Wonder

My Feedback: (7)

I read in one of the PBF threads that the Coroplast should be 4 mill thick. I went to the sign shop today to get some but he didn't know how thick 4 mill was. He gave me a piece big enough to build a Pizza Box Flyer, it is 3/16" thick. Will that work? Can someone please measure the thickness of their PBF and let me know how thick it should be?

Thanks,

Tim

Hummve

just to let you know 3/16 is 4mm so that would be it.

C_Watkins

My Feedback: (10)

You got the right stuff.
Folks are usually talking about millimeters (mm) and not mils, by the way

4 "mils" would be .004".
(Unless you're talking about the outside sheet thickness, that's not very useful)

What's confusing is that sometimes people mistakenly abbreviate millimeter as "ml" instead of "mm".

Wonder

My Feedback: (7)

What I got is a total thickness of 3/16".

I take it then that the 4 mils they are talking obout is the thickness of the material used in making the Coroplast, Right.

Tim

C_Watkins

My Feedback: (10)

It could be, I've never mic'd it to see.

I would bet that the "4 mils" that you've heard refers to 4 millimeters, though.
Most all the places I've seen Coroplast, it was measured in mm, not inches.
4mm is a common size, and is "close" to 3/16", which most us Americans understand better

James Goss

The skin thickness of 4 mm coroplast is around 10 mils thick. The next size up, 6 mm coroplast is around 25 mils thick. Coroplast also comes with different size corrugations. Some will be 1/8 inch square and some will be 1/8 x 3/16 inch. I like the 3/16 better and it weighs a little less. The coroplast with 1/8-inch square corrugations is a little more dense and is stronger. Which type you receive depends on where you order it. If you ask about this when you order your coroplast nobody seems to know what you are talking about when you ask about the size of the corrugations.

ReallyUglyStick

My Feedback: (5)

you're making it waaaay too complicated. the standard sign is made with 4mil stuff, meaning 4 milimeters thick. there is also 2mil stuff, which is great for making wings and such. when you start talking about the thickness of the plastic and the size of the corrugations you've gone out of the realm of importance for our purposes. visit www.spadtothebone.com and you'll see MANY people using whatever's available to do crazy things. some folks use leftover signs, others purchase coroplast from wholesalers. www.harborsales.com is a dealer in coro, and they sell most popular sizes and colors at very reasonable prices.
you can make a PBF out of political signs, real estate signs, or even cigarette signs. bottom line is you can use whatever, 6mil, 4mil, or a combo of those (2mil is too flimsy) to make a pbf. the weight difference is negligable.

Matt Kirsch

My Feedback: (21)

People say, "Four mil Coro," which in longhand is "Four millimeter Coroplast." It has nothing to do with thousandths of an inch, and everything to do with thousandths of a meter

Wonder

My Feedback: (7)

Ok, sounds like what I have will work.

Now if I can just get a day free to go build it!

Thanks for the replys,

Tim

James Goss

ReallyUglyStick

It depends on what your goal is as to whether the skin thickness is important or not. In my case I always like to know all the details while working on a project. You are correct that it may not be important to some, but others may think it interesting to know the difference between the skin thickness and overall thickness. The size of the corrugations needs to be known if like me you purchase basswood to use as filler strips to prevent the plastic from crushing at screw locations. I find it much faster to buy the 1/8 square or the 1/8 x 3/16 basswood strips instead of cutting them from sheet wood. I build a lot with coroplast, about three or four Stamps per week, and I guess this saves me more time than anything.

I am retired now, but my profession was a technical teacher, electronics professor, for thirty-five years. I guess I do tend to look at everything from the technical end by force of habit.

OldRCer

Do your stamps rock side to side while flying . mine acts like I"m
wiggling the stick left/right/left/right all the time. I now know what a death spin is . 10 flights/4 different pilots/4crashes/o broken props. 24''X24'' w/os32sx w/macs tuned muffler 9X6 prop I've got to find a 9X4 prop. Thanks again for your postings.

James Goss

OldRCer

At what speed are you flying when the Stamp is rocking side to side, or is it at all speeds? After takeoff and when they are at reduced speed the Stamp should be very stable. All that I have flown and seen fly appeared to be stable at slow speeds. At high speeds they are liable to do anything. At slow speed with its nose up in the air it is as stable as any plane can be. When you say rocking, is it like the ailerons are being moved? Are your elevon servos mounted in the rear with short push rods? This is an interesting problem and we need to figure it out.

AMainMaker

OLD RCER
I just built a stamp or PBF and mine did the same thing when flying slow in head wind. I have a O.S 40 FP on mine with a 10x6 prop.I also use the side pieces like a few PBF flyers have used. I have found that putting a 24" piece of 5/32 steel rod in the 3rd flute on the coroplast on the leading edge fixes the problem. I can now fly full throttle and kick out some serious aerobatics with it. Plus the extra weight gives a little more up front to help get the CG right.
Hope this helps you out
Jason

JoeLang

My Feedback: (1)

Jason, I would try a 10 x 4 prop on that O.S. 40 FP engine on your Stamp/PBF, which is better for hovering and slow speed flight at which this plane excels. A 10 x 6 prop will make this plane fly too fast at full throttle, which will lead to that flexing at the tips, and it will not respond to throttle changes as quickly as the 10 x 4.
I'm using a hollow carbon fiber arrow shaft across the leading edge that's zip-tied in about six places, and it has stopped the flexing at higher speeds. It is very light, and I haven't broken one yet. :-)

OldRCer

Thanks all , I believe my vert. fin & rudder are not tall enough . my buddy's flys ok & his rudder is 1.5 in taller.