WIP on a foam core jig with CAD links

[Justin]

Hi Folks,

I am adding foam planks to the jig now, cut from flat sheet foam. I think some kind of foaming adhesive would be best for bonding these planks.

I foresee that I will completely re-plank this to make the planks easier to mark out and cut.

CAD files are uploaded here :  

https://grabcad.com/library/quickie-q2-200-fuselage-foam-jig-wip-1

This is just work in progress

 

[Anthony P]

Nice work!

What program are you using?

What tool/feature are you using to assure that the planks come from flat stock with 3/8-1/2" thickness?

After examining a set of factory shells, it seems like the majority of each shell (4 shells total) was made from a single continuous sheet of foam which has many relief cuts to allow for wrapping, warping, and bending as it was pushed down into the female mold. Not sure if this strategy would be easier that what you have planned, but from the CAD and printing templates perspective, they both seem nearly equal.

[Justin]

Hello Anthony,

I do a lot of the CAD work in Rhinoceros, but for detail and assembly work I use my day job Catia. I am considering getting my own Autodesk Inventor license for other projects too.

I would be interested in finding out the thickness of the kit shells. It is likely that was an easier way to go, but foam planking is really easy too. I have made a few boats that way.

[Anthony P]

Total thickness 0.42"

Skin thickness 0.03"

Another interesting detail, the foam seems to be perforated (0.03" hole) on a 1" grid. Maybe to add mechanical bite and/or bridge the inner and outer skins.

[zolotiyeruki]

2 hours ago, Anthony P said:

Total thickness 0.42"

Skin thickness 0.03"

Another interesting detail, the foam seems to be perforated (0.03" hole) on a 1" grid. Maybe to add mechanical bite and/or bridge the inner and outer skins.

Is that .03" on the inside and outside?

[Anthony P]

Yes.

[Justin]

Hi Anthony,

Thank you for that information. The holes on the 1" grid are probably bleed holes to let resin through to a breather layer when the foam is being vacuum bagged onto a skin in a mould.

I forgot to answer your question about flat development of planks. Rhino has a command for this. It will unroll any surface that has 1 degree curvature in one direction; just like a plank has across its width. The surface should have reasonable parameterisation in the other direction, and then this command produces very accurate developments.

 

[Justin]

Just a small screenshot update.

I am re-planking in a layout that uses mostly parallel sided 2.5" wide planks, with tapering in some places. These would bend in the plane of each plank, as well as around the jig templates, so only the width of the plank is relevant. The planks could be cut pretty much straight, with this new layout.

I am inclined to go with 0.5" thickness foam sheet to start with, because something like 0.08" to 0.1" will be faired off. It is likely this core will end up a little heavier than the thermoformed kit core, but I expect the difference in weight would be very small.

[zolotiyeruki]

Do you plan to eventually build an Q200 with this method?  It looks very promising, and very accessible, assuming someone has access to the jig.

[Justin]

2 minutes ago, zolotiyeruki said:

Do you plan to eventually build an Q200 with this method?  It looks very promising, and very accessible, assuming someone has access to the jig.

Well, I don't know. The aircraft fascinates me. Q1 as well. It is such clever design, with a small robust structure.... quite short lifting surfaces.... very easy load paths.... and it is super sleek.

If I built one I would use this technique. Kit cores are probably not available secondhand here in the E.U.  Mine would be a Q260 ! I would use the UL260i engine. It is a tiny bit lighter than the Revmaster. It is a lot more expensive, but has 97hp, fuel injection and FADEC.

I will make the jig design easy for anyone to build. The formers could be mill, water or laser cut MDF 10mm thick. The CAD modeled formers have edges bevelled to the inside of the foam, but they could be cut square, as long as the builder pins the planks on very close to the plank-former contact edge. I have done this in foam boatbuilding. The foam planks strain easily, and need very light fastening pins to constrain them to the jig until the adhesive between the planks sets.

The other part that is also probably not available it the LS-1 round canard spar. I don't like it anyway, and would follow the Wieshaar Doyle idea...      https://aerobase.weebly.com/ls-1-canard.html

[Justin]

Just made an update to the CAD files....

https://grabcad.com/library/quickie-q2-fuselage-foam-update-1

It is completely re-planked. A lot of the planks are now simply 2.5" wide. Several do have some tapering. Most are nearly straight.

There will be some minor tuning to the planks, but the layout is now good enough that I can return to the jig design.