Sterny... wedge pics FYI...
- Thread starter Andrew
- Start date
I had no idea your were so short and steep.
Were I to do it again, I woudl go with adjustable tabs or interceptor plates. I think I have some partially finished tabs in NH that were started but and I dropped the ball on, I think I also have a partially finished decoy of his in one of my garages.
Were I to do it again, I woudl go with adjustable tabs or interceptor plates. I think I have some partially finished tabs in NH that were started but and I dropped the ball on, I think I also have a partially finished decoy of his in one of my garages.
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Tod, those aren't mine, they were Joel Mills'... that link is his website.
Mine aren't that steep. What I did was effectively flatten out the hull. Mine were about 9" long x 3/4"... but lots of sanding and shaping took at least a 1/8" off + epoxy (no glass as I thought they'd be sacrificial). I haven't had a scratch on them - yet !
Mine aren't that steep. What I did was effectively flatten out the hull. Mine were about 9" long x 3/4"... but lots of sanding and shaping took at least a 1/8" off + epoxy (no glass as I thought they'd be sacrificial). I haven't had a scratch on them - yet !
David Stern
Active member
Thanks guys. If I put wedges on, do i have to glass them in? Can I just put some waterproof bond between the wedge and the hull and screw it together? I know it is not the cleanest, but it could be the fastest.
I could not find those interceptor plates that you showed, Tod.
I am still trying to figure it out. Someone suggested that I just put an extra 100 lbs up front when not hunting. When hunting with gear, porposing should not be a factor. Just trying to figure this out.
David
I could not find those interceptor plates that you showed, Tod.
I am still trying to figure it out. Someone suggested that I just put an extra 100 lbs up front when not hunting. When hunting with gear, porposing should not be a factor. Just trying to figure this out.
David
On the interceptor plates they could eb easily made it seems.
On the 100 pounds I'd like to see that work. I can lay across the bow (200 pounds) of mine without wedges and only get to half throttle because of the violent porpoise. With wedges it ie fine. Andrew and I have very similar wedge setups.
David,
For some reason the wedge debate is one of those Duckboats.net legends that seems to have no compromise... ; )
Yes, you could install them like that - Eric P uses tape when he "dials" his wedges in if I'm not mistaken (he affixes them with epoxy later). "3M 3200'ing" some wedges on the back would work. It wouldn't hurt.
People will send emails and tell you that wedges will compromise your boat's speed or even safety -- they won't. Putting 100 lbs in the bow of a small boat like ours is a huge amount of extra weight to carry around. Weight kills speed & performance and in my humble opinion - safety. I wouldn't want to come off of a 4' wave nose down with 100 extra pounds up front - dumb.
A wedge acts like trim in an airplane's aerolone (need spell check). Just a little nudge in the other direction and it adds a stable boating experience at any speed. In my experience, the wedge effect is killed at slow speed. In really big waves, I slow the motor up, adjust the motor tilt and I can get the nose right up, like a displacement hull BBSB. The wedges are NOT working/deflecting at that speed - clear as mud?
No, you do NOT need to fiberglass. Their placement is in a sacrfricial location. My center keel takes the punishment of a beaching, the wedges are tucked up and out of the way. I still don't have a scratch on them after 4 seasons and when I do scrape a rock, which I will, I wouldn't want fiberglass hanging off them, that would be a mess. I wish I could post pics of mine, but I'm a loser when it comes to that stuff.
Good luck.
A>
For some reason the wedge debate is one of those Duckboats.net legends that seems to have no compromise... ; )
Yes, you could install them like that - Eric P uses tape when he "dials" his wedges in if I'm not mistaken (he affixes them with epoxy later). "3M 3200'ing" some wedges on the back would work. It wouldn't hurt.
People will send emails and tell you that wedges will compromise your boat's speed or even safety -- they won't. Putting 100 lbs in the bow of a small boat like ours is a huge amount of extra weight to carry around. Weight kills speed & performance and in my humble opinion - safety. I wouldn't want to come off of a 4' wave nose down with 100 extra pounds up front - dumb.
A wedge acts like trim in an airplane's aerolone (need spell check). Just a little nudge in the other direction and it adds a stable boating experience at any speed. In my experience, the wedge effect is killed at slow speed. In really big waves, I slow the motor up, adjust the motor tilt and I can get the nose right up, like a displacement hull BBSB. The wedges are NOT working/deflecting at that speed - clear as mud?
No, you do NOT need to fiberglass. Their placement is in a sacrfricial location. My center keel takes the punishment of a beaching, the wedges are tucked up and out of the way. I still don't have a scratch on them after 4 seasons and when I do scrape a rock, which I will, I wouldn't want fiberglass hanging off them, that would be a mess. I wish I could post pics of mine, but I'm a loser when it comes to that stuff.
Good luck.
A>
Tod
The interceptor tabs look interesting. When I played around with the math (one of these days I'll get off my butt and post the numbers I came up with) it became obvious the steeper the angle of the edges the more drag. I would think the interceptor concept would create lots of lift but at the expense of considerable more drag.
How come you want something adjustable? Mine are dialed in to be just enough to stop porpoising at full throttle. As you back off the throttle their impact is less and less and at lower speeds if I were to rip them off I doubt I could tell. There are a ton of ways to tackle the porpoise issue but I for one am glad to found a solution that worked for me to the point I never even give it any thought anymore.
The interceptor tabs look interesting. When I played around with the math (one of these days I'll get off my butt and post the numbers I came up with) it became obvious the steeper the angle of the edges the more drag. I would think the interceptor concept would create lots of lift but at the expense of considerable more drag.
How come you want something adjustable? Mine are dialed in to be just enough to stop porpoising at full throttle. As you back off the throttle their impact is less and less and at lower speeds if I were to rip them off I doubt I could tell. There are a ton of ways to tackle the porpoise issue but I for one am glad to found a solution that worked for me to the point I never even give it any thought anymore.
John Robinson
Well-known member
Andrew,
Did you try your Snow Goose without wedges? Until I read a wedge thread last summer, I didn't know porpoising was an issue as our Snow Goose has never porpoised. After reading that thread I asked my partner if he had ever run his boat flat out with a light load and he said he did when he did his first sea trial. We have a console, so the driver's weight is forward, but he ran full speed with a 200 lb buddy sitting on a stool next to him, forward, under deck fuel tank full of gas, no problems. We never speed checked the boat but it is scary fast going up the river.
I'm going to hold off on the wedges to wait and see if I have problems when I launch. If I do I think I might do that adjustable steel trim tab sombody posted back on that other thread.
Did you try your Snow Goose without wedges? Until I read a wedge thread last summer, I didn't know porpoising was an issue as our Snow Goose has never porpoised. After reading that thread I asked my partner if he had ever run his boat flat out with a light load and he said he did when he did his first sea trial. We have a console, so the driver's weight is forward, but he ran full speed with a 200 lb buddy sitting on a stool next to him, forward, under deck fuel tank full of gas, no problems. We never speed checked the boat but it is scary fast going up the river.
I'm going to hold off on the wedges to wait and see if I have problems when I launch. If I do I think I might do that adjustable steel trim tab sombody posted back on that other thread.
Interceptor tabs are "supposed" to be less drag than tabs. I don't know, that is the theory from what I've read anyway.
I would like adjustable trim tabs or interceptor plates for the same reason you like the adjustable cradle
. I'm not completely happy with my performance and I need to put more work into it. I still have a bit of negative motor angle to keep it under control witna light to medium load. I also use my boat in more varied conditions than most, from clamming by myself with no extra weight, to 3 guys and decoys as a transport.
I'd also like to see the mythical 35mph for a snowgoose with a "medium load".
To answer your ?: A lot of Devlin's planing boats have porpoising problems (Cackler, Scaup and Snow Goose). In fact, there are wedge specs in the Cackler plans. So, I just built the wedges in during the construction process while I had the boat upside down.
Tod, I've only clocked my boat once and it was 30 mph on a cell phone GPS when Morton was trying to beat me (he never wins, I don't know why the guy keeps trying ; ) but it was wavy and beam windy... I had the fat lab and enough gear and deeks for just myself + blind. My deeks are light, so I wouldn't say it was a medium load, but close.
I am going to repaint the boat with that slick bottom paint this year and we'll see how she goes. Plus, Hondas aren't known for speed and my prop is stock come with the engine variety. Still, it's fast enough for me.
Tod, I've only clocked my boat once and it was 30 mph on a cell phone GPS when Morton was trying to beat me (he never wins, I don't know why the guy keeps trying ; ) but it was wavy and beam windy... I had the fat lab and enough gear and deeks for just myself + blind. My deeks are light, so I wouldn't say it was a medium load, but close.
I am going to repaint the boat with that slick bottom paint this year and we'll see how she goes. Plus, Hondas aren't known for speed and my prop is stock come with the engine variety. Still, it's fast enough for me.
Bob B
Well-known member
Wedges and down rocker and interserptor plates are long standing design tricks in the boat hull design field. It is proven, early tow test work in NJ for Ocean Yachts and others that speed can be increased at times with these mods. Look at any big sport fish out of the water and you will see nearly all have some means of tweaking the transom water flow exit path to aid in trim and speed under way. Different states of trim may be required due to loading. As stated, height of motor will also effect handling. As most builders are working on a one off they will have to "Feel" their way to the promised land.
A quick check to see if trim can be helped with added down force is to spanish windlass a line tight to the hull all the way around the stern, near the transom. The dia of the line required for the trim angle wanted is close to the wedge/intersceptor required.
Look up volvo trim tabs to see their version of the interceptor concept for big boats. Would be quite easy to fabricate your own version for your boat. Wedges work fine too. I would not rely on 5200 alone to hold them on. Epoxy and cloth. Also a square edge at the transom is better for speed than the typical rounded profile found on home built boats to acomodate the cloth being wraped around the edge. Fair it square with structural putty.
A quick check to see if trim can be helped with added down force is to spanish windlass a line tight to the hull all the way around the stern, near the transom. The dia of the line required for the trim angle wanted is close to the wedge/intersceptor required.
Look up volvo trim tabs to see their version of the interceptor concept for big boats. Would be quite easy to fabricate your own version for your boat. Wedges work fine too. I would not rely on 5200 alone to hold them on. Epoxy and cloth. Also a square edge at the transom is better for speed than the typical rounded profile found on home built boats to acomodate the cloth being wraped around the edge. Fair it square with structural putty.
Bob
Good advice. On my boats the transom edges are rounded for glassing the hull but after that I use thickened epoxy to square the edges up. When you do this you can really see a clean departure of the water from the hull as evidenced by reduced spray and splash. I think some people may get motor well splashing because they got happy rounding all those edges.
JCatizone
Active member
Someone could research their thesis here on boundary layer theory and Reynolds Numbers with all this wedge chatter.
Don't worry your tabs have not been turned into beer cans yet. They are still in the lab under a bench and I keep poking at the design. Did you ever float that block?
Don't worry your tabs have not been turned into beer cans yet. They are still in the lab under a bench and I keep poking at the design. Did you ever float that block?
I sure did float that decoy, it was in my primary puddler rig this year. I won't tell you about the time I had ti float off, but I found it that day - independant little bastard. I shot a lot of birds over that decoy (a lot for me anyway), however, this was one of my worst years ever for blacks - I hope the decoy isn't a jinx. I bet that is because I haven't gotten my end of the trade done yet. Have you done any carving this year?