Author Topic: Fox 35 for Speed. (Read 24170 times)

Speed Demon · « **on:** November 06, 2023, 10:13:51 AM »

Hi new here, and new again to CL after many many years Lol. I had some experience with Goodyear back in the 70's. This said.

I have an interest in the Fox 35 speed event. I am assembling equipment to put some planes together and hopefully have some fun.

What I am interested in learning is. What can be done to the old Fox 35 to make the most power from it possible? I am aware of the basics, stuffer back plate, hemi head etc. I am wondering more about port timing changes, piston/sleeve swaps, increasing inlet sizing? Next level mods.

Anyone of someone knowledgeable in this area, or may even offer parts? Thanks

Dave Rigotti · « **Reply #1 on:** November 06, 2023, 11:06:48 AM »

Polish out the "lip" inside the crankcase inlet transfer.
Get a Bill Hughes hemi head insert. (this alone adds 5MPH)
Super Tiger style needle valve assembly. Turn the OD down to .135" diameter only where it crosses the venturi id.
Mill the bottom of the mounting lugs flat.
Use a FOX brand 35 stunt ABC piston/liner. No timing changes made.
Lap backplate mounting surface flat.
APC 8 x 9 prop
40th or 50th anniversary versions do better.

The above gets to 102MPH.

Dennis Toth · « **Reply #2 on:** November 06, 2023, 11:07:32 AM »

SD,
Since you are coming back I think the first steps should be to get you CL legs back with a sport plane like the Flite Streak or Ringmaster then move to something faster like a combat wing. Once comfortable the FOX 35 speed ships are basic rat racer style ships, lots of plan here: https://outerzone.co.uk/browse_plans/category/results.asp?Level=2&Cat1=CL&Cat2=Sport can do a search at the bottom of the page.

As for engine mods, the stuffer backplate is popular but you could just us the stock one with a very thin gasket and get a similar benefit of keeping the rod from moving to far back. The button head is also popular as are other aftermarket heads that raise the compression. Changing to a better NVA is also something that is done but you can't make the spraybar to small as you need to run suction only so need to have a stable needle. Some have changed the piston/cylinder there are some aftermarket ABC units avialable from time to time. Since the fuel is provided at the contest (by rules should be 5%N) no exotic fuel. Also, no carbon fiber props, commercially available wood or nylon reinforced (APC's or Master Airscrew). Trimming diameter of the props, thinning blades and repitch is allowed.

Best, DennisT

Speed Demon · « **Reply #3 on:** November 06, 2023, 02:40:54 PM »

Thank you both Dave and Dennis. Very helpful, defiantly a good advice to get going.

Dennis I have done some recent flying with a buddies Ringmaster, that's what get me into my current dilemma. Yes I am working on a couple "practice" planes.

Dave luckily, I still have a good 40th anniversary from slow Fox 35 project some 20 years ago.

Speed Demon · « **Reply #4 on:** November 06, 2023, 06:20:55 PM »

Where can I locate fuel, or something similar to what is required?

C.T. Schaefer · « **Reply #5 on:** November 07, 2023, 04:56:39 AM »

Good advice above. Good event that leaves plenty of room for experiments. Weak point is the crank. Not much to be done but hope you get a 'good' one. There is the Randy Smith unit if you can find one. Also many parts from other than Stunt .35 will drop in. TS

Speed Demon · « **Reply #6 on:** November 07, 2023, 05:54:35 AM »

Quote from: C.T. Schaefer on November 07, 2023, 04:56:39 AM

Good advice above. Good event that leaves plenty of room for experiments. Weak point is the crank. Not much to be done but hope you get a 'good' one. There is the Randy Smith unit if you can find one. Also many parts from other than Stunt .35 will drop in. TS

Yes, it is a good formula to be able to compete without breaking the bank. What other parts will interchange?

C.T. Schaefer · « **Reply #7 on:** November 08, 2023, 06:05:43 AM »

Piston. Cylinder, Head from any of the .35's from 1957 onward. CS, Rocket, Etc.

Paul Smith · « **Reply #8 on:** November 08, 2023, 09:53:09 AM »

Quote from: C.T. Schaefer on November 07, 2023, 04:56:39 AM

Good advice above. Good event that leaves plenty of room for experiments. Weak point is the crank. Not much to be done but hope you get a 'good' one. There is the Randy Smith unit if you can find one. Also many parts from other than Stunt .35 will drop in. TS

Fortunately, the world is full of worn out Fox 35 Stunts with surplus crankshafts if you generate enough power to blow a crank.

Speed Demon · « **Reply #9 on:** November 09, 2023, 08:17:05 AM »

Ok guys are there any parts from other engines that fit that will offer more power/RPM?

Will parts from the 35X or 35 Rocket for example?

Bob Heywood · « **Reply #10 on:** November 09, 2023, 09:27:05 AM »

Before you get all involved in "voodoo speed secrets" the most important thing to know is that piston / cylinder fit is 85% + of the engine performance. The thermodynamic efficiency of a heat engine is directly proportional to the absolute ratio of compression of the cycle. You have to minimize blow-by to the max.

Get the Nelson glow plug head button Dave Rigotti advised and a stuffer backplate. Use the ST needle valve. Build the engine.

Look under the Engine Set Up Tips section for "L&J Fox 35" and follow Larry's break in schedule to the letter for a new P&L set. What you are basically doing is lapping the piston / cylinder to a nearly perfect fit. DO NOT take the engine apart after doing this.

Fuel flow management is also very critical for Fox 35 Speed. The fuel tank position needs to be optimized for the launch and the speed run, especially as the venturi is opened up. Dave mentioned turning down the spray bar. That is a good start. I was able to use a K&B Racing Needle Valve assembly by adjusting my fuel tank in order to prevent the engine from surging on launch.

The devil is in the details. Good luck.

Mike Greb · « **Reply #11 on:** April 03, 2024, 07:28:24 PM »

Are the rules posted anywhere? What I was interested in was airframe restrictions.

Dave Rigotti · « **Reply #12 on:** April 03, 2024, 08:18:16 PM »

https://lafayetteesquadrillecl.files.wordpress.com/2017/02/fox-35-rules-feb-2017.pdf

Quote from: Mike Greb on April 03, 2024, 07:28:24 PM

Are the rules posted anywhere? What I was interested in was airframe restrictions.

Motorman · « **Reply #13 on:** April 04, 2024, 09:47:45 PM »

The only airframe restriction is you have to have one wheel min.

Frank Imbriaco · « **Reply #14 on:** April 11, 2024, 10:50:23 AM »

I've got a 35 Stunt with a re-timed Brian Gardner piston/ liner/ rod. Very, very few made. Interested ? PM only.

PaulGibeault · « **Reply #15 on:** April 14, 2024, 11:27:00 AM »

FWIW, Bill Lee acquired an estate collection of many Fox .35 parts notably modified crankshafts & new crankcases for sale at GREAT prices.
If you run a Fox hard enough, you can break crankshafts & more. Can't be beat, try him! Good Luck.

Paul G.

Quote from: Speed Demon on November 06, 2023, 10:13:51 AM

Hi new here, and new again to CL after many many years Lol. I had some experience with Goodyear back in the 70's. This said.

I have an interest in the Fox 35 speed event. I am assembling equipment to put some planes together and hopefully have some fun.

What I am interested in learning is. What can be done to the old Fox 35 to make the most power from it possible? I am aware of the basics, stuffer back plate, hemi head etc. I am wondering more about port timing changes, piston/sleeve swaps, increasing inlet sizing? Next level mods.

Anyone of someone knowledgeable in this area, or may even offer parts? Thanks

Fred Cronenwett · « **Reply #16 on:** April 28, 2024, 07:25:54 PM »

Motorman · « **Reply #17 on:** April 30, 2024, 09:15:07 PM »

I've got a guy interested in making some high compression heads for the Fox speed event. I could have him copy mine but if you guys know something better than me chime in.

MM

Dennis Toth · « **Reply #18 on:** June 17, 2024, 07:40:32 AM »

Did they fly Fox 35 Speed at Brodak? Who won, show, placed, participated?

Best, DennisT

C.T. Schaefer · « **Reply #19 on:** June 18, 2024, 04:41:05 AM »

That event was dropped a couple of years ago due to lack of interest. Sadly. TS

Dennis Toth · « **Reply #20 on:** June 18, 2024, 06:45:01 AM »

Sad, but maybe if the standard rules that are used at all the other venues were used it would have more participation. Just say'in.

Best, DennisT

Al Ferraro · « **Reply #21 on:** June 18, 2024, 10:17:57 AM »

Looks like my Fox Speed MPH of 112.32 set at Brodak in 2017 is still holding the top spot.
Al

Dave Rigotti · « **Reply #22 on:** June 18, 2024, 10:46:52 AM »

Nope. Bill Hughes did 118MPH in St. Louis earlier this year at the ICE-O-LATED contest.

bdt-m · « **Reply #23 on:** June 20, 2024, 04:12:00 PM »

IMO the most ridiculous speed event I have heard, intended for a Fox .35 Stunt engine, that the top speed flyers are building all new internal parts to garner the highest possible speeds. Sounds almost as bad as Perky....

How about if you want to showcase your speed talents, you pick any on the existing events that are 'true' speed classes....?

Dave Rigotti · « **Reply #24 on:** June 20, 2024, 06:40:05 PM »

IMO the most ridiculous reply to a really fun, and competitive event. I "started" my speed flying in this event 4 years ago. Love every minute of it.

BTW.... What speed events do YOU fly?

Quote from: bdt-m on June 20, 2024, 04:12:00 PM

IMO the most ridiculous speed event I have heard, intended for a Fox .35 Stunt engine, that the top speed flyers are building all new internal parts to garner the highest possible speeds. Sounds almost as bad as Perky....

How about if you want to showcase your speed talents, you pick any on the existing events that are 'true' speed classes....?

Paul Smith · « **Reply #25 on:** June 20, 2024, 06:56:56 PM »

Quote from: bdt-m on June 20, 2024, 04:12:00 PM

IMO the most ridiculous speed event I have heard, intended for a Fox .35 Stunt engine, that the top speed flyers are building all new internal parts to garner the highest possible speeds. Sounds almost as bad as Perky....

What's "bad" about Perky? It's just a 15 on suction with 10% nitro. There's nothing trick about Perky.

The problem (for me anyway) is that there is no definition whatsoever of what (if anything) constitutes a Fox 35 Stunt. I'm not an builder so those that are can machine away at their "Fox 35 Stunts".

Motorman · « **Reply #26 on:** June 20, 2024, 09:02:41 PM »

Quote from: Dave Rigotti on June 18, 2024, 10:46:52 AM

Nope. Bill Hughes did 118MPH in St. Louis earlier this year at the ICE-O-LATED contest.

Byron Bednar did 125MPH with his Foxberg.

bob whitney · « **Reply #27 on:** June 20, 2024, 10:15:54 PM »

Perky at Brodak s was won by a Box stock Zalp 15 with a combat head at 115 mph .same setup won over all postal last year at 120 mph flown by Mike Lunki( spelling)

Paul Smith · « **Reply #28 on:** June 21, 2024, 06:47:08 AM »

Quote from: bob whitney on June 20, 2024, 10:15:54 PM

Perky at Brodak s was won by a Box stock Zalp 15 with a combat head at 115 mph .same setup won over all postal last year at 120 mph flown by Mike Lunki( spelling)

Londke

bdt-m · « **Reply #29 on:** June 26, 2024, 04:25:38 PM »

I wouldn't have an issue with Fox Speed or Perky if both events followed some semblance of reason.

Wasn't a "Perky" and Ignition powered upright model? Now it's a side mounted (advantage), Combat/Speed/Custom High performance engine.

Fox Speed would be a reasonable event if the rules defined exactly the requirement for a 'stock' Fox Stunt .35, and not simply a Fox case with all new internal parts. IMO this is not a beginner's event, it is an event for those that want to build engines, therefore and again; fly a real speed event if that is your 'cup of tea'.

To answer this comment; "BTW.... What speed events do YOU fly?"... maybe in a past or future life, I can be as good as some of you...

C.T. Schaefer · « **Reply #30 on:** June 27, 2024, 05:04:53 AM »

I will try to answer your question/s
1. Because of the nature of both events they are attractive to folks who, maybe can't jump in the pylon anymore or who have never done so. In addition to that, how many circles in the USA are equipped with a pylon. Another nice thing is the proto flight profile. No messing about with dolly's etc.
2. The rules as they are written offer many possibilities of design and endless opportunities for 'tinkering' to achieve higher speeds. Just like 'real' speed events.
3. We fly both events here in NJ and have had as many as half a dozen participants who would never have imagined flying 'speed before'.
4. A great many of the c/l population are now officially 'seniors+' so the potential speeds are still manageable to most active flyers.

Speaking for myself, when I look around I see very few of us who are active flyers and consider it a gift to be able to get out a few times a year to fly these seemingly funny things with my pals. When I look back I remember getting to fly/learn from many of the greats in our sport and going toe to toe with them in my class (F 40). Great times. Great memories. Now is a different time to enjoy. TS

bob whitney · « **Reply #31 on:** June 27, 2024, 11:55:52 AM »

i spend most of the year getting ready to go to Brodaks and flying Perky with and against the Jersey Boys ask 2nd place where he got his 112 mph prop. and thanks AL for the fuel.hopefully my new perky wont weigh 23 oz . might have it ready to test at the nats