Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

Viper 500 plane issues

Reply

Old 05-30-2008, 02:50 AM
  #1  
mike240se
Member
Thread Starter
 
Join Date: Jul 2007
Location: Clifton, NJ
Posts: 45
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Viper 500 plane issues

hi i just built a viper 500 and have many issues. my vtail is crooked, when i line it up to the wing, its obvious that the right half of the tail is was connected to the vtail block at a shallower angle. i have no idea how to fix this without breaking it and then glueing it. does anyone else have this problem and know what to do?

also the firewall has no right thrust, do i need to add right thrust? i am concerned putting washers behind the motor mount cause it will no longer be flush with the firewall and it seems like it will reduce its overall strength. i am running a jet racing motor but will be putting on a nelson soon and this thing needs to be strong. do i really need the right thrust? my friends lanier predator ii has left thrust (cause even with washers its still left) and it flies great.

also the tail is very weak, any suggestions to strengthen it?

thansk

mike
mike240se is offline  
Reply With Quote
Old 05-30-2008, 06:23 AM
  #2  
Super Splatter
Senior Member
 
Super Splatter's Avatar
 
Join Date: Mar 2006
Location: , MN
Posts: 432
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

Depending on how you bought it, you could try to get a replacment tail. I had a kit that was missing the tail feathers from the tail and they replaced the whole tail, from Tower.

or get a saw and glue and fix it. All the quickies I see have no right thrust. Use a little rudder on take off.

The if you go digging back there is talk and pics of what to do to fix the tail, but it involves glue, glass, covering. I slapped on some 64th ply on the sides for a couple inchs and recovered it.

Super Splatter is offline  
Reply With Quote
Old 05-30-2008, 09:08 AM
  #3  
DMyer
Senior Member
My Feedback: (2)
 
Join Date: Oct 2002
Location: Potomac, MD
Posts: 642
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

The Vtail itself is typically AOK, but the saddle fit is not to be trusted. Don't worry if the Square/V blocky thing in the middle of the V actually ends up lining up with anything like the FUSE. I would -

1) - bolt tail/wing on - measure rear of wing tips to rear of tail tips. This measurement should be equal.

2) - Set the plane up on a stand and stand back enough so you can sight down the fuse from the rear - the tail tips should align with the wing line. I find this is often not the case(my most recent one had the right tail tip 1.5 inches lower! You can either shim or sand the saddle until 1&2 are both satisfied.

3) - The stab needs about 1 degree of positive incidence to fly right. That means with the plane blocked up so the firewall/fuse and wing are 0-0 (I use robarts incidence meters on the wing. A torpedo level will suffice for the firewall), the stab leading edge will be lower than the trailing edge. The easy way to set this is to tape a small square close to the fuse from the rear of the stab so that the a small bubble/line level can be placed on the flat of the stab and measure it's incidence. Go to the hobby shop and get a 1/4" piece of square aluminum or plastic that can be glued to the top of the square so that you have a nice V on top of the flat part of the stab in order for the bubble/line level to get a good reading. With the wing incidence bubble centered, the tail bubble should be hard on the rear line or at most just barely over the rear line. To get a bubble, buy a cheap plastic torpedo level and remove one of the bubbles. Repeat steps 1 & 2 while adjusting for 3 until all are satisfactory, then glue the stab in place with slow cure epoxy. Glueing in the tail strengthens the structure significantly. Remove the covering on the from and rear of stab saddle areas so that glue area to fuse/tail can be maximized. This will be very close and at most you will only require a couple clicks of trim to fly straight and level.

Sounds like a lot, but with the robart incidence meter on the wing and a square jig for the stab bubble I described, it is not too bad... but it is very critical. Go slow when removing material as a little can go a long way. You may find it easier to shim. IMHO some V-Tails take 5 minutes to align and some take an hour, but it is time very well spent that you will be very glad you did later. My last one I just finished for my son was close on #1 but off a ton in 2 & 3 and took me amost a hour to set. Good luck!!
DMyer is offline  
Reply With Quote
Old 05-30-2008, 03:51 PM
  #4  
Jezmo
Senior Member
 
Jezmo's Avatar
 
Join Date: Jun 2006
Location: Spring, TX
Posts: 2,132
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

Most quickies run 0-0-0 on firewall, wing, and tail. The Viper is a slightly different animal and like DMyer said it needs about 1 deg of pos. incidence on the tail to fly right. I don't have any offset thrust on mine and the wing is at 0. The tail is as described and it flies great as a 424 legal bird.
Jezmo is offline  
Reply With Quote
Old 05-30-2008, 04:29 PM
  #5  
garys
Senior Member
 
Join Date: Jan 2002
Location: Stansbury Park, UT
Posts: 937
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

Personally I'd be more inclined to leave the engine and tail at zero, and put a bit of positive in the wing. The reason the tails are needing to have some negative (LE lower than TE) in them is the tail is pushing down to get the wing to the angle of attack that it needs to fly right.

Therefore, when set up with the engine and wing at zero, and the tail with negative, the whole airplane is actually flying with a bit of positve angle of attack. It would probably be faster with some positive in the wing, and everything else at zero.
garys is offline  
Reply With Quote
Old 05-30-2008, 09:26 PM
  #6  
mike240se
Member
Thread Starter
 
Join Date: Jul 2007
Location: Clifton, NJ
Posts: 45
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

thanks for all these great posts, i will read them all in detail when i get home from work,

just to add, when i sight down the back of the plane and align the LE's of the tail with the TE's of the wing, i can tell that the one on the right looks about 1/2 - 3/4 inch lower than the wing TE when the left one is dead even. Is this too out of whack?


Also what is Pos 1 on the vtail? you mean it needs to be shimmed to give you more up elevator?
mike240se is offline  
Reply With Quote
Old 05-30-2008, 10:21 PM
  #7  
DMyer
Senior Member
My Feedback: (2)
 
Join Date: Oct 2002
Location: Potomac, MD
Posts: 642
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

Make the tail even with the wing... period. It will never track correctly otherwise. You need more lift so either set the tail with a 1 degree incidence that will create lift or shim the wing to raise the leading edge as previously so well described to create the needed lift so it will fly level with no up elevator trim. One thing you will notice about this wing is that it will seem to glide almost forever when landing so manage your speed in a consistent manner during your landing approach. You get this plane setup right and you will be amazed at how well a $119 dollar ARF racer can fly! It is no $500 composite, but, it is competitive or can flat out whip one heck of a lot of the kits and ARFs used over the last 25 years with a good pilot. Good luck.
DMyer is offline  
Reply With Quote
Old 06-01-2008, 09:52 PM
  #8  
mike240se
Member
Thread Starter
 
Join Date: Jul 2007
Location: Clifton, NJ
Posts: 45
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

ok i got a robart incidence meter. i read all these posts in detail and have a few questions.

first, what do you mean by the stab's leading edge would be below its trailing edge? do you mean the stabs's leading edge would be below the WINGS trailing edge? I assume this is what you mean unless i am missing something.

I gotta be honest, i dont know how well i understand #3 above though, maybe i need to just try it and it will make more sense.

what if the v-tail is messed up? as in one fin is glued on at a different angle than the other fin.

now with number 2 above, do you mean i need to shim or sand the wing saddle or the saddle for the vtail? i am pretty sure the vtail mounting saddle or the vtail itself is what the problem is.

mike
mike240se is offline  
Reply With Quote
Old 06-02-2008, 06:55 AM
  #9  
Ed Smith
Senior Member
 
Join Date: Dec 2001
Location: Brantford, ON, CANADA
Posts: 3,305
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

It is a fact of life that an airplane has to be built properly to fly properly. On Incidence meter is not enough,

The pictures show my method of setting the Tail/Wing relationship on both a vee tail and a conventional tail. In all cases the bar of the meter must be parrallel to the fuselage centre line.

Ed S
Attached Thumbnails Click image for larger version

Name:	Ig11239.jpg
Views:	18
Size:	65.8 KB
ID:	962090   Click image for larger version

Name:	Ql35502.jpg
Views:	16
Size:	78.6 KB
ID:	962091  
Ed Smith is offline  
Reply With Quote
Old 06-02-2008, 04:01 PM
  #10  
HighPlains
My Feedback: (1)
 
Join Date: Mar 2003
Location: Over da rainbow, KS
Posts: 5,085
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

e?
HighPlains is offline  
Reply With Quote
Old 06-02-2008, 04:45 PM
  #11  
DMyer
Senior Member
My Feedback: (2)
 
Join Date: Oct 2002
Location: Potomac, MD
Posts: 642
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues


ORIGINAL: Ed Smith

It is a fact of life that an airplane has to be built properly to fly properly. On Incidence meter is not enough,

The pictures show my method of setting the Tail/Wing relationship on both a vee tail and a conventional tail. In all cases the bar of the meter must be parrallel to the fuselage centre line.

Ed S
Two Incidence meters are usually better (I also have two), however, I find it difficult due to the angles to get the incidence meter accurately on the V-tail stab. If the meter leading edge is lower or higher to the fuse longitudal plane the results will not be accurate... a problem not encountered with a flat stab. I prefer to drop a bubble on a flat spot in the center of the V if available, otherwise, I use a jig off the stab trailing edge. Do you do a that looks about right or is there a method to get the rear meter on straight? Just looking for a better way.

P.S. - nice shop... scary clean and organized... you need some balsa dust bags, tool boxes and several kits to explode all over to look like mine. Very jealous.
DMyer is offline  
Reply With Quote
Old 06-02-2008, 05:01 PM
  #12  
Ed Smith
Senior Member
 
Join Date: Dec 2001
Location: Brantford, ON, CANADA
Posts: 3,305
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

I use a jig off the stab trailing edge. Do you do a that looks about right or is there a method to get the rear meter on straight? Just looking for a better way.
OK Try this. Make a platform from flat sheet balsa. Set four pins that will sit at the extreme edgers of the LE and TE without wobbling. My bench top is level with an accurate spirit level. So if my wing incidence meter reads 0-0 then i set the little jig pin legs first on the bench top to read 0-0. I do not do this any more but it does work on an airfoiled tail.

Ed S
Attached Thumbnails Click image for larger version

Name:	Yw68418.jpg
Views:	11
Size:	85.5 KB
ID:	962459   Click image for larger version

Name:	Fb87600.jpg
Views:	16
Size:	51.4 KB
ID:	962460  
Ed Smith is offline  
Reply With Quote
Old 06-02-2008, 07:05 PM
  #13  
djlyon
Senior Member
 
Join Date: Dec 2001
Location: Castaic, CA
Posts: 2,492
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

I scribe a line from the leading edge to the trailing edge perpendicular to the trailing edge. I level the plane using a incidence meter on the wing and then level the stab using combination squares at the leading and trailing edge of the stabs. I use a true angle to make sure the firewall is at 0-0.

Denis
djlyon is offline  
Reply With Quote
Old 06-10-2008, 01:12 AM
  #14  
flyngfrog
Member
 
Join Date: Apr 2008
Location: Guatemala, , GUATEMALA
Posts: 79
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Viper 500 plane issues

Hi, I've built a few pylon racers and the squares method had worked fine for me. The sheet platform for the bubble seems ok. I'll try it next time. I've always used 0 incidence in fuse and stab. 0 to 1 degree (mostly 1/2 degree) at wing and they fly great.
flyngfrog 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