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Old Feb 14, 2015, 06:24 PM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
Build Log
RBC Duo YAK-23 & P-80

My love for the Lockheed P-80 Shooting Star, began early in life. So early in fact, it was the first model airplane I ever built. At 4yrs old, I recognized the plastic model inside the plastic bag, at the grocery store. 25cents was a lot of money to an old quahog family in Apponaug. My grandmother asked me if I thought I could build it, with a resounding yes, she parted with the quarter and a penny for tax, for the 1/72 scale P-80. We always kept a tube of Duco cement in the house, so I was set. It sat in a china closet for 45yrs. I'll take a few pics when I start the P-80.

Several P-80's came into my life, I remember a Berkeley model. But, when entering "E" RC in the 90's, the P-80 rekindled for EDF. The Kyosho T-33 was ugly as sin. Then the Offshore design cam into being. Had to build it. And it was originally designed by Heino Dittmar. It actually used a double in-line fan by I believe to be Ralf Dvorak. Correct me if I'm wrong on this.

RBC (Rob Bulk)acquired the design and redesigned it for built up wings and a mini-fan with the help of Ton v Munsteren.I wanted this as a winter project for this year. Financially I have had a very limited budget for modeling, in recent years. But A local friend and his son had an RBC YAK-23, not built. I offered my services and and I finally have the P-80.

I will be building both at the same time, with the Yak taking the lead. The YAK had a bulkhead sheet missing. But an email to Rob, and he is sending the required CNC cut parts. I would check the mail, but we are in a snow strom right now.
The original threads: http://www.rcgroups.com/forums/showt...light=RBC+P+80 http://www.rcgroups.com/forums/showt...ghlight=YAK+23

These are the only build threads of the two. So, I felt they deserved another. For those not familiar with RBC, they have great flyable balsa designs. CNC cutting. And quite accurate fit. But they are not for the inexperienced. These will be my 6th and 7th RBC work.

Both will use the WeMoTec Mini-Fan EVO. The YAK with an HET 2W-22 on 4s-2200. And the P-80 has the HET 3W25 on 6s-2200. Exhaust and intake areas prohibit the high blade count fans like the CS. I prefer WeMo anyway.

P-80 43-5/16" WS, 39-3/8" LOA, 32oz lightest weight.

YAK-23 40-15/16WS, LOA not known yet, same weight as P-80.

I can see the Yak coming in around 30-35oz, but the P-80 is much more airframe and ply parts. But I may be able to achieve 35oz with careful building and finishing. Speaking of finishing, I like to use a combination of glassing and silk-span and lacquer. Some areas just don't require glassing. and an ounce or two can be saved in these areas.

Compared to other RBC kits, I found the wood in these kits to be heavier than previous kits. Since I'm not performing any kind of review, I repalced some wood, for the wing sheeting, with bargain contest grade from National balsa. And some ply parts are well sanded to lighten them, except were the strength is required.

I like to always start with the wings. I hate wings! First the wing skins, using the tape and alphatic resin method and weighting them down to cure. Hevier wood was used for bottom skins. And all skins are marked as to their orientation, on the inside surface. Outside surfaces are pre-sanded smooth, inside just true.

TIP: Mix a little line chalk with the resin, it sands easier. And I like the Gorrilla white carpenters glue. Fast drying.

One note, not many servo out there that can fit in the wing. Plans call for 9gr servos. Smallest servo I could find was 10.5mm thick. You need a servo that is 10mm or less. The only thing I could do was extend the ailerons in-board two rib bays, to accept the HS-5055(11.6mm)servos supplied by my friend. I thought of strip ail, but even where the spur would enter the aileron, it would only allow thin MW, and cause flex.

Here's pics of the YAK wing, in progress. And I'll be up-dating regularly.

Fuzz
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Old Feb 14, 2015, 11:36 PM
Pro Horder
turbonut's Avatar
upland CA
Joined Dec 2004
7,903 Posts
I love the smell of balsa in the morning....Watching
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Old Feb 15, 2015, 12:07 AM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
Hi Scott! 1am here on the right coast, and smelling more wood and CA. Just did the right wing panels top sheet. Tomorrow I can start on the P-80 wing. I almost opted for the RBC Skyray. Maybe I can talk another modeler into an RBC build, in exchange for covering the cost of the Skyray. Maybe next winter.

I would like my next build to be the John Bell F-80. A big, light 70mm stick build @ 203%. About 52"WS with electric retracts/flaps.

Fuzz
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Old Feb 15, 2015, 07:14 AM
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Larry Dudeck's Avatar
Williamsville, NY, USA
Joined Sep 2000
4,539 Posts
St. Martin,

I'll be watching this one. While not a Yak fan, the P80 is a gem, bringing many fond memories of my T33 (Ed Waldrep plans).

Keep the pics coming, it just might make me want to build something.

Edit: btw, are these kits till available?
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Old Feb 15, 2015, 08:51 AM
EDF Jet Jam 2015 , May 28-31
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
7,015 Posts
Nice Fuzz!
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Old Feb 15, 2015, 09:05 AM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
Hi Larry, the P-80 is dis-continued by RBC. They are developing a composite version. But the kit for both the YAK and P-80 are available from fan jet USA. http://shop.rc-electric-jets.com/70-MM-EDF-JETS_c2.htm I don't believe it was ever a big seller. Old time construction and a lot of it. I'll bet there are a lot of RBC kits out there, never built. Sort of like Guillows.

Hi Kevin, thanx and welcome all!

I'm currently exploring other options for the P-80's ail linkage. The wing is about 1mm thicker than the YAK's. But still to thin. The only servos I have are old GWS nano's that are from 1996 era. They work great, but for how much longer. These fit easy.

Fuzz
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Old Feb 15, 2015, 11:07 AM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
I prefer to cut the ailerons free after glassing. The TE is very thin and I want to preserve the shape and mating of the surfaces, later.

It's important to remember to transfer the aileron outline and the bulkhead notches, before the top sheeting. Also something to thread the servo leads. the plans call for gluing the servos to the bottom sheet. Sealed in the wing. I prefer access. So hatches/mounts were made from 1/16 ply.
A nicely shaped wing. The early YAK series take some getting used to. I like the shape of the vertical on the YAK-15. The RBC is 90mm tho.

Fuzz
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Old Feb 15, 2015, 12:02 PM
Registered User
United States, RI, Coventry
Joined Jun 2014
5 Posts
Hi Fuzz

Wing looks great, much nicer than I could have done. Its great to watch a master at work. Thanks for posting the pics. I look forward to watching the thread progress.

Tim
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Old Feb 15, 2015, 12:44 PM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
Hi Tim! Nice weather, eh? So far no big problems with the build. I'm still thinking the P-80's ailerons through. I may have to go the same route. It's better to have larger ailerons and less throw, than the opposite. Not going to be in a scale contest anyhow.

Fuzz
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Old Feb 15, 2015, 04:58 PM
Da' Cajun
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Lake Charles, Louisiana
Joined Jun 2009
3,037 Posts
Quote:
Originally Posted by St. Martin View Post
......................I would check the mail, but we are in a snow strom right now....................................
Fuzz
Hmmmmm,
We had a great day at the field yesterday.
Low 70's, light to mild winds. Lot's o' sunshine.

You could enjoy all these cool planes if you'd move down South Fuzz.




Watching this build is gonna really push up the P-80 up a couple notches in my build queue.

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Old Feb 15, 2015, 05:33 PM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
Quote:
Originally Posted by Boogie_ View Post
Hmmmmm,
We had a great day at the field yesterday.
Low 70's, light to mild winds. Lot's o' sunshine.

You could enjoy all these cool planes if you'd move down South Fuzz.

Watching this build is gonna really push up the P-80 up a couple notches in my build queue.

Oh...shut-up!

I still want to do the John Bell, Julian. 203% for the correct areas for the CS 10. 200% for the mini pro or EVO/ HET. Plus that laminar flow airfoil is interesting.

Fuzz
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Old Feb 16, 2015, 01:58 PM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
12,669 Posts
P-80 wing

I originally wanted to keep this thread as a simple build, without going into much detail. But, as usual, I get PM's from a few modelers, that either have failed with an RBC or just did not want to attempt the build. But this applies to many builds, and not just RBC. So, for the benefit of those who want to keep trying, I'll get into detail.


The reasons why an airplane does not fly, can be many. Or..simple..huh? One reason for an RBC design not flying correctly, is not building the wing correctly. RBC uses a semi- symmetrical airfoil. I developed a procedure to build the wing. I guess I'll call it my 3-point roll system.

I found it works well, to keep the curved bottom surface of the airfoil, intact. The three points are (1) spar, (2) trailing edge, (3) leading edge. Each area must be done flat on the building surface to achieve a true wing, according to design. But, if the bottom surface has a curved chord, how?

Lets take the P-80 wing skins first. The layout of the skin segments are wrong, in my opinion. The YAK's were correct. The plans show the P-80's TE skin to be an end grain. This does not help keep the TE strait. So the LE segment is in line with the LE and the TE segment is in line with the TE. This requires a triangular section in the middle. The skins are trimmed to match the plans with a slight over-size by 3/16" @ the LE. This because of the airfoil curve, which is longer than the plan top view. Taping them together, folding them back, fill the gap with white glue. Lay flat, wipe excess, and layer each skin with wax paper and weighted down. Leave 12hrs. Then sand the outside surface smooth with a flat sanding tool.

Be sure to establish what skin goes where.( I save the hardest sheets for the TE segments to keep the TE hard and true, and there is not much curve there)

Extend the spar and rib positions on the plan with a strait edge and pencil. Position the bottom skin on the plan(trailing edge of skin matching the trailing edge on the plans) and pin just aft of the spar location from the root to the tip. Transfer the spar and rib locations on the wing skin with the strait edge and pencil. ( I make my skins over-sized from root to tip also. About 1/4". Split the diff when positioning the skin)

Step 1 Spar

Start by assembling ribs #2-#5 to the spar, with NO cement. (My spar required a few passes with a flat jewelers file to receive the rib properly, depth wise) Position the spar and ribs in thier proper place on the skin. My assembly was slightly larger than the skin marks, span-wise. Just split the diff. When your satisfied with the position, Pin the spar to the skin.

Line up each rib with their locations(the LE & TE of the rib will be elevated) Using thin CA, tack the rib/spar joint lightly(tack) and tak to the skin. Move on to all the ribs. Install #1 & #6 ribs. then finish CA the spar only.

Step 2

Pin down the TE about 1" from the skin edge. Remove pins fro spar/ribs. Using a long scrap of 1/4"sq scrap, position the tool under the front part of the wing skin, till the rear of the ribs are in contact with the skin evenly. CA the ribs in their proper position.

Cement the 1/16x3/8" TE flush with the rib ends.(disregard the pics on the CD. They show tapering the bottom skin to receive the top skin. This is the old Offshore method. The new plans show a laminated TE See the side view of rib #5 on plans)

Aileron framing: Transfer the hinge-line and separation line to the inside of the skin.(The separation line is 90deq to the hinge line) Take note of your servo thickness. I had to enlarge the aileron inboard by 1". I stripped off some 3/16" sheet firm balsa for the spars. Notch the ribs to be 1/2" cut, plus, the thickness of a T-pin, to recieve the spars. Make a clean vertical cut with a new single edge. Clean the skin of glue by scraping. The TE spar is separated with a T-pin, as is the separation gap. This allows easier cutting free of the ail later. The two extra sub-ribs are 3/32" sht. Note the fill for the aileron horn area.

I preshaped my spars before installing. Leaving just a little to sand flush, later. After all parts are CA'd, cover the top of the ribs with scotch tape to protect them. (good tip from RBC, I usually use masking tape. Scotch is better)

Sand flush the parts till everything is flush and smooth and is tapered like it was before you built the ail.

Step 3

Un-pin the wing, and prop up the rear of the wing to lower the rib tps to rest flush on the board. Pin the skins near the LE. Ca the ribs in place. You may need a long piece of scrap to slide under the wing skin, pushing the skin firmly against the rib. Use a strait edge to make sure the rib tips are in line. Trim if necc.

Add the false LE. I precut mine to reduce sanding. Use scotch tape to protect the ribs before truing the FLE to the ribs. Trim the skins to the frame. Decide if you are going to perm mount the sevos. I elected to make hatches from 1/16AC ply. Line everything up 90deg to the hinge line. I also made rolled paper tubes for servo wire installation. Not required on the YAK, due to only two ribs involved.

So, I guess thats the 3 point roll But, you should have a true strait, non wavy structure. With the proper airfoil.

Prepare the wash-out jigs. If you familiar with using wash-out, you used to having the thick end out at the tips. DON"T DO IT! It will have double the wash-out. The thick end goes near the root. Tack glue it to the bottom skin, according to plan position. The wing should sit flush at the spar, at the root. The tip rib should be flush forward of the spar. Pin wing in position.

Sand the top skin TE, to butt up flush with the 1/16x3/8" TE. I used carpenters glue on the ribs and spars. Thick CA on the ail spars, rear of ribs, and FLE. Then Weight down the skin with a strait edge and sand bag By the time I wrote all this, the skins are dry. I'll be back later with the ready to glass panels.

Fuzz
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Old Feb 16, 2015, 04:20 PM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
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LE, wingtips, attached and panels sanded. I forgotto mention, before attaching the top wing skin, you must transfer the aileron gap to the bottom sheeting. Then mark with a ultra fine Sharpie. After sanding, a pin is used to transfer the lines to the top sheet.

The YAK will be in the red top, white bottom aerobatic team. I'm favoring making the P-80 as a TV-1. 99% of the AAC or AF schemes were aluminum. Hard to do and still clear coat for the decals/trim colors. Krylon alum looks great till the clear. And it tarnishes. The TV-1 is painted white base. Anyone have any good pics of this version?

Fuzz
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Old Feb 17, 2015, 06:09 AM
Big gov never Works
St. Martin's Avatar
Skunk Water, Rhode Island
Joined Jul 2002
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I wanted to post this pic of the P-80's glassed wing. It shows the better way to orientate the wing skin panels.

Fuzz
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Old Feb 17, 2015, 08:57 AM
Registered User
Schweiz, SG, Wil
Joined Oct 2006
35 Posts
Nice

Hi, keeping your building-speed, your P80 will take the sky before mine.
Second picture shows actual building state, but it is sleeping now.

Regards Aldo
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Last edited by Aldo Rebsamen; Feb 17, 2015 at 09:05 AM.
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