jbloom

I am finishing up my Hobbico Sukhoi SU-31 ARF. I've gotten the cowl in place and I need to drill the hole for the high speed needle. Well, the issue is that the needle is fully enclosed inside the cowl. I have a Super Tigre .90 engine and was wondering what's the best way to extend the needle, but also be able to remove it when I need to remove the cowl. Here are a couple pictures of what I have, and one of what I'd like. First pic shows the cowled engine, the second shows the uncowled engine with the needle in question. The third is a pic of the same plane and engine with a needle sticking up through the cowl. I'm not sure how to make this happen. Can someone help?

campbec

Hi jbloom,

Hopefully Minn or RCKen will supply a photo to supllement my less than 1,000 words.

With the cowling removed place masking tape on the fuse and draw a reference line and measure to the needle valve, (if you are anything like me measure twice and write it down). Now put the cowling in place and transpose the measurement from the reference line to the cowl and drill a pilot hole in the cowl. If it is slightly off centre enlarge with the cone shaped stone on your dremel.

If the cowl is a tight fit around the carby you may have to remove the needle valve and insert once the cowling is installed, (obviously the hole needs to be slightly lager than the greatest diameter of the needles ratchet. However there are various flexible solutions limited only by your imagination and length of "Golden Rod"

Cheers,


Colin

bubbagates

My Feedback: (32)

The needle vavle should have a set screw on the side that you can loosen. Then insert the proper sized piece if control rod (usually a piece of 2-56 rod) that is about an inch longer than what you need. Place it in the needle valve, tighten the set screw and bend an "L" shape near the end like you see in your third pic. Now install the cowl and screw the needle valve in and there ya go

khodges

My Feedback: (1)

I use a 2-56 hex socket screw filed to fit the hole in the high speed needle adjuster, and held tight by the set screw. Then I take a piece of brass tubing, just larger than the shaft of the hex wrench that fits the socket screw, and glue it to a standoff that aligns the hole in the cowl with the needle adjuster. It doesn't have to be removed whenever you take the cowl off, all you see is a small hole in the cowl, and when you put your wrench down the tubing, it's a straight shot to the needle. Here's two different planes set up this way:

khodges

My Feedback: (1)

Just thought, that with the ST engine and the needle adjuster being so close to the prop, you could angle the standoff and tube back some, and if you use a ball-end hex wrench, it would still engage the hex screw and turn it. This would give you some distance between soft, stationary fingers and hard, rapidly rotating prop if you have to make adjustments with the engine running.

tsawyer148

My Feedback: (8)

I have the same trouble with my Yak with a Super Tigre 2300. I ended up soldering a nut onto the needle and then purchased a long nut driver (1/4"). I had to have the nut driver extended so it is a total of about 13 inches long from the bottom of the handle to the end (engine is turning an 18X8 prop). That gives plenty of length and keeps your fingers and hand away from the prop and allows you to approach the needle at a slight angle.

Since the Super Tigre engines do not have the hole in the end or a place for a set screw, this was a good way to keep the installation clean and not have to do alot of mods to the cowl or needle.

T.

jbloom

Yea, the Super Tigre's don't have the set screw. Though I've considered drilling out the little piece of rod and then adding a set screw to the side. But, I'm liking the nut soldering too (oh... um.. ouch.. don't go there)... My only concern about the solder is would it be strong enough.

What about a wheel collar? Could that hold it?

tsawyer148

My Feedback: (8)

The solder has held very well so far. Just use a good solder with the right flux and it should be fine. I roughened up the needle and the inside of the nut with some sandpaper on the end of a control rod in my dremel first. It feels pretty tight and doesn't appear like it is going to be a problem.

T.

jbloom

tsawyer148 - Thanks for the pics, they look great. I have some silver solder that typically stronger than regular solder, so l'll give this a try. I'll let ya know how it turns out.

MinnFlyer

My Feedback: (4)

The rod that is in the end of the needle Valve should be able to come out by loosening a set screw. Just remove it and add a longer one with an "L" bend at the top

tsawyer148

My Feedback: (8)

Which would be the perfect solution Minn, but Super Tigre engines don't have that option, unless I haven't looked real close at the needle.

Silver solder is what I used, but it is old and the flux, (liquid), is an old off brand that I can't remember where it came from. You just have to make sure you get a good bond with the needle post and the nut. ALSO..very important to make sure that you take the O-ring and spring off the needle BEFORE you solder anything to it.

T.

Charlie P.

Yeah. Super Tigre do not have a set screw. (at least the .51 and the .90, it would seem)

How about slipping a length of brass tube of the proper i.d. over the existing stub and sleeving an "L" extension in it, then silver soldering the tube in place? Or using a small wheel collar to crimp the tubing tight with it's set screw and just bending the end of the tube for the "L"?

Lickily, mine is in a tight cowl and I can get to it. What drives me nuts is that I am so used to the leg of the "L" as a visual reference when tuning. I added a folded-back-on-itself strip of tape as a little flag when test benching the engine.

Other than that I love the .51

The ancient and tried method of cowl cut-outs is to masking-tape a piece of manila folder or similar on the fuselage with the cowl off and cut out the clearance holes in that cardboard. Then, remove the engine and slip the cowl on (the pieces have to be long enough to be attached behind the cowl seam, obviously). The cardboard is held down on the cowl and the openings marked using the cardboard as a stencil. It's better to use several narrow strips and do a bit at a time than try to rush it and do multiple openings.

jaka

Hi!
Easiest way is to drill the hole in the cowl large enough so that you could remove the high speed needle everytime you want to remove the cowl from the airplane.
Better yet is to use a remote needle placed where you could reach it, like to the rear of the cowl behind the cowl and fuselage.

Regards!
Jan K
Sweden

jbloom

Is the remote needle something that can be bought or is this a self-manufactured item? That's a great idea too..

tsawyer148

My Feedback: (8)

The remote needle is another good idea and I considered that as well for my Yak. I just like to limit the amount of plumbing on my planes, fewer chances of failures, personal preference only.

I don't know about the Sukhoi but I am guessing it is about like the Yak where the entire length of the needle valve is below the level of the cowl. I have 1/2" of clearance between the cowl and the needle when I put the cowl on, no need to "thread" the cowl onto the plane over the needle post.

I was looking at a few different ways of doing this for the ST engine and also thought about slipping a tube over the end of the needle and attaching it somehow. My fear with doing that is the chance that there may be alot of vibration, (which some ST engines are notorious for having), and with the added length it may come undone more often than I would like.

T.

jbloom

It's my plan to stop by the hardware store and pickup a nut today to solder. I think that will be the fastest solution. But I am interested in the remote needle. Tower does have some for O.S. and Fox has a universal needle. But without having the replacement nipple for the carb, doesn't help me out much. And yea, there is at least a 1/2 inch between the end of the needle and the inside of the cowl.

MinnFlyer

My Feedback: (4)

Well, it's plain to see that I've never owned a Super Tiger.

I like Charlie's solution.

tsawyer148

My Feedback: (8)

Sorry Minn, I didn't mean for that to sound short. I meant no disrespect....

T.

CRAZYRYAN

My Feedback: (1)

hey there i have the exact same plane!! will this be the same with a magnum 91 fourstroke? will i be needing a needle valve sticking out as well? thanks oh jbloom, by the way PLEASE capture a video of your plane i want to see how it flys when i start mine next week!!!!

Newc

For my Moki 2.10 inside a cowl I simply used JB weld to attach a hex head (cut from a hex head bolt) to the squared off end of the neddle valve. I can adjust the valve with a ball driver inserted through the cowl and into the hex head, and since it's a ball driver you can have as much as 15 degrees offset of the driver to help keep fingers out of the way of the prop.

jbloom

I'm going to Maiden it today. But it's most unfortunate that I don't have any means of getting a video. I will get some stills and and let you know how it flies. But I will say I like the looks of the aircraft. The cowl is a good quality fiberglass, seems pretty sturdy. With no movement of any equipment, it balanced right on the point. Total dry weight is 7 lbs 6.5 oz.