlesworth Collection UK

I have managed to create it this time in Autodesk Fusion using the loft feature and rails to follow the contours of the top and side views.

View attachment 249542



View attachment 249543
For the 2022 version I used card stock around a foam board box core but was never really happy with it. For this version the intent is to make it "Master Series" style and use foam board with the paper removed from one side.

Nice!

 

[AIRFORGE]

"Master Series" style

 

[Spitfire76]

I was attempting to make the "skin" of the rear fuselage as one part rather than split it into a number of sections between formers but it looks like I can't convert a lofted section that includes rails to sheet metal in order to "unfold" it. I could make several lofted sections without rails but again was trying to avoid this if possible.

I learnt from @Mr Man that OnShape has a "flatten" feature and I see that this is part of their analysis tools. In the initial testing that I have done it does not seem to complain about a lofted section that has rails (guides in Onshape). I was able to export the flattened skin to a SVG file to load into inkscape. From here I should be able to generate the gcode to my foamboard needle cutter.

I'll attempt to recreate the rear fuselage section of the Bristol M1c in OnShape and cut it together with formers to see how it goes together.

 

[Spitfire76]

Before creating the actual rear fuselage I did a quick test with a similar polygon shape and found an issue. When exported as dxf or svg file there are no internal fold marks. This is fine for cylinder shapes but not for polygons as I would need to know where to perform the score cuts.

I do get marks for the score cuts with Fusion's sheet metal feature but as I mentioned earlier it does not work with loft rails.

OnShape has a sheet metal feature but lofts with or without guides can't be converted and unlike Fusion it does not look like that there is a "loft" flange.

 

[Mr Man]

I was attempting to make the "skin" of the rear fuselage as one part rather than split it into a number of sections between formers but it looks like I can't convert a lofted section that includes rails to sheet metal in order to "unfold" it. I could make several lofted sections without rails but again was trying to avoid this if possible.

I learnt from @Mr Man that OnShape has a "flatten" feature and I see that this is part of their analysis tools. In the initial testing that I have done it does not seem to complain about a lofted section that has rails (guides in Onshape). I was able to export the flattened skin to a SVG file to load into inkscape. From here I should be able to generate the gcode to my foamboard needle cutter.

View attachment 249581

I'll attempt to recreate the rear fuselage section of the Bristol M1c in OnShape and cut it together with formers to see how it goes together.

I recommend exporting in dXf, its easier to modify in Inkscape.

 

[Mr Man]

Before creating the actual rear fuselage I did a quick test with a similar polygon shape and found an issue. When exported as dxf or svg file there are no internal fold marks. This is fine for cylinder shapes but not for polygons as I would need to know where to perform the score cuts.

View attachment 249584 View attachment 249585
I do get marks for the score cuts with Fusion's sheet metal feature but as I mentioned earlier it does not work with loft rails.

OnShape has a sheet metal feature but lofts with or without guides can't be converted and unlike Fusion it does not look like that there is a "loft" flange.

Maybe create super small incisions to mark score cuts?

 

[Spitfire76]

Maybe create super small incisions to mark score cuts?

Thanks, it was a great idea! I tested it and initially I had the small V cut across the entire service and it complained with the following

But if I leave a gap then it becomes a contiguous surface.

I need to do some more testing with lofts and guides but it does look promising.

 

[Mr Man]

Thanks, it was a great idea! I tested it and initially I had the small V cut across the entire service and it complained with the following

View attachment 249602

View attachment 249601

But if I leave a gap then it becomes a contiguous surface.

View attachment 249599 View attachment 249600

I need to do some more testing with lofts and guides but it does look promising.

Nice! Btw, if you import the plane from fusion in a step file, you can flatten it all in onshape.

 

[Mr Man]

Nice! Btw, if you import the plane from fusion in a step file, you can flatten it all in onshape.

But one piece at a time is best.

 

[Mr Man]

How's it coming?

 

[Spitfire76]

How's it coming?

To be honest no real progress since my last post in March. Shortly after that FT released plans for their Super Scout XL and I decided to build one to fly at our club's Everything Electric event and so I was totally focused on that build for the the remainder of March and half of April. Then my friend and I started a very ambitious 3d printed B17 project which has taken up most of my build time since then. Having said that I do want to continue with this challenge.