CEF speed contest Design Discussions

The idea crossed my mind Roddie. For weeks, each time I'm in the shower, I look at the bottom of the Head & Shoulders shampoo bottle.

OVERLORD wrote:The idea crossed my mind Roddie. For weeks, each time I'm in the shower, I look at the bottom of the Head & Shoulders shampoo bottle.

Here's a "Prestone" de-icer trigger-spray bottle for comparison with an engine...




EDIT 1: You could possibly set the engine back 2-3 inches and run an extended shaft in a 1/8" RC car bearing in the nose. (I've always wanted to try that with a P39 Airacobra model.) It would really help with balance on the Caudron.. but you'd have to check the contest rules for model "length".. and where it's measured from.

Edit 2: Here are the bearings you could use. A 1/8" dia. rod of "x" length.. threaded 5-40 on each end, would give you an extended prop-shaft to run in the nose-bearing. You could mount your engine back near the wing.

I wasn't satisfied with my 1/32" ply cowling supports, so I cut them back and installed .005" Brass tabs. I wrestled with this method in my mind a bit...    before hacking away... The new Brass tabs do work well, and support the inner-rear flange of the cowl with a "spring-like" force. The cowling lines-up real nice. It is secured to the nose with #2 wood screws, to the top and bottom fuse rails.. which are 1/4" sq. Spruce.

the 1/32" ply supports... shown; before cutting back




the replacement Brass support tabs in place



Brass tabs "spring-lock" against inner cowl flange.


I need to finish drilling top/bottom cowl mounts, and locate hole position for the needle on the inboard side. Then I will be able to start with finishing. I think...


Thanks all.. for the nice comments. I am enjoying building this model.

Thanks Roddie for checking that out.

During the last 2 weeks I made a jig for forming balsa sheets to the desired shape:



a piece of plywood at rear end of the cowl and 1 fwd where the noseblock will be and a 3rd one in way of the firewall where the cowl changes shape. All fixed to a screw and positioned at the required distances.



I soaked 2mm sheets in water for at least 1 hour and pinned it around the former, then let dry on the radiator. I first wrapped cling film around the plywood so it won't soak any water from the sheeting.



I then glued both right and left pieces together.





Lieven

Beautiful work Lieven.

Jim

Wow, thats some really good work. now filed into my memory banks. If we do this again next year, I will choose something with a cowl to hide the engine. Especialy now I've seen how to make a good cowl. Now I'm thinking a Gee Bee R3. By the way, the reason I'm posting is I now have my Nitro and APC 4.75x4 prop, thanks Ebay. My newly assembled speed engine had  better look out !!!. 
  

Very impressive work Roddie and Lieven I have been keeping up with this building thread and am inspired by the wonderful , hard , work that is going into this project that pays with only pride! some have forgotten about that    damn I sound like SD now ....only funning of coarse it takes us all to make a difference . nice to get to learn some tricks and have a good time too.

So here's one for the mathematicians in the crowd. How much of my 18% fuel do I mix with 16oz of 35% to get 30%????

The scratching my head Jim.

JPvelo wrote:So here's one for the mathematicians in the crowd. How much of my 18% fuel do I mix with 16oz of 35% to get 30%????

The scratching my head Jim.

Well Jim................. 1st of all.. that's a LOT of fuel... Do you really need 16oz of 30%?? (maybe.. if you're doing some hard-core test-runs...) If a 1:1... 25/35% gives you 30%... (correct?) then I would think a .75:1... 18/35 would yield close to 30%...? There's a thread on this somewhere, with a formula for calculating exactly.. but I don't think I'm too far off. (I'm willing to bet that "stated" nitro content can vary up/down within a percent or two with "any" fuel blend...) "Damn it Jim"... (to quote "Bones"...Deforest Kelley-Star Trek) Now I'm scratching "my" head!!   

Roddie

Jim,

I do not know the exact formula to get there but I did some triel and error and came very close.

I started with 1 liter of each:

1L or 100 cl of 35% = 65 cl fuel and 35 cl nitro
1L or 100 cl of 18% = 82 cl fuel and 18 cl nitro

To make it short, when you add 42% of your 1 liter quantity of 18% fuel, you end up with a quantity of fuel with 30% nitro:

65 cl + (82 cl x 0,42) = 99,44 cl
35 cl + (18 cl x 0,42) = 42,56 cl

this makes a total of 142 cl = 1,42 l

When deviding this gives:

99,44 / 1,42 = 70,02% fuel
42,56 / 1,42 = 29,97% nitro

So you need to add 42% of 16 oz of your 18% fuel to end up with 30% fuel

Hope this helps.

Lieven

Thank you both Lieven and Roddie. I will mix some fuel and get some runs in this weekend!

Jim

Should have them in the air Saturday.

Looking good there Jim , you build racers ? Is that  a back up plan or just a lot of spare time, Good luck on the trial runs! I have been having some issues with weather to go w/ or w/out a on board tank, and that's holding up the engine mount I am going to do something today so I can get my CG right  

Congratulations Jim! Both models look AWESOME!! The side profile photo looks like it won the contest already!!! BEAUTIFUL!

Best of luck on Saturday! I hope the weather cooperates for your test flights.

Roddie

Really nice work Jim! I need to get going again, the contest deadline is coming up fast.

Thanks guys,

People in other parts of the country won't like this but if the temps stay below 80 on Saturday it should be fine.

Jim

Very good job. Congratulations !!!

Excellent work Jim. Very impressive.

Nice work, what ya got for power? I did the fuel problem and came up with add 7 oz 18% to bring the 35% down to 29.8%.
I might have got lost in the black hole of math.

good looking planes, Jim, will you make a video on saturday?

crankbndr wrote:Nice work, what ya got for power? I did the fuel problem and came up with add 7 oz 18% to bring the 35% down to 29.8%.
I might have got lost in the black hole of math.

Both engines are black widow cylinders with killer bee cranks. The back plates are bored as big as you can go and still have a Reed seat and enough meat to hold the spray bar. Fine thread needle valves so I can run bladders , Mylar reeds. The Mustsng has an old glo-bee head and the corsair has a galbreath/Nelson plug combo. Performance is identicle between the heads, about a 1500 rpm gain if memory serves. Last time I ran the Mustang engine it held 22k with 18% and an APC 4.75x4. The corsair is 500-700 rpm behind it. I will bench run with 30% tomorrow, if I can figure out how to brew 30%  

Jim

OVERLORD wrote:good looking planes, Jim,  will you make a video on saturday?

I will video Saturday but I won't post them, I don't want to "show my hand" just yet. It is a competition after all!

Jim

JPvelo wrote:

OVERLORD wrote:good looking planes, Jim,  will you make a video on saturday?

I will video Saturday but I won't post them, I don't want to "show my hand" just yet. It is a competition after all!

Jim

Will you be test flying on Saturday with your Son? Has he flown his "Mouse Racer yet? I hope all goes well... I know you are concerned about "nose-overs" when landing. Do you plan to "hand-launch" over a soft grassy flying area; just to log preliminary lap-times? You could save the "paved-circle" for the official flight.

My test-flights will be un-assisted "stooge" launches (as usual)... and I plan to scout-out an area where a R.O.G. is possible... with some kind of adjacent "soft" (forgiving) surface is present... maybe along the perimeter of a parking lot with no curbing. I might just find a grass field... and  make-up 15-20 feet of cardboard "radius" runway segments to launch from, for my first tests.

It's been consistently below freezing here in New England for the last week or so... and it could "stay that way"... well into March. It's just as well... because my airplane entry isn't even painted yet... I'm EXTREMELY envious of your weather there in AZ!!!!!!!

All the Best!

Roddie