Silk Thread Weight

Chrisgoesflying

Chrisgoesflying

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Chrisgoesflying
It's time to put the C-85 back together (about a month later than what I was hoping for). The last hurdle, the manual recommends to seal the crank cases with silk thread 50 wt. I live north of the border and to my surprise, getting your hands on silk thread of that weight is nearly impossible. I could order from the U.S. and pay $100 on express shipping for a $10 item (or wait another week or two with standard shipping) - but before doing that, how important is the weight of the silk? Reason I'm asking, I can get Gutermann 30 wt. silk thread at any fabric store around here with no issues.
 
I thought everyone had gone to RTV these days. You might ask an engine shop or call Continental to find out if that is an option.
 
Kristin said:
I thought everyone had gone to RTV these days. You might ask an engine shop or call Continental to find out if that is an option.
Click to expand...

Some have resorted to packing the engine with Permatex, only to have disastrous results. :eek:
 
Doc Holliday said:
Some have resorted to packing the engine with Permatex, only to have disastrous results. :eek:
Click to expand...

Would take a lost of Permatex to fill the crankcase. As for the mating surface of the crankcase, not so much.
 
Approved, yes, but Lycoming still uses thread.

I know an engine builder that uses Hylomar and no thread. It seems to work fine.
 
t's time to put the C-85 back together (about a month later than what I was hoping for). The last hurdle, the manual recommends to seal the crank cases with silk thread 50 wt. I live north of the border and to my surprise, getting your hands on silk thread of that weight is nearly impossible. I could order from the U.S. and pay $100 on express shipping for a $10 item (or wait another week or two with standard shipping) - but before doing that, how important is the weight of the silk? Reason I'm asking, I can get Gutermann 30 wt. silk thread at any fabric store around here with no issues.

I have a spool of the approved thread. Give me your address and I'll peel off ten feet or so and mail it to you.
 
Stewartb said:
Approved, yes, but Lycoming still uses thread.

I know an engine builder that uses Hylomar and no thread. It seems to work fine.
Click to expand...
Lycoming has started using a "O" ring style seal created by a milled grove in the case to eliminate the leaking.
Many have because of leaking problems

has anyone tried to lay the tread on the case with out using some to stick it to the seal area ?
 
Ly-Con has an approval to modify the case for an O ring seal. I haven't heard that Lycoming is doing it. My Lycoming was factory new about 10 months ago and has thread.
 
Tom-D said:
Lycoming has started using a "O" ring style seal created by a milled grove in the case to eliminate the leaking.
Many have because of leaking problems
Click to expand...
So your position is changed from this earlier post? Why so?
Tom-D said:
Why would it need strength when trapped between to surfaces?
Silk is hard. it will in fact indent into aluminum surfaces, thus seal better than any other material. It has been use from a time when we had no real sealants as we do today.
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Okay - I'm really dumb here, and out of my element, but I'm still curious.

Can someone (feel free to use small words) tell me what's going on here?

Is the thread being used as a gasket between the halves of the engine casing or ?
 
Rgbeard said:
Okay - I'm really dumb here, and out of my element, but I'm still curious.

Can someone (feel free to use small words) tell me what's going on here?

Is the thread being used as a gasket between the halves of the engine casing or ?
Click to expand...

I've been told that the thread keeps *some* space between the case halves so whatever sealant you use doesn't get completely squeezed out.
 
kyleb said:
I've been told that the thread keeps *some* space between the case halves so whatever sealant you use doesn't get completely squeezed out.
Click to expand...

The silk thread is the "gasket". There are numerous other applications that use sealant which is the same or similar to that commonly used on aircraft engine cases which omit the silk thread and do it without concern of of the sealant being squeezed out.
 
Rgbeard said:
Okay - I'm really dumb here, and out of my element, but I'm still curious.

Can someone (feel free to use small words) tell me what's going on here?

Is the thread being used as a gasket between the halves of the engine casing or ?
Click to expand...

it is not dumb.
In fact you largely have it right
here is a diagram

silkthread.png
 
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