Thorp Air Command - T18.net

Supporting Owners, Builders and Pilots of the Thorp T-18 and its variants.
It is currently Thu Mar 28, 2024 10:57 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 14 posts ] 
Author Message
Jwsteele1981
PostPosted: Sat Aug 08, 2020 5:53 pm 
Newbie
Newbie

Joined: Mon May 11, 2020 7:46 pm
Posts: 8
Building a 200-215 hp 360 with a throttle body.
With that hp , anyone out there with a reccomendation on the pitch. I hear 68x76 alot.. but seems those are lower HP units.

Thoughts?

I have a metal prop off a grumman cheetah. Im going to cut and have a prop ship pitch it. Where do i Start with the pitch and that HP.
Appreciate input from others with 200+HP.


Top
 Profile  
 
James Grahn
PostPosted: Sat Aug 08, 2020 7:35 pm 
Hero Member
Hero Member

Joined: Sat Oct 24, 2009 7:16 pm
Posts: 1434
Images: 0
Location: USA
I’d say 68/85. Somewhere close to that.
Cubes


Top
 Profile Personal album  
 
ScottECG
PostPosted: Sun Aug 09, 2020 5:19 am 
Newbie
Newbie

Joined: Tue Jun 16, 2020 6:06 pm
Posts: 31
My O-360 makes 196hp and it has a 68X80.

_________________
Scott Hinton
N149RH
KECG
Elizabeth City, NC


Top
 Profile  
 
fytrplt
PostPosted: Sun Aug 09, 2020 11:46 am 
Hero Member
Hero Member
User avatar

Joined: Tue Oct 20, 2009 8:07 pm
Posts: 1140
Images: 2
Location: Lakeland, Florida, USA
Make sure you read all the written in blood history of cut down metal props before you go much further.

_________________
Bob Highley
N711SH
SN 835
KLAL


Top
 Profile Personal album  
 
bfinney
PostPosted: Sun Aug 09, 2020 4:30 pm 
Sr. Member
Sr. Member
User avatar

Joined: Thu Oct 22, 2009 2:24 pm
Posts: 501
Images: 6
Location: Yelm, WA USA
Me personally, I wouldn't re-pitch a metal prop except to fine tune a degree or two and I would not cut a metal prop down, but that's me. That said I'm running a Whirlwind ground ajustable prop on my O290 68" dia and love it. You can get them in 68" 70" and 72" dia. If you have the long gear you could use the larger dia prop. My prop was $2500, cheaper than a Catto 8). I would give them a call and see what they have to say about a 200 HP engine installation.

_________________
Bruce Finney
N18JF T-18C #262
Yelm, WA USA


Top
 Profile Personal album  
 
leewwalton
PostPosted: Tue Aug 11, 2020 8:48 am 
Administrator
Administrator
User avatar

Joined: Tue Oct 20, 2009 4:09 pm
Posts: 1705
Images: 107
Location: Houston, TX
To Bob's point there are only 2 metal props that will not kill you in a Thorp .. 1970-80s era Sensenich M76 is considered 'safe'. That being said even the M76 should be harmonically tested before use. If the prop you're considering using came off a Cheetah ... it's not safe. The only other metal prop considered safe right now is the type developed for the RV ...

http://www.sensenich.com/product-catego ... l=aluminum

maybe consider one of the ground adjustable Sensenich composite props or a Cato?

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD


Top
 Profile Personal album  
 
jtwigg
PostPosted: Thu Aug 13, 2020 1:25 pm 
Sr. Member
Sr. Member
User avatar

Joined: Thu Sep 03, 2015 10:11 pm
Posts: 192
Images: 0
I never knew that about only two props. Why are the metal props so problematic on a Thorp, Lee?

_________________
John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)


Top
 Profile Personal album  
 
leewwalton
PostPosted: Thu Aug 13, 2020 2:03 pm 
Administrator
Administrator
User avatar

Joined: Tue Oct 20, 2009 4:09 pm
Posts: 1705
Images: 107
Location: Houston, TX
Here's the warning on our SDR list ...

"5. Cutdown Metal Propellers- If your airplane has a cutdown metal prop, especially an M74, replace it immediately. The M74 will fail (every time ), usually with a low number of hours. The M76 is supposedly "safe" for being cut down, but should also be viewed as a risk, especially if it has not been thoroughly tested by a qualified prop shop. Newsletter 79 has a lot of data on these props. If you are looking to buy a new metal prop, check with www.Sensenich.com for new props that are designed for T-18/S-18 engines and flight speeds. Also see NL 47. Recommended Sensenich wood props: W66LM for 125-179 hp, W68LY for 180 hp. (Note: These may no longer be readily available.)"

Here's a link to an article written by Lou Sunderland .. still relevant to date for our airplanes ... in short harmonics.

http://thorp18.com/thorp_files/1972_11_09_.pdf

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD


Top
 Profile Personal album  
 
Jwsteele1981
PostPosted: Sun Aug 30, 2020 9:12 pm 
Newbie
Newbie

Joined: Mon May 11, 2020 7:46 pm
Posts: 8
THANKS GUYS,
WILL GO WOODEN :!


Top
 Profile  
 
PanchoGA
PostPosted: Mon Mar 29, 2021 7:14 pm 
Newbie
Newbie

Joined: Tue Feb 21, 2017 9:54 pm
Posts: 18
Hi All,
I have bought an IO360B1A2 engine for my S18. I would like to hang a constant speed prop on it. Some of the comments here give me pause. Any recommendations?

Thanks,
Pancho


Top
 Profile  
 
bfinney
PostPosted: Mon Mar 29, 2021 9:15 pm 
Sr. Member
Sr. Member
User avatar

Joined: Thu Oct 22, 2009 2:24 pm
Posts: 501
Images: 6
Location: Yelm, WA USA
If I were looking for a constant speed prop I'd start with the ones from Whirlwind, they are designed for the RV series of aircraft so I would think they would be very compatible with a Thorp. Note: they just started selling a 3 blade version. Full disclosure I'm currently flying with a Whirlwind ground adjustable prop and am very happy with it.

_________________
Bruce Finney
N18JF T-18C #262
Yelm, WA USA


Top
 Profile Personal album  
 
James Grahn
PostPosted: Tue Mar 30, 2021 10:54 pm 
Hero Member
Hero Member

Joined: Sat Oct 24, 2009 7:16 pm
Posts: 1434
Images: 0
Location: USA
Those comments are for fixed pitch metal props. The Hartzell CS units have been fully tested.
Cubes


Top
 Profile Personal album  
 
PanchoGA
PostPosted: Mon May 10, 2021 5:37 pm 
Newbie
Newbie

Joined: Tue Feb 21, 2017 9:54 pm
Posts: 18
I liked the Airmaster electric constant speed prop. But it's expensive and in testing it showed vibration problems with the IO360 engine, so not advised. I ended up buying a Sensenich three-blade ground adjustable prop. Should suit me fine.


Top
 Profile  
 
speedbird1
PostPosted: Sun May 23, 2021 1:36 pm 
Jr. Member
Jr. Member

Joined: Wed Dec 11, 2019 8:39 pm
Posts: 66
Catto makes a nice three blade fixed pitch that seems to work well. They will also work with you to re-pitch if it is not quite right and all you pay is the shipping.
Speedbird 1

_________________
N872DD
200hp Lycoming


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 14 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 12 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 : 0.170s | 13 Queries | GZIP : On ]