MB339 possible defect warning
06-18-2002 | 04:20 PM
#27
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From: Bellevue, WA
MB339 possible defect warning
Nice pic, however that is meaningless, the stab seperated from the fuse it did not snap off in the center. The concern is not the strength of the stab but how it is attached to the fuse. The forward pin that slids into the retaining tube to hold the stab in place at the leading edge only protrudes 1/4 inch into the stab. It needs to be longer. The stab after the crash was not broken in half it was in one piece, it had ripped away from the fuse because the forward pin was not long enough. Tam is the one who assembled the kit and he has been shipped the stab for inspection.
Give me your email address and I will sen you a picture, this is a large file so it will take a while to down load on a standard telephone line. Send me your email address to
[email protected]
Regards
Nosedive
Give me your email address and I will sen you a picture, this is a large file so it will take a while to down load on a standard telephone line. Send me your email address to
[email protected]
Regards
Nosedive
06-18-2002 | 05:48 PM
#28
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From: Lakeville , MN,
MB339 possible defect warning
Originally posted by Nosedive
The stab after the crash was not broken in half it was in one piece, it had ripped away from the fuse because the forward pin was not long enoughNosedive [/B]
The stab after the crash was not broken in half it was in one piece, it had ripped away from the fuse because the forward pin was not long enoughNosedive [/B]
06-18-2002 | 06:05 PM
#29
My Feedback: (10)
MB339 possible defect warning
how long is the part that is being held in the vise?
Re: the piece being held in the vice, how is it held in the fuselage? Is it a tube that goes all the way through the fuse?
Is there anyway I can get a copy of ALL of the instructons and addendums that come with this kit, be it from Cermark, Tam ,Electrodynamics, DL whoever.
I need these instructions to make sure the local ARF guys have a chance
Re: the piece being held in the vice, how is it held in the fuselage? Is it a tube that goes all the way through the fuse?
Is there anyway I can get a copy of ALL of the instructons and addendums that come with this kit, be it from Cermark, Tam ,Electrodynamics, DL whoever.
I need these instructions to make sure the local ARF guys have a chance
06-18-2002 | 06:10 PM
#30
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From: Waterford,
MI
MB339 possible defect warning
Nosedive,
I sent email to your address requesting pics.
Mr. Matt,
Please send me an email at [email protected] and I will send you all the updates and addendums that come with this kit from Electrodynamics/Cermark. I am not sure what comes with the DL kits.
Randy
I sent email to your address requesting pics.
Mr. Matt,
Please send me an email at [email protected] and I will send you all the updates and addendums that come with this kit from Electrodynamics/Cermark. I am not sure what comes with the DL kits.
Randy
06-19-2002 | 05:26 AM
#31
Stab updated
I'm loading up my website right now.
Click on MB339 kit to go view the stab modification.
I'll post all the works photos on this kit for everyone to view it.
www.tamjets.com
Brg,
Tam
Click on MB339 kit to go view the stab modification.
I'll post all the works photos on this kit for everyone to view it.
www.tamjets.com
Brg,
Tam
06-19-2002 | 02:19 PM
#32
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From: Bellevue, WA
MB339 possible defect warning
This a emai lI recieved with some adive I thought I would share.
Thanks for the photos.
>
> Sorry about your disaster with the '339. Your photo
> shows that the stab was
> not properly adhered to the fuselage, there is no
> glue adhesion on 75% of
> the gluing surface on the stab. But, the spar and
> the alignment pins were
> firmly anchored in the fuse (they were notched to
> give a good keying surface
> for glue), as designed. But, while this contributed
> to the stab departing
> the fuse, I do not think this is the initiating
> cause of the loss of the
> airplane.
>
> Both front and rear alignment pins were ripped out
> of the stab, and the
> aluminum spar was sheared. which tells me that there
> was severe
> back-and-forth rocking before failure - most likely
> from a flexing or
> dislodged elevator linkage causing stab surface
> flutter. The aerodynamic
> trim tab effect on the stab amplified the elevator
> motion to destruction.
> The front alignment pin is anchored in a balsa block
> the stab, and the whole
> block ripped out, as did the rear alignment pin
> (note elongated hole and
> ripped bottom skin).
>
> You may find your servo mounting dislodged, and
> linkage damage as well - of
> course, it's going to be hard to distinguish from
> damage after the crash.
>
> I do not think that making the alignment pin anchors
> any stronger would have
> saved your airplane, unfortunately - IMHO the root
> cause of the failure was
> elevator surface flutter, and you would have lost
> control anyway. A
> stronger joint *might* have delayed the stab's
> departure from the airplane
> and allowed you to slow down enough to stop flutter
> (if it was springiness
> in the linkage and not servo mount failure).
>
> I will be recommending to customers to roughen up
> the stab-fuselage
> interface with #200 sandpaper for a better keying
> surface and then wiping
> down with denatured alcohol before gluing to remove
> any traces of mold
> release, for better adhesion. The same should be
> done on all servo mounts
> adhered to the inside of the fuse.
>
> In addition, extreme care should be taken to ensure
> a slop-free,
> mechanically "stiff" (i.e., non-springy) control
> linkage, to avoid exciting
> aerodynamic flutter in the elevator. I personally
> recommend 4-40 linkage
> hardware and a supported pushrod rather than a free
> floating pushrod, in
> case of a long pushrod run.
>
> Again, sorry for your loss, and thanks for the
> photos. Compliments on your
> very nice P-80 and the beautiful home in the
> background!
>
> As I am not on RCU, I would be indebted if you would
> post this message on
> the board for me. Thanks!
>
> Andy Low
> ElectroDynamics, Inc.
> Home of "No-Hassle" RC Products
> http://www.electrodynam.com
Thanks for the photos.
>
> Sorry about your disaster with the '339. Your photo
> shows that the stab was
> not properly adhered to the fuselage, there is no
> glue adhesion on 75% of
> the gluing surface on the stab. But, the spar and
> the alignment pins were
> firmly anchored in the fuse (they were notched to
> give a good keying surface
> for glue), as designed. But, while this contributed
> to the stab departing
> the fuse, I do not think this is the initiating
> cause of the loss of the
> airplane.
>
> Both front and rear alignment pins were ripped out
> of the stab, and the
> aluminum spar was sheared. which tells me that there
> was severe
> back-and-forth rocking before failure - most likely
> from a flexing or
> dislodged elevator linkage causing stab surface
> flutter. The aerodynamic
> trim tab effect on the stab amplified the elevator
> motion to destruction.
> The front alignment pin is anchored in a balsa block
> the stab, and the whole
> block ripped out, as did the rear alignment pin
> (note elongated hole and
> ripped bottom skin).
>
> You may find your servo mounting dislodged, and
> linkage damage as well - of
> course, it's going to be hard to distinguish from
> damage after the crash.
>
> I do not think that making the alignment pin anchors
> any stronger would have
> saved your airplane, unfortunately - IMHO the root
> cause of the failure was
> elevator surface flutter, and you would have lost
> control anyway. A
> stronger joint *might* have delayed the stab's
> departure from the airplane
> and allowed you to slow down enough to stop flutter
> (if it was springiness
> in the linkage and not servo mount failure).
>
> I will be recommending to customers to roughen up
> the stab-fuselage
> interface with #200 sandpaper for a better keying
> surface and then wiping
> down with denatured alcohol before gluing to remove
> any traces of mold
> release, for better adhesion. The same should be
> done on all servo mounts
> adhered to the inside of the fuse.
>
> In addition, extreme care should be taken to ensure
> a slop-free,
> mechanically "stiff" (i.e., non-springy) control
> linkage, to avoid exciting
> aerodynamic flutter in the elevator. I personally
> recommend 4-40 linkage
> hardware and a supported pushrod rather than a free
> floating pushrod, in
> case of a long pushrod run.
>
> Again, sorry for your loss, and thanks for the
> photos. Compliments on your
> very nice P-80 and the beautiful home in the
> background!
>
> As I am not on RCU, I would be indebted if you would
> post this message on
> the board for me. Thanks!
>
> Andy Low
> ElectroDynamics, Inc.
> Home of "No-Hassle" RC Products
> http://www.electrodynam.com
04-16-2003 | 08:24 PM
#33
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From: Stone Mountain,
GA
Re: Stab need some mod
Originally posted by tampipes
Folks,
For those of you have not assemble the kit.
Take little time to modify the stab.
I open up my stab to inspect the work. There is no spar go across the stab. The stab possible can fail when flying fast.
Here how I would do to reinforcement the stab. Make 2 spars out of of 1/8" liteply. Cut little slot to insert the spar. Clue with CA or expoxy. Make sure the spar just firmly fit. Not to wide or to narrow. You want the spar to touch both side of the skin.
If you guys already assemble kit. Cut the slot from the bottom to put int the spars. Fill up with aeropoxy and sand it level. Cover with mono coat or painted over to hide the work. Do the same to the fin.
I'll post some pictures of the mod very soon. I stongly recomended everyone to this.
Also strenthen the main former with carbon fiber. Ther gear box also need to reinforcement.
This is very nice flying trainer. It just need some modification to handle the stress.
Also keep this bird under 150mph. My fly with 12lb thrust engine and got the smoke system onboard. My can fly over 150mph if I really pushing it.
This plane is not bullet proof. Put in the speed limiter to kept it from flying over 150mph.
I'll kept you guys posted.
Tam
Folks,
For those of you have not assemble the kit.
Take little time to modify the stab.
I open up my stab to inspect the work. There is no spar go across the stab. The stab possible can fail when flying fast.
Here how I would do to reinforcement the stab. Make 2 spars out of of 1/8" liteply. Cut little slot to insert the spar. Clue with CA or expoxy. Make sure the spar just firmly fit. Not to wide or to narrow. You want the spar to touch both side of the skin.
If you guys already assemble kit. Cut the slot from the bottom to put int the spars. Fill up with aeropoxy and sand it level. Cover with mono coat or painted over to hide the work. Do the same to the fin.
I'll post some pictures of the mod very soon. I stongly recomended everyone to this.
Also strenthen the main former with carbon fiber. Ther gear box also need to reinforcement.
This is very nice flying trainer. It just need some modification to handle the stress.
Also keep this bird under 150mph. My fly with 12lb thrust engine and got the smoke system onboard. My can fly over 150mph if I really pushing it.
This plane is not bullet proof. Put in the speed limiter to kept it from flying over 150mph.
I'll kept you guys posted.
Tam
05-23-2003 | 10:08 PM
#36
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From: Sydney, , AUSTRALIA
MB339 Tams Mods
Here's a direct link to Tams custom modifications to improve overall model strength for the Cermark MB339.
http://www.tamjets.com/id57.htm
http://www.tamjets.com/id57.htm
