SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 19, 2012, 03:19 PM
Registered User
planebldr's Avatar
Brillion,WI 54110
Joined Jul 2009
593 Posts
I am ordering a set of the brass heavy spinner nuts, and new props today. I picked the tap up today for when the nuts arrive so I can have them thread on the prop adapters. The battery boxes are painted and drying. I am going to move the motors out about .75"...made the brackets up for them and they are painted and drying as well. The hope is between these things, I won't have to add much weight.
planebldr is offline Find More Posts by planebldr
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 20, 2012, 10:35 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,151 Posts
I suggest gold. Not only is it available at a bargain price, but will probably increase in value as it performs its function as ballast. What else on that plane will actually be a hedge against depreciation?
Rockin Robbins is offline Find More Posts by Rockin Robbins
Reply With Quote
Old Feb 20, 2012, 10:45 AM
Registered User
E-Challenged's Avatar
United States, CA, Garden Grove
Joined Oct 2000
11,929 Posts
Quote:
Originally Posted by planebldr View Post
I am ordering a set of the brass heavy spinner nuts, and new props today. I picked the tap up today for when the nuts arrive so I can have them thread on the prop adapters. The battery boxes are painted and drying. I am going to move the motors out about .75"...made the brackets up for them and they are painted and drying as well. The hope is between these things, I won't have to add much weight.
You might find shaft adapters that thread into the spinners "as is". Otherwise drilling and tapping, slightly off center might cause wobbling. I found Tru Turn spinner nuts that fit my Scorpion collet shaft adapters for my Reliant.
E-Challenged is offline Find More Posts by E-Challenged
Reply With Quote
Old Feb 20, 2012, 11:06 AM
Registered User
E-Challenged's Avatar
United States, CA, Garden Grove
Joined Oct 2000
11,929 Posts
A lifting stab would tend to raise the tail the faster the model goes but might lose lift at slow landing speeds. Down elevator trim would have similar effect. Best to fly a little nose heavy for maiden/familiarization flights and adjust cg and motor down-thrust angles as needed. My overweight P-26 Peashooter flew nice high speed circles at nearly full throttle, fell out of loops and rolls. More nerve wracking than fun to fly and land. Had to land fast like a WWII fighter on the mains, stalled/boinked during last landing. I repaired it to look OK and it's now retired on a shelf in the garage.

Recommend you keep all climbs and turns shallow and airspeed up during landings. When you feel gutsy, experiment to find stall speed 3 mistakes high.
E-Challenged is offline Find More Posts by E-Challenged
Reply With Quote
Old Feb 21, 2012, 03:45 AM
Registered User
planebldr's Avatar
Brillion,WI 54110
Joined Jul 2009
593 Posts
My overall goal with this plane is more or less smooth circuits. No loops or rolls. So, at least my expectations are not too high. I am on hold for now though until the props and spinners come. Fingers crossed that it helps.......
planebldr is offline Find More Posts by planebldr
Reply With Quote
Old Feb 21, 2012, 05:44 AM
Registered User
Bill Smudge's Avatar
United States, KY, Bowling Green
Joined Jul 2011
1,075 Posts
Tough situation, PB.

Sounds like you have painted yourself into the preverbial corner....

Maybe some of suggestions in this thread will help sort things out, a bit.

I hope you get the Skyrocket able to fly, at least enough to maiden and get a few trips around the field.

BTW she is a very nice looking build, I know it must be no fun at all taking a knife to her trying to get some weight off.

Certainly a lesson learned here for all of us scratchbuilders.

Good luck.

Bill
Bill Smudge is offline Find More Posts by Bill Smudge
Reply With Quote
Old Feb 21, 2012, 09:51 AM
Registered User
USA, WV, Moundsville
Joined Oct 2006
2,779 Posts
i would suggest looking over on RCG there is a guy that sells "hes a pro seller" some very heavy powder "looks like steel granules" you mix with epoxy and pour into the nose "cup" of the cowl we have used it with great success on some old built like brick wall aircraft

actually heres the link idk if it will help you at all but its worth a look

http://www.rcuniverse.com/market/item.cfm?itemId=820826

Good Luck!
Tim
turbored21 is offline Find More Posts by turbored21
Reply With Quote
Old Feb 21, 2012, 10:18 AM
Always Ready!
warhead_71's Avatar
Chicago, IL
Joined Dec 2006
5,135 Posts
I would caution against the heavy hubs using Turnigy motors unless you have everything perfectly balanced. Turnigy is not known for having the best bearings in their motors... you could end up with spalled bearings/races in short order.

I still think you should try to lighten the tail before adding nose-weight. Swiss-cheese the solid empennage, or rebuild it with sticks. Also, you surely can fit a Dremel inside the fuselage and hog some of the over-engineered structure. Lighter pushrods and move the servos as far forward as possible.

Just curious... what is your wing area? You have listed your current weight and expected nose-weight, but we have no idea what your wing-loading or wing-cube-loading is.
warhead_71 is offline Find More Posts by warhead_71
Reply With Quote
Old Feb 21, 2012, 12:51 PM
jrb
Member
jrb's Avatar
Edina, MN, USA
Joined Oct 1999
11,429 Posts
Higley's heavy prop nuts: http://www.harryhigley.com/EngineAccessories1.htm .
jrb is offline Find More Posts by jrb
Reply With Quote
Old Feb 21, 2012, 04:11 PM
Registered User
planebldr's Avatar
Brillion,WI 54110
Joined Jul 2009
593 Posts
Well, .....my wing area according to my calculations is about 1327 sq inches. So figuring on the current weight of 26.5lbs, that gives me a wing loading of 46 oz. If someone wants to double check my math (I was using google to help me figure it all out since I never had to before)......the main section that is constant chord is 16.25X45 inches. The sections with tapered chords are 16.25 at base and 11.5 by wingtips. So I figured the areas to be 731.25 and 298.31 X2. So total area 1327 sq in....or 9.21 ft2. Total weight based on 26.5lbs is 424 oz. So 424 divided by 9.21 is 46oz right? Like I said I never figured wing area or loading before because everything was mostly ARF's or kits that had it all figured out for me already.

I do have the heavy hubs, lock nuts and props coming....so I will figure out totals then. I will probably take a hole saw to the tail later this week and cover over the holes with covering to save weight in the tail as well.

I know that Turnigy isn't known for top quality bearings....but it won't matter much if this thing won't balance out...it'll be too short of a flight to kill the bearings
planebldr is offline Find More Posts by planebldr
Reply With Quote
Old Feb 21, 2012, 04:23 PM
Always Ready!
warhead_71's Avatar
Chicago, IL
Joined Dec 2006
5,135 Posts
That is heavy!!!

http://www.ef-uk.net/data/wcl.htm

Wing Cube Loading of 15.2 which is in the "racer" category. You'll need a really long runway and brakes to stop this thing.
warhead_71 is offline Find More Posts by warhead_71
Reply With Quote
Old Feb 21, 2012, 04:33 PM
Registered User
planebldr's Avatar
Brillion,WI 54110
Joined Jul 2009
593 Posts
That is what I'm used to......my Sundowners on 8s are "slightly" over weight But they are also grossly over powered...which will not be the case on this thing.....

Good thing is the runway is VERY long, and grass. So I "should" be okay as long as it has enough power to actually fly.


Either way.....I think I will be doing the swiss cheese treatment to the tail area. See if I can get it to balance without the heavy hubs at least. Props are a benefit either way being larger and 2 blades...

I just took another trip to the basement....and took another look at the plane since I have it apart again. I take back what I said about the wing being the biggest issue with the weight. The tail is.....about 7lbs by itself...and that is all aft of the CG more or less. So swiss cheese it is
planebldr is offline Find More Posts by planebldr
Last edited by planebldr; Feb 21, 2012 at 04:51 PM.
Reply With Quote
Old Feb 21, 2012, 07:20 PM
ARFs make me BARF
mrittinger's Avatar
United States, MI, Roseville
Joined Dec 2000
8,940 Posts
E, I was just saying , that running a lifting rear section allows some rearward CG placement when compared to a flat or symmetrical section. Even if you go back to 40%, thats a really nice gain. Yeah, takes a better pilot, but it's nowhere near like flying tailheavy
mrittinger is online now Find More Posts by mrittinger
Reply With Quote
Old Feb 21, 2012, 08:05 PM
Fly it like you STOL it!
Endlesslag's Avatar
United States, FL, Daytona Beach
Joined Jan 2011
4,023 Posts
Quote:
Originally Posted by mrittinger View Post
E, I was just saying , that running a lifting rear section allows some rearward CG placement when compared to a flat or symmetrical section. Even if you go back to 40%, thats a really nice gain. Yeah, takes a better pilot, but it's nowhere near like flying tailheavy
And if it's gonna have to fly fast anyway from the wingloading...
Endlesslag is offline Find More Posts by Endlesslag
Reply With Quote
Old Feb 21, 2012, 08:32 PM
ARFs make me BARF
mrittinger's Avatar
United States, MI, Roseville
Joined Dec 2000
8,940 Posts
Some FF types have the CG at 70%! Look at the huge stabs with flat bottom airfoils. They typically float along at one speed.
However, increasing speed does not increase lift unless that section is at a positive incidence.
Have a look at Martin Simons Model Aerodynamics book.
Mark
mrittinger is online now Find More Posts by mrittinger
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion What Would YOU Do if Someone Tried to Injure You ? Chophop Life, The Universe, and Politics 36 Sep 23, 2011 04:06 PM
Discussion What would you do?? HELModels Life, The Universe, and Politics 57 Jul 26, 2011 08:51 PM
Help! What would you do in my situation? brendon7358 Scratchbuilt Indoor and Micro Models 67 Jul 15, 2011 08:05 AM
Discussion What would you do...... rc_boat_lover Dock Talk 42 Jun 14, 2011 07:45 PM
Discussion What planes do you have and which would you replace? jnjloo Slope 17 Mar 27, 2011 01:02 PM