HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 19, 2006, 06:33 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Build Log
Scratch built own design foamie... "Whiplash"

Hi all,

As promised in the 40 for 40 discussion here are some photos of my 'closure' project. After smashing a hydrofoam and needing a new home for a bm2408-21 I started cutting foam to form what the photos below show.

Probably way too heavy for hovering etc, but I am having fun and look forward to finding out if I can come up with a successful design.

Go easy on the criticism - I've never built a 3D before.

glydr
glydr is offline Find More Posts by glydr
Last edited by glydr; Apr 22, 2006 at 04:25 PM. Reason: It has a name now... inspired by the stickers from my son's toy plane :)
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 19, 2006, 06:35 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Wings are hot wire cut polystyrene and the rest is 6mm depron from an art store.
glydr is offline Find More Posts by glydr
Reply With Quote
Old Apr 19, 2006, 10:29 AM
electric convert
joel231's Avatar
Jane Brook, Western Australia
Joined Oct 2005
387 Posts
cool, looks pretty good.

interested to see how it performs.

Cheers Joel
joel231 is offline Find More Posts by joel231
Reply With Quote
Old Apr 19, 2006, 05:20 PM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Consider this an extra slow build thread with scant details and you won't be dissappointed!

I cut the tailplane last night which completes the 'parts' that I need.

All that's left to do is cut/velcro equipment locations, install control rods and glue together. I've been using PVA for foam to foam (e.g. reinforcement at wing saddle) and plan to use epoxy for the wing as it is covered in tape. I wanted to use more yellow on the wing except I misplaced the roll after hinging the ailerons.
glydr is offline Find More Posts by glydr
Reply With Quote
Old Apr 19, 2006, 05:34 PM
Model Bender
OzDragonFlyer's Avatar
Australia, NSW, Newcastle
Joined Jun 2004
2,870 Posts
Looks ok.. I used to make lots of those flat depron foamies a while ago. Destroyed 'em faster than I could make 'em!

Most successful and rugged flat foamie was my EPP P51. 10mm thick epp sheet for the fuse, reinforced with a 10x10 spruce stick in the middle which also held the motor. Wings were EPP symmetrical and cellfoam tail feathers. Then along came the Zoom3D with almost the same idea.

It was even hard ripping it apart to pull the r/c gear from it!

If you have the patience, try using silicone for the joins instead of epoxy, which makes the foam brittle and more liable to crack. There's also styro safe clear glues around from $2 shops (but test it on a scrap first!)

Good luck!
OzDragonFlyer is offline Find More Posts by OzDragonFlyer
Reply With Quote
Old Apr 19, 2006, 06:12 PM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Thanks for the tips OzDragon - wasn't aware of the epoxy problem.

As with yours, I consider this project a disposable plane - cheap and fun.

I plan on doing another for a PJS300 and 10A speedy and using foam for the fuse like your P51 as the depron seems too heavy. I'll also go for a broader chord for slower flight. I have some spruce but will probably use a carbon tube I have handy which is too short for a glider tail boom.
glydr is offline Find More Posts by glydr
Reply With Quote
Old Apr 20, 2006, 03:36 AM
Model Bender
OzDragonFlyer's Avatar
Australia, NSW, Newcastle
Joined Jun 2004
2,870 Posts
Unfortunately no pics of the epp model.. here's a few of the many models I cnc'd out of cellfoam.. after demolishing these in the first 2 weeks, the later ones weren't decorated nearly as nicely

Theses didn't have the full length spruce reinforcement, but used carbon tube (which broke quite easily!)
OzDragonFlyer is offline Find More Posts by OzDragonFlyer
Reply With Quote
Old Apr 20, 2006, 04:13 AM
Registered User
Ipswich Australia
Joined Jan 2006
101 Posts
Glydr,
Whats the details of foam cutting please??? I KNOW how to make a bow already but i need info on the power supply and if you use a light dimmer . what ohmage is the nichrome and what amperage is the supply please. I Assume youre using DC not AC... TIA.. Rod
rredbeak is offline Find More Posts by rredbeak
Reply With Quote
Old Apr 20, 2006, 05:28 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
G'day rredbeak.

I'm not sure about the nichrome - I just bought the thinnest stuff I could get from Jaycar (cheap).

Power supply is about 11.5V at about 5A or less from a computer power supply unit. There might be more info in rcgroups about converting power supply units but a back issue of QEFI showed me the idea.

Basically the yellow and black wires are 12V DC or thereabouts (do NOT go AC!!) - if you aren't sure of what you are doing seek help or a motorbike battery / gell cell as that is cheaper than an ambulance (I am not speaking from experience in case you are wondering - just putting in a warning - please don't take offence!).

Being low voltage I can only span about 450mm and retain effective heat to cut polystyrene. I don't use a light dimmer - only an alligator clip which I can move along the nichrome to adjust heat.

With small wings like this it is easier fasten the bow to the bench and move the foam across the bow rather than the bow across the foam (as with larger wings).

Very simple ultra cheap set up. I have considered using two computer power supplies or both my gell cells to make 24V and therefore a longer bow - but have no need as yet.

Hope this helps!

glydr
glydr is offline Find More Posts by glydr
Reply With Quote
Old Apr 20, 2006, 07:26 AM
Registered User
Ipswich Australia
Joined Jan 2006
101 Posts
TY Glydr,
No i am not intending using AC...Thanks for the description ive learnt a lot from it. I have a car battery that is sitting here doing nothing,that should suffice the motor bike battery.

As for the nichrome i'll follow suit and buy the thinnest also...

I cant imagine mounting the bow and moving the foam,but ill certainly give it a go.

Cheers and TY... Rod
rredbeak is offline Find More Posts by rredbeak
Reply With Quote
Old Apr 20, 2006, 07:36 AM
Dream,Build, Make it FLY
Mark in Aus's Avatar
Frankston,Victoria,Australia
Joined Jun 2005
177 Posts
Quote:
Originally Posted by rredbeak
Glydr,
Whats the details of foam cutting please??? I KNOW how to make a bow already but i need info on the power supply and if you use a light dimmer . what ohmage is the nichrome and what amperage is the supply please. I Assume youre using DC not AC... TIA.. Rod

I use Ni chrome from Jaycar. holds 9 amps at 500mm and gets pretty hot, not that you need to use that much heat.
2-3amps works well

Get your self a 50watt speaker variable resistor from Jaycar
(a big fat volume dial)...about $25 mine was.
Works great. No risk of triggering the built in Overload from the PSU... (If it has one).. Gets pretty warm so I attached a 60mm fan to the back of mine.
Also mounted cooling fans on the resistors which is illuminated from behind.

Converting the PSU is pretty simple. From that nest of wires that comes off the board in side you will need Black- ,Yellow 12v+ ,red 5v.
I used 2x 1 Ohm 10 watt resistors to create the load that simulates a motherboard. One did the Job but the second increased the Amp output.
Run one of the red wires to the 1 ohm 10 watt Sandbar resistors that are in series and the other end of the resistors to the Common (black)
You would be better off reading here 12v DC PSU conversion for a detailed how to.
It's worth the effort.

Mark
Mark in Aus is offline Find More Posts by Mark in Aus
Reply With Quote
Old Apr 20, 2006, 07:46 AM
Dream,Build, Make it FLY
Mark in Aus's Avatar
Frankston,Victoria,Australia
Joined Jun 2005
177 Posts
This was a kind of Big 3D Foamy I scratch built. I only used a Zagi Speed 400 and GWS 3.9:1 gearbox with a 10x5 prop ,8cells. Flew pretty good but not really a 3D'er.
One day I'll put a brush-less in it
Span 1010mm, Fuse 960mm
Mark in Aus is offline Find More Posts by Mark in Aus
Reply With Quote
Old Apr 20, 2006, 03:27 PM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Thanks for adding info Mark, those are two beautiful set ups (the PSU and the plane). You should be proud of your work.

As for mounting the bow - I just jammed it between two tables in the shed and hoped that it wouldn't move as I dragged the blank across the wire.
glydr is offline Find More Posts by glydr
Reply With Quote
Old Apr 20, 2006, 11:43 PM
de-registered abuser
gouch's Avatar
Lake Macquarie, Aust.
Joined Dec 2002
14,097 Posts
Quote:
I have a car battery that is sitting here doing nothing,that should suffice the motor bike battery.
Just to chime in here, stand back when you plug the wire onto the battery terminals, with the average car battery able to supply hundreds of amps, make sure you limit the available current to the wire, or at least get it on video!! Nichrome is resistive wire, but I can guarantee you will blow red hot wire fragments all over the workshop simply connecting it to the terminals!!!

I'm assuming you aren't going to simply connect the wire this way, but it could read that way.

I have used an old 4 amp battery charger many times, works a treat over about 500mm (guessing, memory is fading!) of nichrome at around 13 odd volts. I just hooked up an ammeter to about a meter of nichrome and kept cutting it down until I got the current to around 3.5 amps.

As far as cutters go, a mate ("alkoo" rcgroups name) made a gravity fed cutter, very fancy, yet very simple. The mass of the weights pulls the wire through the foam at a controlled rate via a couple of pulleys. I took some experimenting with the correct current draw, but it cuts a very nice wing.


Glydr: Nice plane I like the style.
One question. Are the main wing, motor thrust line, horiz stab all in line?

Cheers
Paul
gouch is offline Find More Posts by gouch
Reply With Quote
Old Apr 21, 2006, 12:17 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Quote:
Originally Posted by gouch
Glydr: Nice plane I like the style.
One question. Are the main wing, motor thrust line, horiz stab all in line?

Cheers
Paul
Thanks! I quite like the look also - even with the high shoulder wing

They are all practically in line, though when cutting them in I fudged a very slight down-thrust and erred on the side of positive incidence on the wing.

I have another long weekend soon (yay ) so hope to get some servos located and motor mounted.

But I also hope to write about 6,000 words of assignment (I study part time while working full time - I hope it will be worth it )... and the car could do with a wash!
glydr is offline Find More Posts by glydr
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Poll scratch build own design GOJIRADOR Sailboats 22 Aug 14, 2006 12:05 PM
Scratch built foamie: High Tension Nurbs Foamies (Kits) 42 Jul 22, 2004 08:00 AM
How do you design your scratch built jets? Florin777 Electric Ducted Fan Jet Talk 17 Mar 18, 2003 05:34 PM
Scratch built foamie, and flying inverted carterfx Foamies (Kits) 10 Apr 10, 2002 04:38 PM
Scratch Built Foamie Fies!!!!!! coolieo Foamies (Kits) 7 Jul 23, 2001 05:14 PM