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1/4 scale F9F Panther build

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Old 09-17-2010, 03:59 PM
  #1
jroth
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Default 1/4 scale F9F Panther build

Hello,

I have a group of three and we are about to start a build project of four 114" wing span F9F Panther Jets, we are going to use the "Ziroli" techniques of a crutch, bulkheads, stringers, sheeting and glass. We have group experience over 20 years per builder and a cumulative builds of at least 30 scale planes, so I know it is possible, but it might take a long time to complete.

The thought is to make molds for the tip tanks and the nose of the fuselage, foam core wings and balsa built up fuselage. We have a vacuum system to skin the wings and a vacuum system to form the canopies.

Dave Swarbick in the UK and his friend built and are flying two Panthers of the same size, he wrote two articles in R/C Jet International for the October and December 2009 issues.

I was wondering if anyone in the US has been successful with this build.

Please let me know.

Thanks,
John Roth
Chicago
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Old 10-30-2010, 10:02 AM
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Default RE: 1/4 scale F9F Panther build

Well, here is my first update. We got started about a month later than expected and there are five 114" wingspan quarter scale Ziroli F9F Panthers being built near Chicago!

Joe Felonk, John Abrahamian, Bill Jaworski, Vladimir Hollis / Roman, and me.

Vladimir glued up our 3/4" x 1/4" crutches while others cut bulkheads last week.

Last night John and I (the two Johns) recruited Dennis Degregorio to help sand and fit the 1/8" light plywood bulkheads.

Just for scale, the building table is 4 feet by 8 feet, the crutch overhangs the table and we still have the tail to add on.

Then we laminated F9 and F10 with 1/4" aircraft plywood, as they will support the landing gear.

Does everybody have a HABU band saw?
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Old 10-30-2010, 10:13 AM
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Default RE: 1/4 scale F9F Panther build

Today I started fitting the bulkheads to the crutch; there is a little sanding need to the crutch joints and bulkheads. It is almost starting to look like a plane.
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Old 10-30-2010, 11:35 AM
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Default RE: 1/4 scale F9F Panther build


Outstanding subject John & John & all.....it will have the WOW factor....bigger is better!!!
Say maybe you all can do a demo at next years Jet World Master, huh?
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Old 10-30-2010, 11:41 AM
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Default RE: 1/4 scale F9F Panther build

Hi Roger,

You know I will be in Dayton at the Jet World Masters, I will need more than my 6x12 trailer to haul 5 of these monsters!

See Ya.

John
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Old 10-30-2010, 09:59 PM
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Default RE: 1/4 scale F9F Panther build

We made some progress this evening, the bulkheads are glued to the crutches and the top stringers are glued to the bulkheads.
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Old 10-31-2010, 07:36 AM
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Default RE: 1/4 scale F9F Panther build

Very nice! subscribing for this one. [sm=thumbup.gif]


Enrique
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Old 11-04-2010, 01:25 AM
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Default RE: 1/4 scale F9F Panther build

Since John Roth has started this thread I feel obligated to show some more of the progress of our build. I have some limited experience with plugs and molds and such so I decided that this cool jet will need a couple of slick air intakes to guide air directly into the engine. A dirty install would work BUT one evening I invited myself over to Joe's workshop and had Joe set out the plans so I could get some views of the intakes. It seems the intakes are triangular in shape at the front then rise up on the undersides for clearance around a bulkhead and gear and then form the basic round exit at the engine end. I'd made some similar intakes for another project so I decided to use the same technique and make a plug off of which I can pull enough fiberglass intakes for me and my build buddies. I use plain cheap white Styrofoam and cut a top and side view for each intake. I will be adding 1/8" layer of body filler so I cut it undersized by this amount. In this case a Sawzall with a long stiff tree limb blade was used for the cutting. A band saw or hot wire bow is even better but I used what was handy at the time. I then cut 1/8" light ply into the shapes I want for each end, in this case the triangular shape and a half circle. These give me hard ends which I can sand into. I glue these onto the ends of the soft white foam. I cut large chunks of the foam material away with a knife a rasp and sand the rest into the ply ends until I have a nice transition from the triangle back to the engine area. After sanding for quite a while I had a nice pile of foam snow surrounding myself. So I now have soft white foam intakes with hard end caps on them. I then used Bondo (body filler) to make a nice hard surface which I can sand and paint to a super slick surface. This will leave the completed fiberglass parts with a very smooth slick inner surface. Yes-Bondo is polyester based stuff-it will melt away our finely crafted foam parts. As a barrier I brushed some quick setting epoxy all over the intakes BEFORE the body filler application. Alkyd latex exterior paint could be substituted here. At first the intake with body filler looks awfully rough (see the before photos) but after some shaping with 40 grit floor sanding paper all the rough areas are flattened easily. Next some 80 grit takes off the rest. You will then need to work thru some finer grits and maybe some glazing putty before painting. The filler sands easily when it is cured.In the photos you can tell where a second application of body filler fills in some low spots. If you add more hardener the filler has a reddish hue, which is why some parts of the intake look splotchy. I applied 2 layers of filler to build up roughly a 1/8" hard layer on the plug-you will need to take this into account for your finished part. Warning- mix only a 3-4" circle of body filler at a time. It sets up quickly and I hate wasting material. When the filler is still rubbery you can grate it down with a body filler rasp. If you let it set hard then use the 40 grit. After everything is painted to a satisfactory surface the plug sections are waxed and buffed several times. Fiberglass cloth and resin can then be laid up on the plug and pulled after they cure-leaving you with 2 halves needing joining.

Yes this takes a number of hours to fabricate a good plug for parts but I enjoy the process so the rewards are greater for me as I'm not much of an ARF guy. The intakes appear pretty nice-even the somewhat unfinished state they are in at the moment. I will continue with the fine finishing and painting soon. Thanks Joe for letting me make the big mess!

I'm attaching some photos.

The images with the green checks(tabletop) show the early Styrofoam shapes capped with light ply. I like the photo of it held up with a hand attached and label it "A Major Award!" It's not the leg lamp BUT it's pretty sexy looking.

John A
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Old 11-04-2010, 04:00 AM
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Default RE: 1/4 scale F9F Panther build

Very nice explanation thanks for sharing.
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Old 11-06-2010, 09:53 AM
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Default RE: 1/4 scale F9F Panther build

We spent some time last night adding stringers to the fuselage to make it easier to sheet.

We sheeted the nose of the plane and then we cut it off, added a block of foam, sanded the nose cone to shape and we glassed the nose cone. We now have a mold plug that we can make a "female" mold from.

John also worked on the inlets, they are very smooth and they are ready for paint, waxing and buffing, then we can make some inlet parts.

Thanks again to Dennis for helping all night.
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Old 11-06-2010, 01:48 PM
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Default RE: 1/4 scale F9F Panther build

Hi Everyone,

While you guys are way ahead of me in this build here are some pictures of my progress. One is of the crutch over the plans. I took a pass on the hard wood crutch and used some balsa I had laying around. It will work but it will need more supports to hold it level. The red material is see temp I laid it over the plans and then scored it with an xacto, it then snapped out to give me a template. I only see temped half the bulkheads to save material. there are some hidden advantages to this. Zirolis bulk heads while nicely drawn, are not perfect mirror images one half to the other,these are, provided you do exactly half. The lite ply was then doubled up (quadrupled up for two planes) and nailed together. The see temps of the bulk heads being only half can be more tightly fitted on the plywood and teraced out. When you cut them out once you get two halves that get scabbed together to get one full bulkhead. While see temping a set of plans is alot of work, once you do it you can easily trace the bulkheads as many times as you want.
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Old 11-07-2010, 02:43 PM
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Default RE: 1/4 scale F9F Panther build

Here are a few pictures of my bulkheads one of them all still nailed together and another of them ready to go on the crutch. In the foreground you can see f-9 and f-10 doubled up with aircraft ply along the bottom to take the load of the landing gear and wings. I also snuck over to the A- team build site and snapped a picture of the team members as they were sheeting a fuse and working on a fiberglass nose.
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Old 11-07-2010, 02:46 PM
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Default RE: 1/4 scale F9F Panther build

sorry here they are
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Old 11-07-2010, 03:03 PM
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Default RE: 1/4 scale F9F Panther build

sorry still figuring this out.
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Old 11-07-2010, 04:59 PM
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Default RE: 1/4 scale F9F Panther build

We worked for about 5 hours on Saturday.

John worked on the inlets and laid another layer of glass on the nose plug.

Dennis and I started sheeting the top of the first fuselage. We have used a lot of glue and kicker!

I hope to get one more night of group work this week, I have to take next weekend off.
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Old 11-07-2010, 05:28 PM
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Default RE: 1/4 scale F9F Panther build

maybe
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Old 11-07-2010, 07:39 PM
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Default RE: 1/4 scale F9F Panther build

John,

Good project. I have a yet-to-be-finished Ziroli Panther that I blew up to 80" WS. I hope to get it finished this winter.

Not to be super critical, but your fuselage planks should be longer, narrower, and much tighter fitting. It will make the final sanding and shaping much easier...

Bob
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Old 11-07-2010, 09:46 PM
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Default RE: 1/4 scale F9F Panther build

well I started cutting some foam. I had a 9" thick block laying around doing nothing. I was able to cut 2 wing plan views that I got two airfoils out of each and 3 stab plan views, that I got four airfoils out of each. thats the wings for two planes and hoz. stabs for six airplanes. I don't have any more foam for the other three wings. one set is for Vladimir the rest you other guys can figure out. I also made wing skins and started vacuum bagging the foam cores. The 3/32ndx4"x36" sheets I just taped together with low tac blue tape with out butt gluing or truing the edges. Then I hinged two skins together at the trailing edge with tape. I then swung them open,spread the epoxy on them, inserted the foam core, and stuck them in the vacuum bag. The vacuum pump is set to 6" that is more than enough. any more and you will start crushing the cores. the pump runs constantly and is controlled by a bleed screw. the Gast vacuum pump is very quiet and is designed to run for very long periods of time. some people use vacuum systems that use a tank and switch on and off when the vacuum drops. I don't like them because of the wide range they operate in, up to 6" then down to 2" many times during the process always relaxing and then squeezing again. The blue tape comes off pretty easy after being in the bag for a day. In gaps where the epoxy came thru it sticks a little better, a little heat and the tape comes right off.
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Old 11-08-2010, 07:37 AM
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Default RE: 1/4 scale F9F Panther build

Hi Bob,

I agree with you about the planking, I will try to tighten it up during the next building session.

Good Luck working on your project.

John
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Old 11-08-2010, 09:22 AM
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Default RE: 1/4 scale F9F Panther build

John,

You too! I need to get my maintenance issues from this season (i.e., some re-building and re-painting ) finished up and then its on to finishing the Panther...

Bob
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Old 11-08-2010, 10:16 AM
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Default RE: 1/4 scale F9F Panther build

Anyone coming over tonite to the B team location should bring some 3/32nd sheeting so they can make their hoz. stab skins. 10 sheets per plane. 4' wide x 36' long. Also bring along some low tac blue tape to join the planks of sheeting as per my earlier post.
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Old 11-08-2010, 12:21 PM
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Default RE: 1/4 scale F9F Panther build

Jofunk, when you bagged your wings how do you know you did not introduce any twist into them cause you didn't use the chocks they were cut from? When I bagged mine I made sure to put them back in the chocks and weigh them down to keep the wing true.
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Old 11-09-2010, 01:44 AM
  #23
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Default RE: 1/4 scale F9F Panther build

the only twist in these wings is the wash out that was cut into them.I have bagged like this a hundred times and never had a problem with the type of cores I have sheeted. You could run into a problem with a thin long core like a glider wing and a table that is not flat. but with a thicker more rigid piece of foam on a flat table the bag pulls the sheeting down to the shape of the foam. Before I had a bag I used to sheet wings in the saddles with weights on top. I remember once putting more weight in the middle and the wing coming out like a banana.
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Old 11-09-2010, 09:25 AM
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Default RE: 1/4 scale F9F Panther build

Great job guys! With 3 guys building it will go fast and you will learn from each other.
A few questions:
Did you have some parts laser cut, or is it all hand cut? What engine is in the plan? Are you having some gear custom made too?

Jim
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Old 11-09-2010, 10:08 AM
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Default RE: 1/4 scale F9F Panther build

Hi,

We actually have five guys included in the build and Dennis is helping, but he is not building his own plane.

All of the wood was hand cut.

Dave in the UK who wrote the article for RC Jet International is using a 38 pound thrust engine.

We have not really addressed the gear at this time. The mains are pretty straight forward other than not retracting 90 degrees and the nose gear does not seem too bad. Two of our guys know their way around a machine shop, we will have to wait and see what developes.

Thanks for your interest.

John
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