Good job so far! 
TinBoats.net
The original aluminum boat site!
14' Starcraft Modifications
- Thread starter WTL
- Start date
Help Support TinBoats.net:
Thanks, but I might not be doing such a great job. Went again today and the problem is back, I guess it just didn't porpoise enough with another man riding in the front the other day.
It is as if the console is moving 1/2" in my hands when it porpoises at speed, talking 20-25 mph on plane. It doesnt do it when I hit a wake or am going slow. It doesnt do it half way either, when the console bumps its obvious, feels like someone is talking a crow bar and physically moving the thing even though its attatched solid enough to not move when I apply force to it.
It is attatched almost directly to a rib on the floor using great stuff foam sealant, so the next thing to try is going to be getting a better way to attatch it. I'm seriously thinking of running two angle iron strips up the first 8' or so of the boat and riveting them in, then attatching the console to those.
I took pictures for you to see exaclty what I'm talking about. I also considered the possibility that somehow the steering cable is pulling the how setup back when the engine torques, but that transom is feeling pretty rock solid and even though the steering cable is tight, I can't recreate the feeling of the console moving.
BTW, I trimmed her up today to where the cavitation plate was level with the hull and hit 26 mph one time. Its ok if it is glass, but any ripple at all and the bow starts popping up.
It is as if the console is moving 1/2" in my hands when it porpoises at speed, talking 20-25 mph on plane. It doesnt do it when I hit a wake or am going slow. It doesnt do it half way either, when the console bumps its obvious, feels like someone is talking a crow bar and physically moving the thing even though its attatched solid enough to not move when I apply force to it.
It is attatched almost directly to a rib on the floor using great stuff foam sealant, so the next thing to try is going to be getting a better way to attatch it. I'm seriously thinking of running two angle iron strips up the first 8' or so of the boat and riveting them in, then attatching the console to those.
I took pictures for you to see exaclty what I'm talking about. I also considered the possibility that somehow the steering cable is pulling the how setup back when the engine torques, but that transom is feeling pretty rock solid and even though the steering cable is tight, I can't recreate the feeling of the console moving.
BTW, I trimmed her up today to where the cavitation plate was level with the hull and hit 26 mph one time. Its ok if it is glass, but any ripple at all and the bow starts popping up.
Attachments
Captain Ahab
Well-known member
WOW - that sounds like the hull is flexing - a lot. You may need to run cross bracing so that you are using multiple ribs to hold the console in place.
I suggest that you carefully inspect everything - a 1/2" of movement has to leave a wear mark or stress mark somewhere, find it!
Keep us up to date with your progress.
I suggest that you carefully inspect everything - a 1/2" of movement has to leave a wear mark or stress mark somewhere, find it!
Keep us up to date with your progress.
One thing that would amplify the flexing is that the middle deck is touching the front of the console, which means if you have the front of the boat flexing, that deck is moving in a different way than the console which is anchored to the floor and it is pushing the console, possibly...just an early morning, sleep deprived idea....
This might sound crazy.
Especially coming from someone with ZERO experience (If I try to fix anything....ANYTHING, I break it). What about removing the console maybe, adding a floor underneath it and then putting the console on top of it?
Especially coming from someone with ZERO experience (If I try to fix anything....ANYTHING, I break it). What about removing the console maybe, adding a floor underneath it and then putting the console on top of it?
Captain Ahab
Well-known member
Jim said:
That is what I meant by bracing it - putting a floor type structure under t
Jim - you are right if I am just trying to avoid feeling the console move, I think I could solve that problem.
The only thing is, I am thinking there is the possibility that this console bending like it has has been a blessing in disguise, IE it has made a structural problem very obvious that I need to fix. A floor would probably dampen any feeling of the console moving, but if it doesnt correct the structural problem then I am still at ground zero.
Of course there is a possibility that what is being amplified here is harmless and present in any boat....the question is where is one overreacting, and where is something a problem. I think if anyone else drove the boat though, they would be scared when it happens too.
I am going to have to look extra hard for stress marks when I start disassembling, but it didnt leak yesterday.
Here is a paint file of what I think I am going to do, with iron angles going up the middle...attach the console to the iron angles which are riveted into the top of the ribs...
The only thing is, I am thinking there is the possibility that this console bending like it has has been a blessing in disguise, IE it has made a structural problem very obvious that I need to fix. A floor would probably dampen any feeling of the console moving, but if it doesnt correct the structural problem then I am still at ground zero.
Of course there is a possibility that what is being amplified here is harmless and present in any boat....the question is where is one overreacting, and where is something a problem. I think if anyone else drove the boat though, they would be scared when it happens too.
I am going to have to look extra hard for stress marks when I start disassembling, but it didnt leak yesterday.
Here is a paint file of what I think I am going to do, with iron angles going up the middle...attach the console to the iron angles which are riveted into the top of the ribs...
Attachments
GatorTom
Active member
You need to brace the floor and side running bow to stern to keep it from flexing. The benches were holding it together and preventing the flexing (along with the ribs) before. Now without support in the same areas as the bench, you can really feel it (especially with the console attached to the floor). Your drawing looks good. I would consider running a piece down each side as well. I wouldn't run the boat any more until you get it all braced. Each time you take it out and it flexes, it is potentially loosening rivets and seems that can cause major leaks.
Popeye
Well-known member
Have you seen the movie Up Periscope or Down Periscope (whichever, the one with Kelsey Grammer)? Remember the scene where the old engineer had a string from side to side to see how much the hull shrunk? Tape a piece of string side to side on the top of your gunnel and see how much flexing in and out the hull does when it porpoises. If you eliminate that, you should eliminate the porpoising.
F_I_Sherman NY
Member
Is it at all possible that your boat could be overloaded? I have read on other boards that the results of being too heavy cause alot of handling/safety issues and the porpoising etc. you describe are the same indicators. Maybe the flex is a big factor on top of that?
GatorTom
Active member
flounderhead59 said:
Awesome idea!
Thanks, I'm going to try using the string just to get a take on how much the sides are flexing before I try and fix this.
I went today and saw the flexing for sure in the floor right in front of the console where it is attatched. Didn't see any flexing in the sides. I have to get this fixed, theres no doubt about it will fatigue that metal and one day it will break with as much as its flexing. Now I know exactly where to position the angle too. I'm taking it out one more time before I put the angle in cause I am actually on the road right now and I pass a good lake on the way back, but aside from checkin the string I'm going to idle and just fish.
I went today and saw the flexing for sure in the floor right in front of the console where it is attatched. Didn't see any flexing in the sides. I have to get this fixed, theres no doubt about it will fatigue that metal and one day it will break with as much as its flexing. Now I know exactly where to position the angle too. I'm taking it out one more time before I put the angle in cause I am actually on the road right now and I pass a good lake on the way back, but aside from checkin the string I'm going to idle and just fish.
Popeye
Well-known member
If you use several pieces of string, side-side in several places and front-back you should get an idea of where you need to strengthen it? Without putting the seats back in there may not be a lot you can do though.
I understand the physics of what is happening a lot better now.
The sides are bending a little, which enables the bottom to flex. It only happens when it porpoises (as opposed to plowing through a wake or waves) because its bending when the stern is try to lift the bow up. It is not flexing nearly as badly or maybe at all when the pressure is exerted from the bow hitting resistance (such as coming down and hitting the water).
I have trimmed in the motor more and it did nothing to correct the porpoising. When my freind goes, it cannot be made to porpoise. The porpoising is directly related to weight distribution because the bracket has set that motor so far back.
The solution for this is to put as much ballast in the front as possible. I am going to try to move the deep cycle battery up a few more feet, and even the starter battery.
Here is a question, is there a limit to the length of wires I use for the starter battery? I know they draw a lot, so what gauge am I looking at and how far is too far to try and move it (right now the battery is 5 feet from the starter).
The sides are bending a little, which enables the bottom to flex. It only happens when it porpoises (as opposed to plowing through a wake or waves) because its bending when the stern is try to lift the bow up. It is not flexing nearly as badly or maybe at all when the pressure is exerted from the bow hitting resistance (such as coming down and hitting the water).
I have trimmed in the motor more and it did nothing to correct the porpoising. When my freind goes, it cannot be made to porpoise. The porpoising is directly related to weight distribution because the bracket has set that motor so far back.
The solution for this is to put as much ballast in the front as possible. I am going to try to move the deep cycle battery up a few more feet, and even the starter battery.
Here is a question, is there a limit to the length of wires I use for the starter battery? I know they draw a lot, so what gauge am I looking at and how far is too far to try and move it (right now the battery is 5 feet from the starter).
GatorTom
Active member
At least 6 guage.
ky_madman
Well-known member
- Joined
- Feb 5, 2008
- Messages
- 54
- Reaction score
- 0
I have two of those side braces that I took off during my V-Hull build. If you need them, I will send them to you. Take some pieces of aluminum angle iron, bolt to the sides where the seat mounts were, and then run angle iron across the width of the boat, then brace it to one of the cooresponding rib in the bottom of the boat. Do this front and back as support for your deck and/ or bench. It will eliminate your problem. Sorry but I couldn't see your photos. I'll get photos of my boat to show you what I'm talking about. If anyone can repost WTL's pics, please do.
ky_madman
Well-known member
- Joined
- Feb 5, 2008
- Messages
- 54
- Reaction score
- 0
here's some pics
Inside of brace and cross beam
Cross Bracing
Incidently, I measured the open space between the decks, in the middle of the boat and it is 4.5 ft.
From back to front - I used the 1st, 3rd, & 4th benches and eliminated the 2nd. So the distance between the 1st & 3rd seat is ~4 1/2 feet. Hope this helps.
Inside of brace and cross beam
Cross Bracing
Incidently, I measured the open space between the decks, in the middle of the boat and it is 4.5 ft.
From back to front - I used the 1st, 3rd, & 4th benches and eliminated the 2nd. So the distance between the 1st & 3rd seat is ~4 1/2 feet. Hope this helps.
First off I would like to again thank everyone for their advice in this thread.
I decided on doing a drastic change - I could add all the ballast in the worldbut it would never compensate for my weight being so far back. So I reordered a new teleflex cable that would allow me to move the console and my seat up 2 1/2 feet. I am going to try it out tommorow and see if that did the trick. Also I have now extended the middle deck all the way back and added back the rear bench, only I made the rear bench seat about 3 1/2 feet wide - its what the drivers seat is on. I have braced this against the walls. And I took a large road sign post and riveted it into the top of each of the ribs to add longitudinal strength. I'm taking her out tomorow, and I'm going to try and use the "down periscope" string trick as well as just seeing how she feels.
Here is a pic or 2, sorry its dark...
KYMadman, thanks for the offer on the braces. I dont think I need em enough to warrant sending them in the mail, I have been making my own from steel, but thanks again.
I decided on doing a drastic change - I could add all the ballast in the worldbut it would never compensate for my weight being so far back. So I reordered a new teleflex cable that would allow me to move the console and my seat up 2 1/2 feet. I am going to try it out tommorow and see if that did the trick. Also I have now extended the middle deck all the way back and added back the rear bench, only I made the rear bench seat about 3 1/2 feet wide - its what the drivers seat is on. I have braced this against the walls. And I took a large road sign post and riveted it into the top of each of the ribs to add longitudinal strength. I'm taking her out tomorow, and I'm going to try and use the "down periscope" string trick as well as just seeing how she feels.
Here is a pic or 2, sorry its dark...
KYMadman, thanks for the offer on the braces. I dont think I need em enough to warrant sending them in the mail, I have been making my own from steel, but thanks again.
Attachments
Similar threads
