Go Back  RCU Forums > RC Airplanes > RC Jets
Reload this Page >

CARF Mephisto Build thread

Notices
RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

CARF Mephisto Build thread

Old 08-24-2021, 02:31 AM
  #976  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

The tube is a guide, the main load is taken at each end by the hole in the plywood ribs. I’m sure it’s fine if you can bond the tube to the vertical web that’s there too, but you want to remove any ‘knock’ movement as any travel increases the load tremendously when it reaches the stop again.
Once the split is sealed I might coat the inside of the sleeve with a coat of finishing resin (ZAP40)
Ive emailed the factory for comments

Dave
Old 08-24-2021, 07:07 AM
  #977  
husafreak
My Feedback: (3)
 
husafreak's Avatar
 
Join Date: Dec 2004
Location: Livermore, CA
Posts: 1,125
Received 36 Likes on 33 Posts
Default

Thanks Dave. Removing any “play” at the wing rib sounds good.
Old 08-24-2021, 08:59 AM
  #978  
husafreak
My Feedback: (3)
 
husafreak's Avatar
 
Join Date: Dec 2004
Location: Livermore, CA
Posts: 1,125
Received 36 Likes on 33 Posts
Default

A few more pics for the factory. I think they are going overboard with the lightening holes, my opinion. On the looser wing, the side that split, I can definitely see missing plywood bits at the really thin points in the spar. But the CF looks intact, so hard to tell if the defect was there from the factory, or if the flapping motion of the wing has over time torn the plywood apart. CF is not elastic as far as I know.

Missing ply at spar tube from CF/ply/CF spar

Missing ply at other side

Other wing is sound, no missing ply

With gear removed it is easy to see that the white Hysol type glue is only applied on the accessible areas. The other side of the spar receiver tube has none of this. Wether that contributes to the tube splitting, or lost ply, at the point the glue stops I don’t know.
Old 08-24-2021, 10:41 AM
  #979  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

First one we have heard of or seen. I have seen some severe abuse and have several around with over 100 3-D flights. The structure is sound normally.
Talk to your rep too

Dave
Old 08-24-2021, 10:57 AM
  #980  
husafreak
My Feedback: (3)
 
husafreak's Avatar
 
Join Date: Dec 2004
Location: Livermore, CA
Posts: 1,125
Received 36 Likes on 33 Posts
Default

Yup I informed Ray L. Thanks again for your help. I may glue ply plates over those holes since the ply (and CF) on the side we can’t see is gone. The resin in the tubes is drying now.
I like to post this stuff so other Mephisto owners can inspect their aircraft. We’ve seen way too many inflight failures around here lately. Yesterday my flying buddies Havok 210 shed a wing in flight. Thank god no one was hurt and we were able to put the fire out. Wing bolt sheared.
Plus, selfishly, it is pretty cool to post here in the evening and have a response from across the Atlantic the next morning.
The following users liked this post:
AEROSHELDON (08-24-2021)
Old 08-24-2021, 11:24 AM
  #981  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

We don’t really understand how the tube can crack between the support ribs from flight loads. With the wing on could you feel movement, or was it just removing the wing/spar.?

I started answering 5.45am, it’s now 8.20pm. Hobby business people expect answers 7 days a week, weekends are play days for the majority of people so when many people are resting people in the hobby industry carry on. It’s 18 hours a day 7 days a week for me…RCU people are generally not my customers…so it’s relaxation business/technical time 😄
Old 08-24-2021, 11:29 AM
  #982  
husafreak
My Feedback: (3)
 
husafreak's Avatar
 
Join Date: Dec 2004
Location: Livermore, CA
Posts: 1,125
Received 36 Likes on 33 Posts
Default

Well, now I’m mad. Went back out to check the wing and realized there is a big hole in the spar tube that split. And it was built in because you can clearly see the white Hysol from manufacturing. It may not be structurally significant that the factory installed a broken spar tube but it points to shoddy workmanship.
The structure crumbled away over many cycles, ply, carbon fiber, glue, the defective tube split causing me to hear a funny noise. Loose fit discovered, repair in progress.

Ragged hole in side of tube, white Hysol clearly visible.


Better photo
Old 08-24-2021, 11:44 AM
  #983  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

The tube is mainly a guide for the spar. If the tube was not there and the two ribs had holes fitted to the carbon spar that’s most of the strength.
The following users liked this post:
husafreak (08-24-2021)
Old 08-25-2021, 09:41 AM
  #984  
husafreak
My Feedback: (3)
 
husafreak's Avatar
 
Join Date: Dec 2004
Location: Livermore, CA
Posts: 1,125
Received 36 Likes on 33 Posts
Default

Repair finished. Due to the missing material in the spar and inability to patch on the spar tube side I installed a plywood patch. It’s really hard multi layer ply 1/8”. Also after sanding the resin in the wing tubes there is zero play. Thanks for the suggestion.


This ply plate covers the large lightening holes in the spar.
Old 09-08-2021, 02:35 PM
  #985  
AEROSHELDON
My Feedback: (99)
 
AEROSHELDON's Avatar
 
Join Date: Mar 2002
Location: Highlands Ranch, CO
Posts: 1,321
Received 38 Likes on 33 Posts
Default

It looks like I am at 55mm away from the front of the bell, and this cage is hard to manipulate with one person.... best to just subtract 35mm from the hole it was in and then drill it out? There will be a lot of that tab left over too...




Old 09-08-2021, 03:56 PM
  #986  
Dansy
My Feedback: (53)
 
Dansy's Avatar
 
Join Date: Mar 2002
Location: Prescott, Ont.
Posts: 2,618
Received 80 Likes on 78 Posts
Default

I do 25mm (20-30mm) from the straight pipe disregard the bell….or reverse lips…
Old 09-08-2021, 04:01 PM
  #987  
AEROSHELDON
My Feedback: (99)
 
AEROSHELDON's Avatar
 
Join Date: Mar 2002
Location: Highlands Ranch, CO
Posts: 1,321
Received 38 Likes on 33 Posts
Default

Originally Posted by Dansy View Post
I do 25mm (20-30mm) from the straight pipe disregard the bell….or reverse lips…
normally I would but the manual for this pipe says 20mm from the front of the bell
Old 09-08-2021, 04:02 PM
  #988  
Dansy
My Feedback: (53)
 
Dansy's Avatar
 
Join Date: Mar 2002
Location: Prescott, Ont.
Posts: 2,618
Received 80 Likes on 78 Posts
Default

20 is between the range and probably give you 30mm or from the straight part…
Old 09-08-2021, 04:15 PM
  #989  
AEROSHELDON
My Feedback: (99)
 
AEROSHELDON's Avatar
 
Join Date: Mar 2002
Location: Highlands Ranch, CO
Posts: 1,321
Received 38 Likes on 33 Posts
Default

True !
Old 09-08-2021, 10:28 PM
  #990  
LA jetguy
 
LA jetguy's Avatar
 
Join Date: Jan 2012
Location: Los Angeles, CA
Posts: 746
Received 18 Likes on 15 Posts
Default

I always set the turbine the distance equal to half the diameter of the exhaust nozzle from the straight pipe.. ignore bell entrance..

works for all size turbine

David
Old 09-10-2021, 11:47 PM
  #991  
winter1
Senior Member
 
winter1's Avatar
 
Join Date: Sep 2019
Location: Carlsbad - Czech Republic
Posts: 181
Received 25 Likes on 19 Posts
Default

I leave 30 mm. ***winter***

Old 09-11-2021, 05:47 AM
  #992  
AEROSHELDON
My Feedback: (99)
 
AEROSHELDON's Avatar
 
Join Date: Mar 2002
Location: Highlands Ranch, CO
Posts: 1,321
Received 38 Likes on 33 Posts
Default

Thanks guys. The new pipe manual is specific that you leave 20mm from the actual front of the small bell.
Old 09-15-2021, 09:55 PM
  #993  
flyer1966
My Feedback: (3)
 
flyer1966's Avatar
 
Join Date: Nov 2011
Location: Porteville, CA
Posts: 165
Received 3 Likes on 3 Posts
Default Mephisto canopy cap screw

Looks like I have lost my canopy cap screw for attaching my canopy on my Mephisto. Can someone tell me what size the cap screw is so I can buy a few new ones. Thanks
Old 09-16-2021, 03:08 AM
  #994  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

M4 x 16
The following users liked this post:
flyer1966 (09-16-2021)
Old 09-16-2021, 05:33 AM
  #995  
flyer1966
My Feedback: (3)
 
flyer1966's Avatar
 
Join Date: Nov 2011
Location: Porteville, CA
Posts: 165
Received 3 Likes on 3 Posts
Default Mephisto

Originally Posted by Dave Wilshere View Post
M4 x 16
Thank you Dave
Old 09-16-2021, 05:36 AM
  #996  
flyer1966
My Feedback: (3)
 
flyer1966's Avatar
 
Join Date: Nov 2011
Location: Porteville, CA
Posts: 165
Received 3 Likes on 3 Posts
Default Mephisto

Originally Posted by Dave Wilshere View Post
M4 x 16

Dave do you know the thread pitch? 0.5 mm or 0.7 mm? Thanks
Old 09-16-2021, 12:47 PM
  #997  
Dave Wilshere
Thread Starter
 
Join Date: Jun 2002
Location: Watford, UNITED KINGDOM
Posts: 12,170
Likes: 0
Received 330 Likes on 254 Posts
Default

0.7 Seems to be the std M4 thread.
The following users liked this post:
flyer1966 (09-16-2021)
Old 09-16-2021, 01:12 PM
  #998  
flyer1966
My Feedback: (3)
 
flyer1966's Avatar
 
Join Date: Nov 2011
Location: Porteville, CA
Posts: 165
Received 3 Likes on 3 Posts
Default Mephisto

Originally Posted by Dave Wilshere View Post
0.7 Seems to be the std M4 thread.
Thanks again Dave.
Old 09-17-2021, 09:58 AM
  #999  
stuart_80
 
Join Date: Oct 2010
Location: Scotland
Posts: 105
Received 4 Likes on 2 Posts
Default

This useful information table is listed on the website of a UK based supplier of fixings
https://www.modelfixings.co.uk/threa...t%20Dimensions

For future reference if it’s any help to you
Old 09-17-2021, 05:15 PM
  #1000  
AEROSHELDON
My Feedback: (99)
 
AEROSHELDON's Avatar
 
Join Date: Mar 2002
Location: Highlands Ranch, CO
Posts: 1,321
Received 38 Likes on 33 Posts
Default

What's the general rule on the area needed for a Cheater Hole in the center wing section?

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.