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Old Nov 05, 2012, 01:23 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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After putting this off as long as I have, I finally had to dive in and get it done. The hatch!! When I first made the plug I thought of molding in the flanges on the fuse to mount the hatch, which would have been fairly easy. The hard part would have been to figure out how much to shave off the hatch itself, to compensate for the layers of fiberglass, and get a nice fit. Too much work for my first attempt on a glass fuse. So with some guidence from AIR SALLY, I checked out this thread, http://www.rcgroups.com/forums/thumb...=threadgallery and chose that method.

Didn't turn out exactly as I had thought, just neesd a little tweeking. Used 1/4"x 3/8" med hard balsa, strong enough, but still bends some. The slots I put in will not work out. Just don't line up correctly, when you put in the hatch--wrong angles! So I will cut out where the slots are and glue in some ply pieces, on both the fuse and hatch. These will be glued in "flat" or level with cut out on the fuse sides and hatch. Problem solved.

Final fit will be after formers/bulkheads are in place. Right side fits great, left side, on fuse not quite so much. Off by about 1/16" in one spot, (must have been a harded piece of balsa) but bulhead for front wing mount will push it out and take care of that. FYI --You may have noticed the unprimed area, cut lines were drawn first, and taped for primer.

Excess glue. To get as good a fit as I wanted, formers for hatch were clamped to fuse bulkheads (plastic wrap in between) glue put on both ends, and hatch was taped to fuse till dry. Had to invert fuse while glueing , even then the glue ran. Used Hysol E-20HP, which I understand is thinner than the 9462. Live and learn.
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Old Nov 05, 2012, 03:53 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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I have been working on a game plan for the wings, and have most of it figured out. More on that when I actually start to build them.

The wings will be balsa sheeted foam cores with 2 washout. It's been some time since I have done a foam wing, and nothing to this scale. So feel free to correct me if I get this wrong!!

To retain the washout thoughout the entire wing they need to be fully sheeted and pressed/weighted in the cradle to hold shape. Now the flaps and ailerons need to be cut out. The only way I can think of is to allow for the thickness of wing TE, and flap/aileron LE, and cut into the wing that distance. Then subtract that off each flap/aileron. Is that correct? Or is there a better way?

Also, had not noticed the little "jog" between flap and aileron, till the other day.


It's hard to read, but BVM suggest the DS3421 Digital Mini MG Servo for most surfaces. Checking around, Hitec has the HS-5245MG Digital Mini- Could swear the were twins, except for price! Hites's are $50 less.

http://www.jrradios.com/Products/Pro...dID=JRPSDS3421
http://www.servocity.com/html/hs-524...ital_mini.html
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Old Nov 05, 2012, 10:39 PM
Registered User
Colorado Springs, Co
Joined May 2002
97 Posts
My 2 cents - and your mileage may vary.....
When I started building foam wings (my preferred method) Ivan Munninghoff insisted that 1/4 inch washout be placed ... period. Somewhat more than 2* - but I've yet to have a wing that didn't behave nicely ... especially with our lack of Reynolds numbers.
Secondly - look at all the links/forum conversations - and so on - about vacuum bagging. My CST (?) bag and pump setup was something like $35 about 10 years ago, and worth EVERY penny. You get a solid bond and even surface all the time.

I'm also more of a fan of the 5125 - the 245 and 5145 have too many reports of sloppy centering for me - and the specs and $$$ are the same. I use them a lot.

Hinge line: Unless you plan on competing with it ... I tend to go the more simple route and make it a simple straight run. If you need to satisfy the scale thing (BOY! do I understand that! ) cut your slot over-sized and add the appropriate thickness of sheet balsa to the balsa TE stock to correct the differences is size.

Keep up the nice work!

Greg
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Old Nov 06, 2012, 06:12 PM
I make bad look so good.
SteveC68's Avatar
League City, Texas
Joined Sep 2006
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http://www.servodatabase.com/
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Old Nov 07, 2012, 01:09 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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gbmoore thanks for you input. I will have to check into vacuum bagging. I have looked at the Hitec HS-5125MG's, not enough torque. Too bad they don't have one's in the 75oz/in area.

I will check into the "reports of sloppy centering".
As far as washout, that is not set in stone either.

What size and weight of plane are you using the HS-5125MG in? Even at 6.0V, they only have 48.6 oz-in (3.50 kg-cm)
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Old Nov 07, 2012, 01:35 PM
I make bad look so good.
SteveC68's Avatar
League City, Texas
Joined Sep 2006
2,559 Posts
Spektrum has some digital servos that meet the torque requirements and are price competitive. Although they are heavier than the specd Jr.
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Old Nov 07, 2012, 01:55 PM
Registered User
Colorado Springs, Co
Joined May 2002
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[QUOTE=CoolerByTheLake;23203987]gbmoore thanks for you input. I will have to check into vacuum bagging. I have looked at the Hitec HS-5125MG's, not enough torque. Too bad they don't have one's in the 75oz/in area.

Crud.....TyPO! It's the 5625 NOT the 5125 (5125 and 125 are only useful for rudder in smaller planes IMHO - gears are tiny!)
Used the 5625 on aileron and flaps in my turbinized Modellbau F-86D, among others (elevons on my Waldrep F-18 as well)

Sorry for the wrong servo number

Greg
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Old Nov 07, 2012, 02:16 PM
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unclecrash's Avatar
white lake michigan
Joined Oct 2004
3,756 Posts
Did you ever find the vacum pump at walmart. I checked online and only found the small pump. There is a link in my blog Petco sells them too. I didn't see it when you asked in the Draken thread, but since found they are Tetra Whisper Quite
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Old Nov 07, 2012, 03:48 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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Greg, thanks for the correction. Big difference! Those were one of the first one's I was considering, and havn't ruled them out, either. Plenty of torque there. Hitec has a couple others that would work, except they have karbonite gears.

I do appreciate the need for strong, good quality servos, but at what price?
When you need a bunch of them the cost and weight can really start to add up.
I need 7 servos for the surfaces, 1 steering.
If you figure 8-JR DS3421 servos would be $720.00. I don't think so! Even the Hitec's @ $40.00 ea/ $320.00, that's a lot of money!

Then you still have, 1 for gear and depending which way I go for the gear doors, air, 1 more for air + a whole complete system, cylinders, valves, tank, etc. Extra weight and cost. Or mechanical, 2 servos+ linkage. Chris True has some pics in his thread of the set-up. http://www.rcgroups.com/forums/thumb...=threadgallery

Still on the weight issue, my retract units, struts and wheels, complete air kit, will weigh 33oz.
Will keep looking, has to be some kind of middle ground.

SteveC68, I looked them over. weight is not too bad, around 1.7oz ea, good power. Don't know much about them, so some research is in order.
Also put in an e-mail to Patty@BVM about the spar connectors I PM'd you about. Nothing back yet, just might be too old of a part. I can work around it.

unclecrash , Yes I did find it. I don't expest to do anything on the wings and stab till after the first of the year. Closer to tax time!! Can you say-REBATE!
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Old Nov 07, 2012, 06:09 PM
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unclecrash's Avatar
white lake michigan
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You mean you actually get something back from are corupt government.
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Old Nov 07, 2012, 06:25 PM
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unclecrash's Avatar
white lake michigan
Joined Oct 2004
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I do appreciate the need for strong, good quality servos, but at what price?
When you need a bunch of them the cost and weight can really start to add up.
I need 7 servos for the surfaces, 1 steering.
If you figure 8-JR DS3421 servors would be $720.00. I don't think so! Even the Hitec's @ $40.00 ea/ $320.00, that's a lot of money!

Are you looking for standard size servo's? I put a couple Turnigy 1501 in my butcherbird they seem to be tough at 200+ inch oz. I have not got to run them threw any extensive testing other than on the bench but they are stout. You cannot force them the other direction and they do not hum or buzz when doing so. I won't be doing the Maiden till next spring. But then again you never know I might get the bug to go flying if we get a nice little warm up maybe this weekend
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Old Nov 08, 2012, 06:30 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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Quote:
Originally Posted by unclecrash View Post
Are you looking for standard size servo's? I put a couple Turnigy 1501 in my butcherbird they seem to be tough at 200+ inch oz. I have not got to run them threw any extensive testing other than on the bench but they are stout. You cannot force them the other direction and they do not hum or buzz when doing so. I won't be doing the Maiden till next spring. But then again you never know I might get the bug to go flying if we get a nice little warm up maybe this weekend
I don't have a problem finding the standard size servos, lots to pick from.
It's just more about keeping the weight down.

As all things do, as the build progresses, so rises to cost above my initial estimate! Quality and reliability has to come first! Then weight and price.
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Old Nov 12, 2012, 02:05 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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Well through a few PM's and more "search this forum/threads", I decided the Hitec HS-5245MG servos will work just fine. It was advised that I get the Field Servo Tester/Programmer to really tweek them. (That's 8+ oz saved!)
And these are small enough to mount in the stab!

It occured to me that although I had a projected weight at the start, I needed to re-evaluate it. So, here goes.

Fuse- As it stands, with nose gear, canopy and some formers-51.6oz
Power System figured with:
JetFan 90, Neu 1518/1.5Y--(1250Kv), 2-nano-tech 5000mah 6S 35~70C, K-Force 120A-HV OPTO V2 5-12S Brushless ESC------------------78.42oz
( Het 700-68-1200Kv is 3oz less )

Balance of Gear:
Mains, struts, wheels, and air kit------------------------------------------23.4oz
( Once Robart struts are cut down to size, a few oz less)
All servos, RX Batt 6V, gear door sequencer-----------------------------17.92oz

Grand Total------------------------------------------------------------171.34oz = 10.7lb

Still need wings, stabs, tail, ducting, fasteners, wiring, etc, so I guess my low ball figure of 14lbs is out the window! Still, at 15lbs wing loading is 35.7oz sqft. and at 16lbs = 38oz sqft.

Keep this in mind, mine will be 1/7.15 scale WS-651/2" Length-63" Weight-?
(The North American F-86F-30-NA Sabre, has the long, 6-3 wing)
BVM's 1/7.5 scale F-86 is WS-63", Length-60" Weight-17lbs.
SkyMaster 1/6.5 scale is WS-68",Length-69" Weight 18.5 lbs.

At 16lbs with 4Kw it's 250W per/lb,@ 4.5Kw it's 280W per/ lb, @5Kw -312W per/lb

Currently, light snow, 21, feels like 13

That's enough numbers for now. Have a great week.
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Old Nov 12, 2012, 07:17 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
21,257 Posts
cold here too ...but not that cold....is that weight with the batts? i think 15 lbs it will fly awsome .and look very scale speed wise ...the full scale does'nt have a ton of vert ,but once you get it going it will soar up pretty good in the vert.
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Old Nov 12, 2012, 11:51 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,977 Posts
AIR SALLY..
" is that weight with the batts?"--Yes!--10.7lbs. is the total weight with fuse as is, and all components listed.
Power System figured with:

JetFan 90, Neu 1518/1.5Y--(1250Kv),2-nano-tech 5000mah 6S 35~70C , K-Force 120A-HV OPTO V2 5-12S Brushless ESC------------------78.42oz
( Het 700-68-1200Kv is 3oz less )

Way back when, I had talked with John Morgan on doing a plug and pulling a fuse, and I think he thought the airframe would/should be somewhere around 6lbs.. Just have to wait and see what the weight ends up at!
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