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Author Topic: P-30 with CF  (Read 2483 times)
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tgwhitley
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« Reply #25 on: March 13, 2013, 10:21:14 PM »

Sources/source for CF strips suitable for rib caps? Opinions on what thickness and do you strip your own? The Dragonfly has 1/32 ribs with 1/16 at dihedral breaks.

Tim

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sweepettelee
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Simplicate & add more lightness. Keep sanding!



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« Reply #26 on: March 13, 2013, 10:56:42 PM »

I am a bit surprised no one has mentioned Dave Sechrist's P-30, Marie Super Skinny E. 
It is the most fully composite structure P-30 I have ever seen.
If you have access to FFQ issues 38 & 39, you will find not only the plans, but a fine construction article with many pictures.
Does it fly any good? Well, he won the US Nats with it in 2010, if I read correctly.

If you want to subscribe to FFQ, contact Chris Stoddart: [email protected].
There is an Electronic subscription available for discount $.

Leeper
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Leeper
Tmat
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« Reply #27 on: March 13, 2013, 11:36:19 PM »

Sources/source for CF strips suitable for rib caps? Opinions on what thickness and do you strip your own? The Dragonfly has 1/32 ribs with 1/16 at dihedral breaks.
Tim,
I always preferred .003" thick carbon for cap strips and I always stripped my own. However, that thickness seems unavailable now (I think). You can still get 0.005" carbon from CST in California: http://www.cstsales.com/carbon_Laminates_36.html and you can strip your own.
When last I capped ribs (on an F1B stab) I used carbon fiber pultrusion strips from A2Z: https://www.a2zcorp.us/store/ProductDetailNP.asp?Cguid={E4795906-86E3-4C15-861F-9BDEE59C50F9}&ProductID=5618&Category=BuildingMaterials:Carbon%20Pultrusion

I use the 1 mm x 0.12 mm pultrusion for 1/32" ribs and 1.5 mm x 0.12 mm for 1/16" ribs. Since it comes in the correct width already it is easy to use. I also use the carbon rectangular strips for trailing edges (also from A2Z). Keep in mind that a very small amount of carbon goes a long way. For trailing edges on my P-30 stab I used a pultrusion that was 1 mm wide x 0.5 mm thick only. This was a stab covered in 1/4 mil mylar and the trailing edge was bomb proof. For my wing I used 1.5 mm x 0.5 mm carbon pultrusion that tapered to 1 mm width at the tip (I block sanded it after construction).
Most people make the mistake of using way too much carbon because they are used to balsa. Again, a little goes a long way.

I've used slow, rubber toughened CA to apply the caps and also slow(ish) epoxy with very good results. Naturally, you should always sand the glue side of the carbon and solvent wipe before bonding.

Tmat
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tgwhitley
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« Reply #28 on: March 14, 2013, 09:17:01 AM »

Tmat thanks for the link I will order material from this source. Tmat are you talking about CA used by the RC car guys to attach tires to wheel?  Leeper checking on FFQ I do have the P-30 survey in transit from Australia.

Tim

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Tmat
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« Reply #29 on: March 14, 2013, 10:47:52 AM »

Tim,
I don't know what the R/C car guys are using. I was talking about this sort of stuff: http://www.redbaronadhesives.com/products/rubber-toughened-cas.html
Most of the CA companies are now making a rubber toughened CA product.
Here is another: http://www.hobbylinc.com/htm/hlc/hlc120.htm
And another: http://www.hobbylinc.com/htm/hlc/hlc117.htm
You get the idea....

Basically, these products are very good for bonding composites like carbon fiber because they don't cure to a brittle state. They stay slightly flexible and have high peel and shear strength. Also, one factor that I found was that when applying mylar coverings, you use a hobby iron to tack and shrink the covering. The high heat can soften standard CA products and cause a cap to pop loose on the undercamber (very annoying!). The rubber toughened CA's are good to much higher temperatures. For this reason I also prefer epoxy adhesives that can withstand elevated temperatures.

Tmat
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flydean1
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« Reply #30 on: March 14, 2013, 11:00:52 AM »

Tmat,

I have just gone through an ordeal attaching CF strips to rib upper surfaces on a Super Pearl 542.  I used medium CA, and since it does not give much time for working, there are voids.   Now I will have to sand the voids off and "patch" with short lengths of strip.

I was going to use a Loctite brand of adhesive but it takes an hour to dry.  I have no way of holding down the CF strip for an hour.

Do those rubber-toughened CA adhesives allow some time to position and rub down the CF strip?   If I had 5 minutes it would be worth it.

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duration
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« Reply #31 on: March 14, 2013, 11:10:56 AM »

Another source for carbon capstrips is Alex Andriukov. These come in several widths. You can find link to his website on NFFS site (free flight.org). You'll have to look through his product list to find them---I think they may be in several places (wing, stab, and F1A stab caps are available).

Check Disco Kid website for availability of Stan Buddenbohem .003 carbon sheet; also look in classifieds in NFFS Digest.

Louis
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Tmat
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« Reply #32 on: March 14, 2013, 11:19:47 AM »

Dean,
The rubber toughened CA does give a bit more time to position the cap strips. Typically, I use epoxy (3M DP460) and I make a simple jig consisting of a wooden base with multiple small finishing nails around the front and rear edges (they line up with the ribs) that allow me to run some rubber strip (1/8" tan rubber) around each nail and up over each rib. This applies the pressure to hold the strips in place while they cure. I attach little "ears" of magic mending tape to the front edge of the strip to tack it in place, lift the strip, apply the glue (very sparingly!) put the strip back down and clip the free end with nail clippers flush with the TE. Then I add a little piece of tape to secure the TE end of the strip. I do the top and bottom strips all at once and so use slow cure epoxy so that I have plenty of time.

When using CA I do one strip at a time.

Charlie Jones from FAI supplies might also carry rib cap strip sets from the Ukrainian builders.

Tmat

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Tapio Linkosalo
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« Reply #33 on: March 14, 2013, 11:51:56 AM »

And then, if your workshop has a small tabletop circle saw with a diamond blade (I use one with 50mm / 2in) blade, another method of making ribs is: carve a (solid) block between plywood ribs, laminate uni-directional carbon with epoxy on top and bottom, and once cured, use the saw to cut individual ribs. This way carving the ribs from solid block is easy, and also you easily get lighter balsa in thicker sheets. Plus, with the saw you can also cut the carbon spars to desired dimensions!
 
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tgwhitley
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« Reply #34 on: March 14, 2013, 02:51:41 PM »

Ama plan service is the best my original from 1988 was terrible quality could not see ribs on plan. When I ordered plan again on Monday the box arrived on Thursday. I had long conversation with the staff at AMA plan services about RCM and the state of plan services across the country. Talked about my plan quality from 1988. They sent me extra copy and the article, great service I think.

Tim

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Tmat
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« Reply #35 on: March 14, 2013, 04:42:29 PM »

Tapio,
I didn't mention that method as most people don't have the equipment to do it at hand. Also, for tapered wing panels you need a unique block for every rib. Lot's of work and only makes sense imo if you intend to make multiple copies or mass production. for a one off model I'd never think of that method unless I had a constant chord wing or stab.

Tony
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Tapio Linkosalo
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« Reply #36 on: March 15, 2013, 03:54:58 AM »

The only extra tool needed is actually the table top saw, which is really handy in many ways, well worth its price.

For tapered panels/blocks, I've found that making ribs for 2 wings in one block makes the block thick enough, so that the ribs do not taper too much. After all, the tabletop saw makes 1mm wide "cuts", so a considerable amount of block thickness is lost in dust anyway.

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danberry
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« Reply #37 on: March 17, 2013, 09:06:24 PM »

I'm going to "stir the pot" here a little...

Do you think that the subject of this thread and the responses go against the spirit of P-30?

Or, is P-30 just another one of those events that have evolved from what was once intended to be a "beginners" event to just another expert event?

No. The plastic prop is the great equalizer. A 55gm canard P30 can win when it's in lift.
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tgwhitley
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« Reply #38 on: March 18, 2013, 10:39:01 PM »

I received mail form FFQ I enthusiastically opened my envelope and to my surprise the Coupe survey was in package. Well being certain that the order was for the P-30 survey checking my paypal account was confirmed. I have asked FFQ to send me invoice for P-30 book the Coupe copy looks very interesting. Really was pumped to read P-30 survey just a little more time needed now.

Tim

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Ding
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« Reply #39 on: March 19, 2013, 12:21:30 AM »

Tim,
I do build a lot of P-30's and found a strong need for carbon reinforcement mainly spanwise.  Walking back upwind after a retrieval my wing snapped at least on two occasions if my memory serves me right.  I now have on my wings carbon lined spars (under top spar and above bottom spar) and fill in these two spars with very soft balsa webbing.  They now have the strength of a Balsa Beam and do not snap as readily.  Besides it might be easier to apply it to a balsa strip before construction. One can say that the best strength of carbon is in its tension.
I also like Tmat's use of mylar. Another adv is it is easier to set or remove warps with a heating iron that stay and are not affected by temperature or moisture much.
Ding
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