Thorp Air Command - T18.net

Supporting Owners, Builders and Pilots of the Thorp T-18 and its variants.
It is currently Sat Oct 24, 2020 3:00 pm

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 3 posts ] 
Author Message
DrDrift
 Post subject: Spinner Mounting Help
PostPosted: Mon Oct 05, 2020 8:04 am 
Jr. Member
Jr. Member

Joined: Sun Mar 18, 2018 9:36 pm
Posts: 52
I've had terrible luck with spinners on my airplane, and I'm just getting ready to finish and mount my third one. I must have done something(s) wrong on my last attempt, so I have a few questions for the experts (Cubes et al) so this one lasts more than 20 hours.

As background, I bought a new backplate/bulkhead after my original one cracked. That bulkhead has been on for 150+ hours and I've flown most of those hours without a spinner dome. The last dome I had developed a crack just inside the first screw from the prop cutout.

The new dome has mostly-complete prop cut outs and I'm working on the alignment and hole drilling.

1 - what's a good way to ensure that the dome is true to the shaft? I've removed four spark plugs and have been adjusting the seating by spinning the prop and making sure the tip stays centered on a reference point. When I get this aligned, the spinner is not true on the backplate. It also overhangs by 1/4" or so to be flush around the circumference.

2 - How do I mount the front bulkhead? I bought the airplane with the bulkhead mounted with double-sided tape to the inside of the spinner, and I used the same approach when I cut my second spinner. How do I get the bulkhead centered and adhered well inside?

3 - How do I locate the holes for the screws into the rear bulkhead? I have a hole locator tool, but the fit between the dome and the bulkhead is snug.

4 - Do I need to install an additional support / screw hole on the prop cut out? I've seen some folks make an additional bracket to plug the big gap behind the prop and help support the dome there.

5 - How much clearance should I have around the prop in the cutout? 1/8"? 1/4"? Is it ok to have even clearance, or does it need to be biased based on the expected movement of the CS hub?

6 - What are the minimum steps to finishing the dome? Does it need to be sanded smooth and polished?

There are only a few more work nights before KY Dam, and I'm hoping to have a spinner on for that. Of course, I'd rather fly without one rather than rushing and breaking a third dome.

Thanks!


Top
 Profile  
 
pmandel
PostPosted: Mon Oct 05, 2020 5:10 pm 
Newbie
Newbie

Joined: Fri Oct 25, 2019 8:00 pm
Posts: 34
First, the disclaimer: a builder I am NOT, just a fly-boy. However, with Cubes' invaluable help plus all the work done by my A&P/IA, I have high confidence that what was done was done right.

I'll post all the pics I have including the rear bulkhead "before," plus a link to the following video so you can see the end result:

Example of a T-18 spinner front and rear bulkheads w/CS prop https://youtu.be/zzhYP5aPzXQ

Mechanic put one layer of electrical tape around the front bulkhead to prevent walking or chafing. This was recent work, end of August 2020 -- so far, so good. Probably last 100 years, but ask me then.

Original installation was rear bulkhead only. I'm told that's why it cracked. Add front bulkhead, they said, and it will last...well...100 years. (that's not actually what they SAID, but you get the idea)

Image

Image

Image

Image

Image

Image

Image

Image

Image

Image

Image

_________________
Philip Mandel
N118BC
S/N 957
Beaverton OR


Top
 Profile  
 
James Grahn
PostPosted: Mon Oct 05, 2020 9:57 pm 
Hero Member
Hero Member

Joined: Sat Oct 24, 2009 7:16 pm
Posts: 1216
Images: 0
Location: USA
Brother,
Send me a text and I’ll help any way I can. There is a lot to it, but I need to ask some questions regarding what you just asked.
Cubes
702 232-4261


Top
 Profile Personal album  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron

[ Time : 0.728s | 12 Queries | GZIP : On ]