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 3:54 pm

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 12 posts ] 
Author Message
Unclerap
PostPosted: Tue May 15, 2018 12:42 pm 
Jr. Member
Jr. Member
User avatar

Joined: Mon Mar 19, 2018 4:23 pm
Posts: 62
The checkout took longer than I expected, and that;s on me. Finally got the hang of the landing site picture and got them to acceptable levels. 1.75 hrs home, best landing of the day. A couple of things from the xc: #1 I think the prop is over pitched. It's a nearly new 70CM7S16-0-77 that appears to be an RV6 prop. Previous prop was M76 74-68. 9 inches of additional pitch on the same engine has me turning about 1900 static and barely 2100 at cruise. O-320 E2D, no mods. Looking for suggestions. 150mph xc is much lower than I expected. #2 The radios are junk, knew that going in. $$$ will fix that. I need an MX-11 if anyone has one they will part with. Finally, the stab trim cannot be adjusted at cruise, I have to slow to about 110mph to get it to move. I'll dig into the build sheets to figure that one out. Otherwise, it's a tight ship with some upgrades and cosmetics for the winter project.

_________________
Base: KALX
N8786
SN 929


Top
 Profile  
 
Ryan Allen
PostPosted: Tue May 15, 2018 12:57 pm 
Hero Member
Hero Member
User avatar

Joined: Wed Oct 21, 2009 6:10 pm
Posts: 1105
Images: 0
Location: Louisiana
Treat yourself to the Grainger electric trim motor for elevator trim. That and electric aeileron trim were two huge improvements on my plane.


Top
 Profile Personal album  
 
Unclerap
PostPosted: Tue May 15, 2018 5:09 pm 
Jr. Member
Jr. Member
User avatar

Joined: Mon Mar 19, 2018 4:23 pm
Posts: 62
Thanks for the quick response, and apologies from a newbie but can you expand on both? I don't see anything about either in my box of documents. It appears that my left flap is manually adjustable for the equivalent of aileron trim. Is there a forum thread about mods and improvements?

_________________
Base: KALX
N8786
SN 929


Top
 Profile  
 
Jeff J
PostPosted: Tue May 15, 2018 5:17 pm 
Sr. Member
Sr. Member

Joined: Wed Aug 31, 2016 8:18 am
Posts: 583
Images: 0
Location: eastern OK
I need to know the density altitude where you were getting your RPM numbers but, you are correct, they should be higher. You only get 150 HP if it is turning 2700 rpm. The tach could be off too but that would be an awful big tach error. I would expect a static rpm somewhere around 2500. Do you know what the rpm was during takeoff or straight and level with the throttle wide open?

added: 2 other possibilities, 1) not getting full travel on the throttle linkage and 2) same for the mixture.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson


Top
 Profile Personal album  
 
Jeff J
PostPosted: Tue May 15, 2018 5:35 pm 
Sr. Member
Sr. Member

Joined: Wed Aug 31, 2016 8:18 am
Posts: 583
Images: 0
Location: eastern OK
https://www.lycoming.com/sites/default/ ... 297-30.pdf

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson


Top
 Profile Personal album  
 
Unclerap
PostPosted: Tue May 15, 2018 7:14 pm 
Jr. Member
Jr. Member
User avatar

Joined: Mon Mar 19, 2018 4:23 pm
Posts: 62
I should have posted, I did all the basic checks. Throttle is opening and closing to the stops, 1900 rpm static. DA was about 7k ft, WOT 2100 rpm. The old prop was 68" the new one 77", thats alot of twist for a 150 lyc. I preach to my guys at BAC.org about 2700rpm all the time.

_________________
Base: KALX
N8786
SN 929


Top
 Profile  
 
Ryan Allen
PostPosted: Tue May 15, 2018 8:11 pm 
Hero Member
Hero Member
User avatar

Joined: Wed Oct 21, 2009 6:10 pm
Posts: 1105
Images: 0
Location: Louisiana
See this thread for the elevator trim motor: viewtopic.php?f=4&t=6201

Aileron trim thread here: viewtopic.php?f=4&t=6463&hilit=AILERON+TRIM&start=15


Top
 Profile Personal album  
 
James Grahn
PostPosted: Tue May 15, 2018 11:26 pm 
Hero Member
Hero Member

Joined: Sat Oct 24, 2009 7:16 pm
Posts: 1434
Images: 0
Location: USA
Yep. Too much pitch.
Cubes


Top
 Profile Personal album  
 
TonyNZ
PostPosted: Wed May 16, 2018 4:14 am 
Full Member
Full Member
User avatar

Joined: Thu Oct 22, 2009 10:25 pm
Posts: 105
Images: 8
Location: New Zealand
I have one of the original Sensenich 66LM76 wooden props on my T18, apparently designed by Sensenich for the Thorp. I have an O-320 A2A (150 hp). Static is usually 2000/2050 but WOT at 5000' it will get 2800 rpm. Cruise at 8 or 9000' will see a TAS 155 kts @ 33 litres/hr.

Tony Schischka
T18C
ZK-VMS


Top
 Profile Personal album  
 
Jeff J
PostPosted: Wed May 16, 2018 7:31 am 
Sr. Member
Sr. Member

Joined: Wed Aug 31, 2016 8:18 am
Posts: 583
Images: 0
Location: eastern OK
By way of comparison, I have 160 hp O-320 and this is the info I sent to Catto last year but I am still running the Sterba 68x74. Density altitude for everything except the static rpm was 7400 feet:


Airframe: Thorp T-18

Engine: Lycoming O-320-B3B (160 HP)

Prop: Sterba 68x74

WOT RPM: 2690 (verified/digital)

MAP: ~23.3 inches (analog)

TAS: 164 mph (wheel pants removed)

Static RPM: ~2550


I can't remember my specific cruise numbers but I generally cruise 2300-2400 rpm and 150-155 mph indicated well below 7,000'.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson


Top
 Profile Personal album  
 
SHIPCHIEF
PostPosted: Wed May 16, 2018 10:45 am 
Sr. Member
Sr. Member

Joined: Tue Nov 29, 2011 9:05 pm
Posts: 471
Location: USA
If you elect to change props, consider the Sensenich and Whirlwind Ground Adjustable Carbon Fiber props.
Several T-18 owners have them now.
You can dial them in to your airframe and engine, and if you go with high compression pistons later, easily re-pitch yourself.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE


Top
 Profile  
 
Unclerap
PostPosted: Wed May 16, 2018 1:16 pm 
Jr. Member
Jr. Member
User avatar

Joined: Mon Mar 19, 2018 4:23 pm
Posts: 62
Ryan Allen wrote:
See this thread for the elevator trim motor: viewtopic.php?f=4&t=6201

Aileron trim thread here: viewtopic.php?f=4&t=6463&hilit=AILERON+TRIM&start=15



Perfect, just what I need, I'm on it during July, KALX is repaving.

_________________
Base: KALX
N8786
SN 929


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 8 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 : 0.271s | 13 Queries | GZIP : On ]