EZFlap wrote:The VG's will also improve STOL performance to one degree or another, because (as advertised) they add energized air into the boundary layer which keeps the flow attached to the wing at slightly higher AOA than otherwise possible. The slots will also do this same job (as mentioned), but on a Stinson the slots are only on half of the wing. So you should still see a noticeable benefit by installing the VG's, even if the half-span slots are already there. Even if the VG's don't do anything the slots don't already do (arguable), the VG's will be on the whole span which the slots aren't. Although I do not have any personal experience with Stinsons, I would expect there to be some measurable reduction in stall speed and max Alpha with the VG's.

Although definitely NOT do-able on a certified airplane without a bunch of testing and an official approval... adding the VG's likely would allow you to remove half or 3/4 of the twist (washout) on the Stinson wing... because the VG's are now there to get rid of that softened aileron control and tip-stalling problem which the twist was intended to solve originally. Having the wing flat instead of twisted would give you better STOL performance, at the cost of the airplane being less idiot-proof at low speed. Also, you would theoretically have to reduce your maneuvering and gust speeds because the twist lessens the loads on the wing during gusts and hard maneuvering.

Does this include Bruce's Muffler(glass packs) bomber ? He has another 108 -2 now -with another 0-435 lyc. .Bruce has 4 108's and parts for another 2-3 .

182STOL is right... I do have one flight in a Stinson 108, with a hotrod O-435 in the nose and marginal hotrod car mufflers.

On takeoff we had two of those mufflers, and on landing we had one. At about 4000 feet above AZ50 airport, one of them decided to take an early retirement and popped off with an enormous change in the cockpit noise level.

The noise level went from being in the grandstands at NASCAR to on the start line at NHRA Top Fuel ! My eardrums still have not forgiven me...

EZFlap wrote:.... I do have one flight in a Stinson 108, with a hotrod O-435 in the nose and marginal hotrod car mufflers. .....

It's my understanding that the 435 Lyc isn't much of a hotrod- poor power-to-weight ratio with 435ci only producing 190 horsepower. Compare that to the O470 Continental's 225/230 hp, the IO-360 Cont's 210hp, or esp to the Franklin's 220hp from only 350ci. The main reason the 435 conversion was popular was that it was pretty easy to unbolt the whol works off a Stinson L5 and hang it on a 108-- easy, but not necesarily all that great. IMHO, and no offense to anyone who has one & likes it.

Eric (nomex suit on!)

hotrod150 wrote:

EZFlap wrote:.... I do have one flight in a Stinson 108, with a hotrod O-435 in the nose and marginal hotrod car mufflers. .....

It's my understanding that the 435 Lyc isn't much of a hotrod- poor power-to-weight ratio with 435ci only producing 190 horsepower. Compare that to the O470 Continental's 225/230 hp, the IO-360 Cont's 210hp, or esp to the Franklin's 220hp from only 350ci. The main reason the 435 conversion was popular was that it was pretty easy to unbolt the whol works off a Stinson L5 and hang it on a 108-- easy, but not necesarily all that great. IMHO, and no offense to anyone who has one & likes it.

Eric (nomex suit on!)

The reason Bruce Barton likes and has 0-435's is COST vs Power.The 0-435 produces 190 hp -cost was $2500 bucks firewall forward except for prop . $700 bucks for a overhaul kit to basically do a major . Total came up to something less than 5 grand including new plane power Alt. Bolted on a Hartzel prop (overhauled ) for another $1800 bucks . Something less than 6-7 grand firewall forward .

Other engines would more than double this figure --go figure.

EZFlap wrote:.... they add energized air into the boundary layer which keeps the flow attached to the wing at slightly higher AOA than otherwise possible. The slots will also do this same job (as mentioned), but on a Stinson [u]the slots are only on half of the wing......
.. adding the VG's likely would allow you to remove half or 3/4 of the twist (washout) on the Stinson wing... because the VG's are now there to get rid of that softened aileron control and tip-stalling problem which the twist was intended to solve originally.......

Maybe the slots were there to make the wing root stall first, before the airlerons lost authority- same reason that Grumman Yankees have stall strips on the inboard leading edge. If you get rid of the washout, the tip might stall at the same time as the root-- bad news. If you added VG's only on the outboard end of the wing, you could maybe get rid of the washout, but like you said- that's an experimental mod.
I'm assuming that the Stinson VG's install aft of the slots on the "secondary leading edge"?

Eric

The slots could have been put there for that reason, but IMHO washout/twist would do the same thing without the extra complexity of the slot. Many airplanes with no slot and no stall strips still stall at the root first. (stall strips still tall... that's a good tongue-twister for a Dr. Seuss book!)

I'm guessing the slots are there on a Stinson to keep the ailerons working well at and perhaps beyond stall angle. Perhaps if there are any legit trained aerodynamicists lurking around here they can answer this definitively?

Well I'm not a legit trained aerodynamicist, but I can testify as to the efficacy of the slots. They are designed to preserve aileron authority deep into the stall and on the Stinson they do this very well. With a more conventional airfoil, aileron inputs beyond the critical AOA (or the point at which laminar flow is lost and boundary layer separation begins) are likely to generate roll away from the desired direction of roll due to adverse yaw.

The Stinson was designed to be "spin proof" - to achieve this they incorporated the slots and they also limited the up elevator authority with the flaps retracted, premise being that limited elevator authority will only allow you to get so far into a stall. This is where the legit trained aerodynamacist could provide a more credible explanation, but the ailerons remain at least somewhat effective (and more importantly don't generate enough adverse yaw to enter a spin) all the way to whatever the max AOA the Stinson is capable of achieving. Stalls in a Stinson consist of the yolk buried in your lap with a stabilized significant rate of descent - but there is no break, it just mushes down. Rudder inputs are of course more effective in generating roll but the ailerons do still work. When you put the flaps into either of the lowered positions you then have full elevator authority so that you can flare it out in the landing.

Regarding the O-435, I've never flown behind one but I steered clear of any Stinson I found with one when I was in the market. Aside from the generally marginal performance increase there is also a pricy recurring AD on the prop. All other things being equal, if you found a plane with a 435 installed I would value it based on a run out engine. The first time you had to pull the prop for the AD you'd likely start considering putting that money toward an engine that would achieve some real performance gain.

Vick wrote:....The Stinson was designed to be "spin proof" - to achieve this they incorporated the slots and they also limited the up elevator authority with the flaps retracted, premise being that limited elevator authority will only allow you to get so far into a stall. ...... When you put the flaps into either of the lowered positions you then have full elevator authority so that you can flare it out in the landing.......

So you're saying that the flaps are linked to the elevator controls, to disable full "up" elevator unless the flaps are deployed? I'm definitely no Stinson authority, but this is definitely the first time I've ever heard that.

Eric

hotrod150 wrote:

Vick wrote:....The Stinson was designed to be "spin proof" - to achieve this they incorporated the slots and they also limited the up elevator authority with the flaps retracted, premise being that limited elevator authority will only allow you to get so far into a stall. ...... When you put the flaps into either of the lowered positions you then have full elevator authority so that you can flare it out in the landing.......

So you're saying that the flaps are linked to the elevator controls, to disable full "up" elevator unless the flaps are deployed? I'm definitely no Stinson authority, but this is definitely the first time I've ever heard that.

Eric

Vick is right and Stinson is the only manufacture that I've seen do this.

hotrod150 wrote: So you're saying that the flaps are linked to the elevator controls, to disable full "up" elevator unless the flaps are deployed? I'm definitely no Stinson authority, but this is definitely the first time I've ever heard that.
Eric

It's actually a very simple interface. The elevator torque runs just below the flap handle. There is a lip on the torque tube. When the flaps are up (flap handle flat on the floor) the lip on the torque tube runs into a limiter on the bottom of the flap mechanism when the yolk is pulled full aft. When the flaps are deployed the limiter rotates out of the way and torque tube travel is uninhibited, allowing for full up elevator deflection.

I sat in a friend of mine's 108-3 yesterday, and manipulated the flaps & elevator. Didn't notice any loss of travel with the flaps up, or anything different holding full up elevator while deplying flaps down.. Guess I'll have to check it out again. Did the 108's all have this feature?
Re: VG's on a Stinson, I'm guessing that the placement is staggered due to the slotted leading edge- in other words, the VG's are up close to the leading edge on the inboard end of the wing, then are placed behind the slot on the "secondary leading edge" on the outboard end. Hmmm?

Eric

HR150
The aileron VG's are aft of the slats and the flap VG's are forward of the slats. Probably why one gets excellent aileron control at all speeds. Hope that helps.

Micro VG's makes a great/complete product.


And there is about a 5° difference in elevator control with flaps up and down (in my 108-2 at least). I showed a couple people this at the Caveman fly-in.

mountainmatt wrote: And there is about a 5° different in elevator control with flaps up and down (in my 108-2 at least).

As far as I know all 108s have this though you probably wouldn't notice it if you weren't looking for it.

Pull the yolk all the way aft to the stop with the flaps up and hold it there. Then select the first notch of flaps and you should find that you have ~maybe~ another half inch of travel in the yolk available. Like Matt said, it's only about 5 deg difference, but the Stinson engineers evidently thought that would be sufficient to keep you out of the really deep (spin inducing) stalls.

I sat in a friend of mine's 108-3 yesterday, and manipulated the flaps & elevator. Didn't notice any loss of travel with the flaps up, or anything different holding full up elevator while deplying flaps down.. Guess I'll have to check it out again. Did the 108's all have this feature?

Verifying the increase in yoke (and elevator) travel with flaps deployed vs. stowed is part of every preflight check on my 108-3.

-Bill

So, if a person was to see an ad for a low time 108-3 with less than 400 SMOH on a 165 and prop, no damage history, old radios, Scott 3200, metal winged nice looking Stinson what would you expect to pay....? I know, its subjective and needs a pre-buy, but assuming nothing big is found what are they going for these days?

Low 20's unless it's a show stopper, then closer to 30k. There's a few on barnstormers in decent condition for under 20k, which seems like a steal (that's a lot of airplane).

I've seen a couple of the one's you are talking about, I am surprised they didn't disappear in a week. Makes me wonder why?

porterjet wrote:I've seen a couple of the one's you are talking about, I am surprised they didn't disappear in a week. Makes me wonder why?

Franklins...

I've seen a couple of the one's you are talking about, I am surprised they didn't disappear in a week. Makes me wonder why?

Franklins...

Probably true, but there's little reason to be. The Franklin's a fine engine if properly overhauled and maintained, and most engine parts can be had. The tough item is the crank, but even those can be had with persistence. There are several folks offering reliable overhauls.
The key questions on the engine would be who overhauled it, and when. If not done by a reputable builder, I'd approach with great caution.

Metallized wings or fuse on a Stinson are generally considered undesirable for several reasons, incuding weight and difficulty in inspecting the internals of the wing which can suffer intergranular corrosion.

The airframe is fully supported by Univair (the TC holder)- you can buy about any part you need brand new. Perhaps the best thing about the Stinson is that there are several very active user groups including the International Stinson Club (full disclosure- I'm a club officer) and a Yahoo group.

If you're interested in the Stinson and there's anything I can do to help, please let me know. You've probably noticed that there are several proud Stinson owners here...

-Bill

Probably true, but there's little reason to be.

I meant to say that folks are scared of the Franklin, but shouldn't be...