Re: Racing Mongoose

fredvon4 Fri Nov 14, 2014 4:27 pm

Thanks for the video but as a combat guy who loves the Mathis Mongoose I kept waiting for the tail chase this plane can do...LOL.

Do the rules allow you to shape or modify the props or do you have to run them as delivered?

Sounds to me like the engine could be spun a little tighter

Also for a tad less drag make sure on your next build to sharpen the LE and the TE. The wing shape, as designed is intended to turn tight...for pure level flight you don't have to worry about a stall or mush in turns up or down so a less blunt LE should gain some speed. The TE being very sharp reduces parasitic drag

JPvelo Fri Nov 14, 2014 5:06 pm

Fred,

Unfortunately no prop mods. I'm going to try and get the prop rule changed to something like "commercially available props costing less than $5.
Yes it's a bit rich, my thinking is that restarts will be faster with a cooler engine. Judging from our first race the guy with the fastest pits will win this thing. That being said I've seen a tank with the uniflow plumbing set so that the engine richens up the last 1/4 tank to help with the restart. I may try my hand at building one. I've never soldered anything in my life but it's time to try.

Jim

Ken Cook Fri Nov 14, 2014 5:17 pm

Jim, I run these engines balls to the wall and they restart immediately.I If your not getting quick enough restarts due to overheating I would look into opening that venturi which I would be doing anyhow unless they have a restriction on size. Seeing you had that one made, what did the maker base his size from? That engines isn't available as a control line engine. Modern engines are not like old iron. If your engine doesn't want to cooperate, dowse the engine with water or use a soaked wet rag when you pit and immediately grab the head. We do it all the time with engines and they immediately restart. I personally use fuel but then again, fires can happen. Our last racing contest is this Sunday Nov 16. We have Fox sport race and clown both sportsman and fast. Ken

JPvelo Fri Nov 14, 2014 5:24 pm

Ken,
I've not tried a practice pit yet. Four of us are getting together next Friday to practice, I will run it balks out and see what happens.
The venturi internal diameter is the same as an L.A. .25. Rules allow for unmodified .25s only, that's why we went with the L.A. .25 sized venturi.
I'll try and get video of a practice race.

Jim

Ken Cook Fri Nov 14, 2014 5:43 pm

What confuses me here and it's more than likely the rules that I'm dealing with over here is the fact your running plain bushed engines against BB engines. Venturi size will give you a bit more power, but it will also cool the engine a bit more. More fuel equates to more power. The term modified would be questionable to me at least in this event. You already modified the engine by making your own venturi due to it not coming stock with one. A larger venturi may give you a slight power edge, but it's also going to make your fuel economy go down. You need to find a balance between prop and venturi and lap times to suit the event. Most LA .25's I believe used a .265" venturi opening on the .25's. However, I have had some larger as much as .273". They have variables and I certainly wouldn't feel that opening your venturi wouldn't be constituted as cheating. Ken

JPvelo Fri Nov 14, 2014 5:56 pm

Ken,

It's a new event and the engine choice rules seem a little loose. At the meeting Tuesday a long time and very well respected club member said my engine wasn't legal. We reviewed the rules and it's ok. That will change if the BB .25 guys start creaming the fox guys, and rightly so. My understanding is that the Brodak .25 is the hot engine for SSR. I will get one if the rule changes. I also have a new Fox .35 that is super tight but I don't want to abuse it on a race plane .

Jim

**Cribbs74** Fri Nov 14, 2014 6:06 pm

I have never understood why you just can't have a .25 class and open it up to mods. Seems to me that you could really have a good competition that way.

Anyway, the Mongoose is smokin' Jim! I hope you win with it!

Have you considered walking with the plane? All the speed stuff I have watched, the guys in the center walk around as opposed to standing still. Not sure if it helps anything, but they all do it.

Ron

JPvelo Fri Nov 21, 2014 4:05 pm

It's not pretty but I broke down and built my own race tank. It performs flawlessly, even rpm till the very end and 37 lap runs. And yes, the tank started life as a Colman's mustard tin!
Racing Mongoose - Page 2 KWGADJA

**Cribbs74** Fri Nov 21, 2014 4:08 pm

Looks good to me Jim! Good job!

roddie Fri Nov 21, 2014 5:32 pm

Awesome Jim! Thumbs Up

I was hoping you'd give soldering-up a tank a try.. and it ended up being a success! I'm sure you'll build more if you like it as much as I did, after the first time.

That's a cool class.. even with the red tape involved. They'll settle on something soon enough.. and you'll have something that works.. I'm sure.

getback Sat Nov 22, 2014 9:41 am

Nice Job Jim , Looks ant ever thing if it works and serves the purpose that's good enough , I like the way you have it plumed as best I can tell, I don't think there is no way it cant work with the outlet on the bottom . I have a question , why did you decide to put the pressure line on the bottom as well / instead of the top? Eric Cold

JPvelo Sat Nov 22, 2014 9:51 am

Eric,
I put the pressure line next to the feed so it acts as a uniflow. I saw the idea on this thread over at Stunthanger:
http://stunthanger.com/smf/index.php/topic,25610.0.html

Jim

JPvelo Sun Dec 28, 2014 12:05 pm

Today's lesson:
Always always ALWAYS check to make sure lines aren't reversed before launching!
Racing Mongoose - Page 2 5dRn4h5

ian1954 Sun Dec 28, 2014 12:10 pm

Oh dear!

It looks like the spinner and the propeller took a battering but is the engine OK?

Ken Cook Sun Dec 28, 2014 12:29 pm

Jim, that's horrible. One way to stop that from happening again is to use colored heat shrink tubing on your line sets and leadouts and handle. Anyone in control line has visited that destructive path. Ken

JPvelo Sun Dec 28, 2014 1:17 pm

Ken,
Great idea on the heat shrink. I think most of us on the forum have learned that the most painful lessons are also the most valuable. I will check control direction on every preflight from now on.

Ian,
The crankshaft is bent and a mounting lug was broken:
Racing Mongoose - Page 2 Btc2iOX

I already have a new engine on order . The plan is to put the already broken in piston and liner in the new engine and mount it on this model:
https://www.coxengineforum.com/t7618-racing-super-clown-build#95939

**Cribbs74** Sun Dec 28, 2014 2:59 pm

Boom!!

Dang Jim, you made a mess of that thing. Welcome to the busted crank club Neutral

The Clown should make a great racer. Small, light weight and thin airfoil. Can you modify the plane?

If you can add a streamlined nacelle that would look sweet and sleek!

Ron

roddie Sun Dec 28, 2014 4:12 pm

Sorry Jim.. not sure if you're into naming your models.. but if it were me; in memorial of the Mongoose, I'd name the new model "Tears of a Clown".. but that's just me being me. Good luck with the new build.

JPvelo Sun Dec 28, 2014 6:11 pm

Ron,
The model can be modified to "add strength for racing". I plan on adding a 1/8 hard balsa inboard tripleler and an additional nacelle to fair the 1 3/4 spinner into the fuselage. I will also sheet the leading edge back to the spar and go with a single wheel landing gear.

Jim

Theo Kleynhans Mon Dec 29, 2014 3:02 am

Sorry to see Jim

Looks like the plane hit the deck really hard. Glad you got a new engine on the way.

Theo

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