RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Engines (cont)

pic 1-2:
ARGGG: I forgot that I was going to rotate the engines about 20 degrees.
Since the fire wall is epoxied in place, rotating the engine, now, would probably leave a large hole in the fire wall and possibly where a bolt needs to be. That fire wall is pretty small and there's not a whole lot of room for rotation.
I always like to take a picture as it usually shows errors that I can miss but the engine appears to be 0 degree thrust forward and the down thrust looks good.
After looking at the engine, the carb is going to stick out some; at least with a vertical engine, the carb hole is lower on the cowl. The engine is so close to the firewall that there also is no room for the 90 degree carb extension: bummer.

pic 3:
These are all the lite ply parts that I re-cut using aircraft ply (and these are just for the booms!).

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Started gluing the stringers onto the left boom.
As with the center fuse, I numbers each slot on each former to insure I had all slots 'accounted for'.
Tonight, I glued in seven stringers using carpenters glue.
The framing around the doors plus the edges of the doors have spruce stringers.
I used epoxy and applied it with a toothpick to insure the doors edges don't bond with the door frame and each other.
As with the center fuse, the left over stringer from the previous slot was CA'ed to another stringer (with a scrap piece of stringer sistered over the butt end) to use 100% of each stringer.

pic 1:
Door formers tacked CA'ed to boom formers N-3 and N-5.
This time I used a 1/16" spacer to insure enough of a gap around the doors.

pic 2:
Seven stringers glued in.
The crutch was placed and weighted on the risers to insure the fuse remains straight.
I alternated each side, gluing 'mirror' stringers onto the formers to reduce any warping of the fuse.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Sam is there room to add another firewall on the inside? If so then you could rotate the engine with no worry of holes not lining up or weaking the fire wall. Just a thought.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Randy,
I epoxied that fire wall with triangular stock behind the fire wall so there would be a lot of damage done in trying to remove the existing fire wall. Things worked out for the best as any rotation would have moved the carb higher so the hole for that would show on the cowl. This way, there will be some big holes for the engine head and muffler exhaust but it'll all be at the bottom of the cowl.
Thanks for thinking about it.

================
Booms (cont)

Planking:
This morning, I started planking the left boom using 1/8" thick by 4" by 4' long sheets.
In order to insure that the booms stays straight, no additional stringers are added to the top of the boom as this allows the crutch to sit on all my risers: I can thus put weights to hold the crutch in place and add planking to get a ridged, straight boom. Once the bottom is planked, the boom will then be ridged enough to remove it from the risers and then finish up the top.
Planking starts along the bottom, center of the boom (boom upside down) and works out along each side, doing both sides at once to remove the possibility of warping the boom, laterally.
I used carpenters glue for all planking.
I put water on the top surfaces of the planking to get better bending.
I couldn't use the micro wave on them as they are too long.
I put tick marks on the planking at each former location so I can put glue, accurately, on the sheeting as well as on the fuse structure.

pic 1:
Bottom center planked using a 1 3/4" wide piece which goes from the front to N-8.
After N-8, there are compound curves, plus the bottom back ends as a ridge.

pic 2/3:
Two sides planks 1 1/4" wide and tapered at the tail were next glued to the boom.
The back of the gear doors has a change of compound curves so the taper was started there and went to a point to N-8.

pic 4/5:
The next two planks are from the back of the gear door to the last former (N-12).
I could use about a 3" wide piece as there are no compound curves.
This planking also extents past the break in planking at N-8, thus giving more strength to the sheeting (with overlapping sheeting).

pic 6-8:
A 'mostly 4" wide' piece of planking was glued from the back of the door to the front of the boom.
Before gluing on the sheeting, I had to add some 1/8" thick ply along the front for the other cowl hard points.
Planking is one of the few places were you don't have to be neat as, in the end, everything gets sanded and "bondo'ed". Even with carpenters glue, speed is more important than neatness as even carpenters glue starts hardening in about twenty minutes.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Planking.
The other bottom side was done exactly the same as the previous side.
The bottom is now done for the left boom.
Tomorrow, I'll work on the right boom.

pic 1-3:
Lots of pins to hold the planking while the glue dries.

pic 4-6:
Even with only half the planking done, the boom is extremely ridged.
The risers kept the boom straight horizontally and alternating planking kept the boom perfectly straight, laterally.
Before the top planking can be done, I'll have to mount the booms to the center wing as part of the planking will be on the wing where formers (like the doors) will be butted against the booms formers, planked and then cut along the seam to release the wing from the boom.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Right boom (cont)
About a 1/2" of waste was cut off the front of the engine support ply and the fire wall and triangular blocking was epoxied to the boom.
Spruce stringers were used to frame up the gear doors.
Some 1/16" thick balsa was used as a spacer between the door edges and the frame.
Most of the stringers were glued to the bottom of the boom.

pic 1:
The band saw was used to cut about a 1/2" off the front.

pic 2:
I use this rough metal sanding stick from BVM a lot on removing waste quickly: ie, enlarging stringer notches in ply formers.

pic 3-5:
Fire wall epoxied to boom.
The right side gets 2 degree down and 2 degrees right thrust.

pic 6:
1/16" thick balsa spacers keep the door edges from the boom framing.

pic 7:
most of the stringers glued to the bottom of the boom.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Right boom (cont)

Planking:
Final for tonight, I started planking the right boom.
As with the left boom, the right boom is weighted on the risers as the bottom planking is done, starting at the center and doing both sides at the same time.
The center 1 3/4" wide strip first down the middle and then the two 1 1/4" wide strips on each side of the center. Sticking the straight pins at about a 10 degree angle, I can secure the newest inside planking edge to the previously dried plank when there's no stringers close enough to hold the planking to the formers.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

right boom (cont)

Planking:
Today, I put the last sheeting on both sides of the boom to complete the planking for the bottom half of the boom.
As with the left boom, two wide (varied from 3" to 4" wide) sheets of 1/8" thick balsa was glued to last night's planking. The break between the two sheets of balsa was at the back of the gear doors.

pic 1-3:
Final bottom sheeting.

pic 4:
This plane has used up about half a gallon of my carpenters glue, which makes it pretty cheap as a gallon is about 12 bucks.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

The booms were taken out to the shop and the bottom sheeting was hand sanded.

Vertical fins.
I started on the vertical fins.
Having the hard mounts that attach to the horizontal stab positioned correctly is critical.
The hard mounts are sandwiched between R-2 and R-3.
There's also a horizontal ply rib (NS-1) that is sandwiched between the hard mounts and the end of the horizontal stab.
I first drilled holes in the hard mounts and ply rib NS-1 and insured all is aligned with the bolts and blind nuts in the horizontal stab. Everything exactly matched the plans so I used the plans to align the hard mounts between R-2 and R-3 and epoxied this assembly together (there is a left and right assembly).
Next, the vertical stab N-13 was clamped to the boom and R-1 was epoxied to N-13 while laying on the boom formers to insure all is aligned (later, after it dried, I put this assembly on the plans and everything is exactly as it should be).
The vertical stab N-13 was then laid horizontally and the 'R-2/3/hard mount' assembly was epoxied to N-13 using a 'square' to insure a 90 degree angle.
Next R-4 was then epoxied the same way.

pic 1:
Right booms formers all perfectly aligned.

pic 2-6:
Booms sanded in the shop.

pic 7:
Vertical fin plans.

pic 8:
Hard mounts and ply NS-1 drilled for bolts and epoxied to R-2.

pic 9:
R-3 then epoxied to R-2 and hard mounts.

pic 10/11:
R-1 epoxied to N-13 while dry fitted to the booms.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Vertical fins (cont)

pic 1:
R-2/3 assembly epoxied to N-13.

pic 2:
R-4 epoxied to N-13.
Vertical fins were labeled 'left' and 'right'.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Well Sam I just can't keep up :)

In the time you test fit the engines, set the gear, built the booms and started the horizontal stabs, I was finally able to paint the tail numbers -

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Yo David,
That's one impressive plane.
You know you're good when we have to look at the picture for a few minutes to see if it's 'full size' or a model.

===========================================
Booms (cont)

Vertical fins (cont)

Since the horizontal stab is mounted on the vertical fins, I'm using epoxy on all the joints.
The fins are constructed 'dry fitted' only to the booms since there's a 'catch 22': If I build the fins in place on the booms and the booms don't exactly lay horizontal to the wing, the fins may look like an SR-71.
But, I can't also mount the booms to the wing because the horizontal stab is first connected to the fins to insure that the booms are parallel to each other (I'm going to have to 'sleep' on this problem!).
Building the fin 'dry fitted' to the booms also allows me to insure that R-2/3 (where the horizontal stab is attached) is at zero angle to the crutch (used my digital protractor for this).
There are three ply hinges used to hold each rudder to the fin where a 1/16" wire is used to hold the rudder to the ply hinges.
I also sanded the boom hard wooden mounts to size and epoxied them into the booms. These fit between the inner and outer wing support plys.

pic 1:
One of the ply hinges is epoxied into a cut out recess in the top tip block of the fin.

pic 2-5:
Tip blocks, LE and side braces epoxied to the fin, dry fitted to the booms so I can visually check to see that all is 'squared away'.

pic 6:
Digital protractor used to check zero angle on the blocks assembly that will screw to the horizontal stab.
0.1 and 0.2 off on each boom to R-2 rib (close enough for me!).

pic 7:
Fins now removed from booms so sheeting can be done.

pic 8/9:
Sheeting the outside half of the fin from the brace to the LE.

pic 10:
The first sheeting cut was used as a template to make more copies of the sheeting.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

pic 1/2:
Hard mounts for the center wing were epoxied in their respective positions.

pic 3:
Picked up my light olive green paint from HD (already have the gray).
Asked for two quarts and they said they are the same price as a gallon (3rd color down on chart).
I always get the exterior grade, 100% acrylic.
I got some empty quart cans so, after painting the plane, I can pour the rest in individual small cans as paint seems to always go bad when left in a half full can.

pic 4:
I stole this picture somewhere off the web and I like the green with the invasion strips.
This will be easier for me to see especially on those dark cloudy days!

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

pic 1:
Last thing for the night was to sheet the rest of the outsides of the fins.
I almost missed that the fin sheeting overlaps N-13 and is curved (hinge gap covers).
I checked my books and, sure enough, one can see the curved overlap on the fin to the rudder.
I made a paper template to cut out each curved overlap.
I then sanded the inside edge of the curve to give a little extra room for the LE of the rudder.
The balsa grain is cut vertically so the fin should be pretty resistant to flexing.
The bottom rib R-1 is 1/4" thick so I covered half of the thickness with the sheeting so I can glue the booms sheeting to the fin rib for extra strength.
I'll have to install servo trays and covers on the inside of the fins before sheeting those areas.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Sam:

That is MY Borrowed Time, whose picture you stole off the web. Not to mention the Fw in the background.

And the penalty for such thievery is you have to come to my Multi-Fly in September and fly with me ;) !

I agree, it's a beautiful color scheme, and highly visible on even an overcast day, but I can't take credit for it. I bought the plane from Bill Fuoiri.


mt

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Kram,
Iowa looks to be about the same distance as Fond du lac so, depending on what's going on then, I may show up.

=============
Got distracted the last few days doing federal income taxes and fixing my truck heater fan that stopped working.
(not good when it's 20 degrees outside!)

============
Booms (cont)

I needed some more aluminum 'L' servo mounting brackets so I cut up the remaining 'L' channel and made a bunch more.
On getting the fins perfectly vertical, I figure that I can dry fit the fins to the booms and then screw on the horizontal stab to the fins, measure that distance, transfer the distance to the two fire walls, secure a stick to the fire walls to hold the front, then put the center wing on and drill the mounted holes and secure the booms to the wing: I'll then be able to glue the fins onto the booms insuring that they are vertical.

pic 1:
Cut/drilled/tapped for 4X40 button head screws a bunch of aluminum servo mounting brackets.

pic 2:
Where I'll be putting the HS-645's in the fins to control the rudders.

pic 3:
Table cleared for the booms to eventually be secured to the center wing and horizontal stab.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

Vertical Fins (cont)
The servo mounts were epoxied into the fins and then the inner side of the fins were sheeted.
I used some 1/4" thick balsa (each end) and 1/8" thick ply for the servo mounts.
There are two ply ribs (NS-1) that is sandwiched between the fins and horizontal stab.
NS-1 will be epoxied to the outside sheeting of the fins after the fins are sheeted.
There's a gap between NS-1 and the fin which will be filled with balsa filler and bondo.

pic 1:
!/4" balsa and 1/8" ply for the servo mounts epoxied in the fins.

pic 2/3:
Sheeting from LE to the center brace epoxied in place.

pic 4:
Sheeting from TE to the center brace epoxied in place.
As with the outside sheeting, a curved TE was first cut on the sheeting and an angle was sanded along the inside edge.

pic 5:
The fins were taken out to the shop and sanded and the access holes for holding the horizontal stab to the fins were enlarged for the bolt heads.

================================
Assembly of booms, fins and center wing.

Sequence of alignment:
1. Booms were first loosely assembled on the table, fins clamped to the booms, a bar clamp placed under the bottom rear of the booms and the front of the booms placed on risers and horizontal stab loosely screwed to the fins.
2. Distance between booms centers at horizontal stab measured (H=30 1/4").
3. left boom fin adjusted for vertical.
4. square used to get line on table from the back of the fin to the back of the table (B) and to the side of the table (S).
5. the distance B was transferred to the right fin (B') to insure both booms are aligned with each other at the rear.
6. A square was used to align the right fin, vertically.
The bar clamp and the bolts that hold the stab to the fins were used for this adjustment.
7. Distance S was transferred to the front of the left boom (S') from the side of the table and aligned to the center of the fire wall.
8. A 1/4" thick ply was cut 36" long and two center marks placed on this spacer stick 30 1/4" (H') apart to match the vertical fin distance. Two tick marks were put on the spacer stick where the engine mounting plate bolts are. Holes were drilled at the tick marks and the spacer stick was bolted to the booms fire walls.
The booms are now parallel to each other.
9. Re-checked fins vertical alignment and distances H, B, B', S and S'.
10: adjust center wing on the booms.

pic 6/7:
Left fin adjusted to be vertical.

pic 8:
Vertical line from left fin marked on table and distance B measured to back of table and to side (S) of table.

pic 9:
On right side rear, distance S' put on table and back of right fin aligned with this distance.

pic 10/11:
Right fin adjusted to be vertical.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Assembly of booms, fins and center wing (cont)

Presently, all this is dry fitted.
No need to check zero angle on the horizontal stab since this was done while the fins were constructed while they were dry fitted to the booms.

pic 1:
Large bar clamp to hold back of booms.

pic 2:
Left boom front center adjusted distance S' from side of table.

pic 3:
With the spacer stick on the fire walls, this now insures that the booms are parallel to each other and the horizontal stab is perpendicular to the booms.

pic 4:
One spot on left boom needs sanding for proper center wing alignment.

pic 5:
Center wing now sitting flush on the booms.
Everything will be double/triple checked.


pic 6-8:
The dry fit looks good.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Assembly of booms, fins and center wing (cont)

First I bolted the center wing to the booms.
I'll do the fins last as this insures the fins will be perfectly vertical.
Since drilling holes creates movement, I first drilled (3/16" drill)/tapped (1/4"X20) the left front booms inner hole and secured with a bolt, then the right front booms inner hole (I checked for alignment before proceeding) and secured with a bolt. The booms are partial secure now, so I can drill/tap both the left back booms outer hole and the right back booms outer hole (Again, I checked for alignment before proceeding). After these four holes were done, I could then drill/tap the remaining four holes, at once. Of course, all previous bolts have to be removed to tap as well as drill out the larger 1/4" hole in the center wing mount.

pic 1:
First, I drilled/tapped (1/4"X20 hex head bolts from ACE hardware) the left front booms inner hole.

pic 2:
After securing the left front booms inner hole with a bolt, I then drilled/tapped the right front booms inner hole.

pic 3:
After securing the previous two holes with bolts, I could then drill/tap the diagonal opposite holes (and finally the last 4 remaining holes).

pic 4:
A 1/4" bit to enlarge the center wing's hard mounts.

pic 5-9:
Dry fit of most of the parts.
Probably half done now but at least it's the hardest part done!

pic 10:
Come spring (and warmer weather), I'll have two planes to prime/paint.

pic 11:
Once the P-61 reaches the primer step, I'll probably go back to working on the comparf F4U.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Sam, OMG you build like a crazy person...Please take that as a compliment, as your plane progresses I am amazed at how fast you have come to this point...BTW...I do enjoy the trains, as I used to do the same thing, build airplane models and run trains...Do you plan on putting a "detailed" cockpit in and does someone make one...Also, would you feel that the G-38 would fly this bird in the rarified air of Denver...I fly at about 5400 ft, at the club field...I am following this thread in hopes of building one myself...Best of luck and please keep up the thread and the pics...Thanks for reading...Kevin Dube' in Denver, Colorado

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Question:
Sam, do you plan to glue the center and the horizontal stabilizer to the booms? The reason I ask, you have pretty large (weight) engines and you did not mentioned you counter rotate one of them. I'm concerned your airplane goes slightly out of square and flies not that nice anymore.

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.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Booms (cont)

With the booms secured to the stab and center wing, the stringers were epoxied to the top half of the booms.
First, I cut four 4' (or so) extension wire and routed them through the booms for rudders/elevators.
I put tape on two of the wires so I know 'which wire is which'.

pic 1-3:
Here's the extra re-enforcement ply epoxied between N-5 and N-6.
These were sistered to the outer wing support plys.

pic 4:
I just realized those large bolt holes are going to be very visible.
I'll probably cut some thin ply in about a 3/4" circle and screw them over the holes.
There's also the hole to hold the outer wings to the center wing but that shouldn't be too big.
Many posts ago, I wasn't sure if this bolt would be put in from the top or bottom but, now that I see that the bulk of the boom is on the bottom (and covers up access from the bottom), I can now drill/tap a hole for the wing bolts.

pic 5-8:
After seeing the stringers butt ending into the fin sheeting is another reason why I'm using epoxy to get as much strength as possible for the fins.
Initially, I was going to secure the extension wires inside the booms but decided not to as they are light and if I should need to fish new ones in there, the old ones need to be 'free floating' so they can be easily removed.

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Hey there Sam, Many thanks for the response and the input and direction...Are you going with pilot and crew and which ones...Kevin Dube' in WINDY Denver

RE: ZIROLI P-61 BLACK WIDOW BUILD
 

Kevin,
I'll be using Vailly's pilots.

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

Booms (cont)

I started planking the top half of the left boom.
I used some left over 1/8" thick sheeting from some part of planking the P-61 and first did the left front of the left boom. I then made a paper template and did the small section above the fire wall and ends on the wing.
I then used a 4" wide by about 4' long to cover about half of the back of the boom up to the wing.
I did a lot measuring so I could used this one long sheet as I figure that no butt joints will make a stronger boom tail. Epoxy used to get maximum strength.

pic 1/2:
Left front of left boom covered.
I was going to remove the wing to get the wing contour but that was too much work so I used one of the left over thin ply outer wing supports to make the wing contour.

pic 3/4:
Paper template first made and then the sheeting epoxied on the front of the center wing.
Care had to be taken as no epoxy gets on the boom since this section is only on the center wing.

pic 5-7:
The one long sheet epoxied to the back top of the left boom.
Water run over the sheeting to help it form around the formers.
Rib R-1 is 1/4" thick and I, previously, only ran the fin sheeting half way across the width of this rib.
I could then use the 1/8" thick 4' long sheeting and epoxy it the the bottom half of this rib to give me maximum strength to holding the fin. I also left the fin sheeting extra long that ran in front of the one vertical cross brace. This allowed the 4' long sheeting to overlap this fin sheeting for additional fin support.