Spencer Original Design

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tailwind

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Neat looking airplane. it has a lot of extra structure in it. have you come up with a new tail yet? Look at the 110 monocoupe you originally talked about it has a much smaller tail than a 90 monocoupe but it was arrived at with testing.
Tom
 

Rockiedog2

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Neat looking airplane. it has a lot of extra structure in it. have you come up with a new tail yet? Look at the 110 monocoupe you originally talked about it has a much smaller tail than a 90 monocoupe but it was arrived at with testing.
Tom
Thanks. I had to err to the conservative cause not an engineer so yes I know it has lots of room for refinement. If you don't mind would you point out where you see the extra structure. If you'd rather not that's OK. I've been detailing it lately and putting time on it. Had quite a few bugs but the list is down to near nothing now. So will get on the new tail design soon. I see you are Tailwind...does that mean you have Tailwind time? I'm interested in how stable it is as the W8 cantilever tail is one I'm looking at. The plane turned out beautifully stable and I don't want to lose any of that.
Here's a pic of the Aviat 110 Special which is a Monocoupe deriviative. The plan was to put it into production but they decided not...IIRC the reason was that the stability due the small tail was such that it shouldn't be turned loose on the public. Maybe other reasons too, I don't know. Anyway, I'm shying away from downsizing the stabilizers very much cause I really like the stability. i think the small tail on the Monocoupe really looks good...big part of the monocoupe charisma.

https://www.google.com/search?q=aviat+110+special&tbm=isch&tbo=u&source=univ&sa=X&ved=0CDMQsARqFQoTCKXP-6jxnMkCFVPSYwodBDUBFw&biw=1920&bih=943#imgrc=Pvi4ZOIdc3wW_M:
 

tailwind

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Well, to sell the 110 you'd need customers. If people would pay for it, it would sell. Yes it has some not normal handling but that's just training. Ive only got your first pics to work off. from the front of the H=stab you have 3 sets vert members. the first set of vertical tubes are probably redundant. is the v-stab mount there? Im guessing the second and third set are the h stab mounts?

Why the walking beam so far aft and larger pushrod aft of it?
 
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tailwind

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To see a minimalist fuselage truss look at the piper vagabond truss and landing gear. That said the monocoupe probably has the lightest truss for a 2 seat plane.
 

bmcj

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To see a minimalist fuselage truss look at the piper vagabond truss and landing gear. That said the monocoupe probably has the lightest truss for a 2 seat plane.
Not sure what the Monocoupe fuse weighs, but I'm sure the Kitfox and Avid Flyer would give it a run for it's money.
 

tailwind

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I was considering certified stuff. I've seen both of those,( at least early ones) that get bent up pretty easily on stuff a cub or champ or tcart would have had no issue going through.

Not sure what the Monocoupe fuse weighs, but I'm sure the Kitfox and Avid Flyer would give it a run for it's money.
 

TFF

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The problem with the Aviat 'Coupe was flat 4 engine. No romantic dreams about that when all the cool ones had round engines. No round, no need. Monocoupe 90s are not that expensive and they are real, and there are plans that float around if you really needed one.
The tube in a tube Tailwind stab would be a cool way to redo your tail.
 

tailwind

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another thought on the cg issue. rather than change out the tail right away. try an aluminum prop. the best one I can think of was what was on my clipped wing tcart. a McCauley 7154 that was for a Grumman AA-1. the o200 would turn it up to 2850 wot. and something like 130 mph. the tcart is a lot draggier than yours.
 

Rockiedog2

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Well, to sell the 110 you'd need customers. If people would pay for it, it would sell. Yes it has some not normal handling but that's just training. Ive only got your first pics to work off. from the front of the H=stab you have 3 sets vert members. the first set of vertical tubes are probably redundant. is the v-stab mount there? Im guessing the second and third set are the h stab mounts?

Why the walking beam so far aft and larger pushrod aft of it?
Thanks for the reply and pointing that out.
The basic truss came from a W8 Tailwind but with changes. The first set of verticals going forward from the tailpost are to take the tailwheel spring front mount loads and also the HS rear mount is there. The HS front mount is at the second set of verticals. The vertical stab mounts to the HS there also. No separate Vertical stab mount. The 3rd set of verticals didn't need to be there. Reason they are is because I chopped up the fuse in that area and redid it and rather than cut it all completely out decided to jus live with it. Well, it's a prototype and does have warts.
The controls came out of a derelict RV8, thus the bellcrank/tube lengths being what they are. That's just the best I could do with what I had. Typical shadetree...far from elegant
Anyway, Those some of the reasons I want to build a complete new aft fuse and tail.
 

Rockiedog2

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another thought on the cg issue. rather than change out the tail right away. try an aluminum prop. the best one I can think of was what was on my clipped wing tcart. a McCauley 7154 that was for a Grumman AA-1. the o200 would turn it up to 2850 wot. and something like 130 mph. the tcart is a lot draggier than yours.


That likely would move the cg enough that Rockie could ride...that AL prop weighs what? 30#? the WD I got on it weighs 11. If I had one here I would give it a try. Would rather have a 2 blade than the 3 blade thats on it...but once again thats what we had on hand. I got 2 prop extensions here a 4" and a 5" they weigh about 5 # each. That would help a little with the cg and also could streamline the nosebowl more too. May ultimately end up running one of those.
The EW(569) ended up well over what I wanted so am working at reducing # rather than adding. Think I can get 10# maybe 15# outa the aft fuse and tail if work at it. CG fixed and EW reduced...
Mccauley 7154...I'll ask around about a loaner thanks Tailwind
 

Rockiedog2

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The problem with the Aviat 'Coupe was flat 4 engine. No romantic dreams about that when all the cool ones had round engines. No round, no need. Monocoupe 90s are not that expensive and they are real, and there are plans that float around if you really needed one.
The tube in a tube Tailwind stab would be a cool way to redo your tail.
yeah looking at the TW tail closely. Gotta figure the weight as that is priority one. Lotta big tube in there....I wouldn't be willing to change much up other than small dimensional/shape changes...I can't figure the likely result and don't wanta risk flutter so will be fat again. Got a price from the dudes down in NZ on a set of Pitts tailbrace wires. Expensive but not overly so. $600 for the four. The modified Pitts tail is still under consideration cause can build so light and simple. I don't think the 3/16 streamlined wires with cuffs on the clevis will amount to unacceptable drag considering the weight advantage. we will see...
 

tailwind

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The o200 aluminum props usually run 20-24 lbs. Same for o235. Thats one of the big hits by going to an o320 on light aircraft the 320 props hit 30-35 lbs. Also the carbon props have more vibration issues than a certified aluminum combo. I have 2 of the McCauley props for future projects they come up occasionally on barnstormers. 1a105 scm 7154 is what you need.
 
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TFF

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If I went modified Pitts, I would try to scrounge some round wire of a Cub or Tcraft project and make it fit. Your not gong so fast that it will kill the deal.
 

Rockiedog2

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Question...

Let me see if I can ask this so it makes sense

Considering stability only. For a given stabilizer area. Does the stability increase with increased span/decreased chord? or the opposite? or it doesn't matter matter...it's a function of area only.
Considering drag only. For a given stabilizer area. If we increase the span/decrease the chord does the drag increase cause of increased frontal area or does the drag decrease cause of increased aspect ratio?
 
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Orrem31

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I believe it’s safe to say that for conventional homebuilt plane like SS1 the tail area and arm are the critical dimensions assuming the horizontal and vertical aspect ratio’s fall within normal ranges.

Light planes like SS1 commonly have a horizontal tail AR of 3 to 5, I usually like the looks of 4, and a vertical tail AR of 1.3 to 2.0.

The elevator is typically 45% of the horizontal tail chord and the rudder is typically 40% of the vertical tail chord.

I know this is ducking your question a bit, but I think the early design stage should focus on satisfying the tail arm and area required (tail volume) while keeping the tail AR in a normal ranges.

I have found SIMPLIFIED AIRCRAFT DESIGN FOR HOMEBUILDERS, by Dan Raymer a wonderful 143 page intro to the basics.

-jeff
 

mcrae0104

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Question...

Let me see if I can ask this so it makes sense

Considering stability only. For a given stabilizer area. Does the stability increase with increased span/decreased chord? or the opposite? or it doesn't matter matter...it's a function of area only.
Considering drag only. For a given stabilizer area. If we increase the span/decrease the chord does the drag increase cause of increased frontal area or does the drag decrease cause of increased aspect ratio?
For a regular wing, if you increase the span but keep the area the same, it will have less induced drag. Basically, the frontal area of the airfoil is not the determining factor in its drag.

For a horizontal tail, this would also be true, but because we're not asking for much lift out of the tail, the induced drag is so tiny that the change in aspect ratio wouldn't make a measurable difference in drag.

If the tail area and arm are the same it would make no difference in stability.

Also, the main (front) wing should stall first. That is the primary reason I'm aware of that you don't see high AR tail surfaces.
 

Rockiedog2

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Wow. Flew it this morning in coldest temps so far. by about 25 or 30 degrees(35F). 110 mph cruise climb 1800 fpm. 125 fast cruise climb still 1200 fpm. Not only the temp but the motor is loosening up as well. Nice. That at about 830-840#. Fanatical weight control really matters.

I've had a problem with fumes in the cockpit since the beginning. Seemed worse this morning...I'm wondering if the temp is having some effect of the amount of fumes entering. Came back with a headache after 20 minutes and that with the vent blowing in my face. Really got bad right after doing a 2-3G steep turn. That is a clue to something but I dunno what yet. Been dealing with it a while...stopping up cracks, weatherstripping doors etc. Bout to run outa cracks to seal. I think the short stacks are the obvious culprit.I don't want to go long cause of weight and also the cool factor. Looking at the exhaust streak down the left side it's straight back to midway on the cockpit window(below) and that's where the streak stops. No sign of the propwash taking it up to the window or wing root area. I'm now wondering if it's coming in back around the tailwheel and some pressure diff pulling it up to the cockpit. There are some holes back there underneath. Seems the propwash would tend to carry it up and around the fuse rather than straight back to the tailwheel. I expect it varies widely but generally is the aft fuse/cockpit usually a relatively low pressure area that would suck fumes? Any info on that appreciated.
Gonna tape those holes up and find out

Hey Jeff I ordered that book you recommended thanks
 
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Orrem31

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Something like that happens on motorcycles with windscreens. The low pressure behind the some windscreens suck the exhaust forward and up to the riders face. It's common to add a vent in the bottom of the windscreen to solve the problem by reducing the low pressure air pocket.

http://www.clearviewshields.com/blog/clearview-shields-windshield-venting/

Might provide a clue supporting your idea that the exhaust could be entering aft of the cabin.

-jeff
 

Rockiedog2

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Something like that happens on motorcycles with windscreens. The low pressure behind the some windscreens suck the exhaust forward and up to the riders face. It's common to add a vent in the bottom of the windscreen to solve the problem by reducing the low pressure air pocket.

Windshield Venting - Clearview Shields

Might provide a clue supporting your idea that the exhaust could be entering aft of the cabin.

-jeff
I finally got ahead of you on one Jeff(Jeff and I have PM exchanged info for a while...since he knows so much more than me it's been a one sided exchange)

Here are a couple shots of my now retired beloved KLR "Jackass". We shared rides to Deadhorse AK, Key West, San Diego, Goose Bay Labrador, Newfoundland, Nova Scotia and just about everywhere in between. He's dead now, worn slam out. RIP Jackass. Well, anyway, I had an annoying helmet buffet problem...first tried VGs on top but no joy so rigged up the NACA inlet with the ductwork behind the windshield. Worked great...can feel a blast of air coming outa the duct that changed the flow behind/over the top of the w/s so it missed top of the helmet. No more tired neck. So I can vouch that what you said worked in this case. Not exhaust but same principle.

Thanks Jeff

IMG_4428.jpgIMG_4422.jpgIMG_4427.jpg
 
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