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Old Oct 07, 2012, 12:01 PM
Disco Stew is offline
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Question
Foam question...Depron vs Dollar Tree Foam.

Im new to the foamy scene. I am curious as to the difference in all these scratchbuild plans that say they are made with depron. I live in Canada and depron is not easy to get, but DTF is easy to find. So my questions are:

1) Is DTF an equivalent to depron (as far as building goes)?
2) Can DTF be layered to match the thickness of 6mm+ depron builds?
3) What is the structural differences between Dep and DTF? (i.e. stiffness/weight etc)
4) Paper on or off? (Reasons for the difference.....)

I know that modifications to a plan will need to be made to things like insert cutouts to match material thickness.

I'm sure there is probably a thread somewhere in the vastness of RCG that explains all this...but I can't seem to find it.
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Old Oct 07, 2012, 12:15 PM
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Stew Welcome . I have built many depron planes out of dollar store foam . Plans can be modified to work and DT foam is a great option for new builders . I have progressed to using Model Plane foam now and wont go back to the dollar store stuff . Springer has a bunch of One sheet plans designed for DT foam . Depron is not cost effective in Canada IMO . DT foam is softer and less brittle the depron . Always remove the paper as it adds to much weight compared to the reinforcement . you can layer or laminate DT foam but you get closer to 8-9 mm and its not usually needed . DT foam is not as stiff as depron so not as nice for flat plate 3d style planes . more reinforcement needed but it also takes crashes a little better . Remember build it light to fly dont try to reinforce it to survive crashes as it gets heavy and will be damaged more in the end
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Old Oct 07, 2012, 12:17 PM
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1. Readi-Board is not the same foam as Depron. Depron is much stiffer then Readi-Board. But Readi-Board can take a hit better then Depron can. Depron can crack in an impact a little more easily then Readi-Board

2. Yes, you can layer Readi-Board, but since it is 4mm thick, you would have to shave it down to 6mm by useing a hotwire or a lot of sanding. Beter to adjust the plans to work with the 4mm thick material.

3. Depron is stiffer then Readi-Board. Not sure about the weight since the materials come in different thickness.

4. Paper off. The Readi-Board made in the last year and a half or so has been a little different then the stuff made in the past. In the past you would have to "wet" the paper to remove it from the foam. But for the last year I've been able to remove the paper without "wetting" it with anything, and having it come off clean.

This also means that if you fly over a field and dont have the Readi-Board tightly wrapped in tape or something to seal it, when you land in that nice grass with a little bit of moisture on the plants it can cause the paper to lift off the foam. Also, if you try glueing surfaces together, even the glue "wetting" the paper can cause it to lift off the foam. The paper is no longer held onto the foam very well.

Not being able to use the paper that comes on the Readi-Board is both good in bad. Its good to remove it since it is so heavy, but its also a bad thing since the paper adds so much regidity to the foam. I typically will remove the paper, then when done, use clear packing tape to stiffen and protect the foam. The packing tape they sell at Dollar Tree works very well for this. Its good and sticky.
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Old Oct 07, 2012, 12:33 PM
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Thanks for the replies! Nice and neat and too the point
As you two were replying, I was looking at this thread http://www.rcgroups.com/forums/showt...pron+vs+dollar I had watched a bunch of the videos last week, but never did read through the following discussions. But I now see that most every one of my questions (and then some) are already in there.

But since I have your attention... is it ok to join the edges of 2 sheets of DTF together to make a larger sheet? What is the best method?

For a while now, I was always under the impression that depron is far superior over DTF for construction...that I would be stuck with inferior materials.

@Wilfor...Thanks for the link to the model plane foam. I will have to look into that a little more. EDIT:: Wow! $40 shipping to western Canada. That would make my $50 box of foam now $90. If i was to get nicked by customs fees as well, the I would be at $100. Thats pretty "rich" for my build costs. I am assuming that the shipping costs are due to the box size and not it's weight.
Now on to research some DIY Hotwire plans
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Old Oct 07, 2012, 01:01 PM
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Paper on or off? People take the paper off then complain that DTF is weak, so they add reinforcement to try to make it as strong as it was before they took the paper off, and it ends up weighing more. Taking the paper off also takes off almost all of its strength, do you go to the lumberyard to buy plywood and then peel it to use it one layer at a time? DTF is very much like plywood, it has multi layers glued together, and that adds a tremendous amount of strength, I can build all kinds of stuff without extra reinforcement because of the stiffness, but if I took the paper off I would need to add stiffeners that by the time you added the weight of the stiffeners and glue the whole assembly would weigh about the same as if you left it alone, and the paper covered version would still be stiffer!

Since it is paper covered it can be attacked by moisture, so its better if it is covered with packing tape, the tape adds strength with almost no weight, you can use clear packing tape you can get locally or colored packing tape to make it look nice, but you usually have to order it online.

That stiffness only goes so far, as you get bigger eventually you need to add something for stiffness, my 30" DTF wing needs no extra carbon fiber or wood spar, but my 60" wing does. I build DTF stabs with no added reinforcements while a depron stab of the same size and thickness would require a carbon fiber reinforcement.

Depron and DTF are both useful, each have their own advantages and disadvantages, the biggest advantage of DTF by far is the price and availability inside the US.
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Old Oct 07, 2012, 01:01 PM
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I've done it with Gorilla glue before. im sure a few others will have a few more ideas.

Good luck with the hotwire set up. If you can find a good little adjustable benchtop power supply, that will give you the most controlability, but the most cost too. A lot of guys will use a power source and a spare ESC and a servo tester to adjust power.

I went a bit crazy with mine
http://www.rcgroups.com/forums/showthread.php?t=1450332

and im making a new version too
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Old Oct 07, 2012, 01:34 PM
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Quote:
Originally Posted by OutcastZeroOne View Post
I've done it with Gorilla glue before. im sure a few others will have a few more ideas.

Good luck with the hotwire set up. If you can find a good little adjustable benchtop power supply, that will give you the most controlability, but the most cost too. A lot of guys will use a power source and a spare ESC and a servo tester to adjust power.

I went a bit crazy with mine
http://www.rcgroups.com/forums/showthread.php?t=1450332

and im making a new version too
Looks AWESOME! I was thinking of only the vertical cutting wire...but now I see there is more than one way to "skin a cat."
I comment on your other forum as well....just to not get this one too off track
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Old Oct 07, 2012, 01:46 PM
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Disco: believe me, we wish we could get MPF to Canada for less. I've looked at UPS, FEDEX, and USPS/Canada Post, and the latter at $40/box is the least expensive. So far no one has had to pay any extra fees or duties. At the delivered price of $5.63/sheet, it's not the cheapest, but still less than a sheet of depron that has fewer sq.in. Compared to Readiboard, it's almost twice the area (8sqft vs 4.1sqft) and only a little over twice the price/sheet. Ok, sales pitch over

Our biggest problem is the weight vs volume. Too light for the pack size, so we get hit with "dimensional weight" penalties. Very frustrating...

My breakpoint is about 36" span. If the plane is going to be over that, then it'll be MPF. If under, then I'll at least entertain DTF, especially if I can fit onto a single sheet!

On the paper, my understanding is no adhesive is used, just the paper fibers embedded in the foam when the paper is rolled on in process. That certainly explains the variability in adhesion. Not a problem for the "typical" uses of posters and science fair displays. I've tried the paper on, but since I like to fly in early am, when there's typically dew, it doesn't stay on well, so I design for no paper. As Wingman said, the paper is just a stressed skin, so replacing it with a packing tape film does the same job, and it can be applied over curved surfaces (like on the SeaBee), whereas the paper would have to be scored or somehow massaged, losing much of it's strengthening value.

I have edge glued it with Gorilla glue, but i've always put the joint in a location that it's "helped" with other structure.
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Old Oct 07, 2012, 03:22 PM
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Heres something from my early discussion regarding MPF ( modelplanefoam )

It gives you an idea on cost . at $1.25 a sheet plus tax and if you take into account the thickness difference and sheet size difference

Interesting: The size difference (600sqin to 1152sqin) would give a price of $2.40 per sheet of DS foam in the larger 24x48" sheets

So the equivalent amount of DS foam is $2.40 compared to around $5.70 for MPF . Customs should leave you alone as MPF is made in America .

Now theres nothing wrong with DS foam ive used a few boxes of it myself but as my finishing and models get nicer i find MPF way better to work with .

I had priced out depron before and figure the cost per sheet to Canada before as well but cant find that # but recall it made me go

Where in Western Canada are you located ?

Good luck with what you build and make sure you post pics .

Note i see Springer added his 2 cents which is probably better then mine .

Ohh and if you look at shipping MPF inside Canada it actually costs you more
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Old Oct 07, 2012, 03:34 PM
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Thanks for the replies
I guess that since I am a noob to all this, I'll probably start off using the DTF and strip the paper. Once I'm better at building, I'll switch to the better foam (wife's permission pending).
I'm not abstinent to spending good money for good products. But spending good money for poor construction would be a shame (i.e. my poor building skills )
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Old Oct 07, 2012, 04:32 PM
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Quote:
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...Thanks for the replies...
Thanks from me, too. Lots of good info above.
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Old Oct 07, 2012, 05:06 PM
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Take a look at the scratchbuild university (stickied on this forum), and check out how he tapes his DTF. If you try his techniques, you will find that your builds will be very strong and still very light.....while leaving the paper on. Once I tried his techniques, I doubt I will ever remove the paper from my builds. Just my 2 cents.
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Old Oct 07, 2012, 08:12 PM
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I,ll add my2 cents... availability of DTF ++++ ,cost, +++++ I have built at least 25 airplanes with dollar tree foam( all paper off) I find it really hard to beat.Minimal reinforcement is required . Build it light!! I use just plain old scotch tape for hinges, white gorilla glue (very sparingly). I use a thin carbon fiber strip imbeded in the wing for a spar. check out :modelplanebuilder.com for cheep carbon, servos and other goodies Most of all HAVE FUN.,try new stuff. anything with enough power , correct center of gravity and enough control will fly! the fun part is making it fly good.
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Old Oct 09, 2012, 11:49 AM
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Quote:
Originally Posted by Disco Stew View Post
But since I have your attention... is it ok to join the edges of 2 sheets of DTF together to make a larger sheet? What is the best method?
I've joined DTF edge to edge (kinda) for wing spans longer than 30" but it has always been a de-papered 2 sheet lamination using 3M 77 with the seams staggered. I think larger than 30" is likely to be a heavier plane by nature so the additional weight of lamination is not an issue.

Greg
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Old Oct 09, 2012, 04:36 PM
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I've joined DTF sheets edge to edge with White GG. I've built wings up to 40 in this way with no problems. I use 3M 77 spray for laminating.
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