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Old Mar 12, 2009, 07:54 PM
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Cracked my ASW-28 ~help~

This is my first airplane of this type, and I landed a bit hard. I cracked the tail section. The stuff is pretty rigid, so i'm not sure about how to repair it. It's split along the spine on top, but not much. If I grasp the front and rear and give it a twist (lightly), the tail will twist a little. It would probably fly like it is, but i'd rather make it stiff again. What are your suggestions? Can CA fix fiberglass?

Here's the flight and the landing the caused the damage:
Flyflyhobby ASW-28 (1 min 44 sec)



Thanks!
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Old Mar 12, 2009, 08:22 PM
slope'n the Colombian Andes
ShredAir's Avatar
Colombia, Antioquia, Girardota
Joined Mar 2001
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If possible, remove rudder and rudder post. This way, you should be able to reinforce the fuselage from the inside. Some carefully placed drops of CA will help also.

Dieter Mahlein, ShredAir
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Old Mar 12, 2009, 10:24 PM
SoarScale
United States, WI, Wind Lake
Joined Nov 2004
814 Posts
I think this is a fairly small sailplane and this type of fracture is a pain to fix properly. As Dieter indicates, your best bet for a long term fix is reparing it from the inside but even then, this will be fairly difficult to achieve given the small size and cavities you have to work with.

Removing rudder, rudder post and placing glass inside with resin is the best solution but probably not the easiest.

I think just trying to re-glue using CA will provide a temporary solution but I can almost guarantee you it will crack again - CA is very brittle, it has no flexibility to withstand torsional stresses in areas like this.

Dennis Brandt (RCGroups name = S2000) does this kind of repair all the time and has probably perfected some techniques you could probably adapt to this break - search for him and ping him with a PM - maybe he can advise.

I personally would attack it from the inside with glass and blue foam plugs to keep the glass in place. I would wrap the outer surfaces with cling film or similar to keep everything in place first. Once the glass/resin had cured internally, I would use acetone to remove the foam plugs (assuming you need them removed for pull-pull cables or similar).

If you can get some of my favorite "cotton flocking" into that resin mixture, you'll increase the strength of the resin bond in the cracks.

Tony
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Old Mar 12, 2009, 10:40 PM
Dave
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Putnam Valley, NY
Joined Sep 2007
677 Posts
That was a carrier landing! Not recommended with a sailplane. ;-)


Hey there, is that a FLyFly ASW-28? Mine had the whole tail section snapped right off. I soaked the jagged break with CA, jammed it back together aligned as best I could, and wrapped it tightly with tape until the CA set up to keep the form right. Then I peeled off the tape and had a pretty strong joint, but CA is brittle, so I sanded the area down nicely to smooth out the joint and to get some texture in the paint. Then I brushed over the entire area with resin and wrapped two layers of very light glass cloth. Let it harden, sand and paint. It came out strong enough and still very light.
Here is the repaired plane:


The red tape is about where the break was. I think yours is a perfect candidate for using my fix method.

On another note....I was able to buy parts for this plane at Hobby-Lobby....they had some "open box" sales and just might have a new fuse laying around.
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Old Mar 12, 2009, 11:18 PM
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Yes, it is a Flyflyhobby model purchased from hobby-lobby. I previously had their DG-1000 (electrified) until the wings folded at altitude and it became a missle! I'm glad I didn't have my camera on it that day. Luckily, the plane and a couple of servos were the only casualties that day.

Sounds like "resin" and "cloth" are the solution. Are those two things something I can get at say, Ace Hardware? I've never repaired fiberglass before. Is the resin you speak of epoxy? Is there a better source online for that stuff?
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Old Mar 12, 2009, 11:51 PM
Dave
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Putnam Valley, NY
Joined Sep 2007
677 Posts
I used Z-poxy 30minute resin....it's just like mixing epoxy. The cloth is a fiberglass cloth about as heavy as stocking material. You can get fiberglass cloth at a hobby shop or maybe auto repair. Just use the lightest, thinnest you can find and you can do layers.

Epoxy, cloth, epoxy, cloth, epoxy all while the epoxy resin is still wet. Use a brush to work out any air bubbles and to lay the cloth down evenly. It's easy to do on the outside of the fuse. It's not as elegant as an internal repair but for a model of this caliber...I wouldn't worry about it. It will work just fine.
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Old Mar 13, 2009, 02:23 AM
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Roodepoort, South Africa
Joined Aug 2007
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Quick fix

Hi There,
This is a common point of failure on saiplanes as the T whips on landing. Repair from the inside is 1st prize but not always possible.
I would mask of an area about 1cm either side of the split , then I would sand with a hard woodedn block and some 380gr paper a "flat " along the seam line until the glass is paper thin on the split. I would then cut 3 x strips of 106gr thick weave glass cloth 1 x strip 1cm wide , 1 x strip 1.5cm wide and 1 x strip 2cm wide. wet out the sanded surface and lay on the thin stip across the split then the wider one and finally the widest , you can add a little balloons to the resin. Once its cured , water paper with 600 grit and touch up with your airbrush , if you are carefull and match the paint you can achieve an invisible repair and have glass across the split , it will be good for some more heavy landings.
Cheers
Mike
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Old Mar 13, 2009, 03:49 AM
Crikey never leave beer behind
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Mt Annan Sydney Australia
Joined Dec 2003
23,438 Posts
welcome to the ASW broken tail club I've advised many people to do the tail mod straight out of the box . Yes remove the rudder and cut out the rudder post (its Balsa)
do it neatly so you can glue it straight back . Use CA to stiffen from the outside carbon tow and lamnating epoxy on the inside.
Your bush can be the normal art paint brush ,I use a bit of plastic tubing and stick the brush in it for extra reach turn the fuse upside down (eg fin facing the floor) and slop the resin in on the tow , its not as hard as it sounds . once done the tail will be tough as an old boot.
SteveW
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Old Mar 15, 2009, 06:28 PM
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this method will make it stronger ,more ridgid than new with very little weight penalty.i've done it with several turbine powered jets and an astro -jeff that broke behind the wing. get the rudder and post out of the way . get a piece of anywhere from 2 to 6 oz carbon fiber or better still, kevlar cloth that is a few inches longer than the broken area and wide enough to cover the inner circumference. mix up some laminating [finishing ] resin. using whatever works, brush it around the inside of the broken area. soak the cloth in the resin . this sets slow so no need to rush. wrap the soaked cloth around a dowel or pencil or anything that will reach the break . work it around so it comes in contact with as much of the inner circumference as possible .now comes the fun and what makes it rock solid . get a small baloon [ steal from your children if you must], and tape the baloon tightly around a drinking straw . carefully drop this down into the broken area and lightly inflate the baloon, then seal the straw off and wrap the outside of the fuselage with 2" wide masking tape. now go away [ just an occasional check to be sure the baloon has'nt deflated is o.k. ] leave it overnight . tomorrow , remove the baloon [no matter if some stays stuck inside]remove the masking tape . now you can fill ,sand and refinish .
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Old Mar 18, 2009, 04:29 AM
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Joined Mar 2008
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Thank you!

Thank you all! I'll now be able to confidently repair my poor bird thanks to your help! Now that we're finally getting some great weather here in southern Illinois, it might be a little while before I get back into the shop. I'm flying my other birds as much as possible while the weather lasts...trying to get rid of my jittery "winter thumbs." I still get a little nervous at the start of a new flying season. I've been off sticks since last fall. I just got my new Parkzone Radian to help me with that...hopefully maiden will be today.

Thanks again. RCGroups never ceases to amaze me!
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Old Jul 27, 2014, 01:59 PM
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Germany, Berlin
Joined Feb 2009
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Quote:
Originally Posted by jetmaven View Post
this method will make it stronger ,more ridgid than new with very little weight penalty.i've done it with several turbine powered jets and an astro -jeff that broke behind the wing. get the rudder and post out of the way . get a piece of anywhere from 2 to 6 oz carbon fiber or better still, kevlar cloth that is a few inches longer than the broken area and wide enough to cover the inner circumference. mix up some laminating [finishing ] resin. using whatever works, brush it around the inside of the broken area. soak the cloth in the resin . this sets slow so no need to rush. wrap the soaked cloth around a dowel or pencil or anything that will reach the break . work it around so it comes in contact with as much of the inner circumference as possible .now comes the fun and what makes it rock solid . get a small baloon [ steal from your children if you must], and tape the baloon tightly around a drinking straw . carefully drop this down into the broken area and lightly inflate the baloon, then seal the straw off and wrap the outside of the fuselage with 2" wide masking tape. now go away [ just an occasional check to be sure the baloon has'nt deflated is o.k. ] leave it overnight . tomorrow , remove the baloon [no matter if some stays stuck inside]remove the masking tape . now you can fill ,sand and refinish .
That's some Mac Guyver style there with the balloon. I am thinking of doing that mod to learn about working with the mentioned materials.
Any hints on what to use for 'laminating [finishing ] resin' ? I stumbled across Polyester Resin as used in boat repairs.
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Old Jul 28, 2014, 06:53 AM
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Killingworth CT
Joined Nov 2008
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The resin depends on the material your fixing.

Most Higher end fiberglass fuselages are Epoxy resin, the cheap ones are polyester or Vinylester resins.. ( close to the same)

If you are fixing an Epoxy fuse, You must use Epoxy to fix it. Polyester and Vinylester will not stick to epoxy, On the other hand, Epoxy will stick to those two.

You can tell the difference between Epoxy and Poly by sanding it a bit and smell it, If it smells like a boat, its Vinyl.

Epoxy is stronger and more flexible than Vinyl, But much more expensive a material. thats why its on the higher end ships area a rule.

len

RcAerotowing.com/forum
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Old Jul 29, 2014, 02:57 PM
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Germany, Berlin
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Quote:
Originally Posted by Lbuff1 View Post
The resin depends on the material your fixing.

Most Higher end fiberglass fuselages are Epoxy resin, the cheap ones are polyester or Vinylester resins.. ( close to the same)

If you are fixing an Epoxy fuse, You must use Epoxy to fix it. Polyester and Vinylester will not stick to epoxy, On the other hand, Epoxy will stick to those two.

You can tell the difference between Epoxy and Poly by sanding it a bit and smell it, If it smells like a boat, its Vinyl.

Epoxy is stronger and more flexible than Vinyl, But much more expensive a material. thats why its on the higher end ships area a rule.

len

RcAerotowing.com/forum
Thank you for the detailed insights Sir. I have an abundance of hobby king 5 minute epoxy but will go for some slower curing epoxy here then.
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Old Aug 11, 2014, 05:18 PM
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Here's an idea to modify jetmaven's balloon fuselage repair:

A balloon longer than the cracked or to be reenforced area, is inserted completely with a rigid PU-tube (I am thinking 6x4 mm or so, maybe 1.5 m long) and sealed. Now the balloon/tube assembly is wrapped in the repair material using a large enough amount of resin since the area is not pre-treated. Now insert the sticky balloon catheter from the front all the way back into the area of interest and dilate by blowing into the mouth piece which is sealed subsequently.
To reach more control over the PU catheter, some kind of rod could be inserted prior to the procedure.
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Old Aug 21, 2014, 05:54 PM
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After reviewing the plan I realized there is no way this will work, especially considering how narrow the fuselage is in the tail area with the tiny formers. Also lacking any experience with composite, I decided to do the tail reinforcement from the outside.

So I got hold of some 50 g / mē fiber glass cloth and 30 minute epoxy and sanded off some gel coat around the tail area where the vertical stabilizer meets the boom.
Now I plan on wrapping one longer single sheet around the boom and slightly overlapping this with another sheet that reaches about half way up the stabilizer.
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