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Old Sep 10, 2012, 04:41 PM
AMA7224 LSF1832
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Houston....we have a problem.

I am not sure how or even if this one can be fixed. I put together the diherals brace sticks and got them all line up spot on and though I was making track speed with the build on the new Siren. Epoxied on into the wing and let it cure, then did the other. I had the wing leaning up againt the drill press base while curing, then it tipped over and ever so gently hit the base...and...snap went the dihedral brace,snapped clean off at the wing root looking like the end section of a Kit Kat bar. This also lead me to doubt the stregnth of the braces, but the problem now is,can it be fixed?? Ideas?? I've been building for 40 years and have seen a lot of weird stuff when in the shop, but this one has me a bit stumped.
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Old Sep 10, 2012, 05:05 PM
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Ouch! Leadchucker.

A couple ideas might work. Probably the easiest would be to just cut the whole works out from the bottom of the wing and build a whole new joiner assembly. Re-sheet the affected area, perhaps add a little glass to be sure, and you should be good to go.

A way to accomplish pretty much the same thing without carving out sheeting would be to get long drill bit of the appropriate size, if you can find one, and drill a hole to accept a crbon joiner. I'm not sure if the old trick of making a hole saw out of a brass tube would work with ply and epoxy.

Good luck!
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Old Sep 10, 2012, 08:36 PM
The wheels touch down FIRST??
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Australia, VIC, Melbourne
Joined Jun 2009
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Quote:
Originally Posted by KRProton View Post
Motor thrust angles on Siren are supposed to be 3 degreed down, 3 degrees right. This in relation to the horizontal stabilizer - set the fuse so the stab reads zero and the motor should read 3 degrees down. Of course, 3 degrees right using the centerline of the fuse as a reference.

Tim
Thx for the info Tim

Now all I have to do is figure out how I measure 3 degrees down, 3 degrees left.

Probably just take a punt at it in the end - like... visibly down a bit, right a bit ...


Quote:
Originally Posted by Demon 6 View Post
Here's what I smoked up for a paint scheme...Attachment 5146369
You make some truly nice stuff, mate

BJ
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Old Sep 10, 2012, 09:18 PM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
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Originally Posted by Demon 6 View Post
Here's what I smoked up for a paint scheme...Attachment 5146369
Ha ha!

Cool!

I like it!

Very original!

Tim
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Old Sep 10, 2012, 10:16 PM
Dir. of Innovation at Alert 5
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United States, FL, Fort Lauderdale
Joined Jul 2011
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Quote:
Originally Posted by Leadchucker View Post
Houston....we have a problem.

I am not sure how or even if this one can be fixed. I put together the diherals brace sticks and got them all line up spot on and though I was making track speed with the build on the new Siren. Epoxied on into the wing and let it cure, then did the other. I had the wing leaning up againt the drill press base while curing, then it tipped over and ever so gently hit the base...and...snap went the dihedral brace,snapped clean off at the wing root looking like the end section of a Kit Kat bar. This also lead me to doubt the stregnth of the braces, but the problem now is,can it be fixed?? Ideas?? I've been building for 40 years and have seen a lot of weird stuff when in the shop, but this one has me a bit stumped.
I'm understanding that one of the wing sections was being bonded with the stock setup and it fell over, snapping the spar clean?
if so, no biggie... wait for the spars to cure in place, fill and sand flush (both sides), drill dead center of the old epoxied spars to receive a carbon tube and epoxy together... I had the braces fail due to some "issues" and I solved it in that fashion... In fact, on all my subsequent wings I have built since (4), I fill the spar box with a piece of hardwood (maple, ash, whatever) sand flush drill and epoxy a CF tube in place... Its bomb proof!!!
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Old Sep 10, 2012, 10:17 PM
Dir. of Innovation at Alert 5
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United States, FL, Fort Lauderdale
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Originally Posted by KRProton View Post
Ha ha!

Cool!

I like it!

Very original!

Tim
Thanks Tim and BJ
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Old Sep 10, 2012, 10:27 PM
Dir. of Innovation at Alert 5
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Originally Posted by BJ64 View Post
Thx for the info Tim

Now all I have to do is figure out how I measure 3 degrees down, 3 degrees left.

Probably just take a punt at it in the end - like... visibly down a bit, right a bit ...




You make some truly nice stuff, mate

BJ
BJ,

I have a question for you, since you made such a stellar repair to your Sirens nose...
I have a Siren fuse that had a small mishap wherein the "step" where the main wing screws in place (next to the screw), one corner section has broken off... imagine the outer corner of the step completely missing and replaced with a gaping hole... Any ideas on repair?
Filling it with chopped carbon came to mind, but I want to have the step molded and not spend alot of time sanding the step back in...(unless I have too)
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Old Sep 10, 2012, 10:36 PM
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Hey Demon, now I know why you like to paint your wings after glassing them, Is just nicer dude, and you don't have to worry about monocote wrinkles on sunny days and having to Iron them away. I like the design a lot bro.

Bernie
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Old Sep 10, 2012, 11:02 PM
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Very nice, Demon6!

On your other molding question: You might need to follow the old fashioned way and splice in a suitable piece of fiberglass tape or carbon sheet then use epoxy mixed with micro balloons or talcum powder to fair everything in. The tape provides the strength of the glass fibers while actually adding a softer component to the resin gives a very nice finish. I've been using epoxy and talcum fillets, off and on, since before micro balloons were marketed and I have never had one fail and they're very easy to sand.
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Old Sep 11, 2012, 08:27 AM
The wheels touch down FIRST??
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...you could always try WBPU.

Either neat, or mixed with some micro-balloons/fine woodchips (not dust) etc. Probably fine woodchips - as they may 'key' together for a stonger substrate. Mist the internal surfaces with water and insert a blob of your Urethane + whatever 'filler' you've chosen (if any) into the cavity area. Mist that with a little water too.

Then tape the outside to the contour you want - you can use mylar/computer parts bag plastic on the surface of the fuse, then tape to shape. The mylar/parts plastic should give a mirror-smooth finish. Orient the fuse so that the goo on the inside will want to run down into that corner.

Bit of a guess how much glue/substrate to use, but if you guess it right there should be a bit of a larger 'wad' behind the corner that's missing, and that'll help key the hole lot onto the inside of the fuse when the WBPU expands and fills out the corner.

That's probably what I'd try - we use neat WBPU to fill-out dings in the LE of foamie wings etc. Mist the surface, apply a small blob of glue, mist that - then tape wider than the ding. You don't need much glue, as it expands up to around 3:1, depending on how much water you mist it with (as it 'moisture sets').

You could use glass/balloons instead of Urethane too - same deal. Get some in there, then tape the contour you want and orient it so the filler wants to run into that area.

Urethane might just have a bit more 'spring' in it so that it doesn't crack/splinter out like pure glass would (though balloons give it a bit more resilience).

I'd be trying the WBPU with fine woodchips or maybe even a little mashed-up CF matting...

BJ
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Old Sep 11, 2012, 08:53 AM
Dir. of Innovation at Alert 5
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United States, FL, Fort Lauderdale
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Quote:
Originally Posted by BJ64 View Post
...you could always try WBPU.

Either neat, or mixed with some micro-balloons/fine woodchips (not dust) etc. Probably fine woodchips - as they may 'key' together for a stonger substrate. Mist the internal surfaces with water and insert a blob of your Urethane + whatever 'filler' you've chosen (if any) into the cavity area. Mist that with a little water too.

Then tape the outside to the contour you want - you can use mylar/computer parts bag plastic on the surface of the fuse, then tape to shape. The mylar/parts plastic should give a mirror-smooth finish. Orient the fuse so that the goo on the inside will want to run down into that corner.

Bit of a guess how much glue/substrate to use, but if you guess it right there should be a bit of a larger 'wad' behind the corner that's missing, and that'll help key the hole lot onto the inside of the fuse when the WBPU expands and fills out the corner.

That's probably what I'd try - we use neat WBPU to fill-out dings in the LE of foamie wings etc. Mist the surface, apply a small blob of glue, mist that - then tape wider than the ding. You don't need much glue, as it expands up to around 3:1, depending on how much water you mist it with (as it 'moisture sets').

You could use glass/balloons instead of Urethane too - same deal. Get some in there, then tape the contour you want and orient it so the filler wants to run into that area.

Urethane might just have a bit more 'spring' in it so that it doesn't crack/splinter out like pure glass would (though balloons give it a bit more resilience).

I'd be trying the WBPU with fine woodchips or maybe even a little mashed-up CF matting...

BJ
BJ-
Are you talking about "Gorilla Glue"? Sounds fun and easy when you talk about it... WBPU = Water Based Polyurethane? Any brand you can recommend?
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Old Sep 11, 2012, 09:35 AM
The wheels touch down FIRST??
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Yah - WBPU = Water Based PolyUrethane.

Gorilla make several WBPU's - fast-set, stuff the dries white, and normal every-day WBPU etc. Selley's make one called 'SikaBond', and then there's "Vise" as well as many others. They're interesting stuff to use, and work great on foamies as well as bond wood a treat too. Take care with any any over-runs - they'll puff-up on you. Pretty easy to remove though, if you wait until it's dried but not fully set.

You might want to experiment a bit re expansion on setting, final strength, and finish etc.

Just don't get it on you - it's fair mongrel to get off

BJ
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Old Sep 11, 2012, 02:54 PM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
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Bringin' my Siren to NEAT in New York this weekend. We're getting ready to leave in a minute here. Hope to fly it a lot! It's been collecting a little dust in my garage at home.

Tim
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Old Sep 11, 2012, 05:01 PM
Dir. of Innovation at Alert 5
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Originally Posted by KRProton View Post
Bringin' my Siren to NEAT in New York this weekend. We're getting ready to leave in a minute here. Hope to fly it a lot! It's been collecting a little dust in my garage at home.

Tim

Tim-

Have a blast!!!
Hope you have a great outing and it will be good for folks to see what a "Great Plane" she is... Looks forward to some pics too
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Old Sep 11, 2012, 05:03 PM
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Originally Posted by peterlngh View Post
Very nice, Demon6!

On your other molding question: You might need to follow the old fashioned way and splice in a suitable piece of fiberglass tape or carbon sheet then use epoxy mixed with micro balloons or talcum powder to fair everything in. The tape provides the strength of the glass fibers while actually adding a softer component to the resin gives a very nice finish. I've been using epoxy and talcum fillets, off and on, since before micro balloons were marketed and I have never had one fail and they're very easy to sand.
Peter-

I am going to give it a go with an amalgamation of techniques that were offered by yourself and BJ... I'll post some pics as I head off into uncharted waters...

-Dwight
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