What would i have done differently?

Proposal of changes. Useful tips!

I had to stop the project because it took longer than expected in development and it took most of the available money. I was not prepared to go into red.

I admit ...i made mistakes in choices. If i would have done it differently the DragonWing would be flying. Now ...it is just a stack of moulds stored in my garden.



Mould making

Advised by Kees Radius we used CNC cut foams as a positive shape. We would put glassfibre in top of it. Sand it till it shined. Make a negative mould of it. Make that one shine too. Sounds easy. But ...it is also time consuming! 1,5 to 2 months for a single mould with three guys working for me! And i needed 9 moulds at the minimum! Those were very, very expensive years.

Sietse Van Doorn gave me some advise about how i could have started in a different way. His idea was to let CNC cut roughly the NEGATIVE moulds in hard foam. The cut shape would be a few mm less than the needed shape. Apply a layer of gel-coat over it which is specially made as finish layer for moulds. Apply too much of that material. Have the CNC now cut the true shape of the negative mould at its best finish. Let a car-guy sand and polish the inside of the mould. Let him not take away too much material, just take away the CNC cutting lines.

It would cost more in CNC and maybe materials. But those costs you would know in advance. Man-hours to make those moulds in the first manner you cannot predict in advance.

I got in contact with Red Jensen, a model maker at NASA. He made the models for the Prandtl project of Albion Bowers, chief scientist at NASA.

Red gave me a few picture of what i see as THE way to make moulds for a full scale composite hangglider. He says: "The molds were milled out of 15 lb. tooling foam on a 5 axis router. They were then hand sanded and finished with resin then primer."

The large model they made and the interns
that helped to create it together with Red and Al.

This is the way moulds should be made. CNC cut moulds.
The white layer is one of the foams that will become the skin of the model.

Here they also used the type X elevons.
Later it was changed into elevons more like on the PUL-10.

If you want to see more pictures of the NASA models for this project, go see the NASA Prandtl page.



Keep it simple!

I made several proposals for fuselages. Each time it became more and more aerodynamic, but ...also more complex to make. I should have stayed with one of the first proposals. Those were very easy to make as mid section.