Airborne

[JohnsonM50]

Back when I 1st joined Boatracingfacts This was the boat I was most into:



There's other pics here & there, It's a Hal Kelly 'B' Airborne powered by an OMC 31.8CI 25hp twin. It's mounted on a Bass tower & gear case so is alot faster than the stock outboard version of a 25. It's a fun ride but since building it I have gone into hydro racing & have only kept up with cozmetics. It is still a favorite tho but has a longstanding problem I have posted about before & have yet to work out. If I want to turn one of the hydro's & put it between 2 markers > full speed no problem. The Airborne handles terribly compared & is hardly predictable turning. I'm sure it's about where the fin is & have tried several settings. The boat is made for a 20H & would handle ok, tried a MK25'quicky RaT. The OMC is 20 pounds heavier, has a good amount more speed & far more grunt. I drive seated for comfort & didn't like it when I tried kneeling. [I take 30 to 50 mile or more cruises in this]. I tried a larger fin to no avail, it actually turns right better than left. When in a left it lifts off the fin & does a twisted porpoise thing that increases per bounce till the point of not daring to push it farther. I'm thinking a roll up fin to be no good for a 'seat boat'. Since it's also no racer I don't want to adapt a chicken wing but got to thinking, I saw the underside of a Top-o-Michigan Marathoner that had right & left roll up style fins. My guess is they'd cancel each other out & turn flat with some predictability. Any thoughts on this would be appreciated especially if you have driven such a rig. Beyond that centering the fin is an idea but I wouldn't want to disturb the water right before the prop.

[Bill Van Steenwyk]

[QUOTE=JohnsonM50;149822]Back when I 1st joined Boatracingfacts This was the boat I was most into:



There's other pics here & there, It's a Hal Kelly 'B' Airborne powered by an OMC 31.8CI 25hp twin. It's mounted on a Bass tower & gear case so is alot faster than the stock outboard version of a 25. It's a fun ride but since building it I have gone into hydro racing & have only kept up with cozmetics. It is still a favorite tho but has a longstanding problem I have posted about before & have yet to work out. If I want to turn one of the hydro's & put it between 2 markers > full speed no problem. The Airborne handles terribly compared & is hardly predictable turning. I'm sure it's about where the fin is & have tried several settings. The boat is made for a 20H & would handle ok, tried a MK25'quicky RaT. The OMC is 20 pounds heavier, has a good amount more speed & far more grunt. I drive seated for comfort & didn't like it when I tried kneeling. [I take 30 to 50 mile or more cruises in this]. I tried a larger fin to no avail, it actually turns right better than left. When in a left it lifts off the fin & does a twisted porpoise thing that increases per bounce till the point of not daring to push it farther. I'm thinking a roll up fin to be no good for a 'seat boat'. Since it's also no racer I don't want to adapt a chicken wing but got to thinking, I saw the underside of a Top-o-Michigan Marathoner that had right & left roll up style fins. My guess is they'd cancel each other out & turn flat with some predictability. Any thoughts on this would be appreciated especially if you have driven such a rig. Beyond that centering the fin is an idea but I wouldn't want to disturb the water right before the prop.





Have no idea whether this would have anything to do with the turning of the boat or not, but the Airborne is an older design is it not. If that is correct and an early Merc motor turned (rotated) in the opposite direction, could that have something to do with not handling correctly? Most early designs were meant to be run with Mercs I think. If your motor has a heavy flywheel (or heavier than a Merc) that could have an effect also.

I had a Speedliner Typhoon Jr. in the mid 1950's, which I am sure differs from the Airborne in numerous ways. It had a center fin which was the norm at the time for runabouts. I could go to the first turn (or any turn for that matter) time after time and that boat would sit right on its tail and go around the turn just as pretty as you please. Then once in a blue moon, I could go into a turn, same speed, same type of water, everything the same, and it would broach and spit me out the side like a watermelon seed from between your fingers. Never did solve that problem except in one way. I sold the Speedliner and bought a Swift Big Bee. That started almost 50 years of Hydro competition with one exception of one year.

[JohnsonM50]

Thanks for replying Bill, It is a '54 design, the fin started out about where the plan suggested to the port & about 34" from the transom. Until I got the bass set up it was ok but only did to the low 40s. The Bass spins a 'D' prop to the left like a Merc tho so I think the excess power & weight as opposed to fin location more likely part of the problem. From what I gather if it's too far back it won't hold, too far forward & the boat can hook generally as far as utility racers go. 50 Years?, What a ride. I'm in year 7. Anyhow I'm leaning towards & right & left turner that can cruise a nice turn without jumping all over making me look bad.. won't ever have to make turn 1 lap 1 in a crowd.. got the hydro's for that.

[Bill Van Steenwyk]

[QUOTE=JohnsonM50;149824]Thanks for replying Bill, It is a '54 design, the fin started out about where the plan suggested to the port & about 34" from the transom. Until I got the bass set up it was ok but only did to the low 40s. The Bass spins a 'D' prop to the left like a Merc tho so I think the excess power & weight as opposed to fin location more likely part of the problem. From what I gather if it's too far back it won't hold, too far forward & the boat can hook generally as far as utility racers go. 50 Years?, What a ride. I'm in year 7. Anyhow I'm leaning towards & right & left turner that can cruise a nice turn without jumping all over making me look bad.. won't ever have to make turn 1 lap 1 in a crowd.. got the hydro's for that.





I would try moving the fin around and put it in the center. Can' hurt and might help. If it doesn't, move it somewhere different. I assume you have checked to see if the bottom is straight like the plans say it should be? Maybe some of the other guys on the forum have built or had Airbornes and could help. Mike Krier with Krier Boats knows as much about Runabouts as anyone today, but I am not sure if he has a computer now or not.

Also the Bass lower unit is larger than what the boat was designed for when it (Boat) was first designed. Perhaps that is causing a problem of some type with hooking or holding too much in the corners and making it evil. Sounds like it needs to slide more when turning. to help if go round the corner.

Another idea might be the gear ratio of the unit. Most of the 'Quicky's' in the early days were 1-1 or lots of them anyway. Perhaps when you crack the throttle in the corner with the Bass lower unit, if the gear ratio is much different, it "hits" much quicker and throws the boat out of control. Maybe try a 2 blade prop if you have one that will fit the prop shaft?

Just thinking out loud. Hope you get it solved.

[1100r]

Mike - I told you you needed a Krier lol. Bill M Krier barely uses his cell let alone computer. I have tried to get him on the sites but gave up lol. Mike I talk to Krier quite frequently and will mention this to him

[JohnsonM50]

Mike - I told you you needed a Krier lol. Bill M Krier barely uses his cell let alone computer. I have tried to get him on the sites but gave up lol. Mike I talk to Krier quite frequently and will mention this to him

Thanks Todd, I'd like to hear what he has to say.

[JohnsonM50]

[QUOTE=Bill Van Steenwyk;149825]

Thanks for replying Bill, It is a '54 design, the fin started out about where the plan suggested to the port & about 34" from the transom. Until I got the bass set up it was ok but only did to the low 40s. The Bass spins a 'D' prop to the left like a Merc tho so I think the excess power & weight as opposed to fin location more likely part of the problem. From what I gather if it's too far back it won't hold, too far forward & the boat can hook generally as far as utility racers go. 50 Years?, What a ride. I'm in year 7. Anyhow I'm leaning towards & right & left turner that can cruise a nice turn without jumping all over making me look bad.. won't ever have to make turn 1 lap 1 in a crowd.. got the hydro's for that.





I would try moving the fin around and put it in the center. Can' hurt and might help. If it doesn't, move it somewhere different. I assume you have checked to see if the bottom is straight like the plans say it should be? Maybe some of the other guys on the forum have built or had Airbornes and could help. Mike Krier with Krier Boats knows as much about Runabouts as anyone today, but I am not sure if he has a computer now or not.

Also the Bass lower unit is larger than what the boat was designed for when it (Boat) was first designed. Perhaps that is causing a problem of some type with hooking or holding too much in the corners and making it evil. Sounds like it needs to slide more when turning. to help if go round the corner.

Another idea might be the gear ratio of the unit. Most of the 'Quicky's' in the early days were 1-1 or lots of them anyway. Perhaps when you crack the throttle in the corner with the Bass lower unit, if the gear ratio is much different, it "hits" much quicker and throws the boat out of control. Maybe try a 2 blade prop if you have one that will fit the prop shaft?

Just thinking out loud. Hope you get it solved.

The Bass is much larger than a B Merc but is actually narrower. The ratio is 16:17, so pretty close. I was surprised how well it ran up with the smaller power head than designed for but no problem there. The motor fin was damaged & I cut a minimal amount off the clean up the damage & saw no difference but you're right, that could be part of it. I've run 3 or 4 2 blade's & find so far that 3 blade cleavers work best overall- speed & handling about the same but the cleavers take off with much less cavitation at start up with more speed per rpm. Centering the fin is a fair idea, got a ride in a powerful 80mph V8 Garvey. They have 3[?] large center fins in a row front to back, seemed able to bend my vision in a turn.

[1100r]

Mike I will give him a call on Monday. Im working all weekend and doubling back on Sunday afternoon.

[zul8tr]

Tell us what is your setup:

1) prop shaft kicked in or out or parallel to bottom, if in or out how much? If kicked out in a turn the boat will lift on the starboard side and start to porpoise, especially with the extra engine weight over the 20H which is the engine the Airborne was designed for. This effect is more pronounced in a runabout than a hydro. What setups have you tried? Lots of combinations. What do you have for a engine angle adjustment? I hope better than standard pin in the few holes. If so you need a kick out bracket for fine adjustments or you will never get it dialed in.

2) when prop shaft angle is set what is the depth below bottom of rear end of prop shaft? The Bass torpedo is longer and the tip is in alignment with the center of the prop shaft compared to the A/B/C/D Merc quicky with the torpedo tip about 3/8-1/2" above the centerline of the prop shaft. Much different water dynamics of each gear case with the Bass being More Sensitive to water feed to the prop and also a longer torpedo. Thus 1) angle important.

Other:

3) Your fin per Kelly plan would be set to the port side for left turn circuit racing, if you put it in the center it will be better balanced for left and right turns but as you note it will disturb water fed to the prop. But worth a try and play with 1) and 2) before giving up. Do you have adequate wood inside for fin relocation?

4) The cleaver you use has a lot of rake to push the bow up which runabouts usually need, in a turn a high raked prop will lift the outside turn chine especially if the engine is kicked out. With the extra power of the engine you re using compared to the 20H you have enough grunt to power the bow up and hold it, maybe less rake prop would work better and still give the bow up and hold but reduce the turn crazies? But play with 1) and 2) first to determine if any different set ups work better..

5) Do you know the pitch of that cleaver?

6) and change 1 thing at a time and keep good notes.

It is always a challenge to take an older designed hull that was made for a specific engine in mind and power it with a more powerful engine that was never considered. Ex: I have a 1983 Karelson that Ed designed specifically for the 25ss (not the 25xs). It is a pickle style and works great with the 25ss and no doubt the 20H conversion if I tried that. I also have a Y80 that is 25 lbs heavier than the 25ss. Runs great in a straight line but is terrible in a turn with the chine lift and resulting violent porpoising and the extra 25 lbs makes it worse. Tried many set ups but no success so no Y80 on that boat. Just a thought!

Tell us your results ...................

[JohnsonM50]

Tell us what is your setup:

1) prop shaft kicked in or out or parallel to bottom, if in or out how much? If kicked out in a turn the boat will lift on the starboard side and start to porpoise, especially with the extra engine weight over the 20H which is the engine the Airborne was designed for. This effect is more pronounced in a runabout than a hydro. What setups have you tried? Lots of combinations. What do you have for a engine angle adjustment? I hope better than standard pin in the few holes. If so you need a kick out bracket for fine adjustments or you will never get it dialed in.

2) when prop shaft angle is set what is the depth below bottom of rear end of prop shaft? The Bass torpedo is longer and the tip is in alignment with the center of the prop shaft compared to the A/B/C/D Merc quicky with the torpedo tip about 3/8-1/2" above the centerline of the prop shaft. Much different water dynamics of each gear case with the Bass being More Sensitive to water feed to the prop and also a longer torpedo. Thus 1) angle important.

Other:

3) Your fin per Kelly plan would be set to the port side for left turn circuit racing, if you put it in the center it will be better balanced for left and right turns but as you note it will disturb water fed to the prop. But worth a try and play with 1) and 2) before giving up. Do you have adequate wood inside for fin relocation?

4) The cleaver you use has a lot of rake to push the bow up which runabouts usually need, in a turn a high raked prop will lift the outside turn chine especially if the engine is kicked out. With the extra power of the engine you re using compared to the 20H you have enough grunt to power the bow up and hold it, maybe less rake prop would work better and still give the bow up and hold but reduce the turn crazies? But play with 1) and 2) first to determine if any different set ups work better..

5) Do you know the pitch of that cleaver?

6) and change 1 thing at a time and keep good notes.

It is always a challenge to take an older designed hull that was made for a specific engine in mind and power it with a more powerful engine that was never considered. Ex: I have a 1983 Karelson that Ed designed specifically for the 25ss (not the 25xs). It is a pickle style and works great with the 25ss and no doubt the 20H conversion if I tried that. I also have a Y80 that is 25 lbs heavier than the 25ss. Runs great in a straight line but is terrible in a turn with the chine lift and resulting violent porpoising and the extra 25 lbs makes it worse. Tried many set ups but no success so no Y80 on that boat. Just a thought!

Tell us your results ...................

Thanks Pete, 1'st for Bills post, the bottom is good & flat so no bad behavior there. This also had 1/4" square edged chines the last 3', I changed them to the same angle as the sides & that did improve it. I just checked the height/angle, [actually been awhile since I did], there is a BTM 'A' thrust bracket on it. I have tried it from up to where the prop would barely work to down low at all kinds of angles when I was trying to get it to be faster. Not much difference found in speed but a good amount of ride difference is possible. In a straight it's very good. I see what you mean about the shaft angle in relation to turning but it is tucked about 1/2" per foot at about 1-1/8 deep which & know is pretty far both ways. To explain that brings into question the prop. For a long time I've run Ron Hill 'D cleavers, 1 at 11-1/2P low rake & another at 11P hi rake. The hi rake I like better because it gets on plane very well. Both however were slightly over pitched & keep the R's down to about 5400. I now have a 10-1/2 P cleaver that lets the motor go into the low 6g neighborhood where it's best. Good speed, very good acceleration. What I'm looking for tho is to improve not only the turning but the dead spot between 5 & 15 mph where the props get no traction. That can be a pain on public water where slowing down here & there are required. That brings me to the question of whether a european beach start type prop would be better for this? Anyhow the circuit racing roll up fin is definitely out, Putting the backup material in will be easy wherever I want.

Built for speed & comfort... Maybe I
ask too much lol