mattijs

I want to make my first foam wing for a sport plane i am building. I don't know yet what profile it will have but it definetly won't have tapered sections or curved up wing tips.
All i need actually is a sturdy, one-piece 40 something inch symmetrical wing that won't fold if it's used with a .25 OS FX. I am planning on making it rather thick because i am not an expereinced flier so i don't yet need insane speeds....(seeing 40inches isn't large compared to the .25FX that will be sucking them thru the air)

Do you absolutely need a vacuum bag to get it to be strong enough??? and will a normal vacuum cleaner do as a pump???

Do you need spars? (i can imagine hotwiring slots for spars in foam is rather difficult for a beginner)

Is there a site were making foam wings is explained in detail?

BIG THANKS in advance...I already learned a great deal from some of you.

A5fly

http://www.favonius.com/soaring/bagging/bagging.htm

basmntdweller

My Feedback: (9)

For a smaller plane like this, you don't have to use a vacuum bag. Cut your wing skins to their approximate size. brush on epoxy or whatever glue you intend to use and then squeegie most of it off. Put the first skin in the bottom shuck glue side up. then the core then the other skin glue side down. Add the top shuck and then put a board on top of that. Weight it down with what ever is handy being sure to distribute the weight evenly. let the epoxy cure 24 hours. You should end up with a pretty good wing. If you did one panel at a time then join them with epoxy and glass the joint with some medium weight glass cloth 4oz would be fine 6 inches wide. I prefer to cut the cores full span and sheet it in one shot. You don't have to rely on a center joint that way. You can get real elaborate with vacuum pumps and stuff but for ordinary sport wings, weights and straight boards do a fine job. I have a couple formica sink cutouts I got from a building supply place that are real flat that I have used for a couple years.
As long as your wing is an inch or so thick it will be plenty strong fo any 25 size engine.
30 or 60 minute epoxy would be your best bet being a newbie to foam wing construction.
Good Luck,,,basmntdweller

KJohn

I agree that for a 25 size plane there is no real need for vacuum bagging. In the past using appropriate contact cement like 'Sorgum' or some of the earlier 3M spray contact cements that were made to be used on Polystyrene were used extensively. Epoxy is also very good. Use weights to keep pressure on the foam core bucks. Plenty of dead weight is needed. Here is where vacuum bagging shines. It takes a LOT of dead weight on the bucks or a relatively small amount of vacuum to press the wing skins agains the cores while the adhesive sets up.

To obtain the best contact between the foam core and the balsa sheeting sand the surface of the sheeting with a fine grain sandpaper and vacuum the balsa dust off completely. Sand the foam core with fine sandpaper until it has a 'dull' appearance. Vacuum the foam core completely. Again, make sure both the balsa sheeting and the core have been very well vacuumed (cleaned) before applying any adhesives.

If you are going to add landing gear it might be wise to make the support from one landing gear to the other so it distributes the 'shock' during landing all the way across the wing. This will also act as a dihedral brace. Use Epoxy for this installation and allow it to cure completely.

Use a layer of fiberglass and epoxy in the center of the wing, maybe a four inch wide piece that extends 2 inches each side of center.

Use google.com and search for ''foam wing'' ''construction'' or whatever.

mattijs

thanks for all the advice...will a regular guitar string and a car battery do or do ou really need thermo wire?

basmntdweller

My Feedback: (9)

I checked your profile. It shouldn't take but a few seconds for an electronics engineer to figure out the guitar string and auto battery. So, yes it will work, you just have to figure out how to control the power.
basmntdweller

mattijs

not really, guitar strings have protective coatings that could (i didn't know) melt and thus could be unsuitable for foam cutting.

basmntdweller

My Feedback: (9)

Okay, just about any steel wire around .010" to .020" will work. I have used .015" braided line used for controllines on U-control models with decent results. Any coating on the guitar string will most likely burn off unless its a plating. If they are plated it should be okay. Either of the two smallest strings should be fine. A car battery is way too much power. It would light up the wire and burn in two in seconds. There are many options to power a cutting rig. Variacs are popular as are old style model train transformers. There are more sophisticated supplies which "sense" the temperature and compensate accordingly but they are in the $150 range. My cheapest supply is a car battery charger plugged into a wall light dimmer switch.
Good luck,,, basmntdweller

TX-Deck

I'm a little late for a response, but I had this same question several weeks ago. I came up with a press to do the job, and it works rather well for small cores. Check out the thread here, everyone was very helpful with advice they had to offer:

http://www.rcuniverse.com/showthread...hreadid=813650

As far as the guitar string for a hot wire.. I've had good results with stainless steel leader wire, picked up at the local Academy (fishing section) for less than $3 a pack. Something like 20-30 feet in the pack and it should last me for years. Check a local sporting goods store, the stainless wire is used primarily for salt-water fishing.

Good luck,
TX-Deckk