Timthetoolman1

My Feedback: (6)

http://mvvs.nl/prop-power-calculator.xls


With a standard prop on both engines in the above program yields:
Saito .91 = 12 lbs of thrust
OS .61FX = 7.7 lbs of thrust
Does that sound right?
The guys flying here are saying the 4 strokes are not working for them, but they are also using OS 4 stokes. The planes are weighing between 6-8 lbs so but they are running out of vertical. Some are also having engine out problems (I think they're inverted). I'm thinking they aren't tuned right or cooled right because I have 3 Saito engines mounted inverted and they are all reliable.

Any suggestions or ideas?

Has anyone completed a Phoenix V from Early RC. Is the Phoenix a good plane versus a Nutcracker, Tiporare, Curare, or a Tiger Tail?

Thanks in advance.
Tim

pimmnz

Static thrust results have no relation to what will happen when you fly the model. A stationary prop is nearly all stalled, and all you are measuring is the ability of the thing to blow air backwards. Pick the engine you like the most, build your model as light as you can, and then experiment a lot with all sorts of propellers, within the parameters of what you want to do. You will find that the best engine/prop/airframe will often yield pretty poor 'static' thrust results, but you are not actually interested in that...
Evan, WB#12

Timthetoolman1

My Feedback: (6)

Thanks Evan.

What about the plane? Any suggestions?
As a warbird builder I've never considered weight but I'm am now. Fiberglass vs. wood (I do want fiberglass/paint covering), foam or built-up wings (I have a friend with a vacuum bagging setup).

pimmnz

For myself I have always contended that a built up, wooden model is lighter than the equivalent foam and glass version. I have never had much luck with foam wings, so I don't use them. I have a Curare, Super Sicroly, Blue Angel, Warlord, Super Kaos, Superstar and Atlas, and none is heavier than 6lb 14 oz (Atlas). All have .60's and retracts (mechanical) with 2 retract servos (except the Kaos). I use single aileron and elevator servos, just JR811 digitals, and some are still using good old 417's. Engines range from a real old Webra '10ccm' to a couple of T.T .60's. I compete with them in the 'lower' classes down here to good effect, we don't run a separate 'SPA' thing so you have to contend with the usual 2m stuff in the same contest. That I can still place is testament to the fact that these older models are still pretty fair aerobatic machines.
Evan

smacfe

You will find that 80-90% of competition models (gliders, aerobatic and racers) are glass and foam or composite - because of the lower weight advantages. It does take a distinct set of building skills to garner this advantage though. It takes about three builds before you learn most of the techniques to build light glass airplanes. It is also true that the older glass fuses, especially the polyester layups were unnecessarily heavy, and the newer epoxy fuses are much lighter.
Scott

Timthetoolman1

My Feedback: (6)

Well, spur of the moment bit me in the a##. I had a set of Tiporare plans and saw how easy it was to build so at lunch I decided to got with it. I went to my friends to cut some foam wings. Here's where it bit me, I didn't know what the 'actual wing tip is 1-3/8" forward' note meant it was not a straight trailing edge but after I cut the wings I figured it out. That's fine we cut it out of blue foam and it's a bit heavy so I'll try the white and use the blue for the horizontal stab.

Atlanta 60

My Feedback: (18)

Congrats on your decision to do the Tipo...

You may be aware of this stuff already?? Nor am I an expert on foam wing cores but here are two points which I think are pretty important:

White foam is available in different densities...You wanna use 1lb density for your cores...

Use some good 1/16" *contest grade* balsa for your sheeting...


Here are a couple of links you may find useful:

http://www.eurekaaircraft.com/foamwi...amwingmain.htm

http://www.lonestar-balsa.com/


Good Luck with your project!!

Chuck

jmb52760

On inverted four strokes (a little off-topic but mentioned), I was having difficulties with an inverted Saito 100 and a 3-D prop until I installed an on-board glow driver. The kind that "comes on" at a user-defined low throttle setting. Works like a charm. There is, of course, a weight penalty for the additional battery.

Timthetoolman1

My Feedback: (6)

I typically make my own onboard glow and use a small 1.2v rechargable battery but I only use it for starting and landing. My weight penalty would be a micro servo and switch mounted on a thin piece of ply and two blocks for the servo to mount and an external switch. It shouldn't be too bad.

Yep Chuck, I have another friend who has helped me select good wood for other projects. I'll be going to his house today so he can laser what little parts there are. Fortunately Lone-Star openned back up so I'll drive there and pick out my own wood. (Wish the would have stayed in Lancaster but it's only 15 minutes more).

We were discussing the ailerons last night. I might try a ball and pocket type design with Robart hinge points which means the knuckle and the control rod will be in the centerline of the LE of the aileron but I will have to come up with a technique to flute out the trailing edge of the wing. I'll post some pics when I'm done.

teamvortex

My Feedback: (6)

pimmnz,
Is there any chance that you have the plans for the Blue Angel or know where I can get a set for SPA work?

Thanks,

Rich

Deception (2)
Kaos
Beachcomber

rainedave

My Feedback: (1)

I agree with Evan that static thrust and rpm measurements don't tell you much about a model will fly.

What they are good for is comparing various engines against each other and determining whether or not your engine is performing as it should. For example, if you have a 2-stroke Schneurle-ported .61 and it's only spinning an APC 11x7 at 12,000rpm, something is wrong and you need to fix the problem before flying with it. Even so, some engines will unload in the air more than others and measured rpm on the ground can be deceiving. Flight rpm is always going to be different than test stand data. Another advantage of test stand running is troubleshooting a difficult engine. The key to problem solving is to eliminate as many variables as possible (fuel lines, tank height, glow plug, etc). That is much more difficult to do with the engine in the model.

David

pimmnz

Well Teamvortex, '8178' has just completed a BA build on another thread here so he could still have plans, the ones I used are definitely copied from a kit, but with the Yoshioka mods ready drawn. A bit minimum but if I can build one from them, then anyone can... If you are interested then I will get a copy done, or you can try 8178's good offices, he is bit closer to you than I am for sure. Let us know what you want to do.
Evan.

dhal22

there are 2 blue angel threads here (8178's and mine). we both got our plans, canopy, wing and stab cores from the same place. the vendor has a new email address that i don't have right now. although i did a few things different you would want to refer to 8178's build thread for building assistance.

kingaltair

My Feedback: (4)

If you are talking about flying in SPA competition, the Tipo is not SPA-legal. It came along after the Jan 1976 cut-off date. Several people fly the Curare, and a very nice ARC is produced by Steve Byrum. The Daddy Rabbit is a very popular plane, as is the WM Intruder ARF, (for those who want to get out there quickly). It isn't perfect in the upper classes, but it is competitive. The newer models on the block for 2009 are the Deception and Compensator. Both are produced in a partially built state, and plans can be had. The Dirty Birdy is also a popular choice. I know it is kitted by Blue Jay, and an SPA member manufactures a light version of this plane.

6 to 7-1/2 pounds is about the weight they should be. All the models are wood to the best of my knowledge. The O.S. .91 4-stroke is the standard engine, and is often flown on a 13X8 to 13.5X9 Narrow APC prop. The general feeling is that verticals are BETTER with the 4-strokes.

Go to the SPA website, and get on the Discussion List to get all the advice you'd ever want....and more.

Duane

Timthetoolman1

My Feedback: (6)

Ya, we figured that out but I decided to build it anyway and the Dirty Birdi is an option...I'll have to see what turns up.
Thanks.