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Old Jan 29, 2012, 04:31 PM
Watt Waster
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Foam Wing - To Bake or Not?

About a year ago I came across a thread that had a post that mentioned using the kitchen oven to "bake" a fan fold foam (FFF, also known as Blu-core) wing. The model wasn't going to be all that big and would normally be classified as a small park flyer. It was also going to be a design with a short, wide wing with an elliptical shape. I was thinking at the time the design was a bit small for what I was wanting, but the idea a simple flat wing shape could be heat (thermal) formed into an airfoil shape caught my attention. As time passed I continued to look for threads that discussed the details of thermal forming FFF board into a curved shape, be it a wing or fuselage. A few months ago I got the idea to cold-roll various foam board types into a tube for a number of projects I had in mind. Since I kept finding more posts discussing thermal forming FFF, and a few that mentioned other types of foam board, I started looking for the methods used. I needed details about the process, the temperatures used, any devices, or jigs constructed for the purpose, and what advantages or disadvantages the end result might have.

The details are; bake the FFF at 200 degrees F for 20-30 minutes and the foam will develop a hardened skin, giving the finished product stiffness similar to Depron. If the foam has low spots, some, or all of the low spots will disappear, or be harder to notice. The soft spots in a sheet of FFF will stiffen and the sheet will have a more uniform stiffness, but the sheet may still have a "grain", meaning the sheet will bend easier in one direction compared to the other (width vs length). Since the baking process tends to give the foam board a hardened thin skin, a jig or form can be used to thermoform a shape to the thin sheet foam. Simple sheet wings can be curved as per common airfoil shapes and the shape will be retained/remembered, which is useful when wanting an under cambered (UC) wing with the same thickness. If you want to get more inventive, you can construct a shallow male and female mold from concrete, heavy plaster, metal, or wood to "press" the sheet foam into a number of shallow shapes. This includes shallow cones, UC wings (examples; Slo-stick, FlyLite, and etc.), double sheet wings (hallow core, or ribbed), or fuselage parts. You can also build larger scale paper airplane models using thin sheet foam instead of card stock and install RC gear if desired. There are a number of threads discussing the details of this niche' of the hobby.

As with all hobbies, you have to decide if the extra work is worth the effort since it will be difficult, or impossible to compete with manufacturing professionals and Chinese sources if you are thinking of starting a kit producing business. When using heat to form thin sheet foam into a specific shape, taking the time to make the jigs/forms required, you must first be convinced making a dozen of the same thing is a good idea. The basic process is to use a material that isn't sensitive to 200-250 degrees F, cut it into parts, and assemble the device/jig the thin foam will be mounted to during the thermal forming process. Since I wanted to make at least a dozen UC wings of various shapes and sizes, I thought it would be a good idea to make a simple wood jig that could hold the 1/4" thin FFF sheet in the desired shape during the baking process. After the foam had cooled, I would cut it to shape in any number of simple, single sheet UC wing examples. I like the wide, short elliptical wing designs and wanted to try a few on small Dart style park flyer designs others have made and a few I cannot find in the threads in RC Groups (RCG) to date. I have this gut feeling I am not coming up with something new, so in time I will either find a post, or someone will tell me about an old post with the same wing design.

The first order of business is to find pictures of the UC wing jigs/formers others have already made to compare. I will add as many pictures of what I have found to date within an hour or two, unless posting the pictures becomes a problem. More as I can get to it.
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Old Jan 29, 2012, 05:06 PM
Watt Waster
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Jig Designs for FFF Wing Baking

I am adding a few more examples of the fan fold foam (FFF) wing baking jigs/devices for comparison. I am also trying to find a picture of an all wood example. If my information is correct, one of the past members of RC Groups made a simple wood fixture a number of years ago and has since offered the plans through an independent RC foam aircraft internet site. I will try to chase down more information and post it for reference.

I am confident the reason the jigs/devices are not longer had everything to do with the size of the oven used. Mine limits me to 22" across and 18" deep (wide). I have read some hobbyist have made their own wing baking oven to get around the home oven size limitations. Since the objective is to heat the FFF to 200 degrees F, and not more (give or take 10 degrees F) to avoid damaging the foam plastic, a heat box of plywood, metal and foam insulation is an obvious next step. If you are lucky enough to purchase an insulated metal or plywood box, your next challenge is to find a safe and effective way to warm it up to 200 degrees F and not over heat the box or the foam you will place inside. The key word is safe, but no matter what scheme you come up with, I recommend you baby-set the baking process and not risk a disaster. I am kicking around the idea of heat lamps commonly used for baby chickens so they don't get chilled while they mature. I bet someone has already made a good design or two and it is only a matter of finding the information, or having someone tell me about it.
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Old Jan 29, 2012, 05:10 PM
Watt Waster
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Reserved Space

for future information.
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Old Jan 29, 2012, 05:11 PM
Watt Waster
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for additional ideas and show and tell.
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Old Jan 29, 2012, 05:30 PM
Watt Waster
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I am sure there will be a need for more space.
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Old Feb 14, 2012, 11:54 AM
just Some Useless Geek
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Post some bigger pics, man!
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Old Feb 14, 2012, 12:07 PM
Watt Waster
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Want Bigger Pictures?

Quote:
Originally Posted by A Useless Geek View Post
Post some bigger pics, man!
Bigger? How much bigger do you need/want? You do know you can enlarge whatever is on the screen? All browsers I know of offer a zoom option, which is normally at the top right of the screen. Often you will see some sort of tool symbol (like a wrench), click on it, and zoom to your hearts content/need. You can even zoom to the point of seeing pixels if you go over 200%. I think it is an option for those will poor eye sight and I use it sometimes also.
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Old Feb 14, 2012, 12:11 PM
just Some Useless Geek
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Meh. Don't worry about it. I just recently got into the habit of posting images that are about 1200 x 1000 or so instead of the 800 x 600 I used to put up all the time. It's not too great a storage burden on the RCG server, and it's far better to shrink an image that is too big but has lots of detail versus expanding an image that is smaller but has grain.
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Old Feb 14, 2012, 12:14 PM
Watt Waster
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Interesting Advice

Quote:
Originally Posted by A Useless Geek View Post
... I just recently got into the habit of posting images that are about 1200 x 1000 or so instead of the 800 x 600 I used to put up all the time. It's not too great a storage burden on the RCG server, and it's far better to shrink an image that is too big but has lots of detail versus expanding an image that is smaller but has grain.
I will have to remember that when I post some of my own to this and other blog entries. Most of what I am posting is from other resources from folks who have done the same things. If I think I have an interesting option, or some modifications that might be useful, I try to remember to take and post some photos. I really need to build a few Darts myself and experiment with the design options like you have. One I have built ended up in storage before I got around to flying it. I doubt the motor I have on it can power the small park flyer since it came off a smaller and more lightweight bi-wing that seemed under-powered also. Until next time friend.
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