Project Boat and Mod motors

[pops67g]

Sponson length?

I had a hydro that wanted to spin out fairly often. We cured it by shortening the sponsons. They were originally about half the length of the boat and the fin made a nice pivot point. We shortened them up to the next frame forward and it got better in a hurry. Maybe it is just the perspective in the photo but your sponsons look way longer than necessary. Heck don't they only touch the water in the corner anyway?

[blueskyracer]

I had a hydro that wanted to spin out fairly often. We cured it by shortening the sponsons. They were originally about half the length of the boat and the fin made a nice pivot point. We shortened them up to the next frame forward and it got better in a hurry. Maybe it is just the perspective in the photo but your sponsons look way longer than necessary. Heck don't they only touch the water in the corner anyway?

I will take a side view later since the sponsons are really not big..The problem was the sponsons were touching or dragging the water all the time not just in the corners and no speed

[pops67g]

If the sponsons drag all the time you obviously need more lift. Those "shoes" in the rear would seem to be letting out all the air passing under. You wind up with a 30+inch wide tunnel in back. My boats have a tunnel that is about 12 inches wide and also full length air traps that are about 3/4" deep at the rear. The turn fin just skims the water surface at 80+mph and transitions really well into the corner.

[Dave M]

Spin Outs

Mike,

From what I have seen of the boat run, and please don't take this the wrong way, you need more power behind it. A lot more. I think that design is to much for the 40CI Merc. You would need to step back to a 125CCH Euro or maybe a 175CC Euro style. I believe the size boat you built is for a SEH class.

Now for spinning out, I looked but can't recall the depth of the air traps at the rear. In the pics, they look about zero. You need at least a 1/4" to track right. If you can't get that, add a rear fin to track.

I think you might need to move back in that boat. You simply might not found its sweet spot.

I agree with some, if you plan to run a 40CI Mod Merc you need more lift. If you run a 44CI Mod Merc you will still need a little more lift. That is just my opinion though, you built it, and know how it is feeling out there. You need to marry the right power to the design. Once you get it to ride on the pads, you will be amazed at the difference.

[blueskyracer]

And to think this boat was designed for about a 5'5" driver weighing 160 tops with a Yamato 302..It is a experiment that may never work but we will play a little more.. We will play with the 40 one more time and then the 44.. I have no interest in Pro motors so we will forge ahead..Who knows it could end up as wood for a weenie roast

[Geezeracer]

"The problem was the sponsons were touching or dragging the water all the time"

This sounds pretty similar to a nagging problem Will had with our Rotax project. We first tested the 340 Rotax on the same elderly Karelsen D we'd used to work out bugs in our prototype Polaris motor to find the Rotax made it a hairy handful. Will decided to stretch another hull o get better high speed stability, and added about 11 inches to the afterplane of an older A&H D we'd run as an electric.

In tests it ran OK, but didn't have the speed the Rotax appeared to promise. Will decided to race it anyway as a puzzle project. By about the 4th race he was pretty frustrated. The boat seemed stuck at about 60 mph, and was a hunting and darting thrill ride that was beating him up over every ripple. After a rude Saturday at Cullaby he decided that if it wasn't better Sunday we'd drop it off at Newberg as bonfire fodder.

Looking over the boat as Will ranted I saw the Lexan rails we'd added in the electric configuration were still there...They were two of them, each a 2X2 lexan angle about 3 feet long, extending the trap and meant to pack air a little further aft to help lift off the battery pack....Good for a lead/acid E-boat but not for 350. I pointed them out to Will and asked how he saw the boat reacting to them now. Will's immediate response was a close encounter of the Popeye kind, followed by his explanation that they were making the boat run down hill to slow it down and generate all the twitchy behavior.

When we ran on Sunday (without the trap extensions) the boat was totally different...an instant rocket scrabbling for the lead, and when I came in Will was leaping around like a flea on a hot griddle, waving the GPS madly and shouting for me to get the camera.

Pics below:

Will's GPS - The boat as an electric - Will winning post-fix at Lawrence

[blueskyracer]

"The problem was the sponsons were touching or dragging the water all the time"

This sounds pretty similar to a nagging problem Will had with our Rotax project. We first tested the 340 Rotax on the same elderly Karelsen D we'd used to work out bugs in our prototype Polaris motor to find the Rotax made it a hairy handful. Will decided to stretch another hull o get better high speed stability, and added about 11 inches to the afterplane of an older A&H D we'd run as an electric.

In tests it ran OK, but didn't have the speed the Rotax appeared to promise. Will decided to race it anyway as a puzzle project. By about the 4th race he was pretty frustrated. The boat seemed stuck at about 60 mph, and was a hunting and darting thrill ride that was beating him up over every ripple. After a rude Saturday at Cullaby he decided that if it wasn't better Sunday we'd drop it off at Newberg as bonfire fodder.

Looking over the boat as Will ranted I saw the Lexan rails we'd added in the electric configuration were still there...They were two of them, each a 2X2 lexan angle about 3 feet long, extending the trap and meant to pack air a little further aft to help lift off the battery pack....Good for a lead/acid E-boat but not for 350. I pointed them out to Will and asked how he saw the boat reacting to them now. Will's immediate response was a close encounter of the Popeye kind, followed by his explanation that they were making the boat run down hill to slow it down and generate all the twitchy behavior.

When we ran on Sunday (without the trap extensions) the boat was totally different...an instant rocket scrabbling for the lead, and when I came in Will was leaping around like a flea on a hot griddle, waving the GPS madly and shouting for me to get the camera.

Pics below:

Will's GPS - The boat as an electric - Will winning post-fix at Lawrence

Very nice..Maybe this year I can be so lucky

[Guest]

Removing lift

Over the last year we have been working on our C MOD to reduce the nose lift. I think we have solved the issue! We carried 15 lbs of lead in the nose, moved the fuel tank forward, vented the air traps, increased the transom angle and now we have applied the ultimate fix. My son will have to loose a ton of weight.

Alan

[David Weaver]

Suggestion

Try a 4 blade propeller.

[blueskyracer]

Over the last year we have been working on our C MOD to reduce the nose lift. I think we have solved the issue! We carried 15 lbs of lead in the nose, moved the fuel tank forward, vented the air traps, increased the transom angle and now we have applied the ultimate fix. My son will have to loose a ton of weight.

Alan

Poor baby.. Good luck with the weight loss..Does he know yet?

[Guest]

Removing lift

Well this morning the west system should be cured and we can see how it came out. The 3 CM of granite will make a great smooth surface and we won't have issues when we run over something. Post photos later!

Alan

[Guest]

Making progress on the C MOD

The West system is still curing so I will wait a couple days to sand the bottom and prepare for the varnish work. Rolled the boat over and installed the new floor board and checked on the reinforcement installed for the cracked stringers and it went well. Once I get all the finish work done then I will weigh the boat and see what we picked up with the mods and repairs. Will post photos later.

Alan

[S Henderson]

Bottom

Why have you put the small extensions on the back of the main bottom ???
Looks like that could be a problem in the turns.

Stan

[Guest]

Afterplane

We extended the bottom 1.5 inches aft to help control the nose lift. Being that we hit somthing the last race of the season and cracked three stringers along with taking a piece of plywood out of the bottom I decided that I would pad the bottom and add the length to give us more restoring moment. When we test in a couple weeks we will see if the extension is an issue, if so it can be removed quite easily. I will post the results after we run the boat again. One thing I am sure of is that the bottom is sound again.

Alan

[blueskyracer]

I would like to thank all the folks who have PM'd me.I will have pictures of what I am trying first shortly.. If that dont work then we will try a new batch of ideas..I figure if I can get it to go with the 40 then we will see what happens with the 44.. Yippi Ki Ya or Yahoo which ever comes first.. I wont get to test much since we are only going to 2 local NBRA races and two others maybe