Skin modeling with foam sheets - RC Groups
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Dec 17, 2017, 02:52 AM
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osern's Avatar
Idea

Skin modeling with foam sheets


Updated
For whom is interested in scale modeling tech,here is another viable choice than balsa building.
Balsa building is a conventional and respectable tech for majority of scale modelers,solute to them.
Depron board building rather to be long thought of box like or in-durable building tech,it's time to open your mind for them.

Depron boards are plastically flexible in shaping for bending,stressed forming and sanding for finish on surface,with tapes or some covering, they can be stiff and tension stress resisted in light weight,with scribe line or v-notches on the back side,they won't crack as crispy with bending as you image.

Attachments below shows they can be bent almost like a clay into a mask sculpting,you can image how easy to build even easy compound curved surface of airplane models.

Cut out original Profiles of 3-view from some paper or depron board,they could be assembled into a rough 3D box like model,if you furtherly bend those flat surface into slope round surface like the curve of smiling curve,things gonna be different,those board with curve edge sealed and shrunk into round shape unlike tricky paper models with countless cutout and section rings to form up compound curve,for depron boards has ability to shrink under stressed bending.

This tech is unimaginable for most of people,I'm telling you,it's easy and efficient to do modeling,they can use in park flyer or nano model for the light weight and reasonable strength of structure,just with different building blocks.
Skin Modeling with Depron foam board on P40 scratch building (6 min 19 sec)
Last edited by osern; Jan 14, 2018 at 09:13 PM. Reason: change title
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Dec 17, 2017, 07:05 AM
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Captain Dunsel's Avatar
Nice work, Osern. As a life-long modeler who's trying to transition from balsa to foam, I appreciate how different the techniques are and how much it takes -- yet how nice the results can be.

One question: Now that modeling-grade Depron is off the market, where does one get Depron good enough to work with? I've been focusing on house insulation (extruded) foam, cut into thin sheets. But, using Depron would be interesting.

CD
Dec 17, 2017, 07:27 AM
Registered User
osern's Avatar
Thanks,CD
I respect balsa modeling,it's a professional and accurate modeling techniques which you'll firstly think of scale building,in facts I'm trying to learn,too.

I'm not sure if there are some sorts of rating or grades for depron foam boards.
What I have here in Taiwan,It's common in stationary stores everywhere for students' art work or POP bulletin board usage,coming in different thickness,they might resemble to fan fold foam board without paper covering. I believe they are made of the same material.
They might be just like dollar tree foam boards or Readi Board,slice and cut into sheets from high density foam which are different from soft bea foam.
I'm always wondering why people don't get the idea when I mentioned about bending depron boards things ,few of them really get the points,maybe that's because depron boards are rare there in U.S,but I googled it,I can say they should be those alternative ones I'd mentioned.

regards and respect

Osern
Last edited by osern; Dec 17, 2017 at 11:35 PM. Reason: poor English texting
Dec 17, 2017, 12:52 PM
Registered User
Bare's Avatar
Welll.. as you noted Depron is more or less unavailable in North America these days.
That's a problem, with varyingly successful workarounds
Depron IS a different (superior imo :-) material than that found inside cheap grade Foam core board.
Also while your face /mask is an impressive Foam molding result, the airplane models.. not as much.
Exhibiting detail / smoothing issues etc.. all the inherent problems of foam skins that can't be easily sculpted or finish sanded.
Some materials simply work better than others.. is all.
Dec 17, 2017, 07:19 PM
Registered User
osern's Avatar
Quote:
Originally Posted by Bare
Welll.. as you noted Depron is more or less unavailable in North America these days.
That's a problem, with varyingly successful workarounds
Depron IS a different (superior imo :-) material than that found inside cheap grade Foam core board.
Also while your face /mask is an impressive Foam molding result, the airplane models.. not as much.
Exhibiting detail / smoothing issues etc.. all the inherent problems of foam skins that can't be easily sculpted or finish sanded.
Some materials simply work better than others.. is all.
Bare,sir
Thanks,I'm asure you that it's hand work without mold and much sanding.
The mask I posted is not symmetry if you notice,also the fuel tank is not molded which are bent and rolled by bare hands,there is no need to
do mold for round shape if you see the tech,it's a much simple and fast way I'm seeking for.
Some samples I'd shown are bent without taping covered to show its flexibility allowing some little crack or creasing occurred,if I bent them with fully tape covered,it'll be more smooth almost like a molded one.

I purchase RC parts and working materials online mostly,I think if you like,they are available on web shopping.

You see,even a senior modeler like you Bare,sir,won't get the idea,now I realize that there are reasons behind there.
I read about the plug mold you'v been using before, after your discussion of balsa soaking tech with Bill,so I try to build the same He 162 with mini scale to demonstrate the simple and effective way furtherly,if you can source the decent depron boards in case.
Last edited by osern; Dec 20, 2017 at 10:58 PM. Reason: poor English texting
Dec 17, 2017, 08:51 PM
treefinder
springer's Avatar
First, truth in advertising, I sell Model Plane Foam. MPF is a similar foam to Depron in that it is a continuously extruded Styrene based foam sheet. It uses the same chemistry as Dow High Perf LF fanfold that we determined was the best mix of properties of the available fanfolds. It is a little less stiff than Depron but significantly tougher (damage resistant in those unintended landings). For the purposes of this thread, it is also significantly more cold formable than Depron. While most folk apply tape to the outside surface before bending Depron, one can cold form a sheet of MPF to about 3" diameter cylinder pretty easily. With a bit of heat from a heat gun, One can get that down to a 1" dia. cylinder. Tapered cones are easy, and I have several planes where I made the aft fuse/turtleback from a single piece of foam, and pulled the tail together to a 180 degree bend for a line to line surface at aft tip of fuse.

As noted above, the paradigm shifts from building a structure that is skinned with essentially a non structural material to building a structure where the skin is a major part of the strength and stiffness.

MPF is nominal 6mm thick (varies from 5.2 to 6 depending on the run by manufacturer). At that thickness it can be sanded so that any waves or variations can be sanded out without compromising the strength.

Here is the thread that tells the history: https://www.rcgroups.com/forums/show...20plane%20foam

The only caveat to all this is that while original Depron was a dead flat sheet, MPF isn't. It has a gentle curve over the long dimension, and frequently has shorter waves across the short dimension that are about .5mm deep and 75-125mm wide. These often show on only one side, so can be put on the inside of the surfaces. I have had been able to sand out most all these discontinuities in shaped fuses and most wings.

My understanding is that the parent company found it unprofitable to produce the closely monitored sheet that was original Depron, I have an ongoing "discussion" with Adams, the MPF manufacturer to keep MPF as smooth as they can make it with their current process. Some batches are nearly perfect, as smooth and flat as Depron, while some are more like typical Fanfold, (just white, no printing, films or perforations).

So, It's not perfect, but for many guys a viable option and way less expensive than Depron was. In the thread here on RCG and in the gallery on the website, you can see that it has been used for most all genres of aircraft modeling. modelplanefoam.com

Originally we were able to ship it all over the world, but in the last couple of years shipping rates got so crazy that I stopped sending it internationally, so it's a US only product.
Dec 17, 2017, 09:59 PM
Registered User
osern's Avatar
Quote:
Originally Posted by springer
First, truth in advertising, I sell Model Plane Foam. MPF is a similar foam to Depron in that it is a continuously extruded Styrene based foam sheet. It uses the same chemistry as Dow High Perf LF fanfold that we determined was the best mix of properties of the available fanfolds. It is a little less stiff than Depron but significantly tougher (damage resistant in those unintended landings). For the purposes of this thread, it is also significantly more cold formable than Depron. While most folk apply tape to the outside surface before bending Depron, one can cold form a sheet of MPF to about 3" diameter cylinder pretty easily. With a bit of heat from a heat gun, One can get that down to a 1" dia. cylinder. Tapered cones are easy, and I have several planes where I made the aft fuse/turtleback from a single piece of foam, and pulled the tail together to a 180 degree bend for a line to line surface at aft tip of fuse.

As noted above, the paradigm shifts from building a structure that is skinned with essentially a non structural material to building a structure where the skin is a major part of the strength and stiffness.

MPF is nominal 6mm thick (varies from 5.2 to 6 depending on the run by manufacturer). At that thickness it can be sanded so that any waves or variations can be sanded out without compromising the strength.

Here is the thread that tells the history: https://www.rcgroups.com/forums/show...20plane%20foam

The only caveat to all this is that while original Depron was a dead flat sheet, MPF isn't. It has a gentle curve over the long dimension, and frequently has shorter waves across the short dimension that are about .5mm deep and 75-125mm wide. These often show on only one side, so can be put on the inside of the surfaces. I have had been able to sand out most all these discontinuities in shaped fuses and most wings.

My understanding is that the parent company found it unprofitable to produce the closely monitored sheet that was original Depron, I have an ongoing "discussion" with Adams, the MPF manufacturer to keep MPF as smooth as they can make it with their current process. Some batches are nearly perfect, as smooth and flat as Depron, while some are more like typical Fanfold, (just white, no printing, films or perforations).

So, It's not perfect, but for many guys a viable option and way less expensive than Depron was. In the thread here on RCG and in the gallery on the website, you can see that it has been used for most all genres of aircraft modeling. modelplanefoam.com

Originally we were able to ship it all over the world, but in the last couple of years shipping rates got so crazy that I stopped sending it internationally, so it's a US only product.
Hi,springer
You need to promote more,I think if they are able to be bent or fold,they "can" be done with the tech I'd shown like the sort of depron foam boards I'v been using.
When people don't use them,they'll just be vanished,like balsa are relatively rare in Taiwan,because people don't use them that much,but as I know that balsa maybe are produced in North America or some where,it still worth to fight for balsa,both of them should be exist coincidently,IMO .

regards and respect

Osern


No More Depron RC Foam, Don't worry! (12 min 22 sec)

Flite Test - Model Plane Foam - MPF EPF (1 min 34 sec)

Dollar Tree Foam Board (6 min 13 sec)
Last edited by osern; Jan 14, 2018 at 09:13 PM.
Dec 18, 2017, 04:52 AM
Registered User
Hi Oserm,

Good job you did !

For your reference most of balsa trees are grown in tropical areas, mostly in central America, and Indonesia as well. While balsa sheets are from USA and Mexico for modelling, art works and others.

Foam and Depron gave new pages to people of this hobby since 20 years ago. I pressed the edge of depron or foam sheet for sharpening rear ends of all control surfaces always. Your way is way much better. Thank you
Dec 18, 2017, 06:39 AM
Registered User
portablevcb's Avatar
The problem for most of the detail scale stuff is surface texture. To make a good surface for that any foam needs to be covered with something. Tape does not work for this. Too many edges and bumps. Shiny surface. Don't know if it can be painted with detail.

So, scale foam planes are usually covered with fiberglass or one of the paper coverings that can be sanded smooth for painting and detailing. The underlying shape still must be accurate, ie, no seam lines.

Most use fiberglass simple because of the damage issue. Once we have spent many hours detailing a plane we want it to last more than a few years. Bare or even taped foam will get dinged up badly in a short period of time and start to look bad.

But, for those cases where we aren't picky about surface finish the bare foam works ok. It is also used a LOT for the smaller scale stuff, especially the micro.

We can still get some depron from RCFoam but not sure how long that will last. Already hard to get 3mm. But, the cheap foam poster board is a decent substitute.

If the MPF stuff can be made in 3mm and 1mm then you will be filling a 'hole' in the supply chain. 6mm is a bit thick for the smaller planes but would do well for the larger ones, and, as mentioned, it is thick enough to allow sanding down the seams.

charlie
Dec 18, 2017, 09:45 AM
Registered User
osern's Avatar
Quote:
Originally Posted by portablevcb
The problem for most of the detail scale stuff is surface texture. To make a good surface for that any foam needs to be covered with something. Tape does not work for this. Too many edges and bumps. Shiny surface. Don't know if it can be painted with detail.

So, scale foam planes are usually covered with fiberglass or one of the paper coverings that can be sanded smooth for painting and detailing. The underlying shape still must be accurate, ie, no seam lines.

Most use fiberglass simple because of the damage issue. Once we have spent many hours detailing a plane we want it to last more than a few years. Bare or even taped foam will get dinged up badly in a short period of time and start to look bad.

But, for those cases where we aren't picky about surface finish the bare foam works ok. It is also used a LOT for the smaller scale stuff, especially the micro.

We can still get some depron from RCFoam but not sure how long that will last. Already hard to get 3mm. But, the cheap foam poster board is a decent substitute.

If the MPF stuff can be made in 3mm and 1mm then you will be filling a 'hole' in the supply chain. 6mm is a bit thick for the smaller planes but would do well for the larger ones, and, as mentioned, it is thick enough to allow sanding down the seams.

charlie
I'm getting even more confused with those terms of "depron" ,"sheet"," foam board ",foam core" or "extruded polystyrene",
"Depron" seems to be used in house insulation instead of common stationary supply in U.S, that truly is kind of problem.
Another senior RC modeler in Taiwan who tried to import similar products oversea from U.K and Australia which called "Depron aero",they are cheap as he told,but the shipping charge seems to soar up lately causing shortage of depron supply in North America.

No matter of what,I can tell that any depron you'v got,if they are bend-able and thin enough then they are easy to shape with aid of tape covering to bound the cracking,you can still remove them after shaping is done,the finish of surface its self is another issue that can involve in weight consideration or tension stress resisting for thin skin build or it just doesn't care for it's just a light weight building.


The kind of depron foam boards that I'v been using are extremely smooth on both sides and fine textured with barely seen micro grains,there is no large bead grain in them, the surface texture issue may only happens to EPP or EPS bead foam core,no problem with the depron that I'v got here.

They're pretty easy to paint with acrylic or some clear paint over it.
they are smooth that only need minor filler or putty to cover up the seam lines,
Some guys use thinning epoxy as clear paint or furtherly pave with fiberglass to strengthen thin skin,some cover with color packing tapes instead of deal with paint,as for me,I can paint them with/without tape covering ,those creasing of tape can be flatten with hot glue gun "ironing" and some relief cut to tightly cover up the compound curve without air bump.
As covering with paper and sanding ways is troublesome that never heard of any one did like that for ready to crash models,and the depron surface is smooth/flat enough that can take as "finish" surface.

The way I think about skin modeling is aim at those little guys like park flyer or nano scale of models that are light enough with thin skin that should bear for some impact of crash,and easy to build and fix with depron board.
Those tiny models won't fly out on windy days for the most of time,they could just be shelved or hanged up on the wall day by day,so they'v better look scale enough for me and can be built and fixed with simple and fast ways,that's the sprite.

Osern
Last edited by osern; Dec 20, 2017 at 11:01 PM. Reason: poor English texting
Dec 18, 2017, 10:15 AM
Registered User
osern's Avatar
Quote:
Originally Posted by twn Chen
Hi Oserm,

Good job you did !

For your reference most of balsa trees are grown in tropical areas, mostly in central America, and Indonesia as well. While balsa sheets are from USA and Mexico for modelling, art works and others.

Foam and Depron gave new pages to people of this hobby since 20 years ago. I pressed the edge of depron or foam sheet for sharpening rear ends of all control surfaces always. Your way is way much better. Thank you
Hi,Chen
Don't mention about that,your Alula template sharing is a long last thread back there in Taiwan if I'm correct,
The flap part on the back side shrinking is pirated from the idea of Flite Test,nothing more.

A senior modeler told me that he purchased some balsa made in U.S,I thought that might be it,something I just know,not into those detail yet,ha.

Osern
Last edited by osern; Dec 18, 2017 at 10:43 AM.
Dec 18, 2017, 12:58 PM
treefinder
springer's Avatar
Osern, Depron and Depron aero are brand names, trademarks for a specific type of styrene foam board originally used for floor underlayment in Europe. They made a special version for modeling that within the last couple of years they quit making. It was pretty expensive here in the US, but people got used to it. I suppose the most generic term we can use is foam board. But XPS (FOR extruded polystyrene) and EPS (FOR expanded polystyrene - or beadboard) are common terms to describe the different types. Fanfold or FFF, describes the package of 25 two foot by four foot sheets folded like a fan which is used here in the US for house siding and flooring underlay. Lots of terms!
Dec 18, 2017, 02:11 PM
Culper Junior
Is there a video for making these shapes? I can't get my head around manipulating a sheet of 3/16" foam into a thin 3-D face.
Dec 18, 2017, 02:17 PM
Don't look at me like that....
62pilot's Avatar
Yup. Did this years ago. Good job.
Dec 18, 2017, 05:14 PM
Registered User
portablevcb's Avatar
Quote:
Originally Posted by osern
I'm getting even more confused with those terms of "depron" ,"sheet"," foam board ",foam core" or "extruded polystyrene",
"Depron" seems to be used in house insulation instead of common stationary supply in U.S, that truly is kind of problem.
Another senior RC modeler in Taiwan who tried to import similar products oversea from U.K and Australia which called "Depron aero",they are cheap as he told,but the shipping charge seems to soar up lately causing shortage of depron supply in North America.

No matter of what,I can tell that any depron you'v got,if they are bend-able and thin enough then they are easy to shape with aid of tape covering to bound the cracking,you can still remove them after shaping is done,the finish of surface its self are another issue that can involve in weight consideration or tension stress resisting for thin skin build or it just doesn't matter for it's just a light weight building.


The kind of depron foam boards that I'v been using are extremely smooth on both sides and fine textured with barely seen micro grains,there is no large bead grain in them, the surface texture issue may only happens to EPP or EPS bead foam core,no problem with the depron that I'v got here.

They're pretty easy to paint with acrylic or some clear paint over it.
they are smooth that only need minor filler or putty to cover up the seam lines,
Some guys use thinning epoxy as clear paint or furtherly pave with fiberglass to strengthen thin skin,some cover with color packing tapes instead of deal with paint,as for me,I can paint them with/without tape covering ,those creasing of tape can be flatten with hot glue gun "ironing" and some relief cut to tightly cover up the compound curve without air bump.
As covering with paper and sanding ways is troublesome that never heard of any one did like that for ready to crash models,and the depron surface is smooth/flat enough that can take as "finish" surface.

The way I think about skin modeling is aim at those little guys like park flyer or nano scale of models that are light enough with thin skin that should bare for some impact of crash,and easy to build and fix with depron board.
Those tiny models won't fly out on windy days for the most of time,they could just be shelved or hanged up on the wall day by day,so they better look scale enough for me and can be built with simple and fast ways,that's the sprite.

Osern
Yep, not very good finish and still not very durable unless covered with something very durable. Yes, the foam I have used is the "smooth" stuff you are referring to. It still needs a surface finish like fiberglass or paper covering to be suitable for what I would consider a good scale model.

Don't get me wrong, I do make foam planes, just not detailed scale planes. They are still scale, just not detailed. Such as the Pietenpol I am making now and the Citabria that I will make next. They will both need a little forming but not much. But...I do not expect them to last very long without getting dinged up. Kinda like the foamy ARFs that I have had. Good for a year or so. OTOH, my balsa scale models hold up for many years. I have one that is finally showing it's age after ten years of use (and several crashes).

charlie


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