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Old Jun 15, 2012, 06:55 AM
Registered User
United States, NJ, Pompton Lakes
Joined Jan 2011
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Build Log
Quest for 200mph EDF carbon dart

I've decided to scratch build something fast. Or atleast attempt to. The idea is to build a delta shaped really low profile / drag dart shaped 90mm EDF.

Rough specs:

36" Wing span
48" length
Pink foam fully covered in carbon fiber cloth using wet layup with West Systems.
90mm Wemo
ARC 36-75-1.5
12s
11.5 lbs of thrust
goal weight of 5.5lbs



GOing to need some serious thinking about CG because the calculator doesnt show the front section.


Rough shape


vertical stabs came out awsome, so strong I cant even flex them. I'd say 10 times stronger than a fiberglass setup maybe 50% more weight

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Old Jun 15, 2012, 06:57 AM
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United States, NJ, Pompton Lakes
Joined Jan 2011
166 Posts
Here is my fastest plane do date... not an EDF but you get the point
Funjet Ultra ARC 36/65 motor (0 min 35 sec)
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Old Jun 15, 2012, 08:14 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,427 Posts
My question is what tx/rx are you using that isn't affected by the CF.


Check this out, might be something usefull in there.
http://www.rcgroups.com/forums/showthread.php?t=1507491
Mark
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Old Jun 15, 2012, 08:53 AM
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United States, NJ, Pompton Lakes
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Quote:
Originally Posted by CoolerByTheLake View Post
My question is what tx/rx are you using that isn't affected by the CF.


Check this out, might be something usefull in there.
http://www.rcgroups.com/forums/showthread.php?t=1507491
Mark
I use a full range Spectrum steup, never knew carbon caused issues, i'll mount the sattelite outside the fuse if I have an issue.
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Old Jun 15, 2012, 09:09 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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I knew there can be issues with CF. I don't know enough about it yet to know how much it too much. I want to put some in my F-86F, so I need to find out soon myself. I do know that on a 2.4 system the antenna can't be in line with it. Good Luck
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Old Jun 15, 2012, 06:59 PM
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Joined Apr 2004
799 Posts
Carbon fiber has been known to absorb radio waves.

I noticed you are using a very heavy weave. Around 5.75-6.0oz. Why?? Even for 200mph is a bit much. Plus you are using a higher density foam.

To eliminate the weave look, it will become even heavier. Creating even more load on the airframe.

Proper composite sizing is a balance between what will work and what just adds weight.

Just my thoughts.


Steve
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Old Jun 15, 2012, 07:45 PM
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United States, NJ, Pompton Lakes
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It's really not heavy. I couldn't find lighter carbon cloth. I could have gone with fiberglass but I'm going outside the box. The airframe has no spar of any kind. The foam weighs next to nothing yet it's like steel. I'm not going to make it smooth, I'll try the golf ball dimple method

Top layer done

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Old Jun 15, 2012, 11:06 PM
that's gonna leave a scar
KCinNC's Avatar
United States, NC, Mooresville
Joined Aug 2007
3,481 Posts
freakin crazy man...can't wait to see that fly !!! nice work
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Old Jun 15, 2012, 11:55 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
20,798 Posts
that looks like #582 C/F typially used for car hoods these days.a plan weave 3.6 oz C/F would be better.the composite store has it cststore.com is there e-mail i think. ...not sure the golf ball dimple thing will work ......no full scale plane have used it .who know you might be on to somthing.i think if you get close to 200 all the dips low spots are going to cause proplems ....it's going to take a ton of power to get close to 200 ."Knifelittle" tried it a few years ago ...i cant remeber if he made it or not.
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Old Jun 16, 2012, 07:00 AM
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United States, NJ, Pompton Lakes
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Quote:
Originally Posted by AIR SALLY View Post
that looks like #582 C/F typially used for car hoods these days.a plan weave 3.6 oz C/F would be better.the composite store has it cststore.com is there e-mail i think. ...not sure the golf ball dimple thing will work ......no full scale plane have used it .who know you might be on to somthing.i think if you get close to 200 all the dips low spots are going to cause proplems ....it's going to take a ton of power to get close to 200 ."Knifelittle" tried it a few years ago ...i cant remeber if he made it or not.
thanks for the info, I've been looking for lighter weight cloth. I've been using http://www.jamestowndistributors.com...Plain+Weave+3K

If I could cut the cloth weight down, its the perfect material because it needs no reinforcements at all in the foam. This is really just a prototype to see how it fly's on 6s first, work out the bugs and then build a second one for 12s possibly go to EffluxRC for a hot 90mm 12s setup.
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Old Jun 16, 2012, 09:12 AM
Carbon fiber is our friend
Steve C's Avatar
United States, CA, Lodi
Joined Feb 2001
4,216 Posts
Foamular 250 isn't heavy. In fact it's quite a bit lighter than the commonly used Dow blue foam. I think the cloth you used is ok. I have been using up a roll of it for years because it was really cheap compared to fabric made with 1k tow.

Where you can really improve next time is by vacuum bagging. When you lay up composites out in the open like this, you end up using way too much resin and you still need more to make it smooth. Take some time and learn about using vacuum with mylar for parts without compound curves, like the wing. You can squeegee the cloth out on the table first, on top of some plastic and then pick the plastic up with the fabric and flip it over on top of the foam. Peel the plastic off and smooth out.

BTW, the homebuilder guys mix up a slurry of resin and micro to squeegee out on the foam first. If you have sanded the foam, it can end up absorbing resin, so this seals it up with stuff that is lighter than straight resin.

Good try. I could have helped a bit more if you posted when you first started, but that's okay. I learned a lot by trial and error when I started messing with composites. No internet back then and people who knew this sort of stuff didn't like telling others too much about it. Lots more sharing going on these days!
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Last edited by Steve C; Jun 16, 2012 at 09:20 AM.
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Old Jun 16, 2012, 09:25 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,427 Posts
Foamular 250 is great stuff. Most of what we have up here in MN is the 25# density. And we have lots of it, ALL year long. Weird trade off, you can't get it, but can fly year long! We have foam all year long, and can only fly for a few months. BTW, Foamular is very nice to hot wire!!
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Old Jun 16, 2012, 09:50 AM
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United States, NJ, Pompton Lakes
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Quote:
Originally Posted by Steve C View Post
Foamular 250 isn't heavy. In fact it's quite a bit lighter than the commonly used Dow blue foam. I think the cloth you used is ok. I have been using up a roll of it for years because it was really cheap compared to fabric made with 1k tow.

Where you can really improve next time is by vacuum bagging. When you lay up composites out in the open like this, you end up using way too much resin and you still need more to make it smooth. Take some time and learn about using vacuum with mylar for parts without compound curves, like the wing. You can squeegee the cloth out on the table first, on top of some plastic and then pick the plastic up with the fabric and flip it over on top of the foam. Peel the plastic off and smooth out.

BTW, the homebuilder guys mix up a slurry of resin and micro to squeegee out on the foam first. If you have sanded the foam, it can end up absorbing resin, so this seals it up with stuff that is lighter than straight resin.

Good try. I could have helped a bit more if you posted when you first started, but that's okay. I learned a lot by trial and error when I started messing with composites. No internet back then and people who knew this sort of stuff didn't like telling others too much about it. Lots more sharing going on these days!
Thanks Steve! yes I wish I had someone to teach me vacum bagging. It really is the best way to do it. I could save like 100g of resin on a 600g total weight airframe as it sits right now. Do you know of any good vacum bag kits that are sold? even for small parts so I get the concept first then I can make it on a large scale.
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Old Jun 16, 2012, 09:51 AM
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United States, NJ, Pompton Lakes
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Originally Posted by CoolerByTheLake View Post
Foamular 250 is great stuff. Most of what we have up here in MN is the 25# density. And we have lots of it, ALL year long. Weird trade off, you can't get it, but can fly year long! We have foam all year long, and can only fly for a few months. BTW, Foamular is very nice to hot wire!!
Yeah other than the mess it makes carving and sanding, this foam is perfect and I get it in 8x3 ft boards at home depot for $9
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Old Jun 16, 2012, 10:30 AM
Do it Right, the first time!
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United States, MN, Hermantown
Joined Dec 2008
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Sounds like a good price. Here the 2"x 4'x8' sheets of foamular 250 are about $23 and change. Have a Menards just a 1/2 mile away. Need a touch more bondo for my plug, so I suppose I HAVE to go there later!
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