Getting a handle on handling.

[Entler]

Hey guys!👋🏻
Soooo, I've been playing around with an old A/B boat that I scooted around in occasionally as a kid, and actually tried racing for a season in like 96 with the Intercity Racing Commission. There I learned how to cross the start line first and enter the first turn last...near drown and sunk💦💦😲! It was all good fun being the only B boat amongst a bunch of C boats, not to mention how old my ride and power were.
At any rate, I've been battling/trying to sort out an issue that I've been experiencing since I brought the boat back out on the water. It's difficult to describe the sensations that I'll feel in the boat, much less would I think anybody would be able to diagnose online. In the video (there's more on YouTube) that slightly show an effect that almost acts like a torque steer. Problem is, sometimes it's more drastic than that and occasionally a bow steer no control issue can occur inducing fears of it grabbing/side stuffing/dumping me.
My quickie lower units skeg has been shaved down and rounded over the years from trimming damages. Could lack of skeg pose such a symptom?
Also, this is a little boat. It's like an old Swift hydro, and is about 8ft. Since the days of me racing , I've gained about 50lbs. I have done a few changes like Replace the Kg7 w a Rat motor(mk28 I think?!) and a Creary prop, and fuel tank hanging off the steering bar to hop things up to compensate for my fat ass. The boats got aluminum air traps that taper to about 1 1/2" at the transom. I tried running the numbers on lift, as per the Adams novice pamphlet (wish I'd had that to read many moons ago!) and came up with good numbers,(can't remember off hand) but felt that my weight was missing from the equation.
I realize that there's a ton of numbers and setup info that may be needed at the moment, but I thought I'd wing it and see what kind of opinions arise. Thanks in advance for reading,viewing and to thoughts and replys, Steve Entler.

[Entler]

[ZUL8TR]

1st what are those ugly trim tabs doing on a hydro light weight ? If they are set to keep the nose down, why would you want to do that ? Also you note the alum air traps taper to 1-1/2" at the rear, not sure what you mean. The question is what dept below the bottom at the rear do the traps extend, like 1/8", 1/4", etc. That depth is designed to raise rear but proper set up needs to also keep the bow up and sponsons off the water.

My guess from the little I can see in the video is the back is lifting probably caused by excessive rear trap depth and/or the trim tabs set to lower the bow and raise the rear probably causing rear side shift. Not sure of the rake of that prop, rake affects rear or bow lift.

What is the depth of the rear prop shaft center below the bottom? Is the prop shaft level with the bottom or tucked in or out?

A modified gear case fin is also not good and contributes to the handling issues.

Dump the trim tabs and tell us what the real trap depth is at the rear. Note these old hydros were not real floaters with sponsons off the water a lot and lift was not that great thus the bow needs to go up. Good designed air traps will help that by keeping the correct amount of compressed air under the hull and release it at the right place to get the bow up. Full traps to the rear may not be the best set up for that hull with not so good aero lift top side and a lot of driver exposure. I experimented with traps on my hydro (Avatar) back when racing to get it to float just right at speed and handle right in the turns.

Also where do you position yourself in the cockpit are you a steering wheel hugger, a high up face bug catcher, or rear down butt low profile rider?

[johnsonm50]

Interesting, I like the idea of problem solving, & agree right off -the tabs probably don't help beyond getting on plane. Whether they are more of a problem than just extra drag once going is a question to think about.If they are causing 'bow plow' that could be the root cause of the steer issue.

[GrandpaRacer]

It looks like the boat is not lifting much in the bow in the video. If the sponsons are dragging they can make to boat dart right or left. I agree with the othe comments about the trim tabs. Now, if you take them off you have a rather short boat for the power you have available and it may go too fast and lift too much in the front. That motor should easily make a properly set up hydro go over 60 mph. Be careful! A current A hydro is minimum 102 inches long with a longer after plane than your boat. Such boats are more suited for the low mid 50 mph range. You probably should stay in that lower speed range.

[GrandpaRacer]

Another caution, when you get going up to the potential of that motor things can happen real quick. Add to that floating debris in the river can be bad. A helper in a safety or chase boat should always be part of high speed testing.

[johnsonm50]

Such boats are more suited for the low mid 50 mph range: Very true, been there - done that.. I'd feel safer in a modern hydro at 70 than in an older design at 50. Thing is even as modern racers in their time they weren't that fast. At 8' +/- you have an A boat with a B motor. Correct me if I'm wrong, a MK28 is 22 hp alot more than an A. Not only is more speed than intended potentially trouble but the torque that motor delivers [it sounds great btw] can be a handful.

[Shane_B]

Potentially another problem may be your turn fin on the hull - is it on your sponson or mounted off-center on the after-plane of the hull? If on your sponson, is it parallel to your air traps? If not, that will cause the boat to roll and act funky.... you can check by either clamping a laser level to the fin and measuring the beam's location just aft of the fin and again at rear of the boat - should be same measurement. Other method is clamping a long straight edge/level to the fin and take same measurements. A 4 degree vertical cant of the fin inward may also help (but horizontal must be parallel to air trap). Also agree with getting rid of the trim tabs - folks posting above have many decades experience, heed their words!

[jeff55v]

Question:
Was that boat originally designed with air traps? I think early hydros were true three point design. Meaning they were not made to lift the front sponsons up, and had three points of contact with the water. Early hydros did not have air traps.

[johnsonm50]

Now that much of what can be wrong is identified what can you do? The fin, as Shane wrote: It is critical to be straight with the traps The motor, Is it centered between the air traps & perpendicular to the bottom? The air traps, I'd assume they're about 2-1/2 deep at the sponson tails & 1-1/2 at the transom? It could be too much air at the rear allowing a prop walk situation to occur [rear of boat veers left onto the fin, the boat rolls up] If it does that it's almost a guaranteed swimming lesson. Last but not least, being safe, a boat can be most dangerous while working on getting it dialed in, you should have as GrandpaRacer pointed out a chase boat with a capable driver. A helmet, jacket & if possible kevlars would be wise too. When you make changes take written notes, making one change followed by a test run & a note is advised so you know & can research exactly what each change result is. Concern with handling before worrying about speed but when you go into speed testing you'll need as true of speed & rpm specs as possible. If in fact the motor turns out to be too fast for the hull [probable] you can curb it with the throttle cable adjustment to 7/8 or 3/4. To some degree prop choice -the old acceleration /speed trade off but that can over rev the motor if your not careful. Good Luck & keep us posted.

[jeff55v]

Another question:
Are those springs I see in the steering? Most racers recommend against them.

[DeanFHobart]

Hello,

It is not a Swift Hydro. Most likely is a design from a magazine or Glen - L or possibly a home design and build.

It sure is a clean looking outfit however. You might bring it out to a Region 10 race and some of the guys would help you. Lots of help at a boat race.

Keep up the good work and keep at it.... And eventually you will figure it out. But most of all, have fun doing it. Be sure to wear a Helmet and Life Jacket, and a Kill Switch on the motor... Like a switch on a Jet Ski...... If you exit the boat, a tether from the switch to you pulls the switch and kills the motor..... Also a full butterfly in the carburetor.

[T Chance]

I don't think it is a Swift either, it is similar to an A-B Swift though. Back in the early 1960's I raced an A-B Swift with a B Hot Rod and an A Konig (both alcohol burners) speed was probably 62 to 65 mph. It handled good with both motors. It is the boat I won my first race with. Anyhow, your boat is similar so the first thing I would recommend is getting rid of those trim tab afterplane things. My swift has wooden airtraps that started at the end of the sponsons and ended about a third of the way to the transom.To check proper depth, run a string from sponson to transom and measure the depth 1/3 of the way back from the sponson. My fin was centered side-to-side and right under where I kneeled. Your boat is pretty much like I had back then and with a lot less horsepower than I put on my Swift back then so I would think that once you get a good set-up it should perform just fine.

[Entler]

Ugly?! ****, do you have any idea how many hours I've spent polishing those? 😉
Actually we had experimented with setting the motor back and up, and the tabs were attempts to lengthen the boat.
I just recently put those back on to see how it would change it. They pose more headache than reward. So from here on out tabs are gone, and motor will be hanging in the original spot.
Next step that I shall be doing is trimming excess air trap depth. I've got at least 1 1/2" trap depth at rear. If it truly does lift the rear, that may explain another odd sensation that I'll experience. I can get the boat into a plane and it'll feel healthy and skipping along just fine and around 35-40mph, with no real rhyme or reason, I'll get a sensation that feels like a gear shift or torque converter lockup as if the prop suddenly found clean non aerated water or something. I didn't mention it before, because I figure that that will go away with getting things setup better.

To see how the boat would act, I buried the prop to depth of about 3 inches with a cpl degrees kicked in. I'm 6'2" at about 200lbs. I'll kneel at the midland area. Def not a steering wheel hugger, and def not hanging ten of the back. Butt down tuck on straights. Face in the wind for set and lean for turn albeit turns are not something that I've felt cozy with for awhile.
I really appreciate the reply! Being able to hear from experience and know how helps a ton. I've just had a few too many questions in my head and/indecisions.

Wow! I'm giddy like a little girl over all of this attention! Thanks for everyone's replies!

Why do most racers go against steering system springs? And yes, it is equipped with em.

What are the symptoms of a boat with too much motor?

[dwhitford]

No steering-cable springs because they make for mushy steering, bad handling, & loss of positive control. You want your steering setup to be 100% positive, not at all ''mushy'' and wiggly on its own. The same is true on whatever tension you have on the steering rotation.

On a Mercury set of clamp brackets, you have a tension bolt that you can run down for ''tighter'' steering, You need to set this so that you can barely swivel the engine by hand, grasping onto the steering bar.

On my Koenig-bracket (bolt-on setup), I must resort to shims for the clamp on the driveshaft housing to adjust tension on the thrust-bracket yoke.

If you let go of the steering wheel while underway on plane, and the boat wants to turn left on its own from propeller torque, you need to tighten steering tension until it won't . . . lest you go onto your head into the drink!

[Entler]

I wish I had started this process last spring so I could actually make changes and go test it. Instead we are in the middle of the remnants of a typhoon and the river jumped up about ten feet over night complete with logs, fast current and the promise of being unusable till prolly June. 😩

Btw, I do try to be safe.
Helmet, and kill switch and floatation and horn. Unfortunately my old jacket is too small. Was military-ish with crotch belt and mild flack panel on the back. At any rate, I'd love to have the latest and greatest in cut suit and floatation but cost exceeds my tinkering with the boat. If I was on course, I'd make the investment. That being said, I'd hate to ever have a prop catch me!

[Entler]

About the hull design, it originally was a three point with no air traps. The traps were an add on.
Supposedly and I mean "supposedly" this boat did 64mph back in the sixties. With the purchase of the boat back in the early '80s came the "legend" or ?! Who knows. It was supposedly built by a "gypsy" boat builder. I've never peeled back to look for markings. Legend has it that this guy would build a boat for an interested party if he could crash in the garage while building it. In evolution, it makes sense. Bartering chickens and beads eventually becomes hydroplanes.

[johnsonm50]

About the hull design, it originally was a three point with no air traps. The traps were an add on.
Supposedly and I mean "supposedly" this boat did 64mph back in the sixties. With the purchase of the boat back in the early '80s came the "legend" or ?! Who knows. It was supposedly built by a "gypsy" boat builder. I've never peeled back to look for markings. Legend has it that this guy would build a boat for an interested party if he could crash in the garage while building it. In evolution, it makes sense. Bartering chickens and beads eventually becomes hydroplanes.

Makes for a good story.. had to be free beer too I'd hope.