428 pylon and foam wings
 

hey guys, getting back into pylon. with the advent of the newer motors for 428 will a properly built foam/balsa wing withstand these new motors/speeds. i have a cnc foam cutter that i have used to build many an imac plane and would like to use it on q500 designs. not trying to start a war, but would like honest opinions and building techniques to be utilized. thanks, toby silhavy....

RE: 428 pylon and foam wings
 

No war needed, easy answer. YES. A foam/balsa constructed wing can hold up to 428. With proper carbon/glass reinforcement, no worries.

RB

RE: 428 pylon and foam wings
 

I''m still using your motors and they are still going strong, so you can''t have them back.

Denis

RE: 428 pylon and foam wings
 

I hope properly built means 3/32 balsa for the top skin.

RE: 428 pylon and foam wings
 

Actually I use 1/16. But I lay in two 1 inch wide strips of bi-directional .014 carbon on the top and and a 1 inch strip of mono directional .014 carbon on the bottom. I do a lot more but Ed Smith would say I was building rail road bridges and not wings and he would be right:) . But hey the weight increase to 3 3/4 lbs gave us this.:D

Denis

RE: 428 pylon and foam wings
 

denis, glad you are still going strong with the nelsons! i''m thinking of making wings using 1lb density foam, carbon fiber strip top and bottom. 1/16" sheeting, then glassing the whole wing with 1/2 oz cloth then painting. what do you guys think? to me this is easier than making up my own molds to do wings. in the past i would set up around 10 wings and i could have them done in about a weekends time. thanks guys! denis-what times have you posted with the engines? toby....

RE: 428 pylon and foam wings
 

I'm on a budget (poor retired guy). I have been using three strips of carbon fiber tow on the top and four on the bottom.

[sm=thumbs_up.gif]But I've been thinking about trying filament strapping tape wrapped around the wing core in a couple of places. I suspect we are over building our wings, but I don't want to be the one to find the lower limit!

I used to make a flying wing based on the Gremlin for combat and that's what we used on those wings. I wrapped the tape around in one continuous band and then skinned the wing by bagging it. I never had a wing fail. Anybody try something like that? In my next batch of wings I'm going to make one that way. I'm sure it would be more than adequate for 424 I just don't know about as a 428.

Just an idea CF and Kevlar are getting out of hand.

I have a Kevlar car cover my wife almost sold at a garage sale last month. It must be worth a couple of thousand now, bought it for $250 several years ago.

I too use 1/16 top and bottom and I always have. I've never had a wing fold, but I have had the skin separate due to being too stingy on the epoxy and or not cleaning the core adequately. My wing core templates are set up for 1/16" skins to give me exactly 1-3/16" before covering.

SD

RE: 428 pylon and foam wings
 

Hi Toby

My times aren't very good but that's nothing do to the engines or the planes. Poor times are all about me. Those 2 engines were just as strong as the most recent AAC SS engines. The LS is stronger no doubt about it. But the record set by an SS 2 years ago still stands. In addition to the carbon straps I put on top and bottom of the wing I build the wing leading edge with 2 strips of .04 carbon fiber. 1 strip of carbon between to strips of 3/16 backed by the other carbon strip to form a .04 carbon "T" section balsa filled. This is my leading edge. In the trailing edge I sandwich a .014 by 1/2 inch strip mostly as a sand to point. The center section top and bottom is 2 layers of 2 oz fiberglass. Then I glass the whole wing with 1/2 oz. As far as strength for 428 this way overkill. I do all this to try to get better stiffness. My wings come out 18 to 20 ozs with servo and linkage.

Denis

RE: 428 pylon and foam wings
 

Hi Toby, I am not an expert, but here are my experiences.

For 424, I began using 1/16" sheeting (top & bottom), 1/2" x 48" .007 carbon strip spar (top & bottom), 1# density white foam cores, 1/2" wide .007 carbon strip for the trailing edge (for a straight sanding line), a 3/8"x1/2" Balsa leading edge and finished with 1/2oz. cloth.

I tried this lay up with a variety of adhesives.
ZAP laminating resin - good strength and weight - tends to yellow with time in the sunlight.
West Systems 105-206 - good strength & slightly stiffer with no yellowing - short working time and the heat of the cure would melt the foam some.
Gorilla glue - the bond and weight was good - wing was flexible and the glue sanding dust is toxic.
MGS 285 - excellent bond, super stiff and clear as day - have to buy in gallon sizes.

I have used weights on the shucks to cure as well as vacuum bagging. The vacuum bagging is by far the best way. More psi, equal pressure and not near as much space needed. My final lay up for 424 is this:

1/16" balsa skin
MGS resin
1/2" x 48" .007 carbon strip spar and 2" 1.4oz glass trailing edge strip
MGS resin over reinforcements
Foam core
MGS resin
1/2" x 48" .007 carbon strip spar and 2" 1.4oz glass trailing edge strip
MGS resin over reinforcements
1/16" balsa skin

Finish by adding the leading edge, shaping the trailing edge and cover with 1/2oz cloth and MGS resin. This method allows me to shape the trailing edge to a sharp point (better than the carbon strip) and is even stiffer.

I am testing my wings for 428 now, and have added two layers of 1.4 oz. cloth (top & Bottom) in the center section with the carbon and trailing edge reinforcements. We will see how that works out!

Hope this helps you some.

RE: 428 pylon and foam wings
 

We use full span 3mm fiberglass dowels in the top and bottom of RC combat wings. This produces a very strong wing.

RE: 428 pylon and foam wings
 

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Skin-It Epoxy
Laminating and Finshing System

Skin-it Epoxy is the best long cure low viscosity adhesive you can ever wish to use. Skin-it works great with both balsa and glass skins, and is perfect for vacuum bagging. Skin-it also makes a marvelous finishing resin that sands very easily. It is a must to help you get the show plane look you want. Pot life is 30 minutes, giving you time to make adjustments. The mix rate is a 4 to1 but is very forgiving.