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flykolb(at)pa.net
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 Posted: Sun Aug 15, 2010 6:02 pm Post subject: Kolb flying boat |
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Chris,
You were probably correct in your thinking that the tube by itself would not have been stiff enough – the reason for this is that because you were using the hole for wing folding you were necessarily limited to only a ½” dia tube because that is the hole size in the spar for folding. I forget what size tube was typically used for the sponsons, but it was at least ¾” and possibly even 1”. The larger dia tube would have been much stiffer than the ½” tube. I recall building one of these float plane wings and as I recall I used the same dia tube that Jim Lee used and I winced at putting such a large hole through the spar. But it was far enough outboard of the spar fitting that the stresses due to lift were just a small fraction of what they were at the H-section. I saw at least one example where a sponson that was bent back because of a low altitude stall where the airplane hit the water at an angle. The tube was bent way back but the spar was not harmed. This was good because the bending tube is a weak link that will dissipate the impact force to the wing: stiff enough for normal loads, but flexible enough to bend before breaking something in the wing.
Dennis
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of chris davis
Sent: Sunday, August 15, 2010 9:40 PM
To: kolb-list(at)matronics.com
Subject: Re: Kolb flying boat
Dennis, Thanks for the come back It was a while ago and as I remember the reason I put the stays on was because the wing foldinsertion tube didnt seem like it would take any large amount of stress and being new at sponsons as I had twin floats on it for 3 years prior to the unifloat which I didnt care for I thought that the stays were agood insurance policy!
Everything you said in your post made sence as usual .
Chris Davis
KXP 503 492 hrs
Glider Pilot
Disabled from crash building Firefly
From: Dennis Souder <flykolb(at)pa.net>
To: kolb-list(at)matronics.com
Sent: Sun, August 15, 2010 7:25:12 PM
Subject: RE: Kolb flying boat
Chris,
With your KXP arrangement the sponson loading would have been divided between the cable and by the wing fold insertion tube. It would be hard to say how much of the load would have been carried by each - this is essentially a statically indeterminate problem since there are two load paths and each is somewhat elastic. The load sharing would require some complicated math to solve.
If it was evenly divided, for instance, then the leading edge would carry half of the total loading vs. 100% of the loading with the arrangement on the flying boat Kolb.
If the cable was not strung very tight, then possibly the wing fold insertion was carrying most of the load.
Also the leading edge tube is larger and better supported from the main spar. But even so, I would not choose to use this either. Yours held of ok under reasonable loading usage; it might or might not hold up if more stress was applied.
Dennis
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of chris davis
Sent: Friday, August 13, 2010 1:01 PM
To: kolb-list(at)matronics.com
Subject: Re: Kolb flying boat
Dennis , When I had a monofloat on my KXP I mounted the sponson on the wing fold holding tube with cable stays going to the leading edge and to the wing tip ? This seemed to be well supported to me as the wing fod tubes were intended to hold the weight of the wing ? It worked out well but I never hit anything and most of my landings were on reasonably calm water. What do you think of that rig ? Thank you
Chris Davis
KXP 503 492 hrs
Glider Pilot
Disabled from crash building Firefly
From: Dennis Souder <flykolb(at)pa.net>
To: kolb-list(at)matronics.com
Sent: Fri, August 13, 2010 7:25:12 AM
Subject: RE: Kolb flying boat
Ron,
In addition to the probable excess weight issue, I’d also check the internals on wing at the sponson float attach point. If there is no internal reinforcement for the rib(s) where the sponson attaches at the rear wing spar, then that is placing too much stress on adjacent wing rib(s). It looks like one rib would take the major portion of the load and no rib is capable of handling the potential sponson induced loading. If that rib weakens and fails, then the load would be taken up by the next adjacent ribs. And they in turn could be overstressed and eventually fail. This damage can be hidden because the wing fabric is flexible and can look normal even after the ribs are broken underneath. The trailing edge is not strong or stiff enough to take the loads imposed by a sponson float. The danger here is that internal damage could start and grow unseen until the wing was seriously weakened. When imagining this scenario don’t think about a smooth lake surface with the nice small ripples, imagine some winds that have stirred up some waves or a motor boat had just sent out a large wake and you don’t see it and the sponson dips into this wave. Or you bump a dock or rock on the shore. The sponson is on a long moment arm and can exert a lot of force on the wing.
All Kolb mono floats that I have seen attach the sponsons directly to the main wing spar. The sponson is supported by one stout tube that goes completely thru the 5” spar. This is placed far enough outboard where the lifting loads are no longer a major part of the spar load and the spar can afford a large vertical hole thru it.
Dennis
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of ron schick
Sent: Friday, August 13, 2010 12:40 AM
To: Kolb-list
Subject: RE: Kolb flying boat
Dan and all thanks for the pics and the input. Yes the plane is near complete, but there are some tractor mechanic things I would want to address before I flew it. First would be weights and balance, then the hinged windshield would need more attachment for my liking. The fuel and wiring would need the blue auto connectors to the coil removed and the glass cleanable fuel filter thrown in the trash etc. Beyond that my concerns would be the handling caracteristics with the tail group behind that big old boat possibly blanking the tail. My biggest concerns are the paperwork to get a registration, and the purchase price in case I have to part it out. The water is always a little cold in southwest Oregon so getting out of a swamped wreck has me a little concerned as well  I'll try to attach a few more pics, but have never seen it off the trailer. I'll throw in a pic of my VW Fox for the redrive crowd. Ron NB Ore
From: h20maule(at)hotmail.com
To: kolb-list(at)matronics.com
Subject: RE: Kolb flying boat
Date: Thu, 12 Aug 2010 11:15:29 -0400
Ron, here are pics of my FS amphib...do you have any photos of the whole plane?
Daniel Myers
407 920 7700
From: roncarolnikko(at)hotmail.com
To: kolb-list(at)matronics.com
Subject: RE: Kolb flying boat
Date: Wed, 11 Aug 2010 21:21:24 -0700
I am thinking of buying it, but if the gear is a design flaw and not just for beaching I wonder if it should be returned to a conventional Firestar.
I have built a 582 Avid A model and Kitfox 4 with a VW redrive so I'm used to the experimenting. The fiberglass would probably need test drilled, banged or something to make sure it would withstand landings on choppy water. The plane has been through a few hands and the main builder has passed away.
Date: Wed, 11 Aug 2010 23:01:06 -0500
Subject: Re: Kolb flying boat
From: aslsa.rng(at)gmail.com
To: kolb-list(at)matronics.com
Now this truly puts the experiment in experimental aircraft. Are you thinking of buying this, Ron? It would be great to watch your progress as you bring this to the air, and water. Very cool.
Rick Girard
On Wed, Aug 11, 2010 at 10:25 PM, ron schick <roncarolnikko(at)hotmail.com (roncarolnikko(at)hotmail.com)> wrote:
I've found a Kolb Firestar two that has been converted to an amphibian. The workmanship looks very good, but the gear must be for beaching only. The leverage of the gear to lever is about 4:1 and could not be done in flight. Has anyone else heard of a Kolb amphibian? I'll try to attach a picture. Thanks Ron
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