Author Topic: How to incorporate composites in our BOM world (Read 3625 times)

jose modesto · « **on:** November 01, 2011, 01:53:05 PM »

This is written after Bob Hunt recent article (AMA Mag) and his request on how we can use Composites and Meet the current AMA BOM.
When i started my adventure into composites my main influences were Windy u.(greatest BOM modeler ever) Al rabe and Kaz Minato.
Windy and Kaz were using very expensive space age materials (nomex carbon fiver and kevlar,) Al rabe used traditional Balsa and ply wd. Since i was just starting out(2002) I searched for a Method that on a budget you could produce Nat's level models.
In 2002 I purchased from Aerospace Composites a video that showed how to make a glider wing
From this video i developed the following system.
WINGS: Mylar folder,foam wings,glass cloth,epoxy
Anyone can construct a composite wing using this method
1) Aerospace composite, Mylar. This material is cut to the shape of the wing panel top and bottom. The top and bottom Mylar are taped together at the trailing edge. This creates a folder
2) wax the interior surface and polish
3) layout the following in this order .5 Glass cloth,color taffeta,.5 CF mat. Starting with the .5 glass cloth layout into Mylar folder with epoxy squeegee excess epoxy. add the additional materials with epoxy
4) insert foam wing into Mylar folder (cored or uncored wings can be used, my first wings were all cored as they were wings i had on hand)
5) place Mylar folder into bottom cradles place top cradle, use a 3/4" plywood same size as the wing core. Load with weight and wait 24 hours

jose modesto · « **Reply #1 on:** November 01, 2011, 02:01:24 PM »

The cost for this type of wing as follows
1) one yard .5 glass cloth $7
2) foam wing $35
3) taffetta $2 yds
4) .5 carbon fiber mat $5
5) epoxy 1.5oz per panel $5
6) mylar $15 Reusable
Note Balsa is optional
Photo of same system with balsa and glass cloth.
photo 2 and 3 show the mylar folder.
Jose Modesto

Tim Wescott · « **Reply #2 on:** November 01, 2011, 02:06:58 PM »

What does the weight come out to be, with how big of a wing?

jose modesto · « **Reply #3 on:** November 01, 2011, 02:39:49 PM »

The yellow wing is 7oz with the bellcrank and pushrod installed at 630Si
the completed model came in at 52oz with Big Jim ST46
Note: those wings are foam and cloth with out balsa.
At the time i was working with John Duncan he would cut the wings for me.
A further development was to have john Duncan cut a UN cored wing with the holes through the core for future coring. John then made for me a set of templates that i called super core. The template removed additional foam which made them lighter. since john and i lived several hundred miles apart it was cheaper for me to do my own foam coring.
with this system you should use the .5 CF mat as this gives some stiffness to the outer surface, with out it you can dent the foam wing during heavy use.
Jose Modesto

Tim Wescott · « **Reply #4 on:** November 01, 2011, 02:48:12 PM »

So you're being conventional in that you're building wing halves and joining them, not trying to make the wings in one piece?

Have you vacuum bagged? Does it make much difference?

Peter Nevai · « **Reply #5 on:** November 01, 2011, 02:56:56 PM »

Love it, vacuum not required. Bagging alows you to use less glue, but not so much less that It makes a ton of a difference. Vacuum bagging is advatageous for those parts that do not redily have a handy outer mold like foam core wings do with their cradles. My question is about wrinkles. I gather the mylar is stiff enough not to induce wrinkling? Oh BTW do you put the CF under or over the glass? I suppose you can use all CF if you have the $$$

proparc · « **Reply #6 on:** November 01, 2011, 03:22:00 PM »

Just want to chime in here. Foam wings and composites became really popular on the East coast many years ago, because of the crappy weather-Sorry Jose. They were, and are considerably more stable in that environment then anything else. If you hang out at the RC forums like I do, you will find this stuff very common. There is a guy with a kick-ass F3A ship made entirely out of Coroplast-I'm not kidding. While my work along these lines extended to foam and plywood,(and will continue) I like how Jose is rolling with the cost aspect.

I personally think he is hooking it up here.

jose modesto · « **Reply #7 on:** November 01, 2011, 03:22:57 PM »

Tim working on a complete wing panel is difficult to handle. I tried the full wing first but it was a hand full.
The system presented utilises a foam wing as the basis for the composite. Tim the Mylar on a full wing would not lay down as it does not want to follow multiple curbed surfaces.
As far as wrinkles these are taken care when the cloth is laid out onto the Mylar.
This system is for a foam wing. NOTE: if you are going to use a foam wing and not use balsa you have to get the foam wing cut to the larger size as if its allready covered.
the sequence from outside in is .5 glass cloth then color then .5CF mat the mat abuts the foam. The .5oz glass cloth is the finish.
Tim attached photo of full top wing panel
Peter my current models are Vaccum Bagged Wings,fuse, stab flaps elevator with balsa fin and rudder
the system shown is From 2002 and 03
Photo #1 complete top wing panel
photo #2 female mold and male plug
photo #3 balsa CF cloth composite wing panels

Howard Rush · « **Reply #8 on:** November 01, 2011, 03:41:08 PM »

When I made Snorts for the 1990 WC, I found that putting the .5-oz. carbon mat on the surface gave a smoother, harder finish.

proparc · « **Reply #9 on:** November 01, 2011, 03:45:01 PM »

Quote from: Howard Rush on November 01, 2011, 03:41:08 PM

When I made Snorts for the 1990 WC,

Whats a Snort?

jose modesto · « **Reply #10 on:** November 01, 2011, 03:56:08 PM »

Peter if you go to the electric forum and look at William Demauro composite SV22 partly built in my shop you will see the current state of my composite construction. Williams Model is shown on Bob Hunt's control line column.
Photo of William's SV22

Jose Modesto

jose modesto · « **Reply #11 on:** November 01, 2011, 04:16:55 PM »

Howard for me i have to use the .5 glass cloth on the exterior this gives a much smoother outer surface with minimal pin holes to fill later at the finishing stage.
One caveat with this system when finishing with dope is to apply a water base clear coat ( min wax polacrilic clear)
this clear coat will fill any pin holes.This clear coat prevents solvent base paint From damaging the foam
If the model is electric water base paint can be used. Better for our health.
Jose Modesto

Howard Rush · « **Reply #12 on:** November 01, 2011, 04:28:03 PM »

Quote from: proparc on November 01, 2011, 03:45:01 PM

Whats a Snort?

http://clcombat.info/snort.html , http://www.flickr.com/photos/fesselflug/2424715115/in/set-72157604437799488/ , http://www.flickr.com/photos/fesselflug/2425528152/in/set-72157604437799488/

Most of the leading edge shells had a 1-oz. Kevlar surface, which got increasingly lumpy with time. The ones with the mat on top of the Kevlar were much smoother. That's about the only thing I've found that the mat is good for.

Tim Wescott · « **Reply #13 on:** November 01, 2011, 04:30:19 PM »

Quote from: Peter Nevai on November 01, 2011, 02:56:56 PM

I suppose you can use all CF if you have the $$$

I recall reading articles on vacuum bagging glider wings where the authors were using a mix of CF, glass and Kevlar, citing different strength characteristics for each and claiming to have a better whole with the mix.

That's all I remember, though, so don't ask for details -- Google is your friend.

Brett Buck · « **Reply #14 on:** November 01, 2011, 07:46:26 PM »

Quote from: Tim Wescott on November 01, 2011, 04:30:19 PM

I recall reading articles on vacuum bagging glider wings where the authors were using a mix of CF, glass and Kevlar, citing different strength characteristics for each and claiming to have a better whole with the mix.

That's all I remember, though, so don't ask for details -- Google is your friend.

Vacuum bagging is not nearly as good as doing it the way Jose shows, and it's nowhere near as repeatable. And it tends to be a lot heavier for the strength. I think the molded method is by far the best way to build a wing, with, unfortunately, a lot of overhead and up-front work. But once you did it once, it's done.

Brett

Howard Rush · « **Reply #15 on:** November 01, 2011, 08:01:10 PM »

Better yet is vacuum bagging in a mold.

Tom Niebuhr · « **Reply #16 on:** November 01, 2011, 08:11:54 PM »

Jose,
What type of epoxy do you use?

Wynn Robins · « **Reply #17 on:** November 02, 2011, 06:25:48 PM »

where do you get the mylar and .5oz carbon cloth from?

also - what do you wax the mylar with car wax???

this is something I want to try (seeing as you wont sell me anything HA)

Jeff Traxler · « **Reply #18 on:** November 08, 2011, 10:29:55 PM »

Quote from: Howard Rush on November 01, 2011, 08:01:10 PM

Better yet is vacuum bagging in a mold.

I good friend of mine Kevin Matney owns Matney's Models.His company makes all kinds of molded composite kits.Kevin and his designs have done very well at both the National and World level in Electric and IC pylon racing.Kevin vaccum bags all of his components in the molds and the result is a very light and strong component with a ready to paint finish.Some of his pylon racers he puts decals and whatever else in the mold and bags it all together.the result is a finished,ready to use component.I have been spending some time at his shop and he is steering me in the right direction with all my plugs.I am planning to bag all my components in the mold.I am getting the vaccum components gathered so I have them when the molds are ready.Since I am making my own molds I qualify but what if I loan the molds to someone and they mold their own components?Bagged components are light,strong,stiff,and repeatable.Just what is needed for CLPA.

Derek Barry · « **Reply #19 on:** November 09, 2011, 08:37:13 AM »

Hey Jeff, you can most certainly loan your molds to someone as long as they do the act of laying up their own components.

Derek

Bob Hunt · « **Reply #20 on:** November 09, 2011, 01:40:38 PM »

Gee, Derek, we finally agree on something!

Isn't this precisely what I wrote about in my last MA column?

Bob Hunt

jose modesto · « **Reply #21 on:** December 09, 2011, 09:05:04 AM »

When I first posted this method I should have included that Mr. Bob Hunt has developed a similar system for finishing a sheeted foam wing.
Bob has solved the challenge of wrapping the finish around the leading edge, without incurring fabric fold that were constant in my Mylar/foam wings.
Bob has developed a lighter Mylar folder finishing system,that incorporates different materials.
Bob has also developed a do it yourself composite foam finishing system,that does not require a vacuum system.
Currently I use the Mylar folder for flaps and elevators.
Since Bob no longer post on this forum,and you are interested in his development,you can contact him via Stunt News.
Jose Modesto

Avaiojet · « **Reply #22 on:** December 09, 2011, 09:35:48 AM »

I've been looking into CF for reinforcement. This stuff is seriously expensive!

Minimums are required for purchase.

Anyone know where the stuff can be purchased without minimums?

CB

RC Storick · « **Reply #23 on:** December 09, 2011, 10:45:08 PM »

Quote from: jose modesto on December 09, 2011, 09:05:04 AM

Since Bob no longer post on this forum,and you are interested in his development,you can contact him via Stunt News.
Jose Modesto

According to Bob he no longer posts on any forum.

john e. holliday · « **Reply #24 on:** December 10, 2011, 08:26:02 AM »

That is our really big loss. The man has untold info in that head of his and I am still waiting on his book to be finished.

Avaiojet · « **Reply #25 on:** December 10, 2011, 09:31:19 AM »

Quote from: Robert Storick on December 09, 2011, 10:45:08 PM

According to Bob he no longer posts on any forum.

I wonder why?

CB

jose modesto · « **Reply #26 on:** May 02, 2012, 09:43:48 PM »

"D" take a look at this