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top flite p-51 giant scale build

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Old 11-12-2007, 11:55 AM
  #601
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Default RE: top flite p-51 giant scale build

May I butt in? I have used hard maple motor mount bearers for about 50 years, as I like to spread the load across at least 4 ribs. You can also drill and tap the wood with the threads for the mounting screws you use, typically 4/40 up to about 15-16 lbs and 6-32 above that to about 30 lbs. It eliminates blind nuts, nuts of ANY kind! Wood has this nice little characteristic of swelling back into the hole a tad after drilling. I have NEVER had one come out or even loosen! After it is tightened, come back about an hour later, and try to loosen one: it will "snap" as it breaks loose. Lee Robinson W. Palm Beach.
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Old 11-12-2007, 05:47 PM
  #602
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Default RE: top flite p-51 giant scale build

Hi brian /Robinaire

I ve examined the retract system and I ve put a lot of thought into it , heres what I have to say .

The retract system sits on a table , and in all sence the table has 4 legs . If we were to remove one of the legs , it would lose a lot more than 25% of its capacity it would be unballanced , althought its only one leg . I ve been lookng a lot at rib #4 were the cylinder goes through it . at the bottom of rib #4 there is a 1/4 inch made up of three plys ( it would be at the top of rib #4 if the wing was right side up ) . I did a small experiment . I took some small scraps of ply , the same quality , glued three strips to-gether with epoxy , gave it plently of time to dry , and did the snap test . IT SNAPPED WITH NO PROBLEM AT ALL . It wasn t very strong at all . so I did another test . This time I added 1/8 alluminum on each side , that was bolted in with 4-40 bolts . The results were not the same at all , I had to force it to break .

I ve repaired three TopFlite P-51 Giants to date , and the all had the same breakage , rib #4 . I truely feel that the weak spot is the rib #4 ( the one leg in the table ) at the area were the cylinder goes through the rib .


I also believe that engineres know what there doing and they have given us a solid three table support , and yes I did say three , if the fourth support was stronger , it would dirrectly affect the strength of that table going into the spars . What my idea is to strenthen the #4 rib with fiber board , or even carbon fiber , just that area . make a U-plate , bolted in . I believe that the structure is sound the way TopFlite made it . It just needs a little help , in that area . Please these are only my believes ond I certainly aint no enginere . But I have seen a lot of production machines in my time . And these are only my thoughts .
I hope that I have discribed my thougts correctly or you guys might think that I m a totally nuts , ain t no different than what my wife thinks of me

Robinaire , youre right to add tee-nuts only adds weight and work for no reason at all . I ll be useing simple wood screws , put in with a pilot hole , thats plenty strong .

Since I ain t no three D pilot , I m going with what the instructions call for . So the servos that I will be useing will be JRS-821 s simple 75-oz standard servo . It costs about $30.00 each and it is very reliable , its made its name for itself

Well thats it back to the building

Mike [8D]
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Old 11-13-2007, 05:29 PM
  #603
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Default RE: top flite p-51 giant scale build

Makes sense to me! Thanks for the advise. Thanks to the other Mike,Berrick, Dragonfly and everyone else whos tips will make it easier to build.

Brian
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Old 11-13-2007, 05:56 PM
  #604
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Default RE: top flite p-51 giant scale build

Hi All

I keep looking at rib # 4 and I m trying to imagine that the plane is comeing in for a hard landing . The retract will be pushed back and the first thing to let go will be rib # 4 because of its lack of support , which will lead to the weakening of the other three , if any landing is hard enoegh , nothing will hold it to-gether . A 2-G landing is fairly hard , wouldn t you say . with the doublers that TopFlite has put in I d say thats its plenty . And those doublers go behind the spars . Glue and fiberglass is only as strong as the fiber the wood is made of .

This is what I m doing : I m going to add a 1/8 rectangular piece of alluminum , with a window for the cylinder , this will be screwed to the doubler 4- Z ( to-wards rib #3 ) . This will reinforce the bridge thats there , and help that part of rib #4 were it is weak . It won t be a large piece , just eneogh to reinforce that rib I believe that all the glue in the world won t help it , won t add much weight to the plane , and it is forward of the C/G , were I m sure this plane needs weight

Well.................. time tells all , We ll see if I m right

Mike [8D]
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Old 11-13-2007, 07:12 PM
  #605
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Default RE: top flite p-51 giant scale build

Hi Mike et al. Why do you think I always want to spread the load across at least 4 ribs? I haven't seen these plans, but from what people have been saying, it sounds like a piece of horshoe-shaped ply between 2 ribs. To me this is a ridiculous way to mount something that will take the high stresses which we modelers "skilfully" apply to our landing gears!! Maybe someone can describe exactly what this models mounting system is. Thanks. Lee Robinson
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Old 11-13-2007, 08:11 PM
  #606
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Default RE: top flite p-51 giant scale build


Is there a way of hidding those control linkages?

the only thing thata looks weird on the '' scale'' model....

let me know,

Phil
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Old 11-13-2007, 09:23 PM
  #607
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Default RE: top flite p-51 giant scale build

Hi

Phil......Are you building the P-51 Giant ?
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Old 11-13-2007, 09:36 PM
  #608
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Default RE: top flite p-51 giant scale build

I will be soon......

got a solution?

Phil
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Old 11-14-2007, 06:57 AM
  #609
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Default RE: top flite p-51 giant scale build


Quote:
ORIGINAL: Robinaire

Hi Mike et al. Why do you think I always want to spread the load across at least 4 ribs? I haven't seen these plans, but from what people have been saying, it sounds like a piece of horshoe-shaped ply between 2 ribs. To me this is a ridiculous way to mount something that will take the high stresses which we modelers "skilfully" apply to our landing gears!! Maybe someone can describe exactly what this models mounting system is. Thanks. Lee Robinson
Have a look at page #8, Post#180, picture #2 and you can see what the stock gear rails are like. Nothing more than two small rails attached to rib#3 & 4.

The horseshoe plate between two ribs being referenced here, is what I felt was a better alternative to take some of the load away from the ribs and distribute it over a wider area to the shear web & spars....reference Post #187.
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Old 11-14-2007, 08:15 AM
  #610
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Default RE: top flite p-51 giant scale build

Hi Countryboy. Thanks so much. I just looked at the pics and see why! That original system was easy for the designer (didn't have to think too much!). Your change is definitely better, but spreading the load to more than 2 ribs is even better. But yours will definitely stand up better. As to stronger doing more damage, 9 times out of 10 a crunch hard enough to tear the gear out, is probably a "re-kitting"!! I blushingly admit this from personal experience! Yes, I think I did have a crash once! ??? Lee
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Old 11-14-2007, 06:39 PM
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Default RE: top flite p-51 giant scale build

HELLO ALL,
JUST WANTED TO FLAG THIS FORUM.
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Old 11-14-2007, 09:17 PM
  #612
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Default RE: top flite p-51 giant scale build

TUSCALOOSA!!! Gee, and all this time I thought it was an imaginary place!! Lee Robinson W. Palm Beach
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Old 11-14-2007, 09:19 PM
  #613
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Default RE: top flite p-51 giant scale build

By the way, as of tomorrow, this old dial-up address will go away! New one, hi-speed, is robinairerc@comcast.net. Lee
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Old 11-18-2007, 03:07 PM
  #614
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Default RE: top flite p-51 giant scale build

Hello-Hi

I ve finished the right wing , except fpr the skin . There was nothing difficult nor was there any surprises , very straight forward . I shimmed the trailing edge of the wing and the flap leading edge with plastic spacers , so that I will have a gap that they ask for . I ended up with about .040 gap , which is suficient for when it will be cut out . I couldn t find out when to add the servo bay 1/4 inch square balsa for th servo bay covers , so I added them during the wing build . Now its on to the left wing , which will be a lot faster , as everything was already prepared as I was building the right wing .

Hopefully I will be able to put the wing halfs to-gether by the end of the week . I don t even have a table to fit the size of the total wing span . Just another problem

Mike [8D]
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Old 11-18-2007, 07:54 PM
  #615
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Default RE: top flite p-51 giant scale build

Hello guys. Excuse my off-topic entry, but I have been trying to put my new email address in here, and can't seem to find an entry on the system home page! Any suggestions? This old one is disappearing. New one is robinairerc@comcast.net. Lee Robinson
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Old 11-24-2007, 09:04 PM
  #616
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Default RE: top flite p-51 giant scale build

Hey all you guys using the Keleo scale exhausts....who makes the piece to go around the exhaust where it comes out of the cowl to make it look more scale. Is it fiberglass? Thanks
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Old 11-25-2007, 05:27 AM
  #617
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Default RE: top flite p-51 giant scale build

Hi

I believe that Kelvin makes them at Keleo http://www.keleo-creations.com/
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Old 11-25-2007, 11:13 AM
  #618
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Default RE: top flite p-51 giant scale build

Corwin38,

I believe you are looking for the valve cover mock up that surrounds the exhaust stacks. The best one that I have seen is by Pacific Aircraft. [link]http://www.pacific-scaled-aircraft.com/[/link]

It dose look nice. I'm thinking of incorporating this with the Kelo exhaust also.

Have fun

later Guys,

Mike
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Old 11-25-2007, 12:48 PM
  #619
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Default RE: top flite p-51 giant scale build

Actually Mike, this is the website I ordered from.... http://fiberglassspecialtiesinc.com/catalog.htm but I will be interested to see how yours work out.
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Old 11-25-2007, 02:05 PM
  #620
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Default RE: top flite p-51 giant scale build

Hi

I mentioned keleo for the reason a friend of mine has a set of mufflers for his inline Saito and he received them with the exhaust system . but since you guys have the correct source thats great or different sources even better THANKS

So far I have the tail feathers finished , the two wings framed but unsheeted and now I am preparing to put the wings to-gether . the only thing that isn t done is the hardwood mounts for the retracts , which I haven t received as of yet

Mike [8D]
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Old 11-26-2007, 10:18 AM
  #621
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Default RE: top flite p-51 giant scale build

Hi Scalebirdman
I have just found the photo`s of your P-51 with the G62 fitted and I must say the finished plane looks really nice as does the installation, can you tell me if you made the silencer yourself or is it a bought one? if so could you let me know where to get one from also is your model glassed and painted or is it film covered.
many thanks and I hope my P51 looks as good as yours when it is finished.
John
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Old 11-26-2007, 03:11 PM
  #622
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Default RE: top flite p-51 giant scale build

Hi guys

I was getting ready to mount the gear today and noticed they sit too low in the wing. When the gear is retracted the bottom of the strut will hit the top wing skin. Looks like I need to shim the inboard mount rail out a bit, maybe 1/16.
Anyone else run into this problem?

Thanks
Brian
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Old 11-26-2007, 04:31 PM
  #623
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Default RE: top flite p-51 giant scale build

Hi Upton

I have completed my two wing half's , but have not installed my retract rails as of yet . I haven t received my retracts of yet , but will receive them by Thursday . This is not as the instruction manual says how to do it , but this may come to be an advantage to me . I will be putting the two wing halts to-gether before I put in the retract rails . This way I can make sure that the are straight and identical . May I ask what type of wheels that you are using . I m putting in Dubro 5 inch , the 500 model

Mike [8D]
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Old 11-26-2007, 05:50 PM
  #624
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Default RE: top flite p-51 giant scale build

Mike

I'm using the same wheels and gear as you.
I haven't epoxied anything yet so I should be able to shim the rail up to give the clearance I need.



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Old 11-26-2007, 07:48 PM
  #625
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Default RE: top flite p-51 giant scale build

Hi Upton. Enon Valley?? I'm from Freedom, and when I was in high school, 1944, I had a pen pal, John Hillman, whom I later met in person after I got out of USAF in '48. I actually flew my '47 T-Craft out there, with a local buddy, with planes for a ukie contest!! By the way, anytime you build a retract plane, wait until you get the gear,before putting the mountings into the wing. Some of thse combos seem to have a little hooker built in!!! Lee Robinson W. Palm Beach, FL
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