Questions and Answers If you have general RC questions or answers discuss it here.

fuel tank to engine distance

Reply

Old 05-10-2003, 02:11 AM
  #1  
speed-is-good
Junior Member
Thread Starter
 
Join Date: Oct 2002
Location: CO
Posts: 4
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

I'm working on a plane that is seriously nose heavy and am thinking about putting the fuel tank over the CG. What is the furthest distance from the engine anyone has tried putting the tank without having a fuel feed problem?
speed-is-good is offline  
Reply With Quote
Old 05-10-2003, 05:00 AM
  #2  
JohnBuckner
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,431
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

Without resorting to a pump or a pressure system such as the Kline the only tanks that will function on the CG are bubbless tanks from Tetra or Jett and this is up to a max of about seven inchs behind the engine. These are an entirely different type tank that use an internal bladder and muffler pressure is introduced between the hardshell and bladder. This type of tank is now the norm for pylon racing and almost always used on the CG. The Tetras are avaliable from Central hobbies in sizes up to 16 oz.

John
JohnBuckner is offline  
Reply With Quote
Old 05-10-2003, 10:44 AM
  #3  
Jemo
Senior Member
My Feedback: (5)
 
Jemo's Avatar
 
Join Date: Dec 2001
Location: in, FL
Posts: 1,924
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

Glow or Gas,??????/
Jemo is offline  
Reply With Quote
Old 05-10-2003, 12:47 PM
  #4  
speed-is-good
Junior Member
Thread Starter
 
Join Date: Oct 2002
Location: CO
Posts: 4
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

It's a Q40 plane that I'm putting a TT 46 in for sport flying. I guess the TT is a lot heavier than the normally used Nelson/Jett.
speed-is-good is offline  
Reply With Quote
Old 05-10-2003, 01:08 PM
  #5  
JohnBuckner
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,431
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

The TT .46 ABC with stock muffler is about 1 Oz. heavier than the Nelson Q40 AAC. The tank you need is the Jett bubbless CG 6oz tank and you will need the Jett tanker fueling syringe.

John
JohnBuckner is offline  
Reply With Quote
Old 05-10-2003, 06:41 PM
  #6  
hookedonrc
 
hookedonrc's Avatar
 
Join Date: Dec 2002
Location: Tulsa, OK
Posts: 2,872
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

I have an ultra stick 60 with an OS61FX on it. I put the back end of the tank right at the CG and have about 7.5"- 8.0" to the engine and it runs like a top. I have pointed it straight up and never lost any RPMS as the plane climbed. However, the engine is brand new, and I really do not know if this will hold true as the compression gets less after many runs. However, as it was pointed out to me when I asked the same question on this forum. You will be balancing with an empty tank, so you are only compensating for the weight of the tank when you move it back. I did mine just to have little change as the tank empties during the flight.
hookedonrc is offline  
Reply With Quote
Old 05-10-2003, 06:42 PM
  #7  
hookedonrc
 
hookedonrc's Avatar
 
Join Date: Dec 2002
Location: Tulsa, OK
Posts: 2,872
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

Sorry, meant to add that I used the tank that came in the US60 ARF. I didn't change from the original.
hookedonrc is offline  
Reply With Quote
Old 05-10-2003, 07:58 PM
  #8  
DBCherry
My Feedback: (4)
 
Join Date: Jan 2002
Location: Hubbardston, MA
Posts: 5,550
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

hooked is right. If you're balancing the plane with an empty tank, which you should always do, the palne will still be "seriously nose heavy". Of course, it would be even more nose heavy with a full tank.

How heavy is "seriously heavy"? It takes about three ounces of nose weight to compensate for one ounce of tail weight. Could you get away with adding an ounce or two to the tail?

Where's your battery pack? Could you move it back, use a larger one? Could you use a lighter engine mount?
Dennis-
DBCherry is offline  
Reply With Quote
Old 05-10-2003, 08:11 PM
  #9  
JohnBuckner
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,431
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

Of course The purpose of a CG tank is zero CG change through out the flight and not to provide initial balence However on this airplane a CG Jett tank is very important, a properly prepared(422) Q40 (which is the fastest AMA rulebook pylon class) with a Nelson or Jett Q40 engine will reach speeds near 185 miles per hour and this is done on only a 608 foot course. One of these flown with all fuel stuffed into the nose will be quite difficult to land on an empty tank an this is only typically 6 0z. This is a small airplane and the CG is very critical because of the enormous speed range.

Sport flying one should be fun but keep in mind even with the TT it will be an eye opener. Don,t think about flying it with more than an eighth inch throw both ways in pitch and roll. A good starting point on the prop for the TT .46 would be APC 8.8 X 8.5/8.75. Do not use APC sport props labeled C-2 only D-1 props which have a heavy hub for safety at the high RPM's. A TT .40 used in Q-500 sport quickee racing with a 9x6 turns 16500/17000.

Speed is good - I suggest you come on over to the pylon forums on this board and you can get an even more educated help. I am still flying the two Q-500 classes which is adrenline enough for now. These two classes 424 and 428 are doing about 125 and 155 mph.

John

By the way I neglected to mention standard size servos are gonna present balence problems typically Hitec 225's or the equivilent JR are used battery if a Nicad will be a 260/270 and I suspect some of your problems are using standard stuff. Do check at the Q-40 sub forum.
JohnBuckner is offline  
Reply With Quote
Old 05-10-2003, 08:13 PM
  #10  
mikenlapaz
Senior Member
 
Join Date: Dec 2002
Location: La Paz BCS, MEXICO
Posts: 1,986
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

This may be a bit more precise than:
It takes about three ounces of nose weight to compensate for one ounce of tail weight.

real time CG adjustment (post # 15)

Found this site for CG sling which seems to be a different but workable alternative to a balancing stand. I visualize it with 1" webbing for the slings. I would be interested in any comments on its drawbacks, if any.

http://www.northlandflyer.com/Tips_...g/cg_sling.html
mikenlapaz is offline  
Reply With Quote
Old 05-10-2003, 08:46 PM
  #11  
mikenlapaz
Senior Member
 
Join Date: Dec 2002
Location: La Paz BCS, MEXICO
Posts: 1,986
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

This may be a bit more precise than:
It takes about three ounces of nose weight to compensate for one ounce of tail weight.

real time CG adjustment (post # 15)

Found this site for CG sling which seems to be a different but workable alternative to a balancing stand. I visualize it with 1" webbing for the slings. I would be interested in any comments on its drawbacks, if any.

http://www.northlandflyer.com/Tips_...g/cg_sling.html
mikenlapaz is offline  
Reply With Quote
Old 05-11-2003, 03:40 AM
  #12  
speed-is-good
Junior Member
Thread Starter
 
Join Date: Oct 2002
Location: CO
Posts: 4
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

JohnBuckner,
I am thinking along the same lines as you in that I don't want the CG to change through the flight. I don't have servos/battery pack located yet but can tell already that I will probably have to add some lead shot in the tail to get it balanced, even with these components located behind the CG. The plane is a Miss Foxy Lady from Dan Kane. I've raced in the 424 class before so know a little about props/engines. I've also built another 428 plane, complete with Nelson engine, that is hanging in my garage. I cruise the racing forum occasionally but tend not to post, as I felt like I got a little verbally raped there once.
speed-is-good is offline  
Reply With Quote
Old 05-11-2003, 03:54 AM
  #13  
jacs
Senior Member
 
jacs's Avatar
 
Join Date: Jan 2003
Location: Uddevalla, SWEDEN
Posts: 394
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default fuel tank to engine distance

This link work a little better I think
http://www.northlandflyer.com/Tips__.../cg_sling.html
jacs is offline  
Reply With Quote

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