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Old May 18, 2009, 12:57 AM
mlee8249 is offline
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Hi Roydor,

The layup of this model is a full carbon skin wing. This is very evident with this model as they used a minimum of paint in the mold, making the skin just a bit easy to see the CF fabric underneath. Will it take windy day launches? I would sincerely hope so, as she is made to handle the extremes of F3J competition. If flying from a winch, and in windy weather, I would be more afraid for the winch line snapping. I realize the the 2-man tow can be brutal, but I also have confidence in the design and construction of this model. Many pilots advised me that the wings of my Shadow model flexed too much,....better not do an F3J launch with it. I reckon that was some misguided info, as many Shadows, including mine, flew in the WC events and despite some wing flex, they launch just fine. So, I'm not worried about the strength of the wings under severe conditions. For the most part, I would just opt for flying the original version instead. The X-38 is for light, or no thermal type conditions. Thanks for asking.

Telling from the long posts concerning the coupled flaps and ailerons, I reckon I'll just leave mine the way they are. Thanks for that, guys.

MIke Lee
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Old May 18, 2009, 01:24 AM
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Just my opinion, if anything, Mike, I'd try to get some differential in the flaps. Not sure if you'd notice the change, but it should help in theory, anyhow.

For a hot roll rate, come fly my Ceres on the slope; it'll do a roll in a second on low rates... Yeah, the flaps are mixed on it. Flying close to an ocean cliff, I find it comforting to know that I have some good roll authority when i can get turbulent.

VR,
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Old May 18, 2009, 05:52 AM
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Mid Air Repair


I figure no Xplore thread is complete without some pictures of repairs. Here's some of the repair from a midair. I am missing a whole set of pictures and can't find out where they are ... but these should be enough to give an idea.

I'll show how I finish the repair within a few days, but I wouldn't hesitate to fly it with the replacement part just taped on .

I know there are easier ways to do this. This is just one way. Enjoy!

T
Old May 18, 2009, 06:22 AM
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What am I missing?


Mike, how is the 3.8m X coming out so light? My 3.5m dbox is going to weigh around 75oz. 71oz for a 3.8m span seems very light. What's going on?
Cheers
Paul
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Old May 18, 2009, 06:33 AM
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Very nicely done, but I would not trust exactly that kind of repair. Firstly the part you molded is glass, not carbon. Secondly, the repaired part is not not overlapped with skin, making gluing area very small. Fortunately the damge is in tip panel... (?)

The integrity of a wing depends mostly on spar and L/E joint. Spar is not an issue here, but I hope you wicked plenty of green ca to L/E both sides of the damaged area to re-glue all possible small damages.

A more simple way to repair similar damage is to hack away the damaged part of a wing, glue block of rochacell in place, and sand it to shape (0.5mm less than skin). Then cover with 45 deg carbon cloth, seams slightly original overlapping wing skin around the area. Sand/paint to final finish as you wish.
Old May 18, 2009, 08:11 AM
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Quote:
Originally Posted by Tuomo
Very nicely done, but I would not trust exactly that kind of repair. Firstly the part you molded is glass, not carbon. Secondly, the repaired part is not not overlapped with skin, making gluing area very small. Fortunately the damge is in tip panel... (?)

The integrity of a wing depends mostly on spar and L/E joint. Spar is not an issue here, but I hope you wicked plenty of green ca to L/E both sides of the damaged area to re-glue all possible small damages.

A more simple way to repair similar damage is to hack away the damaged part of a wing, glue block of rochacell in place, and sand it to shape (0.5mm less than skin). Then cover with 45 deg carbon cloth, seams slightly original overlapping wing skin around the area. Sand/paint to final finish as you wish.
Tuan,
Nice job, but as Tuomo suggest, it could be improved quite a bit ...

OK yes, you had has already done it , but if would like to improve it...

Tuomo proposal is simple, quick, strong enough, but not so ligth !

But since you was already build a proper mould of the damaged area, instead of a simple gfk layer glued only to the head (may about 1mm or less lguing surfaces between parts..), your mould should be re-used to make-up a suitable piece of a "sandwich" inlay, may with a wider gluing surfaces

To do a top quality reparation, without adding valuable weight to the tip terminal, the edge of the demaged area removed, must be beveled with a low angle respect the external surfaces, in order to offer a good/enough gluing surface to support the new sandwich inlay (4 to 6 mm of bevel should be nice).
The sandwich material will be cut to size of the cut, and its contour will be beveled with the same angle applied to the corner edges of the cut itself.

With the mould you can replay an inlay quite exactly the same as a cut-out from an other original tip.... , to be glued in position when already hardened, and with its edge sanded to perfectly sit on its proper place

Antonio.

PS: unfortunately I doesn't have any picture to explaing that job, may I should get it as soon as I'll arrange some more reparation on moulded wing pieces... , in the meantime I hope the above shoul be enough clear
Old May 18, 2009, 10:17 AM
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One layer of 3.2 oz. carbon on a bias laid inside your fiberglass, and overlapping inside will be strong enough, and add only a few grams to what's there already.
Old May 18, 2009, 10:31 AM
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I agree, using a block of rochacell adds weight. But not much - a small piece is only 2-3 grams.

Using a mold is more elegant solution, but as said also by andreis and schrederman, what we want is the srength of carbon and well overlapped glue joints

Flyingwise small weight increse (less than 10g) or little rough surface is no issue, but nicely done repairwork adds planes resale value. Maybe this is why why I sell my competition planes so cheaply...
Old May 18, 2009, 10:43 AM
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To Paul, RCPC,

How is the 3.8 coming out so light....I can only tell you that you need to ask SUSA about that. I know what you're talking about, as my original production prototype is in at 74-oz., full carbon. This latest model is not the only lightweight X in my hanger. Number 2 is also very, very light.

FNNWizard...when did you get into a midair? Or is this the injury you suffered back in Phoenix?

Thanks!
Mike
Old May 18, 2009, 10:58 AM
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Mike: Yep that is the ding from Phoenix.

Andreis, Tuomo, Shrederman: I am not done with the repair yet. The part is just taped on for now. I still need to add some ~ .7mm balsa to the inside of the molded part so it matches the wing's skin thickness. Then another layer of glass, then 1/2" of "seaming" to bond the part to the repair area.

Thanks for the pointers though!
T
Old May 18, 2009, 03:16 PM
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In competitions and especially wc's we collect parts when people crash. When we get a damage like this we cut out the broken part and do a similar part from crashed models. Doing as small overlay on the inside (just some skin pieces) and glue it all together with CA. This is almost as good as original.
To fix this kind of leading edge damage only takes 10-15min if you have done it before. Use medium or thick CA and you can scratch of the CA sticking out before it is fully cured.

Delamination is also fixed with CA. Lots of small holes are punctured in with a needle and thin CA is applied and the skin pulled or squizzed in the right position. Scratch off the CA with a knife 90 degrees to the surface before it is fully cured.

Yes I can post here now as I will have a 3800 Explorer in my house soon... And my own design. Thanks to Primoz and Nikolay
Old May 18, 2009, 03:53 PM
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Nice color design Jojo.
Please let us know how you like the Explorer 3.8 and how it compares to the other aircraft in your fleet after you get some stick time.
Cheers,
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Old May 18, 2009, 04:08 PM
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Old May 18, 2009, 04:08 PM
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Very nice is the wing Lay-up any different that original Explorer?

sj

Quote:
Originally Posted by jojoen
In competitions and especially wc's we collect parts when people crash. When we get a damage like this we cut out the broken part and do a similar part from crashed models. Doing as small overlay on the inside (just some skin pieces) and glue it all together with CA. This is almost as good as original.
To fix this kind of leading edge damage only takes 10-15min if you have done it before. Use medium or thick CA and you can scratch of the CA sticking out before it is fully cured.

Delamination is also fixed with CA. Lots of small holes are punctured in with a needle and thin CA is applied and the skin pulled or squizzed in the right position. Scratch off the CA with a knife 90 degrees to the surface before it is fully cured.

Yes I can post here now as I will have a 3800 Explorer in my house soon... And my own design. Thanks to Primoz and Nikolay
Old May 18, 2009, 04:19 PM
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