HPA

Mrs JMK gave me a 3D printer for Christmas and I have been playing with it and making things to help me to make better planes.

Here are some things I have made and used:

• wing and tail rib templates
• various sizes of squares to hold things at 90* to the building board
• a prop to set a rib at the right angle at the dihedral break
• a sanding block
• upper and lower sanding blocks to match the wing airfoil

The sanding block with a knob and the squares I found on Thingiverse.com.  The others are the result of my first attempts at using FreeCAD. 

I am going to have to find out more about things like wall thickness w3hen I send my FreeCAD files to the slicer program to generate the gcode file that instructs the printer.  The notches in the rib templates are sized at 1/16" (the model I am building was drawn in imperial measurements - it is a Coupe from  the 1960's -but they print out much smaller and need to be opened up with a needle file.  But otherwise, this is pretty good fun and makes helpful stuff.

BTW  I see that Thingiverse.com has a pattern to make a replacement fuel tank and tank cover  for a Mills 1.3,  Since I have a few Millses missing their tank. this might be a project for the next day or so.

Quote from: Jmk89

• wing and tail rib templates
• ...

Rib templates, now that is a good idea.

I took the liberty of removing the posts from the "What did you do..." topic, and starting a new one here, hope it is ok.

3D printing is and actual fact of modelling life these days and should be treated as such.

There are indeed many uses to make templates and jigs and CAD is not that impossible to learn, in order to be able to make your own parts. It takes some time but it is doable.

Having a 3D printer is another thing, but the simple ones are not so expensive anymore. Where to put them is another issue.

Whether it takes the fun out of traditional modelling or not, is another, open to discussion.

As is the penalty of using one or any modern technology for a scale model for competition, according to BMFA rules at least...

Please forgive my lack of knowledge and inexperience as I am a total newbie, but as I understand the BMFA-rules, so far I know them, it is seen differently wether the modern technology part (3DP, LaserCut, etc.) is directly used on the plane, or as a tool/mold, isn't it? Plus, doesn't it make a difference, wether you took it from anywhere, or designed it yourself?

Hi Sven,

nice cookie 

You got the rules quite right.

When it comes to scale classes where craftsmanship is also a factor to be judged, the BMFA rules dictate a reduction in points awarded. And these items have to be declared in the declaration form that will be handed to the static judges.

Contrary to FAI rules, which do not, as long as it is not a bought 3rd party item. IIFI follows this line.

However, it is a very unclear matter. Who 3D designed the part? who made the printing, who did the finishing etc. all this should be taken into consideration when deciding how much to reduce the score. No clear guidelines, for years now.

I was (unfortunately?) a pioneer in this discussion, as I 3D printed a dummy engine and other parts back in 2013 when all this was very new and it started a relevant discussion.
Blast from the past, HPA from 2013:
https://web.archive.org/web/20130823101845/http://www.hippocketaeronautics.com/hpa_forum/index.php?PHPSESSID=f7288cb0a0730603ba5db589294fbf3e&topic=15029.0

The same goes for other "modern" technologies, such as laser cutting, printed tissue etc. But the problem for me still remains. How much reduction?

Even worse is it when this applies to jigs and templates as well, which are not even visible on the model. That is another Pandora's box.
Personally I think the BMFA rules need to be revised.

Bill Dennis correctly posed the question back then and this led to the following thread
https://web.archive.org/web/20130823090122/http://www.hippocketaeronautics.com/hpa_forum/index.php?PHPSESSID=f7288cb0a0730603ba5db589294fbf3e&topic=15033.0

Plenty of familiar names, also in this forum after all those years. (Andy S., where are you? Somebody let him know... Sadly, some other names no longer with us at all...)

But, to close the subject from my side, to your question, if it is not a scale competition model, then there is no issue at all as it will not be subject to judging.

But leaving BMFA competition aside, 3D printing is a reality and a great tool if you can use it.

Such a tricky area. I used to fly F1D which basically had a builder of the model rule - then it got a bit fuzzy when people started buying/producing components like variable-pitch hubs etc which is now ok I believe. Just as buying components or whole models in the other classes (F1A/B/C). My youngest son now has a 3-D printer so I might get him to print me some parts! Or is that child labour    Maybe he can teach me...

Quote from: THB on Dec 30, 2025, 09:45 AMwhen people started buying/producing components like variable-pitch hubs etc which is now ok I believe.

No, it isn't...

Quote from: THB on Dec 30, 2025, 09:45 AMOr is that child labour 

No, it isn't...

 

I used a 3D printed pilot head and a VW boxer engine block in my Erla 5A. Both designs came from Thingiverse. At first I wasn't sure how to feel about it but considering similar components are commercially available ready-to-finish, I convinced myself that the use of 3D parts wouldn't be blasphemous   (e.g. Williams Brothers vacuum formed engines and pilot figures come to mind). Though I still don't know how much is too much, as at the extreme one can print an entire model airplane. Since I don't compete in scale, I'll keep using 3D printed parts, at a level which hopefully respects the spirit of the hobby.

(Pilot figure was created by Thingiverse user Wernersen, and is licensed under Creative Commons - Attribution)
(VW engine was created by Thingiverse user Maker_Flal, and is licensed under GNU - GPL)
 

PRINTED  SPOKED WHEELS      post  1 of 2

Tue Feb 24 2026

     When I went to the local Canadian Aviation Museum  here in Windsor.  my computer guru gave me these test pieces of 3D Printed spoked wheels,   1  1/2"   diameter, that he printed.    There were some globs,  and  some fallen and collapsed,  and missing,  spokes in a few places.     But after I worked on them with an Xacto knife,  and  side cutter ingrown toenail clippers,  they cleaned right up!    I can spin two halves of the one wheel set (two halves per wheel),  centered on each other,   spin it until I get the best evenly spaced kaleidoscope of spokes,   and that is where I will glue them up,  and nobody will know the difference,  for the most part ....

Pic #1     1679     Upper right.   The white and gray wheels are both halves glued together.   The bottom white wheel is just a single row of spokes.    The other four gray wheels  are just one half wheel each.   These four I will clean up and glue together.

Pic #2     1693     The four front gray half wheels  are cleaned up.

Pic #3     1695     The stacked gray wheel on the left has a gap between the halves.   That is because the center hub of the spokes stick out further on one side than the other side of the same wheel half.

     The two halves on the right,  have been clamped with the long sides of the center hubs,  pressing against each other in the middle.   This pushes  out the  "dome"   or "dish" of the spokes.    The gray and the white completed wheels in the background are dished.

Lastwoodsman
Richard

PRINTED  SPOKED WHEELS      post  2 of 2

Tues Feb 24 2026

Pic #1     1697     Mandrake and Bloodroot drill the center holes with a  #59  pin vise.

Pic #2     1703     Even though the plastic is very hard  ( the thin spokes are surprisingly very hard ),  the printed part will give a nice curled chip of material,  when drilling a hole.

Pic #3     1705     Two  wheels  ( four halves )  to glue up.   Paint comes after -   a darker gray than the spokes and rim.

     I think I can use these on my  30"  Dumas Gipsy Moth ....

Lastwoodsman
Richard

I wonder if we could create a 3r Printing section of the Plan Gallery and upload stl or 3mf files of our own 3D printing designs with helpful notes to users to there.  That will be easier to navigate than Thingiverse etc

Yes we can and it will be done.

George

What about Laser-Cutting, would it be a good idea to have another section for that as well?

When I went to the box that should have had bobbins for the CdH that I have built for the postal comp, I had a Mother Hubbard moment (from a nursery rhyme - "when she got there, the cupboard was bare").

So 10 minutes on FeeCAD and now I have two 16mm bobbins with a 6mm "axle" with a 4mm hole - which I hope will slide easily over a 3mm or 1/8 aluminium tube rubber peg.