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New member building a PA18-95

I'm a Patrol builder so I'm partial to Bob's designs. I would like to be present sometime when the LSA is weighed. 738 with a C-90 seems light. Bare bones J-3's weigh more than that.
 
Bob barrows told me a few years back that he didn't like to have to re trim after adding flaps and that is why he uses a plain flap design. If you can add flaps and not have to retrim, that tells me that the flaps aren't doing much more than adding drag.
My cub has flaps similar to those on a husky and my plane weighs less than 800 and they make a HUGE difference in takeoff and landing. I suspect that if the bear hawk and the patrol had more of a fowler flap, they wold make quite a difference. Don't get me wrong, I like bob's designs, but I think fowler flaps on the lsa would be the cat's meow.
 
Cub Junkie,

I know what you mean, I'm skeptical as well. I really want to compare the plans and see how it is accomplished if it is indeed true. How do you like working from the Patrol plans? I just noticed you live in scenic Indiana. I grew up outside of Star City and still have family down there. I usually make the journey to the farm in the fall to deer hunt and visit with relation.

Jim Allen
 
Clint,

Please tell me more about your plane. J3 syle fuse? Wood or aluminum wing? How did you stay under 800#? Did you work from Wag or Northland plans? What airfoil did you use?

Thanks,

Jim
 
Jim, I have a Super Cub fuselage, all aluminum 14 rib wing, one 18 gallon tank in the left wing and absolutely bare bones on everything. I used univair drawings and used the stock piper airfoil. I did add 1.5" to the chord of the flaps and ailerons. It's all the details that make a plane heavy. Little things like the wheels for example, I switched out my single puck grove wheels for the matcos and there's about 4 lbs right there, (the groves are for sale by the way) I can now run 8.50-6 tires tubeless and there's another 4-5 lbs again. .060 or .080 plexiglass for side windows instead of 1/8. lots and lots of the little things and you can find 100 lbs pretty quick.
 
CLint,

I may have asked this before but it's lost in the fog somewhere...do you think the extra cord in the ailerons bought you any significant slow speed control?

I've thought about Fowlers but they are more complicated than just a simple hinged torque tube activated flap and heavier.
 
Jim,

http://www.supercub.org/forum/showthread.php?41880-Super-Cub-95-Weight&p=523092#post523092


Here is a thread about empty weight for PA-18-95’s. You can get them under 800 lbs if stock. Out of the factory they had a nice glossy butyrate dope job over cotton. If you want to add flaps and big tyres and keep the weight the same you just need to drop things like interior and the glossy paint job.

Super11XP’s Cub is under 800 lbs.

There was a long thread on J-3Cub dot com about empty weights and the mid-700’s was common for a J-3, but some of them were around 700 lb.

Rans S-7’s are generally in the mid-700’s but that is with a Rotax, which could be 60 lbs lighter than a C90.

From the photos I have seen, Bob Barrow's aeroplanes are very plain. He doesn't embellish them much. That may be the secret to his light weight, as much as the design. I have a vague recollection that Bearhawks built in the "field" with "embellishments" were coming out heavier than Bob's planes, probably in the weight range you would expect.

There is a lot of data out there to gauge where your PA-18-95 replica should end up, but we have only one data point for the LSA Patrol.

What I come back to is that if you build a PA-18-95 replica and aim as close as you can to what Piper built them you know exactly what you are going to end up with. Guys like Glenn will tell you exactly how well it will fly. But if you build a Patrol?

Cheers,
Andrew.
 
CLint,

I may have asked this before but it's lost in the fog somewhere...do you think the extra cord in the ailerons bought you any significant slow speed control?

The extra chord could likely increase the control stick forces.

I've thought about Fowlers but they are more complicated than just a simple hinged torque tube activated flap and heavier.

You could move the hinge point further down to get a little more aft movement with a larger slot opening. Take a look at the Husky flap hinges and compare them to a Super Cub. The extra long flaps on my Cub with standard hinges, are so effective that I often get the feeling that I need to be shot down. It just floats and floats.
 
Barrow's designs are only as light as any stock piper except he doesn't run any electrical systems. Its real easy to become a "moron". That is a term of endearment Curtis Pitts used one time when I was hanging out around him at an aerobatic contest. Guys keep putting more on and more on then all of a sudden their airplane gained 90 pounds.

@Jim A. Bob's plans are good in my opinion but I have built and repaired a lot of tube structures. He expects you to scale off the drawings unless he draws the parts in full size or gives dimensions. Star city is almost chicago to us southern indiana hillbillies. I have said it many times on this board, I don't expect anybody to be excited about the BH or the Patrol on this cub board.(exception would be if you have a C-180(or C-170) then you are kool on this board.) I would like to see a lightweight Patrol in the hands of one of the grizzled bush jockeys that come to Valdez to see how it really stacks up against the similar equipped 18. @Clint, can you share a part # for the Matco wheels/brakes? What size axles. I know Barrow's put them on the LSA.
 
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Sky,

I took your suggestion to move the hinges down seriously and have discussed it with my IA at length and we're going to come up with a plan to do that when I get started on the wings. He can't understand why there weren't flaps on there to begin with.

Cub,

I'm using 6" Matco triple puck 1.5" axle but my gear is upsized one tube size along with everything from the back of the door forward because of the 0-320. I have a C-170...does that mean I'm not Kool???
 
I edited my post so you are kool too. The reason there are no flaps on the LSA is for the very reason we all have discussed, Barrow is a lightweight freak. He had his reasons. You make a lot of reference to your IA as your engineering advisor. An Inspection authorization part of a maintenance certificate. Not saying your IA doesn't have some engineering ideas or maybe he has an engineering degree but when you make wholesale changes to a design you are in the dark without the help of an engineer. Thats why they call it experimental as we know but the major changes that have been done to cubs have all been looked at by engineers and tested to destruction by many.
 
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Lowrider,
My suggestion of a Husky flap hinge was only as an illustration. Personally I hate that hinge as it is mandatory that you wear a crash helmet while anywhere near that wing.

One thing to pay attention to is the shape of the trailing edge of the wing just ahead of the flap. It should flow smoothly from the bottom of the wing to the top of the flap/trailing edge junction. If it is not in a smooth lazy S shape it will generate turbulence over the top of the flap thus reducing good laminar flow over the flap. This means less lift. I used balsa wood to make a nice smooth shape on mine. It could be made from thin curved aluminum.

Another thing is the width of the gap when the flaps are down. The gap will be greater when using the Husky hinge rather than the Piper hinge. I welcome input from an aerodynamicist here. I am of the opinion that the more narrow gap of the Piper, will generate a higher velocity flow over the top of the flap thus reducing/preventing flow separation on the top of the flap. This will result in more lift at lower speeds. If the gap is large with an angular wing trailing edge, there will be turbulence with a reduction of lift from the flaps. This will be evident with a reduction of stick back pressure at landing and stall speeds.

This could get into a heated discussion of long Vs short flaps and their effect on pitch trim, so I will sign off for now.
 
Thanks Cub...I feel Kool now!!

Totally agree with you about changes and that's why I am trying to follow tried and proven methods and incorporate them into my plane.


Sky,

Won't some version of a flap gap seal mitigate the over the top of the wing/flap flow?

We should move back to my thread under "Lowrider LSA".

Jim A, I'm sorry we hijacked your thread!!!
 
Cub it shall be.

I sheepishly called Bob from Bearhawk again last Friday and asked him if it was too late to cancel my plan order. Thank goodness for snail mail, checks, and understanding people. He hadn't received my letter yet and said cancelling my plan order would not be a problem at all. I felt horrible about making the call, but Bob was not upset in the least and we actually had a lengthy conversation about first time building and the pleasure of flying a Cub. I hope others help him fulfill his dream of seeing more Bearhawk LSAs in the sky.

After reading everyone's replies to my thread and weighing my take on the pros/cons of a different design, I have come to this realization. I've spent enough time and money comparing plans. It's time for me to start building my Supercub. Why would I build anything else? Don't answer that, I need to stay focused. To keep me focused, I've created what I'm going to call "Jim's Building Code", JBC for short. Remind me of it if I seem to stray from course.

Jim's Building Code

1). I'm going to scratch build a mostly stock PA-18-95 with flaps.
2). It will be built to operate primarily from wheels and skis with future floats in mind.
3). I will involve my family in the build as much as I can.
4). It will weigh 792lbs. or less when I am done.
5). It's wing will have aluminum spars and ribs.
6). It will be powered by a C-90.
7). I will not compromise safety to make my target weight.
8). I will scrutinize everything that goes into the aircraft and everything that I leave out.
9). I will build it as inexpensively and as quickly as I can within a budget of $20,000-$30,000.
10). I will fabricate as much of it as I can.
11). I will log my hours, track spending, take photographs and document the build from start to finish.
12). I will rely on others who have built before and/or are qualified to provide inspiration, information, and help with my build.
13). I'm going to start on June 1st. 2013.
14). I'm going to finish no sooner than June 1st. 2017 and no later than June 1st. 2020.
15). I will need to spend on average 8-14hrs./week on the build in order to finish it within my time frame.
16). Above all I will enjoy the building process and be happy with what is created in the end.

Over the next few weeks I will be finishing up some projects that my wife would like to see completed before my family and I embark on this journey.

Expect a new thread in "Member Projects In Progress" on June 1st!

Thanks again,

Jim Allen
 
Jim,

Looks like you have set goals and priorities that will get you a very nice airplane...more importantly, you'll enjoy the journey and by involving your family, it will be more meaningful when completed. Good luck on the build and I will be checking back on your list to make sure I haven't forgotten anything!!
 
I sheepishly called Bob from Bearhawk again last Friday and asked him if it was too late to cancel my plan order. Thank goodness for snail mail, checks, and understanding people. He hadn't received my letter yet and said cancelling my plan order would not be a problem at all. I felt horrible about making the call, but Bob was not upset in the least and we actually had a lengthy conversation about first time building and the pleasure of flying a Cub. I hope others help him fulfill his dream of seeing more Bearhawk LSAs in the sky.

After reading everyone's replies to my thread and weighing my take on the pros/cons of a different design, I have come to this realization. I've spent enough time and money comparing plans. It's time for me to start building my Supercub. Why would I build anything else? Don't answer that, I need to stay focused. To keep me focused, I've created what I'm going to call "Jim's Building Code", JBC for short. Remind me of it if I seem to stray from course.

Jim's Building Code

1). I'm going to scratch build a mostly stock PA-18-95 with flaps.
2). It will be built to operate primarily from wheels and skis with future floats in mind.
3). I will involve my family in the build as much as I can.
4). It will weigh 792lbs. or less when I am done.
5). It's wing will have aluminum spars and ribs.
6). It will be powered by a C-90.
7). I will not compromise safety to make my target weight.
8). I will scrutinize everything that goes into the aircraft and everything that I leave out.
9). I will build it as inexpensively and as quickly as I can within a budget of $20,000-$30,000.
10). I will fabricate as much of it as I can.
11). I will log my hours, track spending, take photographs and document the build from start to finish.
12). I will rely on others who have built before and/or are qualified to provide inspiration, information, and help with my build.
13). I'm going to start on June 1st. 2013.
14). I'm going to finish no sooner than June 1st. 2017 and no later than June 1st. 2020.
15). I will need to spend on average 8-14hrs./week on the build in order to finish it within my time frame.
16). Above all I will enjoy the building process and be happy with what is created in the end.

Over the next few weeks I will be finishing up some projects that my wife would like to see completed before my family and I embark on this journey.

Expect a new thread in "Member Projects In Progress" on June 1st!

Thanks again,

Jim Allen

Heck, I wish I could be as focussed as that!
 
Jim

Awesome. Gotta love a man with a plan.

I look forward to following your build. You will have to fight yourself to hit the target weight. It is soooo easy to fall into the trap of......"it'll only add a little weight and it'll be worth it". Congratulations and good luck.

Bill
 
Good choice on which airplane to build. You should build what you think you will want in the end result. Flaps on a light cub make sense and make a big difference. In choosing a cub clone if it comes to a time that you don't want to build a particular part you can buy it knowing it will fit and work. I'm going to remember that 792 goal. Bob Barrows responce is no surprise, long before he designed the Bearhawk line of aircraft he built a variety of different homebuilts. He is truly a homebuilder and his designs reflect what he has learned over the years.
 
Ribs

If I buy a Carlson full rib for a pattern, will I be able to make a cut down version of it to make 3/4 ribs, butt ribs, tank ribs, nose ribs, etc? Or are the other ribs just enough different that I will need to buy more patterns to make them? This may be a question for Carlson. Another thought I had was to buy just the extruded T rail and make my own Piper truss style ribs from the Northland drawings. It looks like a guy could make the truss webs on his own, but an impossibility on the T. It also sounds like Carlson removes the bottom of the T to accomplish the bend at the leading edge and they don't do any shrinking on the top chord. Is this correct? I don't want to buy any more patterns than I have to and I don't want to get all screwed up using Carlson style ribs in the Northland drawings. I kind of like the idea of making Piper truss ribs because I have drawings of them that I could copy. It would take more time for sure. Safe? Possible to build? Too heavy because of the extruded T?
 
Jim

I hate to sound like a broken record but you can easily add 5 to 10 pounds to the total weight by using the wrong ribs. The original Piper Ribs were 6.8 oz. I do not know about Carlson but there are a lot of aftermarket ribs out there that weigh close to 13oz. It does not seem like a big deal until you multiply it by 26 or 32. If you are going to make your target weight you are going to have to watch every ounce. Don't start off by adding an unnecessary 10 pounds. Cub Crafters makes a light rib as does Javron. It will cost less to build your own and now you have an idea for a weight to shoot for. 1 oz on the rib will equal close to 2 pounds total. Just a suggestion.

Hope this helps

Bill
 
Bill,

I couldn't agree more. I want to build my own ribs. From what I understand, the Piper T doesn't exist anymore except on original ribs. As close to the original rib weight is what I'm after and I've heard that Carlson's ribs are the lightest out there but they are heavier and they are different. I' m just curious if I could build ribs like Piper truss ribs using the extruded T that is available, and not be heavier, preferably lighter than what the Carlson rib is.
 
Carlson will sell you the rib capstrip extrusion already milled out for the nose rib radius almost as cheap as if you bought the material and did it yourself. As Bill pointed out, ribs are an area that gains weight fast. Carlson's ribs are pretty heavy when compared to a Piper. They seem to be a similar weight compared to a Dakota Cub rib.
 
Jim,

You can do what you describe, I am doing just that except I am using some stocks of Piper T-section and W-section that I have. I don't know what I will do when I run out; I have a few ideas, and using the Carlson T-section is one of them.

Building Piper ribs is very fiddly and a real compromise and may not be what you want to do with your spare time. Because the Piper sections are not available if you use other sections or material you will tend to over-engineer it unless you do a structural analysis. Indeed anything you can fold up will not be as stiff as the Piper W-section pound for pound.

Piper ribs are quite delicate and both the Dakota Cub and Univair ribs have been engineered to be more robust to stand up better in service. That advantage doesn't come free in the weight stakes of course.

A trade off you will have to come to terms with is trading weight savings for dollars. Can I use this slightly heavier thingy and save myself fifty bucks. Or shall I spend the fifty bucks and save the weight. Ask Bill Rusk about his drilled brake discs!

Cheers,
Andrew.
 
Called Javron and Cub Crafters

I made two phone calls today. I talked to Jay at Javron and Mitch at Cub Crafters. Their ribs are both 2-3oz. lighter than the Carlson rib. The problems are I won't be able to make them and to buy them seems to go against Bill's cost/weight breakeven suggestion. Man, they do look like nice ribs though. Jay and Mitch were very helpful and straightforward. I'm sure I'll be speaking with both of them again in the future. 4 to 5 pounds will be the weight cost in the ribs. I don't like it, but like Andrew said, I have to choose.
 
Has anyone weighed a D&E stamped rib? I wish I would have weighed one of mine. They sure seemed light to me but had nothing to compare to. All this talk of extreme weight saving wasn't around when I was building mine. I just put it together and have a nice flying Super Cub.
 
This is a bead roller. You can make dies of most any shape that will fit on it. If you have the desire to build your own ribs you could get some light weight sheet aluminum and make your own. These tools are available in many places for a reasonable price. I would think that you could make some ribs out of 0.016" 2024-T3 similar to Piper's, maybe with a "U" shaped cap strip. The curve could be formed using a shrinker or crimper. I'll not enter a sheet metal forming discussion here. It will be time consuming but satisfying and cost reducing in the end. You could calculate the weight in advance. 2024 aluminum weighs 0.101 lbs per cubic inch. This: http://www.onlinemetals.com/calculator.cfm is a calculator which may help.
WFBeadRoller1.jpg
 
Piper "T" section

P1150824.JPG

This is my answer to the rib problem. Click on the picture until you get the + sign and then click once more for a large picture where you can see the detail of the T section close up. I ordered the main ribs from Dakota but manufactured my own "T" section for the "in between" nose ribs. Making the 24" t section was more a developed skill over several hours of trying out different ways to try and accomplish the goal. In the end the needed tools were a 3 in 1 (shear,brake,roll) machine, a modified bead roller (my own dies), A roller crimping machine, and a cheapy English wheel. After many failures I can now crank out 24" T section in under 10 minutes from .016" 6061-T3. I am not happy with the roller crimp (Chinese) dies I have so the final product is not exactly what I want yet but it will get there. I am doing this for fun and education (the reason for experimental)

P1150827.JPG

Current box of shame. Those are mostly roofing flashing prototypes as is the properly bent structure in the first picture. The "T" section is 6061-T6 which is tougher to bend.
 

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That looks great gsmx440. You seem to have the procedure down. Can you get 6061-T3? That should work easier.
 
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