CEF speed contest Design Discussions

SORRY   didn't read the post or something /?? I just ripped off the the landing gear and my damn weight was in the forward position on wing tip engine  and I am kindy [bleep] at me !!!   old pic I am was further along my cg was [down at any position ]   down at any position without a mount ,also when I put the lead out on for the lines had the plane upside down of coarse , but turned around the WRONG SIDE though about just going left hand at that time.....    that's that s all for now folks ....ERIC? YEA I know the hinges are on wrong geeees

P-40Q?

that's correct Mark  , Curtiss P40-Q  ,    updated landing gear ,still got to finish them end   I hope u do fly the Bi- wing plane looks good!!Eric  I made that rear wheel its 2X1/16 " ply sandwiched

I'm coming up a little short on the Pitts length. I have another idea using the production backplate, I'll see if I can try it tonight. I know some of you really want a bipe in the race.

duke.johnson wrote:I'm coming up a little short on the Pitts length.  I have another idea using the production backplate, I'll see if I can try it tonight. I know some of you really want a bipe in the race.

Would a trim tab on the rudder count towards length?

Small trim tab yes, three inch tail wheel extension no.  

Hey the tail wheel idea might help with it being nose heavy.  

duke.johnson wrote:Hey the tail wheel idea might help with it being nose heavy.  

Yes Duke... not sure if you read this part of my previous reply: "You could also make-up a tail-gear using 1/16" music-wire with a (heavy) tail-wheel made from a small steel fender-washer.. sandwiched (glued) between two thin discs cut from sheet-plastic (or thin plywood..) for the hubs."

... it would add "functional" weight... if nothing else; it would help keep the tail down when R.O.G.... As I mentioned; "PAINTING" will offset your models' current "nose-heavy" state... I have been weighing my Bearcat through the painting process. Applying x2 coats of primer-sealer (Kilz brand-white pigmented) has added .5 oz. to my models' airframe... and I still need to apply the base and trim paint.. as well as final clear-coats. Seeing that my "base color" is also white.. I may elect to just apply my trim color over the white primer, and finish with the clear-coats.. foregoing the gloss-white base that I had originally planned.

If I somehow end up "tail-heavy"... I have a carbon-fiber push-rod option to help offset this. Again; "functional" trimming is a much better option than adding dead-weight to the nose or tail.

Roddie

Roddie
That's the plan, "funtional trimming". I'm trying to make the bipe work for those who want to see it in the contest. I still need to finish the P-40, it's the back up plan. I got lazy last night and didn't work on anything last night.

duke.johnson wrote:Roddie
That's the plan, "funtional trimming". I'm trying to make the bipe work for those who want to see it in the contest.  I still need to finish the P-40, it's the back up plan.  I got lazy last night and didn't work on anything last night.

Hey Duke.. I hear ya'... my being on lay-off since last June.. the Bearcat should have been done months ago.   but that's part of the delay... I get to feeling guilty for working on it... when I could be out making $$ as a male model.. or exotic dancer  

Actually... I try to at least do at least one little thing every day.. even if it's sanding-out a blemish, adding a detail/note to the drawing or pre-gluing a part. It's one "less little thing" I'll have to do later.

Roddie

 Curtiss p40-Q got some makeover on the landing gear, now higher in the front looking more like image I am using..engine  mostly together, off to Boomer to see my son today then a few more days off as work still very slow , give me time to stat on the engine mount.. This has been a lot tougher than I had imagined being I have not even built a kit in over 30 yrs. But I am not willing to give into the project . Thinking I really need to get a couple kits and work my skills? up   got another load from the bay I want to try the finger handles out anyone used these before??    Eric

getback wrote:  Curtiss p40-Q got some makeover on the landing gear, now higher in the front looking more like image I am using..engine  mostly together, off to Boomer to see my son today then a few more days off as work still very slow , give me time to stat on the engine mount.. This has been a lot tougher than I had imagined being I have not even built a kit in over 30 yrs. But I am not willing to give into the project . Thinking I really need to get a couple kits and work my skills? up   got another load from the bay I want to try the finger handles out anyone used these before??    Eric

Hey Eric, The Curtiss is looking good! I'm sure you'll get a lot done in your upcoming free time. Nice "eBay load"!!! Not that I've "been around"... but I've never seen those finger handles before... They look really cool... and I want one!!!!   
I'd think that they're what you'll want to fly the Curtiss with (using a narrow line spacing).. They're a much better choice for your 1/2A airplanes.

Roddie

Hey these models are looking great. I'm interested in trying to use a fuel bladder. Where can I find out how to use/make/get one. I didn't realise they were good to use on reed valve engines Are they as good to use as I've read? Once you used one you never go back.
Seeing some of the models with cowls, makes me wish I'd chosen one instead of the Bugatti, although its an interesting looking shape. I haven't flown it yet, still waiting for some calm weather. If anybody could advise me on where the CG should be on a speed model I'd be greatful. If there's a next time, I think a GeeBee R3 is in order.
Now to clean up my workshop and start my next project. An electric Baby Flight Streak. Yes I know it hasn't got a real engine, but I can walk to my local flying field and fly it without upsetting anyone.
Cheers Mike  




Cheers Mike 

Love your plane Mike... It's so radical!!! I don't have any experience with bladders... but Jim, Rusty, Ron and many other CEF flyers use them "exclusively"... and will surely help you out with advice.

You can "purchase" everything you need from Texas Timers though... including a fine-threaded (128 tpi) needle valve assy. for the "reed-valve" engine that you'll be using... (highly recommended) Check out the Texas Timers website.. and at the top of the page.. click on "Helpful Hints"... scroll down to the 5th and 6th topics from the bottom, where you'll find info. on setting up a bladder. The guys "here" will also surely give you some helpful hints!

Roddie

Thanks Roddie, I hoped that would be the case. I'll check out their website.

Mike  

NICE !! Mike that plane looks like it about on the strike ..CG NONE THAT I have heard of I have yet to find anyone say they have?? I think mind is some were close to the engine    back to you!!

My bladder making and using videos are pinned, but I was still new at it when I made them, and have simplified it a lot since then. Jim - JPvelo has made it even more simple using o-rings to secure the bladder to the feed fitting since then.

Here's my clunky old pair of videos:
https://www.coxengineforum.com/t3317-pressure-bladder-how-to-videos-parts-one-and-two

Rusty

Mike,
There are two things critical to running a reed valve engine on bladder pressure, a fine thread needle valve and a filter to step down the tubing size. The valve can be purchased from Texas timers or scavenged from a postage stamp backplate. Here's what the filter/step down looks like:


There's an explanation of the setup here:
https://www.coxengineforum.com/t5911-super-mouse-build-thread
It's a short thread, scroll down until you see the same picture I posted above.

Rustys videos will show you the fueling and starting procedure.

The beauty of bladders is that you are no longer dependent on Venturi vacuum for fuel draw. This lets you drill the Venturi out for maximum airflow. I'm not home and I don't have a drill index in front of me but I think I drill through with a 11/64 and drill to just past the spray bar with a 13/64. That should get you about a 1000-1500 rpm increase.

Jim

RknRusty wrote:My bladder making and using videos are pinned, but I was still new at it when I made them, and have simplified it a lot since then. Jim - JPvelo has made it even more simple using o-rings to secure the bladder to the feed fitting since then.

Here's my clunky old pair of videos:
https://www.coxengineforum.com/t3317-pressure-bladder-how-to-videos-parts-one-and-two

Rusty

Rusty.. those are GREAT videos! I had never seen them before. You are very organized and concise in your instructions (doesn't surprise me   ) Your reference to having safety glasses and an eye-wash bottle nearby, is something that anyone running a model engine should know... and include in their flight box/caddy.

Roddie

I take it you remove the corse thread spray bar from your backplate (how) and replace a with the fine one. Does this work with a Killer Bee backplate   

ebeneezer wrote:I take it you remove the corse thread spray bar from your backplate (how) and replace a with the fine one. Does this work with a Killer Bee backplate   

Mike, read through this thread a bit... Mark Boesen explains how he swaps-out the needle valve assemblies... Jim comments as well.

https://www.coxengineforum.com/t6170-modifiying-horseshoe-backplates#77616

Roddie

Thanks Roddie all is clear now. It had no idea Cox did different needle valve thread Pitches

Cheers Mike

ebeneezer wrote:Thanks Roddie all is clear now. It had no idea Cox did different needle valve thread Pitches

Cheers Mike

Yea... you'll notice in that thread, that there's some confusion on just how many threads-per-inch the fine needle has. I have come to understand that the early Cox needles were 128 tpi. The "current" Texas Timers needle is 128 tpi... and there used to be a company in California called "Kustom Kraftsmanship" (sadly no longer) that produced fine-thread NVA's for Cox engines. The Tee Dee style was 128 tpi ... but the reed-valve style's "pitch" is not specified in my old catalog... and it obviously has a different part number than the Tee Dee's. There's a possibility that it "may" have been the odd 124 tpi needle that's out there on some modified engines. I should point out though; that the KK custom reed-valve engines were of the "tank-back" style... and NOT "Postage-Stamp" or "Horseshoe" types... so this would not apply to running a bladder set-up. (at least from the info on KK that I have)

Roddie