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J-3 engines and floats

John Melnick said:
The other Cub with the C-85 has wooden spars and a tapered crank - both of which are ok but are real problems if things do not work out as you hope they should.

Mr. Melnick,

I'm not sure I understand this last statement? The taper shaft will fit any propeller you could use on the engine, you just have to use the hub. If you switch between two props and you have two hubs, the time to swap props is less than for a flanged crank.

I realize that you are up in CN and I'm not sure if you have the option, but down here, if you had to overhaul the C85, you could, by STC, install the O-200 crankshaft. You'd get (potentially) more hp and your flanged crank.

I'm not sure why people shy away from wood spars. There is no difference in strength (or aircraft GW) vs. metal spars. All parts are available new (as with the metal spars). So what is the problem?

Per the type certificate both the C85 AND the C90 are limited to 80hp continuous. They can respectively produce 85 and 90 hp on takeoff (if you can turn them up to the RPM limit), but probably the real difference is in the (more) torque available in the C90. You MAY be able to swing a longer prop with the C90, but no longer props (except wood, which I don't think you will use on floats) are approved on the TC.

Down here, I'd say that the C85/O-200 crank engine is the optimum engine for a certified J3.

Good luck with your search!

John Scott
 
John,

I agree with you on concerns regarding wood spars. Unfortunately, recent AD's on several aircraft, and the fear of litigation, etc, have made wood spars a potential liability.

You're absolutely correct that they can be just as strong as metal spars. Unfortunately, they are VERY hard to THOROUGHLY inspect for cracks, or other damage. I've seen perfectly good wood spars condemned because of what turned out to be surface blemishes. You can argue that this was because of an inexperienced or overzealous IA, but neither was true of this guy.

THere's several good reasons that American Champion offers pretty good deals to replace wood spars with metal in their aircraft...

Liability....it's just something we all have to deal with.

If you buy the wood spar airplane (and I wouldn't be scared of it) find a REALLY good mechanic who knows wood spars, and get him to take a really thorough look at it. Then be choosey who does your annuals in future.

MTV
 
John Scott and MTV thank you both for your thoughtful replies and taking the time to write.

On the tapered cranks I have heard (?) that the keyway can be a cracking problem and moisture in the crevice can lead to corrosion which can accelerate the cracking. Just something I'm watching for and discount my offer price accordingly.

I'm just getting educated on the small Continentals and have come to the conclusion that the C-85 with an O-200 crank and a C-90 cam & pistons might be the real ticket. But I wouldn't want to pay a premium price for a J-3 and then have to spend time and money on engine repairs (done that before) so I'm trying to be careful.

On wooden spars I actually prefer them personally - no fatigue problems, flexible and more than strong enough. Planes like Skybolts have been pulling mega G's with wooden spars and there's no problem if they are looked after. Problem is finding an inspector that's knowledgeable about wood, not brainwashed with all of the wood spar AD's and not gun shy about small (insignificant) defects. Resale value is also potentially affected although I'm not buying a plane to flip it.
 
Tapered crank is not a problem. Wood spars are strong enough, but I have never had the pleasure of rebuilding a wood spar wing without at least one scarf joint. That is probably different now that everybody keeps them inside.

Thirty five grand ought to get you a C85 metal spar J-3 in good condition. If you want perfect, fifty ought to be enough, but that should be zero time engine and cover plus radio.

All opinion.
 
1400+ hours on a 1973 overhaul is definitely something to consider.

I didn't realize that the PK 1500s are longer than the EDO 1400s. In any event they work well on my Chief.
 
Don Sword of Don's Dream Machines echoes your thoughts about the engines: high time / long ago overhaul a sign of potential problems.

We also had a discussion about wood spars and his experience is that properly cared for there's no problem with Cubs.

Going to look at two other machines today and it's going to be a tough choice!

Both around the same asking price ($40,000C) but one has metal spars, long ago overhaul, Grove brakes, strap on skiis and a set of tundra tires.

The other has more recent / extensive engine work and cover but wooden spars and tapered crank (non issue now).

Both have been hangered and both were refurbished by people who know what they are doing.

I may need your help with a decision.

By the way, anybody had experience with the strap on skiis - good or bad?
 
mvivion said:
John,

I agree with you on concerns regarding wood spars. Unfortunately, recent AD's on several aircraft, and the fear of litigation, etc, have made wood spars a potential liability.

You're absolutely correct that they can be just as strong as metal spars. Unfortunately, they are VERY hard to THOROUGHLY inspect for cracks, or other damage. I've seen perfectly good wood spars condemned because of what turned out to be surface blemishes. You can argue that this was because of an inexperienced or overzealous IA, but neither was true of this guy.

THere's several good reasons that American Champion offers pretty good deals to replace wood spars with metal in their aircraft...

Liability....it's just something we all have to deal with.

If you buy the wood spar airplane (and I wouldn't be scared of it) find a REALLY good mechanic who knows wood spars, and get him to take a really thorough look at it. Then be choosey who does your annuals in future.

MTV


Mike-

Quit comparing apples to oranges. There is a big difference on how a J-3 or J-5 wood spar wing is designed compared to a champ.
 
Wood has no memory like metal does, but mice cant chew on metal spars, like they do on wood ones.

Doug
 
Wood spars are fine. If you have the choice, choose metal. It is just that simple. Engines that sit for a long time between flights are usually due for overhaul, no matter what. Ask Lycoming.
 
behindpropellers said:
3977P said:
Wood has no memory like metal does, but mice cant chew on metal spars, like they do on wood ones.

Doug

Doug-

Post a picture of a spruce spar/rib that a mouse has chewed on.

I've seen one but don't have photos. It was a Stearman.

Jon B.
 
From my Champ.

IMG_1962.jpg

IMG_1963.jpg


nkh
 
Yeah - to remove dry rot. Look at that rib - moisture got in there at some point. Do you think that spar is still good with that much material gone?
 
No it was mouse damage; you can still make out teeth marks and there's a note in the logs when they dressed out the damage.

Bob, I flew the airplane for 10 years; always paying close attention to the spars looking for any kind of movement, and wasn't concerned by it. A failed glue joint finally condemned the spar.

Yeah Steve, as soon as I can take a break working on airplanes to work on MY airplane. :wink:

Here's the rest of the story... so far...
http://www.joea.com/phpBB2/viewtopic.php?t=2045

nkh
 
Behindpropellers,

Granted there are different AD's associated with wood spars in Champs and Cubs, but tell me what makes the spars themselves "apples to oranges" please??

As I noted, I'm not down on wood spars. The point is, however, that a lot of folks, many who hold an IA, now ARE paranoid about wood spars. I wouldn't worry so much about the spars as about the inspector of the spars.

Just keep the beavers away from em.... 8)

MTV
 
Here's an ad for a really sweet looking L-4 from the Washington Seaplane Pilot's newsletter:

$49,750 Beautiful L4 Cub currently on EDO 1320s, 70 hrs since complete restoration in 2003, 2070TT airframe, recent upgrade to C90-8 w/20hrs TTSMOH to serviceable limits. Awesome performer and a real blast to fly, excellent condition and a real eye catcher. Full greenhouse, Metal Spar, intercom, Cleveland brakes, Fresh Overhaul on McCauley Metal Prop, sealed struts, and more. Comes with tight EDO 1320s, wheels, covers, and lots of fun! Currently on floats. REDUCED PRICE, ready to move! • Contact Tedd Goth, Owner - located Lakewood, WA USA • Telephone: 907-750-2220 9/4/08

MTV
 
John, the plane is still a J3C-65. That has to do with the Type Certificate, not the size of the engine installed on the plane.

The dash 8 is included in the Type Certificate and does not require supplemental paperwork. If the 90 is a dash 12, then supplemental paperwork is required.
JimC
 
Thank you so much to all, I enjoyed the thread and learned a lot from your comments. In the end I did buy the 1946 with wooden spars, C-85 and tapered crank. So far I have flown it 15 hours or so and it really is a different airplane and by that I mean it is "special". I don't have to tell you old hands what I mean but it is even noticeably different than the 1948 7DC Champ I used to own - not that one is better than the other to other than their owners, but they are different. If the C-85 gives me trouble the O-200 internals are in my future but so far no problems. I'm going to try skiis again this winter (been 20 yeas since last on them) and I'll keep you posted .......
 
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