Speedy-Gonzales

My Feedback: (202)

My statement of forward fuselage insignificance pertains to the small size of the model and the rounded shape of the underside. Through calculations you may find that the change in CG due to this non lifting area ( unlike on the SR-71 and F-15 which is a lifting surface ) may be minimal. Yes I am wrong in stating that it is insignificant but it is minimal on such a small model. The SR-71 and F-16 incorporate a forward "chine" which is specific for genertaing lift with angle of attack and generates no lift in SLF. As I suggested, use the CG calc chart. Get it running and walk out to the tall grass and launch it. It will be one of 3 things. Tail heavy, nose heavy, or close enough to correct with some trim. Now if this was a $16,000 turbine powered model I would be more concerned. You guys, in theory, are correct. I will admit that but I have calculated many wing and airframe designs and have yet to find a substitute for actually flying the model. Sometimes you can calculate the exact CG to find that you still missed your mark. Bicycles do not come with instructions. You have to get on it and ride to learn. Put an engine in that yellow bird and let us know how it goes! Please excuse me. I am a speed freak not a mathematician!

mk1spitfire

speedy what would you power it. ic, size motor?

Electric?, I have an axi 4120/18 to much???

AXI 4120/18
Suitable for models weighing between 3500-5000g
No of cells 16-22, - RPM/Volt 510 - Current Capacity 55A/60s - Dimensions 49.8 x 55.5mm - Shaft Di. 6mm - Weight 320g

Speedy-Gonzales

My Feedback: (202)

What is your wing area and span? I would say a hot .15 for starters. Another factor would be the weight needed to balance the model. Tail heavy...smaller engine. Nose heavy...bigger engine. This is hilllbilly math/aeronautics plain and simple. Electric???? I have no idea. Remember........"Screamin Nitro" is my game!

mk1spitfire

yer me to!!!

The wing length on it is about 33" fusalage length about 32"..

I though more 50 size engine

Speedy-Gonzales

My Feedback: (202)

mk1spitfire, I finally meet someone as crazy as I am!!! A .50!!!! How about a O.S. 25FX or .32SX? I see you posted a bare airframe weight of 2 lbs. I think the .32 SX would not generate the need for nose weight required using a .50. A .50???? Now that there's funny!!! The only downside I see to a pusher is finding a good muffler setup. I better slow down on my posts. I usually find myself in the middle of an arguement by now!

evan-RCU

.35AX, TT .36, or something like that will give you the R's you need. If you do a mathematics determination of the CG make her nose heavy from there or it will fly tail heavy, I'd say by a good 3/4 to 1".

I am a mathematician (at least its a BIG part of my job) but have been a plane designer and builder longer.

Speedy-Gonzales

My Feedback: (202)

Hey Evan...will you do my taxes for me next year???? [sm=49_49.gif] You designing/building full scale aircraft or models? Just curious. No sarcasm intended.

evan-RCU

Just models... models are my thing, I've been doing it since I was 8 (43 years) and will be doing it until I can't, hopefully another 30+ years...

evan-RCU

You look like you've been doing this awhile too!

vicman

My Feedback: (10)

When he toots dust comes out[X(]

mk1spitfire

Nice to meet you speedy!!!

Would there be any detrimental issues running a full length pipe with exhaust end facing front. Is there any thrust produced from the exhaust?

Speedy-Gonzales

My Feedback: (202)

Look for a tuned pipe that is used on a DF model preferrably a pipe that the stinger exits from the side. I believe the guys that are flying these BOBCAT pusher prop jets are using them. I think Morris Hobbies handles them for their Rossi line of engines. Hope you can find one for your engine size. I just had a brainstorm of an idea! Make a mousse-can muffler! Speedy

mk1spitfire

Does the exhaust gases have to exit rearward?

mouse can, w t f is that?

Electric Delta

My Feedback: (13)

Weston UK http://www.westonuk.co.uk makes some very nice tuned mufflers for pusher applications, and can even custom-build one for you for most any engine.

mk1spitfire

yer, Have had excellent service from them before. I'll check it out but really wanted to know of any reason the exhaust gases can't face foward other than covering your plane in oil or if gas thrust comes into play?


would the wind give extra pressure blown up the pipe?

Razor-RCU

My Feedback: (50)

MOUSSE- Hairspray can modified into a tuned muffler/pipe.

vicman

My Feedback: (10)

He lives!

Flyboy Dave

My Feedback: (21)

Speedy-Gonzales

My Feedback: (202)

Razor-RCU and I have suggested the simplest and cheapest and possibly the highest performance muffler you can make. The "Mousse-Can" muffler will give you the advantage of light weight,very high performance,and low cost. It will also allow you to place the exhaust facing any direction you desire. Having the exhaust opening facing forward into the airflow most certaily will not help under any circumstance. I have never seen a vehicle land/sea/or air with the exhaust pipes in the front! Never! Hmmmmmmmm.........this makes the reason obvious. Let me know if you need some pictures or info. Go to the R/C Combat Association's (RCCA) website. These are the guys that instigated the mousse-can muffler design. They work and they work great especially on the .25 to .45 displacement 2 stroke glow engines. Why pay $100+ for a custom exhaust when you can make your own for about $15.00! If you cant make a header then buy the MAC header that fits your engine and you are half done. Buy a can of mousse for $1 and be sure to empty the entire contents on your head so it isn't wasted. Seriously...let me know if I can be of help. I'm sure Razor-RCU will help too. Speedy

mk1spitfire

Mouse can as in hair?[X(][sm=bananahead.gif]

ok, that sounds different. Want to enlighten please?

Speedy-Gonzales

My Feedback: (202)

mk1Spitfire, Here is a link about mousse can mufflers. ( as in hair ). Don't be afraid to ask questions. We all learn from others.

Mousse can links:
http://webpages.charter.net/rcfu/ConstGuide/MCM.html
http://www.personal.psu.edu/dmd7/RC%...can%20mods.htm
http://www.extremeflightrc.com/manua...l_date0308.pdf

The last link is an article on the OUTLAW delta wing and shows a great picture of the muffler on the plane. If link does not open direct, copy and paste into your upper URL search box and hit enter.



My favorite saying..." We learn more from our mistakes. That is why I'm so damned smart!"

mk1spitfire

Cheers Speedy.

When you said mousse can I thought you were taking the piss only to clearly see the outlaw all moussed up, Blimey I've seen it all now.!!!!!!!!!!

Speedy-Gonzales

My Feedback: (202)

British humor. I love it! Winston Churchill stated that Great Britian and the USA were two countries seperated by the same language. As like all great men, he was disliked by his adversaries and unappreciated by his allies but he went down in history as one of the greatest leaders of the 20th century. Cheers to you my friend! Speedy

mk1spitfire

Churchill is legend and his large cigars! and so is the spitfire he commissed supermarine to build under Mitchell's guidance.

Now I wonder what churchill would make of us speed freaks? How about converting a Winston Churchill single cigar case tube into a replacement mousse can muffler??????????

Behold, we have the Havana tuned pipe.

vicman

My Feedback: (10)

Blimey indeed!
I like the Havana pipe idea!