sticktickler

That would be me was asphalt252 but changed it to sticktickler now. I got your e-mail give me call so we can work out what you want.

Mustang Fever

My Feedback: (2)

Sabre:

My Mag 91FS turns almost 10,000 on the ground running 15% and a 14x6 Master Airscrew K series. The Thrust/HP software shows this adds up to 58 mph. I don't think that's fast enough for a Mustang. Topflite says we're to expect a wing loading between 25-30 oz per square foot. I have an article from the Sep 02 issue of Model Aviation, "Matching Propeller to Model Mission" that has a chart of expected stalling speeds vs wing loadings and altitude. At sea level, a 30oz per square foot bird can be expected to stall at around 23 mph.

On the surface of it, this should all be ok, as 58 mph is more than twice the stalling speed, and I've read in more than one source that a cruising speed of twice stall is the minimum you should have. However, what happens on a day when you're flying in a 20 mph breeze, and the wind upstairs is stronger (say 30mph), like it usually is? Making a quick 180 from upwind to downwind can cause the airspeed to go from 88 mph (58+30) to 28 mph (58-30), just above stall. If you don't have 58 mph groundspeed, you're in trouble quick. (None of this applies if you make a big, lazy turn and give the bird time to pick up ground speed downwind, but field conditions will determine whether that's practical or not.)

I'm offering this because I have had high wing loading birds fall out of the sky under the conditions described. We can factor in that some airfoils don't fit the chart that well, but the overall effect is still there. When I first saw this article I tended to ignore a lot of what the author said. In the years since, experience has proved him right. Any of you guys with more knowledge and experience in this area, please jump in, but I try to set my birds up for a max speed of at least three times stalling speed.

sabre1205

Well you got me thinking now
Here is a chart I found on lift
I think I saw somewhere that the TF P51 has a 5 degree positive AOA
Whats your opinion on this?
Also why would Top Flite say the folowing
Engine Required: 2-stroke .61-.90 cu in (10-15 cc) or 4-stroke .91-1.20 cu in (15-20 cc) if a 91 size motor is not enough
to fly the plane?


Sabre1205

Mustang Fever

My Feedback: (2)

As I mentioned, not all airfoils fit the curves- my 4*60 for example, has a much lower stall speed than what the chart indicates because of the "turbulators" on the LE. I'm not sure what your chart is showing.

The kits and ARFs out there where the specified engine is not enough for the job are LEGION. Ask around.

If one built the Mustang w/o retracts, did no scale detailing, and took care to keep it as light as possible, then a 90 FS would probably be adequate. My opinion only.

sabre1205

We will see
I am almost done so i will have a weight here soon and then
I can do the math

Thanks

Sabre1205

mikemedic2

Alright Gentlemen.
I have been reading this entire post for day's now and my eyes are bleeding. First off I would like to thank zp for starting this thread, and to all here for posting there build's especially with pictures!!! You guy's are doing outstanding work!!! I can only hope to get 1/7th the job done.

Now I have one of these kit's sitting in it's box under my table. I have been waiting to build it after I finish my GP 20 cub, which is my first build and is coming along pretty good. I have had the kit for approx. 6 years and have been too afraid to build but the GP kit has taken that away for me. I can say that It is a lot of fun to build! (except the balsa dust, oh and glueing my fingers together and to the plane....repeatedly, some guy's just don't learn.[])

I plan on starting the build soon as I only have the covering for the most part left on the first build, but before I get going I would like to order some of the stuff I need IE: retracts. I do plan on using the 85' retracts and problably robart but which model?[] Everyone here basically is using different ones and there doesn't seem to be a consensus as to which ones are better, mainly a better fit for the doors,and the wings themselves. Any help with this would be greatly appreciated!! I am working another job to save for retract's engine etc. (delivering oil stink's) So far I have enough saved up for the retracts which is why I am bothering you guy's with the question.
Thanks in advance
Mike.

sabre1205

I am using the Robart 605 retracts with the 380 series 3/8" diameter struts and 3 1/4" wheels
The wheels look a little small but I also have the cheap wire covers for the 3 3/4" wheels
I will see when I fly which one I like on the plane the most

bull51

sabre1205,

I am using the robart 551rs, 85 degree. Ordered them directly from robart.

saramos

I will be using the Robart 530RS retracts and the 663R/L offset struts with 4" wheels. The 530s are 90 deg., so I may end up having to switch them for the 85 deg. 531s. The RS are robostrut ready and do not require a wire stub. These have the cylinder to the outside which makes them lower profile, and will keep the cylinder out of the wheel well. My hope is that these will fit into the wing easier and will leave more room in the wells for the struts, wheels and detail. Here are some photos. I also modified the struts so there is a two stage spring action. I cut off about 5/8" off the factory springs and added a 1" spring that will compress about 1/2" under the weight of the plane before the original springs compress. This should get the stance of the plane closer to scale on the ground while still retracting with the strut extended to the scale location.

Scott

Mustang Fever

My Feedback: (2)

Saramos:

Make sure when you install those retracts you don't have the right strut in the left retract (or vice versa) like you do in the pix. Tee Hee.

saramos

Good eye! I just grabbed one of the struts and retracts for the photo and stuck it in. Also, I've been working on the retracts on my Spitfire which are in this (reverse) configuration too.

Scott

mikemedic2

Thanks guy's for the quick response.
I ordered the set saramos has. So if they don't work well or fit well I will install working machine gun's on the plane and shoot his down. just kidding of course. I went with them for problably the same reason you chose them. Hope they work into the wing well. Again thank you all for the post's and especially the pictures. I used this thread to shop for the part's and to compare the part's to hopefully get the (better) set. Doesn't much matter if I don't because that is part of the hobby to overcome and adapt. The pic's are definatly worth a thousand words and because of them I will problably try some of the mods. I would like to try the gear doors cause they look soooo good when there on.

saramos

Mike,

Did you go with the 85s or the 90s?

Scott

mikemedic2

Saramos I went with the 85's to keep a more scale appereance. I also went with the retractable tail wheel and the 1/2 " throw air cylinder, I hope that is enough throw as no one has reported back on that but I will make it work

bull51

If you use the robart 121 tailwheel, it calls for a 3/8" air cylinder

saramos

The 121 retract calls for the #165 cylinder, which has a 1" stroke.

Scott

bull51

right, my mistake. Its a 3/8" diameter w/1" stroke. Sorry for the confusion

mikemedic2

You guy's are right it is my mistake misread the number and I am exchanging it for the 1" stroke, thanks guy's for the heads up

tlgibson97

When I installed my tailwheel the 1" stroke was too long so I added some spacers to the inside of the cylinder. I just experimented with different thicknesses until it functioned without trying to flex the rod I was using from the cylinder to the tailwheel. I don't know if anyone else has had to do something similar to this or if I just have a wierd setup.

sabre1205

On my tailwheel, I setup a rod and used two connecters
they are the ones where the rod goes through and you tighten them up with a setscrew
I have about 1/2-5/8 play in between the two connecters so there is 1" travel but no strain on the tailwheel assy

sabre1205

I am stiil working on the numbers, but what setup(Prop) would you reccomend to fly

Mustang1964

sabre1205:
Do you have a shot of your tail wheel set up?
How are you getting the steering working?
I still have not finished the wings yet, but I am looking forward to getting to the fuse.
Mustang1964.

sabre1205

Here is my setup
I took the rod setup for the tailwheel and moved it up forward and put a bellcrank(its a big servo arm) and mounted it just behind the former
The rest is just 2-56 pull pull wire

SVX

Hello Gents.

I've started my own Mustang, building the B model if Tower ever gets the conversion kit in stock. May post some pics later but now it just looks like everyone elses. By the way great pics guys. I'm just curious, are we all forking out $75 for the Tru Turn Spinner? I know Dave brown has one for less but as I understand it just doesn't look right. I can't believe there is not a plastic Mustang alternative out there?

zope_pope

Ofcourse we are. I am spending 350 on an engine, 40 on a battery, 60-80 per digital servo, 110 for pnuematic retracts, 100 for robostruts, another 100 for the up2 valve, and even more on fiberglass, band aids, CA, blades, etc... The 75 dollars seems like pocket money after all that. Not to mention a nice 40-50 dollar CF prop.