RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair  
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RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/25/2008 2:09:43 AM   
rt3232


 

Posts: 2289
Joined: 12/4/2004
From: hastings, MN, USA
Status: online
Winston

Well except for the ignition flopping around it looks and sounds good to me just wish I would have done a little mor research be for I built mine.

Cheers Bob T

Corsair Brotherhood #5

(in reply to cimara)
       Post #: 4301

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/25/2008 7:06:47 AM   
aceisback


 

Posts: 43
Joined: 4/21/2002
From: West Terre Haute, IN, USA
Status: offline 		Thanks! I meant dome/hub, I think I said spinner out of habit. The one you have is what I was looking at from TruTurn. Are you using a 22x10 prop? If so, is the Hub the 1 1/2" or 1 3/4" hub?

Duane

(in reply to rt3232)
       Post #: 4302

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/25/2008 1:52:41 PM   
rt3232


 

Posts: 2289
Joined: 12/4/2004
From: hastings, MN, USA
Status: online
Duane

The dome is a 11/2 A type tru-turn and the step washer is home made, did not like the looks of the stock and the dome washer stacked so picked up a pc, of 2" alum bar stock and turned my own.

I am using a Zinger or zinger pro, hand balanced 22 X 8 on the ground I get 7,000 to 7,300 depending on the weather, this seams to be what my engine likes the best, have tryed 20 X 10, 20 X 6-10 and a coupla of outhers I have not run the numbers for tip speed, but you want to stay subisonic,


Cheers Bob T

Corsair Brotherhood #5

(in reply to aceisback)
       Post #: 4303

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/26/2008 1:16:29 AM   
Twistawrecka


 

Posts: 212
Joined: 7/12/2003
From: Menomonee Falls, WI, USA
Status: offline 		Just FYI, for a 22 inch prop to go supersonic (over 770 mph plus or minus a few mph depending on altitude, temp, etc) it would have to turn around 11700 rpm.

formula works like this

{([piXdiameter]Xrpm)X.00095}=mph

where

tip speed = {([3.14x22]x 11700)x.00095}=767mph

the .00095 is a ratio between miutes in an hour and inches in a mile.

at 11700 rpm the prop TIP travels 808236 inches/minute.
there are 60 minutes in an hour so it travels 48494160 inches in an hour (at 11700 rpm's)
there is 63360 inches in a mile (5280 ft X 12)
so divide 48494160/63360=765.375 miles traveled in an hour by the prop tip.

if we ran the ratio (.00095) out a few more decimal places it would come out the same 767 vs the 765 figuring it the long way.

try the formula with any prop size and rpm you like, you'll see it really takes a lot of RPM's to get a prop to go supersonic.

like 8 inch prop turning at 17000 rpm is only 405mph.

or 12 inch prop turning 12000 rpm is only 429mph.

or 20 inch prop turning 7000 rpm is only 416 mph.

I'm not an engineer and I didn't sleep at a Holiday Inn Express last night, but I did have the assiatance of a aeronautical engineer at work to help figure out the formula.

Have fun!











(in reply to rt3232)
       Post #: 4304

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/26/2008 3:31:58 AM   
rt3232


 

Posts: 2289
Joined: 12/4/2004
From: hastings, MN, USA
Status: online
Twistawacka

Will take your word for it on tip speed ,Its been 40 plus years sence I have even thought about that formula, but I did see some photos on RCU of a C/F prop with tip that were reported to have gone supersonic as I recall it was over on the gas engine forum,

Main thing is be safe and have fun.

cheers Bob T

(in reply to Twistawrecka)
       Post #: 4305

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/26/2008 11:46:39 PM   
cimara


 

Posts: 776
Joined: 9/1/2006
From: atlanta, GA, USA
Status: offline 		Ok guys here is a recent conversation between George and the designer (Craig) of the TF Giant corsair . George asked me to post to help clear up the engin offset issue hope it helps
quote:

Craig, Thanks for the quick reply.

If I follow the instructions in the book about cutting the crutches and cut them where the top and bottom crutches attach to the sides (pg. 23) in the book, the engine offset will end up being around 3 degrees. Should the offset be 3 degrees instead of the 2 degrees on the plans? or have I received a bad fusetop crutch and bottom fuse crutch?

Thanks for your help on this issue

George H.

ctflyboy



Hi George!



Sorry for the delay in response. It's been 11 years since I've had to think about the design of the Giant Corsair - I've slept since then.. LOL!



In looking at my manual and plans, it appears that the desired right thrust is 3 degrees (as shown on the plans). I believe if you use your top and bottom fuse crutches as supplied, you'll be fine. Unfortunately, I don't have any parts to measure.



This doesn't mean that TF has changed the parts since my employment there. I do, however, find it unlikely that they changed anything - too expensive.



I hope this helps!



Warmest Regards,



Craig



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Winston
Corsair BrotherHood #6

(in reply to rt3232)
       Post #: 4306

RE: GROUP BUILD - Top Flite Giant Scale... - 3/28/2008 12:28:47 AM   
cimara


 

Posts: 776
Joined: 9/1/2006
From: atlanta, GA, USA
Status: offline 		I squirted some paint on the corsair today untill it got too cold for this water based paint and it started a few runs a light sanding should fix those .I dont know why i couldnt get a consistant color over it I have light and dark patches I think i will do a light sanding over the entire thing and apply one last coat in a week or two what do you all think about this fix I am no painter and any help would be greaty apprecated

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Winston
Corsair BrotherHood #6

(in reply to Thunderbolt47)
       Post #: 4307

RE: GROUP BUILD - Top Flite Giant Scale... - 3/28/2008 2:27:17 AM   
rt3232


 

Posts: 2289
Joined: 12/4/2004
From: hastings, MN, USA
Status: online
Winston

With out going back what paint are you using?? and it may be ok with a little weathering and such I guess I would mabe pm smugater I am the last to give paint advice

Cheers Bob T


(in reply to cimara)
       Post #: 4308

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/28/2008 2:42:51 AM   
cimara


 

Posts: 776
Joined: 9/1/2006
From: atlanta, GA, USA
Status: offline 		Bob I am using warbird colors .The color is the correct in the dark areas its just so translucent that the light gray primer shows through and only in certain light conditions

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Winston
Corsair BrotherHood #6

(in reply to rt3232)
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RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/28/2008 3:20:11 AM   
devens



Posts: 295
Joined: 12/27/2006
From: Decatur, IL, USA
Status: offline 		Sounds like you need more coats of paint. From what I read warbird colors go on very thin!

The exhaust looks great! Is the diameter close to scale? Looks small on the test stand but what does that mean . I would grind the welds if you can. Grinding is pretty common thing to have to do with welds.

I am a Mechanical Engineer so don't tell your Aero buddy I asked this dumb question Aceisback! What happens when a tip goes supersonic? I assume bad things with potential catistrophic failure but I mean in more detail. My guess would be cavitation due to the sonic boom and subsequent shock wave would damage the prop.

I have a compressible fluids text in a box in the garage that deals with super sonic flows I should dig it out and see what I can find.


D

< Message edited by devens -- 3/28/2008 4:33:47 AM >

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Corsair Brother #2, Waco Brother #80 AMA#497873 Member; Decatur Aero Commanders

(in reply to cimara)
       Post #: 4310

RE: GROUP BUILD - Top Flite Giant Scale F4U Corsair - 3/28/2008 3:43:26 AM   
cimara


 

Posts: 776
Joined: 9/1/2006
From: atlanta, GA, USA
Status: offline 		Thanks deven I was thinking more paint also but wanted more opinions than mine i am no painter . On the exhaust the outlets are a little larger than scale there are 6 1/2 id pipes that make up the sorta scale looking outlets .I used the 1/2 inch pipe to get the same flow that the original muff had . On the welds i was so sick of them i just didnt want to deal with the thing any more they dont show with the cowl on anyway thell add to the 3 pounds of nose weight the books says i will need

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Winston
Corsair BrotherHood #6

(in reply to devens)
       Post #: 4311