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-   -   New foam designed airplanes (http://www.Wattflyer.com/forums/showthread.php?t=73709)

oldnrinkled 05-08-2014 12:55 AM

New foam designed airplanes
 
I am so impressed with todays designs. I just viewed the Dynam Smart, what a great designed airplane. I experimented with foamies in the late 60's and was laughed out of the club. What a great improvement todays foamies have over my flyables from the past. This is my quandry, I am wondering if one of you has tried to skin a foamy with something other than fiberglass? It would stiffen up the airframe and also make it more resistent to dents etc. There are hundreds of products that are commercially available. I'm thinking something like a fine mesh cloth or light weight paper. I realize more layers would result in a stronger surface, I doubt if weight would increase to a point where the model would suffer from flight characteristics. Chemicals other than fiberglass resin would be desirable. They were always so messy to deal with. What do you guys think about these ideas? Are there any posts that are already doing as I am suggesting? regards Duane

Abuelo 05-08-2014 01:48 AM

Read where folks are covering foamies with lightweight silk and water based polyurethane.

Silk is available in several weights from Dharma Trading Co, mail order. I have some of their lightest silk and have used it to cover a wing the 'old' way, with nitrate dope. Pretty nice stuff and not particularly pricey. Polyurethane is available in my area at both Lowes and Home Depot in quart and gallon cansunder the Varathane label. Supposedly Minwax also has some but haven't seen any.

Haven't tried it yet but will when the occasion arises. You'll see references in forums as WBPU.

I have used aerospan (also called polyspan and dress interfacing) with epoxy with good results. Its best for flat or single curve surfaces as it shrinks with heat but does not stretch. Being a non-woven fabric it does not want to tear and the epoxy or dope permanently adheres it to the balsa.

Hope this helps. If you find a solution that works for you, please post.

fhhuber 05-08-2014 02:30 AM

Remember that skinning it will add weight and thus you will probably need to add power.

CHELLIE 05-08-2014 08:04 AM

Quote:

Originally Posted by oldnrinkled (Post 947700)
I am so impressed with todays designs. I just viewed the Dynam Smart, what a great designed airplane. I experimented with foamies in the late 60's and was laughed out of the club. What a great improvement todays foamies have over my flyables from the past. This is my quandry, I am wondering if one of you has tried to skin a foamy with something other than fiberglass? It would stiffen up the airframe and also make it more resistent to dents etc. There are hundreds of products that are commercially available. I'm thinking something like a fine mesh cloth or light weight paper. I realize more layers would result in a stronger surface, I doubt if weight would increase to a point where the model would suffer from flight characteristics. Chemicals other than fiberglass resin would be desirable. They were always so messy to deal with. What do you guys think about these ideas? Are there any posts that are already doing as I am suggesting? regards Duane

Tower Econokote works great with foam, its a low heat covering its stronger and lighter than silk. i used it on my Giant scale Bi Planes wings.

http://www.wattflyer.com/forums/showthread.php?t=42680


http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHX49

NOTES FROM OUR TECH DEPARTMENT EconoKote is a patented, flexible high-gloss polyester film that is inexpensive easy, clean, and (when compared to "old fashioned" coverings) quick to use. FEATURES: Super strong with a tensile strength of 25,000 psi (pounds/sq in) Lightweight at only 0.2 oz/sq ft Dry adhesive activates when heat is applied Shrinks to a drum-tight finish as it cools High gloss finish Fuelproof and waterproof Stronger and lighter than traditional silk and dope coverings May be cleaned with glass cleaner, "409", or MonoKote Cleaner/Polish
INCLUDES: One roll (6' x 26") (Jet White) White covering, instructions
REQUIRED: Sealing Iron (TOPR2100 Heat Gun (TOPR2000) Iron Sock (TOPR2175)
COMMENTS: This is applied at Low-Temperature onto foam, fiberglass, and most plastics! For covering balsa at High-Temperature suggest (TOPQ0200 TOPQ0706). (EconoKote can be used on top of, but not under MonoKote.) If using 3 or more rolls of the same color, suggest a 25' roll (TOPQ3604) to ensure the same dye lot for the entire plane. Temperature range: Attaching to foam (activating the glue): 205F (105C)

http://www.wattflyer.com/forums/atta...9&d=1238377779

Hi Everyone :ws: well I got a little more done, I finished the top wing, I used some low heat towercoat covering and some trim tape, just One more wing to go ::o why do BiPlanes have 2 wings ???? :D :D :D Take care, Chellie



http://www.wattflyer.com/forums/atta...2&d=1233824474


Yes its a 9mm Flat wing 80" long :D

http://www.Wattflyer.com/forums/atta...9&d=1233824474
as you can see, I had to make a basswood and balsa frame around the foam wing and add 10mm Square CF and brace the central section of the wing

fhhuber 05-08-2014 02:18 PM

Sorry... Towerkote has nowhere near the strength of silk. Silk is appx 10 times the tensile strength of steel. You have to go to titanium or carbon fibre to beat it.

solentlife 05-08-2014 02:27 PM

Quote:

Originally Posted by Abuelo (Post 947704)
Read where folks are covering foamies with lightweight silk and water based polyurethane.

Silk is available in several weights from Dharma Trading Co, mail order. I have some of their lightest silk and have used it to cover a wing the 'old' way, with nitrate dope. Pretty nice stuff and not particularly pricey. Polyurethane is available in my area at both Lowes and Home Depot in quart and gallon cansunder the Varathane label. Supposedly Minwax also has some but haven't seen any.

Haven't tried it yet but will when the occasion arises. You'll see references in forums as WBPU.

I have used aerospan (also called polyspan and dress interfacing) with epoxy with good results. Its best for flat or single curve surfaces as it shrinks with heat but does not stretch. Being a non-woven fabric it does not want to tear and the epoxy or dope permanently adheres it to the balsa.

Hope this helps. If you find a solution that works for you, please post.

On Foam ? You'd have to be very careful what foam you used Dope on .. even the fumes are enough to dissolve many foams ...

I assume you meant on TRADITIONAL 'wood' wings ? Or Veneered that had ALL possible areas sealed ?

Nigel

Larry3215 05-08-2014 07:33 PM

Quote:

Originally Posted by oldnrinkled (Post 947700)
I am so impressed with todays designs. I just viewed the Dynam Smart, what a great designed airplane. I experimented with foamies in the late 60's and was laughed out of the club. What a great improvement todays foamies have over my flyables from the past. This is my quandry, I am wondering if one of you has tried to skin a foamy with something other than fiberglass? It would stiffen up the airframe and also make it more resistent to dents etc. There are hundreds of products that are commercially available. I'm thinking something like a fine mesh cloth or light weight paper. I realize more layers would result in a stronger surface, I doubt if weight would increase to a point where the model would suffer from flight characteristics. Chemicals other than fiberglass resin would be desirable. They were always so messy to deal with. What do you guys think about these ideas? Are there any posts that are already doing as I am suggesting? regards Duane

Covering the foam will add strength. Almost anything will work to some degree, but the best options are some type of fabric that has a very low stretch thats bonded to the foam with the absolute minimum of adhesive.

Polycrilics (like Minwax polyurethane) with light weight carbon fiber, fiberglass or silk cloths are the best combinations of light weight and strong. Using epoxy is stronger and can be lighter. However, unless you are good at using minimums of epoxy and can vacuum bag the parts, it will almost always end up heavier.

The next best I know of is using thinned aliphatic wood glue (carpenters wood glue) and paper - but its a LOT heavier.

With that all said - they are all almost always too heavy for our little foamies.

Even just adding a layer of paint will add a large percentage to your all up weight and will make a huge difference in how a small model flys.

Very few people believe this at first no matter how many times it is said in the forums. I have seen many many examples of guys building beautiful models that are glassed and painted to look wonderful and are super strong - but they fly like crap because they weigh a ton.

When I build foamies I dont even paint them except for an absolute minimum of accent color. Even then, its usually just a strip or two of that super thin colored packing tape or magic markers.

Weight is your enemy with foamies. Well, actually with all our models in most cases.

Good luck!

fhhuber 05-08-2014 08:04 PM

You can stiffen the foamie planes a lot with just some carefully placed clear packing tape...
You don't have to cover the whole thing. Just put it where you need it to protect from dings and to add stiffness desired.

As noted, we don't do the full coverage with anything without a good reason... too much weight. That means more power to fly and adding power means adding weight... its a losing proposition.

Abuelo 05-08-2014 10:49 PM

3 Attachment(s)
Quote:

Originally Posted by solentlife (Post 947760)
On Foam ? You'd have to be very careful what foam you used Dope on .. even the fumes are enough to dissolve many foams ...

I assume you meant on TRADITIONAL 'wood' wings ? Or Veneered that had ALL possible areas sealed ?

Nigel

Nigel, as always, you are correct. The plane is a Vic Smeed British design from the early 1950s, and designated as either free flight or radio controlled. Goes by the name Tumbletot, of unknown significance

The wing is of traditional balsa with lightweight silk and thinned nitrate dope. All else is balsa with aerospan and thinned nitrate dope. Weight is, prior to any electronics, 109 grams with a 590 mm x 130 mm wing (3 7/8 oz and 23.25 "x 5.125"). The nose area has 1/2 oz fiberglass cloth with epoxy.

Will be assembled and flown once
1. The new motor from Headsup arrives, and
2. The wind slows way down.

solentlife 05-27-2014 06:31 PM

Vic Smeed ... mmm a name that I know .... having been brought up in Brit modelling !

Years ago - I was threatened with divorce ... having doped an airframe .... Veron 1 1/2 Sopwith Strutter ... and whole apartment stank with it !!

Cheers
Nigel


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