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Old 02-04-2010, 03:17 PM
  #272  
samparfitt
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Default RE: ZIROLI P-61 BLACK WIDOW BUILD

Kevin,
I'm not a fast builder but I do like putting in very long hours on a project.
See Post # 215 for the Dbalsa cockpit install.
A mile high seems like 38's would make 'take offs' like a full size plane with a full load of bombs, taking the entire runway to get air born. Seems like 45's would do ya' with no problems. I've added a lot of extra weight with full cockpit, operating cockpit, doors, new ply, rotating landing lites, nav lights, functional cowl flaps, four servos in the tail and everything bolted together so I figured that I needed the 62's.

G-Pete:
Everything is bolted together.
When I bolted the eight bolts to hold the booms to the center wing, I was thinking: if this plane ever crashes, the last thing that will be separated is the booms from the center wing: anything is possible but I don't think those booms are going to be doing any shifting.
That's one of the reasons that I bolted all members together: in case that I've hosed up an alignment, I can loosen the bolts and correct the problem.

I've been thinking of the advantages of all parts glued together:
1. lighter since no hard mounts and large bolts.
2. more scale since no gaps between the booms and center wing and center fuse and no holes where the bolt heads are showing on the wing surface.
Advantages of a bolted assembly:
1. Ease of adjustments if alignment is incorrect.
2. Much easier to repair a part should you try flying below zero altitude.
3. Much easier to detail the plane: with all the panel lines and rivets that I'll be adding, holding each part and easily rotating it to detail it will be much easier to do.
4. I can build it in the basement without worrying about if it will pass around the 'L' at the top of the steps.

==========================

Assembly of booms, fins and center wing (cont)

After securing the booms to the center wing, the next step was to epoxy the transition piece of ply NS-1 that is between the horizontal stab and the vertical fins. I used small pieces of balsa and epoxied NS-1 to the fins only: this all done while the booms were bolted to the center wing and the stab bolted to the fins as I want to insure everything stays in alignment. Later, I'll remove the stab and add more epoxy to NS-1.
After NS-1 was dry, I then removed the clamps holding the stab/fin assembly from the booms; added lots of epoxy to all common surfaces and clamped the stab/fin assembly back onto the booms.
After that dried, I then began installing the stringers to the top half of the booms.
I noticed that, once I cut out the main gear doors, there's not a lot of 'boom' surface between the gear opening and the center wing so I cut some aircraft 1/8" thick ply for each side of each boom between the N-5 (former that butts against the TE of the wing and also the back edge of the gear door) and N-6.
I cut paper templates to get the exact shape: the inside ply are about 2" wide and the outside ones are about 3" wide. The outer wing support plys only go back past N-5 by about 1.5". Thinking ahead, I would have made these longer and wider to extend to N-6 for additional support.
I remember reading about a pilot that had his Ziroli P-38 break at this location so I thought I'd be 'safe versus sorry', for not adding this (a lot easier now than later!).
I'm also concerned about glue strength along the rear of the booms so I'm using epoxy on the stringers as well as the top sheeting.

pic 1/2:
Epoxied small balsa pieces between NS-1 and the fins.
No glue between NS-1 and the stab since they are bolted on.

pic 3-6:
First, I took the stab/fin assembly off, epoxied all the common surfaces and clamped the stab/fin assembly back on to the booms. The bottom ply hinge for the rudder has only been dry fitted, thus far and now was epoxied, as this hinge is the only one that goes into the boom formers (the other two ply hinges are attached to the fin).

pic 7-9:
The center wing formers that hold the sheeting for the booms was glued to the center wing with 1/16" thick pieces of balsa to provide a gap between the wing and the booms.


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