Devfus foam

[wanttobuild]

For the LARGE AMOUNT OF LABOR SAVINGS, one might want to rethink about the impractically of glassing the inside of the fuselage structure. Uncomfortable? depends on your method. Manageable? yes
When the fuselage is comprised of small slices, access for reinforcement placement IS granted. Non traditional? you bet! Will it work? no doubt about it. YMMV

 

[BJC]

For the LARGE AMOUNT OF LABOR SAVINGS, one might want to rethink about the impractically of glassing the inside of the fuselage structure.

There are significant advantages to using sandwich panel construction.

For an example, take a look at the Vision plans-built composite airplane. A poster named Vision (are you still here?) built one. It uses moldless sandwich construction for the fuselage and wing skins. https://pro-composites.com/Vision Builder Photos.html


BJC

 

[stanislavz]

From mine point - you can use sandwitch. And you can use parabeam 3d fiberglass. You only need female mold for it.

Or you can use black aluminium, and copy paste metal construction - ie longerons hat shaped + minimal bulkheads. You already have all templates..

Or if go for male mold and loss foam - cut bulkheads from fiberglass using same g code, as for slices. + some u shaped longerons.

 

[Lendo]

Stanislavz, - Love your enthusiasm, however nothing beats proper research and planning. Are you Croatian?

Jim Marske's manual is good up to a point, but he fails to address buckling (Beam Buckling) of the Web. All Beam Buckling formula are on the Internet, I don't have it in front of me. You will find a Spar will start to fail in the Web, taking the Caps with it, the trick is to take the Web strength beyond that of Possible Buckling. Pretty logical really. You can't beat the Carbon rods for weight and strength

Carbon is light and strong, but fails catastrophically, great weigh savings can be made with Carbon, but hand lay-up it's about as strong as S glass, but much stiffer.
Remember the more weight you save on glass the more weight you save on resin.

On Foams, a good European standard is Divinycell, Last-A - Foam (LAF) crumbly structure - easy to sand, poor for bonding. You can bend Divinycell easily by heating it. Is is stronger in all categories except compression strength, get samples and test them.

There is already a discussion on Mazda Engines on HBA, have a look for it, however there are other discussion groups which address the issues on conversion. Personally I love the Mazda Rotary engine, just wish it were Lighter and the promised PSRU was available at this point in time for those who need it. All comes to he who waits. Be very careful on what you settle for in a PSRU.

The Vision Plans build Aircraft manual has good information of plies and their orientation, plus a great deal of other information you could transfer to any other design, provided it's in the same size and weight range. You could convert those Glass materials into comparable Carbon Weaves, if you wanted to save weight - all available at Spruce Supplies.
Hope that helps.
George

 

[stanislavz]

I am from Baltic region. And not even close to any kind of structural design.

 

[proppastie]

Wanted to post it into current cnc foam cutter thread, but I think, it is worth separate one. Making a fuse mold from foam slices.


Using this piece of software : http://www.devcad.com/eng/devfusfoam.asp

Tried with 10000 mm long fuselage, and 100 of slices - looks to be working slow, but ok. And you can make even thinner one slices, but cutting from same piece of foam, make sanding close to none,, and with foil on foam plug making - do it in really fast manner.

nice work...but .....if one has a 4 axis traveling hot wire or mill/router ....sure,.. you can cut almost any shape ....engineering the structure for strength seems to me to be the elephant on the table.

 

[stanislavz]

.engineering the structure for strength seems to me to be the elephant on the table.

And i did not mention a structure in any way. This is only the one possible way, how to build the mold, or plug for the mold.

Not the perfect one, but the easiest and safest one..

4 axis foam cutter for this task can be built in a few days. I have bailed two in past.

 

[Exian]

Sailplane cockpit female mold made with lots of hot-wired slices.



IInner surface then glassed for release with the molded part.

 

[stanislavz]

Sailplane cockpit female mold made with lots of hot-wired slices.
View attachment 89133
View attachment 89134

IInner surface then glassed for release with the molded part.

Any sanding or no sanding ?

 

[Exian]

Yes, sanding and even some filling.
Even with 90 mm slices and a sleek shape like a sailplane, deviation from perfect curve can still be close to 1 mm in some spots, and would be later 1 mm of filler on our flying plane. Better to remove it at the beginning than having to carry it on the plane...

Hot wire cuts were still made by hand with templates.
I defined my fuselage shape in a classic 3D CAD software (CATIA), and made cuts every 90 mm to get the various sections.

Sections are printed on paper with a laser printer so that I can epoxy the paper on plywood (epoxy will blur standard ink). This way there is no error in the transfert from computer to template. Your sawing skills are the limits...
.

 

[Exian]

Light plane fuselage positive plug made with lots of hot-wired slices.


Hops, thread drift, sections were not defined in CAD but by hand!

 

[stanislavz]

On cnc foam cutter, cutting xps, i could a 0.2mm accuracy. It is more depended on foam internal stress and positioning whan cnc itself

 

[stanislavz]

Hi all.

Two general questions.

1. Kind of rule of thumb - Hat reinforced fiberglass panel, ratio of mass in hat to ratio of skin mass. Which extremum is better ? Maximum possible masse/size of hat elements - close to tube and rag fuselage. Thick skin - stressed skin..
2. Trapezoid flat plate vacuum infusion. Like this one / \ resin start to flow from bottom or top ?

 

[stanislavz]

Small update.

Got extra profiles for larger cnc hot wire cutter :



And -

This is a structure behind this airplane:

Full patent is here : https://patentimages.storage.googleapis.com/9f/62/62/9413de545b728e/US8210466.pdf

Less safe, but if one do not want to weld - why not. And skin is only a skin then..

 

[stanislavz]

And one more photos of icarus

 

[Vigilant1]

Stanislavz,
Thanks for your posts on BoKu's Carbonmax puddlejumper thread. I poked around the DevCad site a bit, they have a lot of products, and there seems to be some overlap. You are familiar with some of this, I'd be interested in your recommendation. I'd like to be able to draw a plane (flight surfaces and fuselage) and then make female foam molds (hot wire cut from XPS sheets, then stacked? CNC cut from one large block? I'm not sure which would be best/available in my area). I'd >prefer< to start by drawing in 2D (automatically mirror-image left and right sides), with the ability to see 3D. Maybe I'll someday want to export to SolidWorks.
Yes, I could probably do a lot of this with SolidWorks or other high-end CAD software, but having the airplane-specific templates in these DevCad applications would offer some structure that might make it a lot faster and easier for me to start making progress.

Observations:
- It looks like if I buy DevFus Mold that I'll get the capability to 1) Draw the fuselage (just as if I was using DevFus alone) and 2) Cut male or female foam molds
- - It looks like if I buy DevWing Mold that I'll get the capability to 1) Draw the wing, with ribs andother internal structure (just as if I was using DevWing alone) and 2) Cut male or female foam molds (for ribs, skin, etc.)

I assume there's some way to stitch the DevFuse and DevWing drawing together to have an entire airplane.

I know your aren't a DevCad representative, I'll contact them directly next. But do you have any insights or ideas on which products would be best for what I want to do? I'm not at all proficient with CAD tools--more of a graph paper or MS Draw guy. At least right now . . .
Thanks.
Mark

 

[stanislavz]

I know your aren't a DevCad representative, I'll contact them directly next. But do you have any insights or ideas on which products would be best for what I want to do? I'm not at all proficient with CAD tools--more of a graph paper or MS Draw guy. At least right now . . .
Thanks.
Mark

Hi !

Use sketchup/or other cad tool instead. You are dealing with straight lines for big parts, like tail part of fuselage.


But am a fan of devfus, of its easy to model thing. But they are quite limited to having only "sliced fuselage" Which is maybe okay for a model, but will provide ugly results in real life without sanding. Not talking about hyperbolic paraboiloid paths . But is ok to use it for more curvy areas like engine canopy.

Having two independend x/y gantries of ~ 1.5 x 1.5 travel - in my garage is quite an hard on space. But having one and using tapered cutting - is ok. I am cutting styrofoams for 10 yers in total. Hardest way is to hide an glue line. Nor it is easy cutted nor it easy to sand, unless it is parallel to cut. So - pay an fortume, and find a way how to order full cube of foam. In my country it is sized at 1 x 1.2 x 4 meters.

And i would cut two halves from both sides, it will provide best possible geometric stability. :

 

[stanislavz]

And you can make molds for wings too :



Or some from inside, plento of foam left :

 

[daveklingler]

It's easy to create plane sections (slices) in SolidWorks if you're an EAA member and already have it as part of EAA membership.

Not that I think the devCad prices are in the least bit unreasonable.

 

[Geraldc]

I have downloaded a trial and can't see any way to cut tapered sections inside each other to save foam.Any tips?