RE: Viper Jet 2M Pointers/ tips.
 

Hi Alan,
I've got the engine moved as far forward as I'm willing to move it (see previous post) , and my pipe sticks out of the tail cone by 1-1/4".
If the pipe were short enough to only stick out 1/4" like yours I would leave it alone. But that's not the case with my pipe.
So I've decided to shorten the pipe, and will shoot for 1/4" sticking out of the tail cone like yours.

Whatkind of finish didyou put on your tail cone? Looks very nice.

Thanks for the feedback.
Jim

RE: Viper Jet 2M Pointers/ tips.
 

Jim as i look at your photos you are measuring the distance of the pipe and the tail edge of the fuselage. With the tail cone attached your pipe does not protrude past the tail cone based on where your motor is located in the airframe.

I am only going by the photos you have posted and as such you need to move your motor rearward to allow the pipe to exit the tail cone.

I used Black Baron presto to cover my tail cone and you can also use monokote chrome trim sheet, i need to replace it as wrinkles are starting to show up now.


[link=http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXB231&P=8]Coverite black baron presto[/link]


I will take a few photos of my motor and pipe installation and upload them tonight or tomorrow.

Alan

RE: Viper Jet 2M Pointers/ tips.
 

Jim
I was just looking at your photos and looking at the explanation that 3DHELINUT was giving... If what 3DHELINUT stated is correct then you do not have enough gap between your Turbine Tail cone and the bell mouth (which is not shown)

Also as 3DHELINUT stated the pipe can protrude out of the fiberglass (silver) tail cone section

RE: Viper Jet 2M Pointers/ tips.
 

Hi Rich and Alan,

According to Bob at JetCat the gap from the lip of the pipe (not bell mouth) to the edge of the exhaust nozzle should be 25mm (about 1").
The pics I posted were 1]. with the 25mm gap (tail pipe and tail cone protruding out the back of the fuse 1-1/4") and 2]. with the tail cone in place on the fuse (this results in the front lip of the pipe covering the exhaust nozzle). Pic was taken for demonstratrion purposes only.
I think the pics and explanations may be confusing, sorry. But bottom line is, where I've got the engine mounted as shown in the pics, the pipe would stick out of the tail cone 1-1/4". I can live with 1/4", but not this much.

Sooooo, I've cut the pipe to the length (thanks Ian for the Dremel suggestion) I needed which is front lip torear edge of pipe: 570mm. This gives me the 25mm gap at the exhaust nozzle (not including the bell mouth), and the protrudes past the tail cone a tiny bit less than 1/4" I'm satisfied this is the best outcome I can get given shortening the pipe.
Shortening the pipe is a whole different story, not for the faint of heart...LOL.

With that hurrdle over,I'm onway to equipment installation. Will post pics on progress.

Thanks to everyone who replied and assisted.
Best regards, Jim

RE: Viper Jet 2M Pointers/ tips.
 

Here it is>>>

RE: Viper Jet 2M Pointers/ tips.
 

Yep, i'm changing the power plant on mine from a P80SE to a Merlin 140. The P80SE is fine for take off from the tarmac runway i've flown at but not so great at my home field unless the wind is directly down the strip.Hopefully my viper will become more like my supersport powered boomerang in that I can just fly and not worry if she's going to get off the deck.

RE: Viper Jet 2M Pointers/ tips.
 

Guys
take a look at

RE: Professional Viper 2M Build - <span class="ultrasmall"><font face="Tahoma">7/19/2010 2:44 AM</font></span> ....... post 39

Rich

RE: Viper Jet 2M Pointers/ tips.
 

Rich,
Post #39 is Couch Potato talking about polishing the plane.
I couldn't find a post on 7/19/2010 2:44AM?
What's it about?
Thanks, Jim</p>

RE: Viper Jet 2M Pointers/ tips.
 

This is the other Rich!

Look here

http://www.rcuniverse.com/forum/m_98..._2/key_/tm.htm

BTW I have something almost ready for you;)

RE: Viper Jet 2M Pointers/ tips.
 

sorry Jim
It was another thread - The other Rich has the link - it talks about notching out the turbine mount to position the turbine further forward which helps the tail pipe problem.
Rich
Perhaps id better sign off Richard from now on!

RE: Viper Jet 2M Pointers/ tips.
 

Could someone measure the dimensions of the retracts?  I'm out the country at the moment and don't have access to mine to measure.  <div>
</div><div>I'm trying to work out which airpower retract side plate to order to replace my bent one and I've narrowed it down to the RA-215 or 230, the latter I can get the dimensions from alshobbies.</div><div>
</div><div>Cheers,</div><div>
</div><div>Colin</div>

RE: Viper Jet 2M Pointers/ tips.
 

Hi Colin,
I think I might have the correct side plates in stock. I will send you a pair as s gift when I send your lovely new Merlin 140 that I have with me ;)

RE: Viper Jet 2M Pointers/ tips.
 

Ali, thanks :)<div>
</div><div>Do you know what model the retracts are for future reference as I'm sure other people will do the same thing since they are made out of aluminium.</div><div>
</div>

RE: Viper Jet 2M Pointers/ tips.
 

Hi Rich and Rich (Richard),

Thanks for the tips. Good info from KFX450. I ended up installing the engine as far forward as I dared. I cut away the web to clear the starter so far it has an opening in it now between the seans. So ended up with the set up you see here. The pipe was cut to 570mm. Anyone have an idea how to finish the end of the pipe after its been cut? Its rather ragged now.

I'm trying to save weight, especially at the tail. So I made up the ventral fins you see here: 1/8" CF laminate, dood dowels, and aluminum rod.Stock fins weigh 1.75oz. each, the new ones weigh 0.50oz each. I'm also considering using the DS3921's instead of the old DS8411's, that will save another 1oz. each. But only if necessary to offset having to add nose weight.

Replaced the std. aluminum wing tube with a CF one: Saved 7.8oz.
Installed 'future' smoke tank in location shown - B&amp;B 32oz. square tank. I've decided to use only the front cockpit so that has opened up a lot of options for the equipment installation.

Thanks for all your support and ideas.
Regards, Jim

Rich, I PM'd you. Thanks.

RE: Viper Jet 2M Pointers/ tips.
 

Sorry, totally lame when it comes to uploading pics,
Here's the tail pipe cut end, ventral fins, wing tubes and smoke tank.

RE: Viper Jet 2M Pointers/ tips.
 

Sorry again, I guess I need to take the upoad 101 class at RCU. I'm also fighting with bandwidth issues on my DSL.
I'll try again, my apologies.

RE: Viper Jet 2M Pointers/ tips.
 

I ran up my new merlin 140 yesterday outside on a workbench and it's the noisiest turbineI'veever owned! I thought my supersport was noisy but the merlin has a certain high pitch whine in addition to the 'normal' turbine sounds. Next time I'll be wearing my ear defenders as my ears were ringing for quite a while after.<div></div><div>However, it did manage to move trees &amp; bushes at least 20m away which is rather impressive... can't wait to get it in my viper :D</div>

RE: Viper Jet 2M Pointers/ tips.
 

Hello Colin,
I know what you mean about the sound, my Jet Central Cheetah is basally the same construction, and it is LOUD when you standing right next to it!

I think it may have to do with the short exhaust cone....

RE: Viper Jet 2M Pointers/ tips.
 

Hmm, could be since the airflow is not being slowed down? Its certainly a high pitch whistle and not the grumble my P80SE has.

To do the run up I took it round to a friends who backs onto trees and a river which is about 1/2km away from where I live. On my return my wife told me that she could hear us spooling it up and she was indoors :)<br type="_moz" />

RE: Viper Jet 2M Pointers/ tips.
 

Hi there
Im just about to ballance my viper2m - when you say you ballanced it 12mm forward of the main spar do you mean 12mm forward from the centre of the main spar?
Regards
Rich P
</p>

RE: Viper Jet 2M Pointers/ tips.
 

12mm in front of the main spar, or 12.5 mm from the center of the main spar.

either way a mm more or less will not affect the flight envelope.



Alan aka Mako

RE: Viper Jet 2M Pointers/ tips.
 

Richard if you go back to post #314 (page 13 of this thread) there is a pdf document of a balancing fixture that shows the recommended positions;)

RE: Viper Jet 2M Pointers/ tips.
 

sorry for the late reply but thanks for the tips guys!
All ballanced 12.5mm in front of the main spar and 2 successful flights under my belt!

Richard

RE: Viper Jet 2M Pointers/ tips.
 

(12.5mm from the center of spar) - as per Rich's drawing

RE: Viper Jet 2M Pointers/ tips.
 

So did you use the fixture in the drawing to balance yours?