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Herr Pitts Special Kit Build Thread

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Herr Pitts Special Kit Build Thread

Old 10-30-2007, 01:01 AM
  #51  
somegeek
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Default RE: Herr Pitts Special Kit Build Thread

Started on the upper wing tonight...



Next, the instructions state to cut a piece of sheeting to fit between the TE sheeting and the spar. Will be easier to let these pieces dry and then remove them to trace what needs to be cut on the 1/16" piece of sheeting. Having a photocopy of this section of the plan would be nice to cut a template for the sheeting piece.

somegeek
Old 10-30-2007, 08:34 AM
  #52  
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Default RE: Herr Pitts Special Kit Build Thread

SomeGeek,
If I may ask...
What is the function of the clothespins?
You 1/2A guys have such clever build ideas I just have to ask.
I've never seen it before.
Thanks!
JLK
Old 10-30-2007, 10:05 AM
  #53  
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Default RE: Herr Pitts Special Kit Build Thread


ORIGINAL: jlkonn

SomeGeek,
If I may ask...
What is the function of the clothespins?
You 1/2A guys have such clever build ideas I just have to ask.
I've never seen it before.
Thanks!
JLK
I wanted to pinch the blocks against the spars so I put pins on both sides and used a clothes pin to pull the ends together.

somegeek
Old 10-31-2007, 02:23 AM
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Default RE: Herr Pitts Special Kit Build Thread

Got the lower middle sheeting cut and in place... but cut a little narrow. Didn't follow my sig - measure three times, cut once. Was able to use the cut-out from the bottom though to fill the sides since the angles were complimentary...



Added the middle ribs. The laser cutting process seems to slightly taper the edges of the wood material as the one side of the cut where the laser hits is clean and open whereas the bottom of the cut in the material is more narrow. Used pins to keep those ribs square that needed the support...



Time to start altering the wing for the upper ailerons. The ribs require minimal alteration to allow for the installation of the upper aileron and you can use the bottom ribs as a template for the TE. As you can see in the following pic with the lower wing rib placed atop an upper wing rib...



I'll need to cut slots for the sheeting and the TE piece... but it's 12:20am - time to sleep.

somegeek
Old 10-31-2007, 07:39 AM
  #55  
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Default RE: Herr Pitts Special Kit Build Thread

lookin' good
Old 10-31-2007, 11:51 AM
  #56  
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Default RE: Herr Pitts Special Kit Build Thread

Ironic I found this thread, my kit is in the mail as we speak! I can't wait.
Old 11-01-2007, 12:19 AM
  #57  
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Default RE: Herr Pitts Special Kit Build Thread

Somegeeks build threads are a great help 'cause his pics are clear are excellent, and details well written and to the point.

Makes it alot easier to build the same kit when someone has gone to all this effort both for themselves and others.

Thanks SG.

Now if you could also build a Herr Mustang, I'd be muchly appreciative
Old 11-01-2007, 02:36 AM
  #58  
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Default RE: Herr Pitts Special Kit Build Thread

Thanks for the kind words guys.

Got the majority of the modification done to the upper wing to get the barn door aileron slot area created.

1) Cut the TE sheeting on the outer edge of the rib #2 in the pic so the rib can sit on it.
2) Install rib - this rib will need to have the top TE sheeting groove cut into it.
3) Place the TE lower sheeting piece in place and trim to length. I did butt the lower TE sheeting against the ribs numbered 2 and 5 in the pic. You could notch the lower side of the ribs to sit on top of the sheeting as well.
4) Install 3/16" TE strip(leftover spar pieces worked here along with a few inches from a new spar stock piece).
5) Install outer-most rib - this rib will need to have the top edge sheeting groove cut into it(I forgot to do this in this pic).
6) Install T-5 Rib with doublers. If using Titebond or a variant, make sure you clear out any extra that might be in the groove before you set this piece in place.
7) install rib - alter this to look the same as one of the lower wing L-3 ribs.



I've still gotta do some clean-up on the area where the upper TE sheeting will sit. Forgot to clear the area on the outer-most rib for the TE sheeting so will do this before I add that piece. As stated above, use a rib from the lower wing for a template to shorten your ribs and as a guide to easily trim your ribs using a straight edge razor.



I didn't like the torsional flex in the wooden dowel used to join the elevator halves so I replaced it with a piece of 1/8" carbon fiber rod and secured with flash black rubberized CA. Should be solid now.



Looking forward to pulling this off the board tomorrow and seeing if this made the elevator that much more rigid.

somegeek
Old 11-01-2007, 04:51 AM
  #59  
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Default RE: Herr Pitts Special Kit Build Thread

The dowel in the elevator halves that you replaced, is it to flimsy?

This might seem naive, but why rubberised CA, and not epoxy?Weight saving?
Old 11-01-2007, 09:50 AM
  #60  
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Default RE: Herr Pitts Special Kit Build Thread

ORIGINAL: Krener
The dowel in the elevator halves that you replaced, is it to flimsy?
I thought so myself. I tried to add a few drops of CA to see if it'd absorb to make it more rigid but that didn't do the trick. This carbon fiber rod is much more rigid so this will work.

This might seem naive, but why rubberised CA, and not epoxy?Weight saving?
I don't have thick CA so I used this. Sets up really solid despite being called 'rubberized'.

somegeek
Old 11-01-2007, 10:02 PM
  #61  
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Default RE: Herr Pitts Special Kit Build Thread

Would you be looking at any weight saving by making holes in the control surfaces and horiz stab?
Old 11-02-2007, 12:23 AM
  #62  
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Default RE: Herr Pitts Special Kit Build Thread


ORIGINAL: Krener

Would you be looking at any weight saving by making holes in the control surfaces and horiz stab?
Unless you're going for a super-light build, the weight savings would be negligible.

somegeek
Old 11-03-2007, 01:17 AM
  #63  
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Default RE: Herr Pitts Special Kit Build Thread

Got the TE sheeting and wing tips in place. Sanding the wing tip joint surface slightly to angle it yeilded a better joint I think. Propped up 1/4" with some scrap.



The instructions state to crack the spar to angle it but I made a small groove about 3/4 through the spar and filled with glue before gluing in place. Cleaner result I thought. Someone correct me if this was not the best way for this.



Got the top and leading edge spars in place...



Took some work to make sure the Titebond got into the rib grooves where the spars sit. The spars scrape down the sides of the groove when you insert them. With some of them, I slightly bent the ribs back and forth a little to work the glue into the groove to assure a good solid joint.

somegeek
Old 11-04-2007, 11:11 PM
  #64  
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Default RE: Herr Pitts Special Kit Build Thread

Since I am installing ailerons on the upper wing I had to install this small piece of sheeting by itself. The clothes pins helped to hold it in it's bent position as the glue dries overnight. I also added a piece of sheeting between the main spar and this piece of TE sheeting to give the wingtip some added rigidity.



Finished the bottom sheeting...



Remaining items to install on this upper wing are the shearing web pieces and the top sheeting.



somegeek
Old 11-08-2007, 03:20 AM
  #65  
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Default RE: Herr Pitts Special Kit Build Thread

Got the center top sheeting in place...



Started on the bottom wing...



Note the inner most rib is angled slightly when glued in place so it will sit vertical when the other wing half is mounted due to the dihedral.

somegeek
Old 11-08-2007, 12:38 PM
  #66  
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Default RE: Herr Pitts Special Kit Build Thread

I noticed you cracked the spar opposite the way I was taught. The way I was taught was to make the cut 2/3 - 3/4 (or more as required depending on the severity of the bend angle) through outside part of the joint. After it has been glued in place, fill the crack with epoxy to bring the strength back to it. Its worked on several Sig J-3 Cubs (the old 1/6 scale). But I don't see where your method wouldn't work just fine either, especially considering how light your plane will be. If you get into a situation where the break be in a high stress condition, add some doublers from sheet on either side (if possible) of the stick at the break point - learned that the hard way when I had an inflight structural failure on one of my Sig Clipped Wing Cubs.

Your build looks great - nice and clean.

Hogflyer
Old 11-08-2007, 01:58 PM
  #67  
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Default RE: Herr Pitts Special Kit Build Thread

Thanks for the info hogflier. Will note that for future builds.

Just noticed my lower wing looks like a voodoo doll in that pic. I used a bunch of smaller pins to make sure that sheeting lay flat while I was gluing the ribs in place.

I now have four different sizes of push pins - from the thick T-pins to the smallest ball headed pins. The smallest are awesome - just picked them up this last weekend. Note in the pic I have some inserted vertically through the ribs at the spar - no splitting of the rib material and it really held the rib secure for the joint to cure. Works great!

somegeek
Old 11-08-2007, 04:04 PM
  #68  
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Default RE: Herr Pitts Special Kit Build Thread

I just found this post, so please excuse me if I'm a little late in "helping", but I just finished my Herr Pitts, but haven't flown it yet. I'm running a K&B BB .18 and it fit fine. I've also got a 4 oz. tank in the bird and it's a little tight, but no big deal in getting it to fit. The major change I made was making both the lower and upper wings bolt on, vs. rubber band. With lots of power, I wasn't about to have a wing shift or fly off. Let me know if you have specific questions and I'll try to respond.
Old 11-08-2007, 04:18 PM
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Default RE: Herr Pitts Special Kit Build Thread

ORIGINAL: drobbs
I just found this post, so please excuse me if I'm a little late in "helping", but I just finished my Herr Pitts, but haven't flown it yet. I'm running a K&B BB .18 and it fit fine. I've also got a 4 oz. tank in the bird and it's a little tight, but no big deal in getting it to fit. The major change I made was making both the lower and upper wings bolt on, vs. rubber band. With lots of power, I wasn't about to have a wing shift or fly off. Let me know if you have specific questions and I'll try to respond.
.18 - that's gonna cruise!

I like the idea of bolt on wings very much... do you have any pics of how you went about executing this modification? This plane is so small, breaking it down won't really be necessary to transport.

somegeek
Old 11-09-2007, 03:13 AM
  #70  
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Default RE: Herr Pitts Special Kit Build Thread

Got the left half done minus the sheeting piece at the back and block on front of the wing tip. Gotta cure overnight since the next step is to tip it up 1 3/4" to build the other half.



This lower wing is building up a lot quicker than the top... just realized this is because I was figuring out the top wing as I went to create the aileron slots.

somegeek
Old 11-09-2007, 09:55 AM
  #71  
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Default RE: Herr Pitts Special Kit Build Thread

Your wings look great! I've always loved Pitts Specials. I learned to fly full scale when I was 18 and I always wanted to fly a Pitts, a J-3 Cub, and a P-51D Mustang in my lifetime. I eventually checked out in a 1946 J-3 and rented it for a couple of years taking my friends and family on lots of fun flights in it. I got an aerobatic ride in a Pitts S2-B in 1999 at the Sun-N-Fun Fly In in Lakeland, Florida. It was a blast! I doubt I'll ever get the chance to fly a Mustang, though.[] Keep up the good work on your model.
Old 11-09-2007, 06:07 PM
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Default RE: Herr Pitts Special Kit Build Thread

Like I said - I bolted the wings on because I was nervous about the wings holding location with rubber bands. Rubber gets weak if you don't change it occasionally and with a strong engine, or tumbling or flying "crazy", I didn't want the wings to go "out of sync".
Bottom wing - fill in the area behind the leading edge with balsa and then sheet it. Drill a hole for a dowel and insert. On the fuse side, you glue a 3/16 ply plate vertically cross fuse and drill a hole to match the wing dowel. Reinforce the edges with triangle stock if you're so inclined. On the trailing edge, you put another ply plate cross fuse (horizontally), build up the wing area with balsa and then sheet with 1/16 ply. Drill holes and thread the fuse plate. Done with the bottom wing - except watch your aileron linkages to make sure they have full throw. I had to cut out the fuse plate a little to get full throws.
Top wing - I filled the area behind the leading edge and in front of the trailing edges with balsa and then sheeted with 1/16" ply. Between the cabane struts, I put a 3/16" ply plate with beveled edges to match the angle of the cabanes. To insure the plate wasn't going anywhere, I pinned the plate on both sides with straight pins and then cut off the ends. I also cut off the leading and trailing edges of the cabane "forms" that normally support the wing (I'm not using rubber bands, so get rid of the weight). I drilled and tapped 4 holes (overkill I know) and then the wing bolts on. For screws, I'm using nylon 10-24s. I'll try to upload some pics later. Any questions?
Old 11-12-2007, 02:26 AM
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Default RE: Herr Pitts Special Kit Build Thread

Thanks for this, drobbs. Will reference this when I do my bolt on wing mod work.

Got the lower right side of the wing spar in place. Elevated the left side of the wing with a square piece of sheeting and also used pins to keep it square and level while I build up the right side of the wing.



Ribs and sheeting in place...



To install the spars and assure good coverage of Titebond II I installed the spars first and centered them in the center groove until they set up. To install the ply dihedral braces, you can get them wet with glue on one side and kinda tip them into their place so you don't scrape off the glue when you place it. Also adding a few drops of glue to the middle area where it's gonna be tight helps get good coverage.



I'm not going to install servos in the wings. Would be a very tight squeeze if at all. Instead, I will install two aileron servos in the fuselage to use the torque rods. To connect to the upper ailerons and assure that there is no differential from the angle at which they'll be connected, I'll install arms the length of the aileron material on the bottom of the ailerons as close to the fuselage as I can to minimize torque effect to control the upper ailerons and equidistant from the point of pivot. I added some sheeting to reinforce the area where I will be cutting grooves in the TE sheeting to accomodate the control rods and arms. Should be relatively concealed when sitting on the ground with regards to aesthetics.



Red Xs show where the sheeting was extended/added as part of this mod...



Pretty exciting when you start running low on material from your kit... means you're getting close to being finished. I see a few solid evenings of putty and sanding ahead in the near future.
somegeek
Old 11-12-2007, 11:52 AM
  #74  
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Default RE: Herr Pitts Special Kit Build Thread

I used an HS-81 in the fuse and I don't think I'll have any issues. Two servos might be overkill + the weight factor. Also, according to your drawing, you're running the control horns under the wings, facing forward and having the connecting rods run through the wings. Is this correct? I made ailerons top and bottom and run the connecting control arms on the top of the bottom wing and the bottom of the upper wing...... which I think is normal. What did I miss?
Old 11-12-2007, 11:59 AM
  #75  
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Default RE: Herr Pitts Special Kit Build Thread

Man - maybe I am thinking too hard on this one... when the lower surface goes down, with the surfaces staggered like this, isn't there a point where the lower surface will be pulling on the upper control surface vs swinging it down further? Guess I am talking about high deflection when I am thinking of this scenario...

somegeek

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