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Dan's Ziroli P-61 Black Widow

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Dan's Ziroli P-61 Black Widow

Old 12-09-2021, 07:02 PM
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ohnow
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Default Dan's Ziroli P-61 Black Widow

Hello there! Calling all Experts!

So I've acquired this at a swap meet. If you know who built it, please don't mention names publicly. It was love at first site and love blinded me. I'm trying to transition from H9, Saito 1.0 sized warbirds to giant scale....so I bought this I'm considering selling it versus fixing it, or trading it for a more RTF WWII Giant Scale fighter, i.e.; Spitfire, Zero, FW-190, MIG-3, P-38, P-40 a different P-61...maybe a Jug if priced low enough. It would be ideal if they just needed livery before flight. I have lots of questions and concerns. They call it growing "pains" for a reason
  1. I see concerns about the build
    1. Retracts are mounted where I can see through between the wood mounts & side of the fuse
    2. Servo blocks aren't very straight/professional
    3. scrap wood used as support in an area where people would see. After all the rivet and panel details, I wouldn't have expected it
    4. The external, starboard stab rib isn't flush by about 1/8". The adhesive doesn't appear broken, as if the wood expanded/contracted so, they must've built it that way?
    5. Soft balsa blocks are used, with no sealant, with self-tapping wood screws, without CA on the threads to hold the cowl on a gasser. Imo, I would've used metal female bolt retainers in ply. Thoughts?
  2. There seems to be de-lamination in some areas
    1. The starboard rudder will need rebuilt. It's the worst area. It's next to the rib mentioned in 1d but again, the glue joint doesn't seem broken. I don't see signs of liquid damage.
    2. The top of one wing, where the slats raise and lower is warped
    3. The top center section has split from the former
    4. There are a few cracks in the fuse, that I'd guess are from wood expanding/contracting
    5. THIS IS MY BIGGEST CONCERN...one wingtip has the aluminum tube adhered to the fiberglass wing tube. On the other wing, the tube slides out and I don't see signs of roughing it up before it would be glued AND, the fiberglass tube has broken almost entirely loose from the ribs and spars.
    6. For such a major structural component, should I try a quick fix like a really long static mixer, if they make them, to "hopefully" re-glue it?
    7. Do I remove one side of the wings covering, do it right, AND inspect the other joints?
    8. If I see this & other delamination, what's happening that I can't see? So, I probably need to remove the skin of one side of the other wing at a minimum. I haven't done glass skin or rivets/panel lines yet but, I do want to learn. Is there a method of removing skin from one side where I could glue it back when I’m done? Maybe use triangle stock as a shelf to set the cut skin onto and the cuts would coincide with panel lines?
    9. Overall, with 2 gas engines, the weight of the plane, the G-forces and landings, I'm really concerned of the overall structural integrity. Am I being paranoid? I've flown many birds held together by tape, a wing and a prayer but not this scale.
  3. My other BIGGEST CONCERN...I saw the wing failure vid on YouTube and it broke my heart. This model has a couple guide dowels, but I don't see a strong way the wings would be held on. On the wing where the aluminum tube appears to be adhered to the fiberglass tube, there is a tiny hole, maybe 1/8" on the top. I see the same hole on the other wing tube. I slid the wing in and traced where the tiny hole would be and, sure enough, there's a tiny hole in the center section as if a tiny pin is just dropped in. There's no way that's supposed to be the strongest way to hold the wings on a plane this size?? If it's not, what the hole for and more importantly, how do I strongly secure the wings?
  4. Pushing on the wheels, the shocks feel "sticky" or "gummy". These are my first this size. Maybe they need rebuilt, if that's a thing? Maybe they're normal?
  5. The wheels are air filled. They have brass tubes I haven't seen before. Haven't had a chance to lookup what they are. I'm assuming maybe to fill but they slide so it doesn't seem like they would hold air, even if some kind of cap was put on them?
  6. The rear canopy is broken, but I've bought a replacement
  7. There are round, faux panels where some have fallen off. I'm holding one in one of the pics. Are these stickers or, how did they make a circular panel which is cut?
  8. There are "hooks" on the top of the center section, towards the front. What are they for? Going back to build quality, if hooks were needed, IMO, why wouldn't you use to matching I-hooks or J-hooks when you know people at the field are going to be all over this bird? If corners were cut here, where else?
  9. At a quick glance, the servo arms don't appear to be setup mechanically correct. The servos are older.
  10. Looks like there were either mistakes or there was a change in engine based on mounting holes in the firewalls. That's an easy enough fix. I don't see signs of combustion, and I don't see wingtip scuffs, etc. so I don't think it's been flown? Thoughts?
  11. There's some hanger rash, but how couldn't there be on this model Most of it won't be noticed.
  12. The wood panel under the center nose cone has been broken and glued. Probably from handling. Not worried about that other than the pride of how it looks when showing it off.
  13. I haven't tried cycling the retracts yet. Does anyone know the make/model?
  14. For the 12 main mounting bolts, I have 4 nylon with 2 different lengths.
    1. I also have 5 metal at 2 different lengths. I don't know if any of this is right or just what the builder had at the time. I assumed the nylon would be for the center section.
    2. All but 1 bolted in fine. One got stuck to the point it felt like I would cross-thread it if I put more force into it.
    3. It seemed like the shorter bolts would've worked for any mounting so, I'm not sure what lengths I really need and where they should go?
    4. The bolts screwed into wood blocks, which were threaded. I don't see CA to harden the threads. I couldn't find any blind nuts or even epoxied hex nuts. I know threaded blocks is one building method, but for this size/weight model, I would've thought there would be blind nuts or hex nuts and lock washers or the metal female retaining things you install with adhesive and I think screwing them in counter-clockwise. Am I being paranoid?
    5. I don't understand how the nylon bolt got stuck if the threads weren't hardened. Maybe I just couldn't see the blind nut (thus the name ), or maybe the threading stopped.
When loading it in the trailer a guy shared a story of his buddy who has one. His friend said he had 40 cc's on it but, if he had it to do over again, he would've done 50-60 cc. A gentleman at the DLE booth came and looked at it with some engines and based on size, weight, probable CG, he thought 61 CC's could be good. I didn't get the impression he was trying to upsell me, just an honest best guesstimate at the time.

Whether these issues are from heat, age, building techniques, adhesives used, properly mixing adhesive, etc. etc. I'm concerned for the overall structural integrity. Am I being too paranoid?

Again, please do not mention the builders name in any posts. I mean no disrespect at all. I'm experiencing the emotions of buyer's remorse so I'm a little disappointed in myself at not inspecting this thoroughly before buying it. It was just sooooo pretty sitting there....looking for a home.....my home If I keep this, it'll be a several year project, I'm sure. I haven't been able to read other threads yet. There are enough "unique" things to fix on this one, I figure it's worth posting. If I keep it....after I've fixed everything...previous threads on engine sizes, balancing and flying will probably become more of a priority. Can't believe I saw threads back to 2001! An earnest "thank you" for reading all this...and especially for helping.


























Old 12-09-2021, 07:15 PM
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ohnow
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Old 12-09-2021, 07:24 PM
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Old 12-09-2021, 09:25 PM
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Txmustangflyer
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Ok..first those gear supports..they gotta go. Do a goid rebuild on the mounting. The brass tube in the tire is a new one on me, look to Robart for nive replacements. The retracts themselves look solid. The damage to the rudder looks like a bad Hanger rash accident, internet shouldn't be too bad, but save the pieces, cut new wood, using the old as a pattern. It's a thin area so new wood would be better, some if the servo mounts need attention and just a general re-engineer, to avoid sloppy control feel.
overall though, the prognosis should be good. You are right, you got some work ahead, with some planning towards making her healthy she should be a good scale flyer.
Firewall drill holes, patch with dowels and epoxy, sand smooth, and fill the low spots left then when you remount em, use some good blind nuts and waters to avoid crushing the wood.
couple of months of tlc and you'll be very pleased I think. She's not on life support, she's just been a little abused.
Most of that you know..the cracked nose area..I'd use some of this, laminating the wood. Go full length if you can inside the fuselage after doing a repair to the wood itself. It will add strength without adding a bunch of weight..
https://gator-rc.com/deluxe-material...tem-no-dlmbd66.
The nose retract mount should be a full width ply, cut to the shape of the retract with a layup of additional ply as mounting rails. My guess is what you are seeing is the result of a hard landing and subsequent repair there.
if you do that, you could incorporate the servo mounts into that same ply, but you would have to look at how it affects the servos and what they control.
Those futaba's look like they been there a while, my suggestion is a new set of servos just for piece of mind.
If you can source a set of plans or someone who has the same bird, as a reference would be very good.
is the skin fiberglass? Or Monokote/ultrakote over a fully sheeted structure?


the dowel/tube set up on the wing is kind of typical. But, yeah, another set of dowels at the other end as added bit of security ain't a bad thing.

and the tygon....ditch that. Replumb it with Viton. You'll never have to do it again.
hope you get her back in top shape.


Last edited by Txmustangflyer; 12-09-2021 at 09:32 PM.
Old 12-14-2021, 08:40 AM
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Txmustangflyer
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To add to my previous response..I think it was originally intended at 50 to 60 cc..I think...if you can find someone with the plans, it will give you a better idea.
being a complete zirolli it's worth taking the time to repair and resurrect it. If I had the space, I'd make you an offer.

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