efurche

need plans or a wing kit for a 1/6 PICA spit. Is PICA still in business??? they previously said they couldn't help me.

Ed[]

spitty

Red B , that´s the Way.
What I wanna do is setting like on FullScaleAircraft a " Datum-Line" on CG. Then I wanna compute ( exactly als possible ) how much weight I´ll save by lightening the bulkheads and formers. FE : Dead Weight above the EngineMount means 15 " forward of
" Station " . Saving 5 gramms on Former F18 ( 42,5 " behind Station ) = saving ( cause we have do ad weight! so we can SAVE instead of adding ) arond 14 Gramms Dead weight.
Seems to be not pretty much , but I think at the end it will be a lot.
I saw a guy writing of his Spit - complete without covering a weight of 14 Pounds !! That sounds good

Spitfire7856

My Feedback: (1)

Are you talking about the 88inch wing for the 1/5 Spit? If so, you should be able to get a set of plans after the new owners resume operations. Might suggest you look into a wing from the Yellow Int'l 1/5 Spit since the Yellow was built off the Pica plan.
Hope this helps!
Regards
A3

Red B.

Spitty wrote: Actually its a little bit better than that
Assume that lead is added 15 in. in front of the intended C.G. and that you can save 5 gram of weight in a former located 42.5 in. behind the intended C.G. By doing the moment calculations it is correct that 5 grams at the rear position equals 14.2 grams at the front:

mass_front = mass_rear*momentarm_rear/momentarm_front = 5*42.5/15 = 14.2

The total weight saving however is 14.2 + 5 = 19.2 grams, i.e. the total weight loss is almost 4 times as much as the weight removed in the rear.

If you want to calculate it, here is the complete formula:

total_weight_loss = (momentarm_rear/momentarm_front +1)*mass_rear = (42.5/15+1)*5 = 3,83*5 = 19.2

Do a lot of weight savings like that and eventually you will end up with a pretty light Spitfire :-)

/Red B.

spitty

as I told You " Dr." Red B , I will keep You updated
A very interesting link!!!
http://modellbau.roskothen.de/docs/test5.html

Lighter Airplane => smaller and lighter engine => smaller fueltank => smaller servos and so on.
Can You explain why You can move the CG on a lighter aircraft aftwards? My opinion: You don´t have to
produce so much lift,so the nessesary angle of attack can be smaller and the difference between the CG and the ( sorry , in Germany we say " Neutralpunkt " ) maybe in english : Point were all vectors are centered) can be greater.
Hope You´ll understand
Thanks for any idea
Andy

Red B.

The simple answer is: I don't know! I haven't even thought about it.

I can however do some handwaving while waiting for somebody better qualified than me to provide a correct answer :-).

If it is true that a lighter aircraft can fly with a more rearward C.G. than a heavier one I suppose it has something to do with the relationship between inertial forces arising from the movement (pitch, yaw, roll) of the aircraft and aerodynamic forces. It seems plausible that if the aircraft is made heavier with everything else remaning the same, the inertial forces will increase whereas the aerodynamic forces tending to restore the original flight path following a disturbance, will remain more or less the same. Thus, more stability (more forward C.G.) is needed to restore the ratio between aerodynamic and inertial forces to its original value if the aircraft is made heavier.

If you look up standard stability and control textbooks you will find that weight is not a factor in static stability calculations. Dynamic stability is another matter.

BTW, I read David Innes article about his superlight Spitfire in Flying Scale Models a couple of years ago. That article was the inspiration I needed when I built my Pica Spit. Because I was using a ST-3000 engine I didn't go to extremes when it came to weight saving exercises but I still ended up with a fairly light Spit that handles like a dream in the air. Take-offs and landings requires a fair amount of concentration in order not to nose over though.

/Red B.

IFLYRC-RCU

My Feedback: (28)

Flew mine for 5 years on a Q 42 at 26 lbs. Worked fine.Glassed and scaled out

I "Cheated" and added roughly an inch to the nose of the plane while building. This moved the engine out which reduced the needed nose weight. I did nothing to minimize weight in the tail as this was my first scaled out and glassed plane years ago.

Flew great.. I always had some trouble landing it.. I think that might have been inexperience back then ....( aka pilot error )

Cheat the gear as far foward as possible.. angle them foward.. I used Likes line retracts and thin wheels. Still have those in a box somewhere .....Got it all to fit. The plane wants to tip on it's nose ( well, mine did anyway ).

I've seen many fly with the Super Tiger engines well. Very nice areobatics, great 4 point rolls. I fly a FiberClassics Spit these days ....

Good luck and have fun !

spitty

Red B,calling You Doctor was the right choice,hope it´s okay for You.
Thanks for Your time answering so exactly.
( At first I´m in hope that Your Spit is still alive )

You wrote :....inertial forces arising from the movement (pitch, yaw, roll)....more stability (more forward C.G.) is needed to restore the ratio between aerodynamic and inertial forces to its original value if the aircraft is made heavier"

I think You´re right with Your Idea ,and that´s the reason while a TAILHEAVY Acft is so nervous on using Elevators
Thanks again
Andy

Canardman

My Feedback: (7)

I just finished mine, I put a ST 3000 in it with a 20x8 prop. I also had some CG problems. I had to move it back about 1.5 inches.
A 2 lbs lead weight on the front firewall did the trick. I also had to bend the landing gear forward a bit. If you look down across the wings leading edge, you can see about half the wheel. This fixed my problem with the prop becoming a "weedeater".

Ruudje

Check out my progress at:

You can see the 3W muffler here and some speedregulators I used for the retracts! Retract time is now 6 seconds!!!

http://www.rc-forum.nl/viewtopic.php...r=asc&start=24

DocYates

My Feedback: (102)

Well here is my SPitfire, a 1/5 scale Pica kit which I picked up at a swap meet for $300 including the retracts and a NIB ST2500. I had to finish building the fuse and sheet part of the wing. I glassed it with MinnWax polyurthane water based varnish and then painted it PPG base coat and covered with Flex n' Flat. The paint is not scale, but close enough for me. It is powered with a Moki 2.10 and a customized Slimline muffler. She weighs about 23 pounds, and required about 15 ounces of weight in the nose to balance it out. The test flight was great except one of the Robart tires rolled over on me and caused it taxi off the runway. The flight was awesome and will only get better as the engine gets more broken in.
I am happy with my swap meet Spitfire, and I hate letting it sit for 2 years before I ever got around to finishing it up. I'm also glad my flying buddies had not taken me up on selling it...
Now I need to start the Y/A SPitfire I have in the storage building.
So many planes, and not enough time.
Tommy

LA7flier

My Feedback: (1)

I found on my Pica (scaled out and all) with the retracts exactly at scale location with the correct CG, I could balance the plane on it's main tires (in a wind protected environemnt like the garage) and it would balance there indefinitely with the tail sticking straight out parallel to the floor...quite an interesting site. I found it challenging to fly off of grass but learned to 3-point h plane and stuck most of my landings. What the Spitfire lacks in ground handlling is more than made up for in the sky....

LDM

My Feedback: (15)

I have the Pica P40 , my suggestions to make your spit light are as follows , and you & I will get a ton of "no that will not work "but it does help .
Go the shyshark website , take a look at how the lasor cut kits have holes everywhere , the ribs , the fuse ect ect . Get a digital scale (if you dont have one ) and weigh everything .Get a good cutting tool for holes and make the stretegic holes in the ribs and fuse supports . Lighten everything , even if it only saves you 2 oz , do it .
Sand , sand and sand agiain so that less filler is needed to cover inperfections .
Hollow out your pilot if you add one , tape all your servos on and balance it , see if any of them can be moved to help weight , if weight is needed try to add battery weight first so its functional .I have seen big discrepencies in the weight of Pica planes , the 1/5 have been 20 pounds up to whopping 24-25lbs . that is way toooo heavy

wulf190

My Feedback: (19)

I've found the exact same balancing as LA7. It balances exactly on the wheels with the tail level. At least I know I'm right here. I await flying tests as it's now ready to go. It won't taxi in my yard grass at all. Any advance of the throttle brings the tail up. Pavement it's good. We'll see how it does on the shorter grass at the field......

Bish Wheeler

I think that balancing "on the tires" will most likely give you an erronious reading as to the C.G. You will more than likely be nose heavy if you look for the C.G. that way. Imaqine if you had a plane with forward mounted gear (which the Spit does not) and you balanced it "on the tires". It would be way nose heavy. The only way to find out the location of the C.G for sure is to suspend the plane at the design C.G. You do that by drilling a hole up through the fuze and passing a heavy cord or wire throught the hole and hang the plane from the ceiling. In order to make the Spit behave it has to be balanced "flat" in this manner. When you do this you will probably find you have too much weight in the nose which certainly contributes hugely to the nose over problem.

Bish

wulf190

My Feedback: (19)

Could be Bish. I balanced with the G.P. CG machine with the gear up and liked the accuracy of using it. I felt it really helped out to get the right amount of nose weight added to get at the 4 1/2" mark. If it's a little nose heavy at this point, I'm o.k. with that, as I would like to get it in the air and go from there, something that's a little less likely to happen if the CG is too far to the rear. So I'll try it this way and see how manageable flight is first.

Bish Wheeler

Well that works. I misunderstood and thought that you were just using the wheels as the balance point which would make me real nervous.

Bish

wulf190

My Feedback: (19)

A good shout out for the Great Planes CG machine by the way. My first time using it, I found that it was superior to any method I've tried so far, especially so for a large plane since they're so unmanageable to lift and carry and all that.

Bish Wheeler

Gawd, I know what you mean. I went to the hang it from the ceiling thing about 5 years ago when I built a 1/4 scale Goshawk. I was getting a lot of hanger rash from banging it into things and my back was protesting. It's amazing how heavy 20 or 30 lbs can seem when you are trying to hold it at arms length!! Built a MiG 3 and Tiger Moth both of the 1/4 scale persuasion and the "hang it thing" has worked so I'm sticking to it. I sweat CG probably more than I need to, but after all the work that goes into these damn things, I want every edge I can get.

Cheers, Bish

Spitfire7856

My Feedback: (1)

Hi Bish
I think 41/2 inches back from the leading edge, wheels up and inverted is correct. Let me know how she did after you fly it

Best of luck and regards
A3

wulf190

My Feedback: (19)

CG doesn't matter much when power isn't up to the task. So the advice of others is learned the hard way during my maiden today. It was an inglorious end for the effort, 10ft. of flight to a perfect tip stall on the left wing and pinwheeled it into the ground. Worst I've probably ever wrecked a model in fact. Everything seemed good, take off roll straight, nice and lengthy, acted like it wanted to fly itself off, so I gave it a little up elevator and she lifted clear. I tried to keep the angle very slight, but really wanted to get some altitude while I could get a chance to get some feel of what it was going to do. Wasn't really given any chance at all as I corrected some aileron to straighten, had to keep the nose up in order to bank, and that was all, just didn't have the authority it needed to keep pulling. Of course all of the could haves and should haves come into play now, but I really think I did what's called for to try to correct. I've got enough experience with flying and setting things up that I think everything was right, except for having a Moki 2.1 in there for extra confidence. I hate learning this way, but must move on.

The wing is a wash. Outer panels survived, but the center section is trashed. The gear, god bless em, are undamaged other than a broken axle insert on the lower oleo. All radio and engine/spinner survived as did canopy, cowl and most all of the rear fuse. As might be expected front fuse is trashed. I've got all the parts but why rebuild now when a fiberglass fuse and foam wing on a new one takes the sime amount of time and is lighter and straighter? What to do now though?

I've now got a lovely running ST3000 without a home, a set of Shindin retracts for a 1/5 Spit, 9 servos, all the wiring, switches and extensions and a 5" spinner and a couple of 4" wheels that need a model! Do I:

1)Go Brian Taylor f/g fuse with a foam wing cut, or could build a wing I guess and use some of the stuff I've got?

2)Go with an American Eagle kit, 84" f/g fuse and foam wing and use all the stuff I've got

3)Dish the Spitfire project and use the retracts in a Don Smith Me110 that I was planning on building this winter, selling the engine and various items leftover from the Spit?

Seems like the cheapest route is to simply scrap the Spit project and use the stuff in the 110, but that's tough to come to grips with as I've now got the Spitfire blood pumping and don't like to say die very easy. I'm all ears from you guys. May BS459 rest in peace.

spitty

She should rest in peace.....oh what bad news, sorry for that ,hope after a few days You´ll feel better.It´s always a tragedy,ok,no
full scale pilot died,but think You died a bit with Your Spitty.

Hope Your next Project will be more sucessfull

Regards

Andy

wulf190

My Feedback: (19)

Thanks Andy, I'm on the way to another wing soon and can easily repair the fuselage, so I'll try again. While I figure out what best to do, I bought a 1/5 FW190 D9 to finish in the mean time. Talked with CJM about a foam wing kit and also have the templates for the wing ribs so I shouldn't have much trouble getting her back up with a bigger engine, the CG moved ahead a small amount and a new wing with the gear moved forward a bit. I felt a good deal better after getting the 190 though, funny how that works.

LDM

My Feedback: (15)

wulf , good luck with the re-build , I have a Pica P40 in the box waiting for come alive , I know there a lot of work so if it crashes on its maiden I guess you have to enjoy the building as much as the flying and I know it happens to the best !!!! . The good news is if you can build a Pica kit , you pretty much an accomplished builder , the amount wood , sanding , and more sanding is intense and modern day kits are a breeze to the Pica kits .
Good luck agian , dont give up

Moggy

My Feedback: (9)

Wulf,

Sorry to hear about the Spit. I'd hate to see you give up on a Spit. You can fast track it if you go for a Yellow Spit or if you want an earlier mark you can go with a Brian Taylor wing and a fiberglass fuse from VICRC. If you like the Tiger that much the Taylor would be a good fit. I'm finishing up my Yellow Spit and I am going with a 3w60 as the power plant. Good Luck!