Monos built strickly for SAW?

[Rickard Andersson]

Yep "piloting" at low level, and that's what I do then, on and off work, SwAF.

Rille

 

[dwilfong]

If you get the chance put that 91RS in the 39" Cal Craft and see what it will do.

Now that will be flying a boat.

 

[ids987]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

 

[John Finch]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

 

[ids987]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

Thanks John - for th detailed reply. I'm trying to figure a pulling right issue with a non SAW boat - though there's not always much of it in the water when it gets going. I didn't want to take the thread off topic, but figured that the effects of longer / shorter rudder would apply to both. It's already got offset strut (about 1/4"), and offset rudder (about 65mm). I've run strut up high, rudder further back, and tried shimming left too - all to little avail, so I wondered about aspects of rudder size and shape. I won't describe any further, because I don't want to hijack the thread.

Thanks again: Ian

 

[John Finch]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

Thanks John - for th detailed reply. I'm trying to figure a pulling right issue with a non SAW boat - though there's not always much of it in the water when it gets going. I didn't want to take the thread off topic, but figured that the effects of longer / shorter rudder would apply to both. It's already got offset strut (about 1/4"), and offset rudder (about 65mm). I've run strut up high, rudder further back, and tried shimming left too - all to little avail, so I wondered about aspects of rudder size and shape. I won't describe any further, because I don't want to hijack the thread.

Thanks again: Ian

The thing to keep in mind with SAW and heat racing boats is that without a rudder the boat would make a right hand turns because the prop is what is dragging the transom to the left thus making the boat turn right, The rudder is what keeps the boat from turning right, so a larger rudder helps to keep the transom from being dragged by the prop. Maybe it is your rudder servo not having enough power to keep the rudder straight! This is especially noticeable when your boat comes out of a corner, you let off the rudder, and the boat continues to keep turning rather than straighten out. If that is what is happening you need a stronger servo. What boat, engine, prop, and servo combo are you using in this "could be a SAW boat if you got it to go straight?"

 

[dwilfong]

John I have a question on the rudder?

Many talk about tilting the rudder forward and back to adjust the ride of the boat.

Now when I set up my boat I make the pivot point of the rudder at a 90 deg angle to the keel.

I use shims to adjust this relationship as all transoms are off this 90deg angle to make removal from the mold possible.

When talking about adjusting the rudder angle is this with the bolts that mount the rudder to the turning assembly on the rudder? or is this shimming the whole assembly that mounts to the transom? thus changing the pivot angle of the rudder.

I think these are two different adjustment as I see it.

Any thoughts on this?

David

 

[John Finch]

I adjust the pivot at the location where the rudder attaches to the bracket that mounts to the transom. It is easier to do that than offset the bracket at the transom. Same result. What I don't like is mounting the rudder parrallel to the transom like you said because all transoms are not square. I like a bit of kick back like 3 degrees if the boat will ride with the keel at 3 degrees angle of attack because if you set the rudder straight up and down on the boat stand or sqaure with the keel.......then the bottom tip is forward of the pivot pin when the boat is at full speed. It doesn't take much rudder in front of the pivot pin to make the rudder shudder. Notice most of the rudder blade is behind the pivot point. That is the best setup. As you move the rudder forward of the pivot pin the front of the rudder grabs water and tends to pull in that direction. On slow boats in the past we had a lot of rudder in front of the pivot pin to help the servo because the servos were weak. I don't like changing pivot point angles to control the boat. I would rather adjust the ride another way and have the rudder perpendicular to the line of travel. I have however kicked the rudder back for a SAW rigger run where the transom did not get up quick enough to hit the traps at speed. The kick back with a quick twist of the rudder lifted the transom free of the water so the boat could get on the pipe quicker.

 

[ids987]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

Thanks John - for th detailed reply. I'm trying to figure a pulling right issue with a non SAW boat - though there's not always much of it in the water when it gets going. I didn't want to take the thread off topic, but figured that the effects of longer / shorter rudder would apply to both. It's already got offset strut (about 1/4"), and offset rudder (about 65mm). I've run strut up high, rudder further back, and tried shimming left too - all to little avail, so I wondered about aspects of rudder size and shape. I won't describe any further, because I don't want to hijack the thread.

Thanks again: Ian

The thing to keep in mind with SAW and heat racing boats is that without a rudder the boat would make a right hand turns because the prop is what is dragging the transom to the left thus making the boat turn right, The rudder is what keeps the boat from turning right, so a larger rudder helps to keep the transom from being dragged by the prop. Maybe it is your rudder servo not having enough power to keep the rudder straight! This is especially noticeable when your boat comes out of a corner, you let off the rudder, and the boat continues to keep turning rather than straighten out. If that is what is happening you need a stronger servo. What boat, engine, prop, and servo combo are you using in this "could be a SAW boat if you got it to go straight?"

Thanks John, The servo is a Hitec 755MG (I think). Quarter scale, metal geared, and seems to be very torquey. It doesn't seem to have any trouble pulling the boat straight and upright (with the aid of left rudder), or even turning left. I did previously suspect linkage flex - especially since it's in "pull to go right" mode, but took measures to eliminate bends etc, and it's pretty rigid now. The hull is a big old bus of a Giant Apache clone, known as a Makara, powered by a CMB 90. Not exactly straightaway material, but probably does over 50 (guesstimate) - which isn't much on paper, but quite a lot for any of the Giant Apache clones. They also have quite a lot of lift, so it's running pretty light on the water at that kind of speed. Fastest props so far have been X462/2, and P260. The motor acts like it would pull more prop - even in that boat, but the issue seems to be speed related. Accelerating away, it will run relatively straight at first, but will gradually start to veer and lean right - increasing with increasing speed. It is worse with the above props than with smaller props, but I "think", partly because it is not going as fast. It seems like, as it airs out, and loses the support of the water, it is following what it wants to do. It has double trim tabs, and the outermost right tab is significantly further down than the left side tabs.

 

[John Finch]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

Thanks John - for th detailed reply. I'm trying to figure a pulling right issue with a non SAW boat - though there's not always much of it in the water when it gets going. I didn't want to take the thread off topic, but figured that the effects of longer / shorter rudder would apply to both. It's already got offset strut (about 1/4"), and offset rudder (about 65mm). I've run strut up high, rudder further back, and tried shimming left too - all to little avail, so I wondered about aspects of rudder size and shape. I won't describe any further, because I don't want to hijack the thread.

Thanks again: Ian

The thing to keep in mind with SAW and heat racing boats is that without a rudder the boat would make a right hand turns because the prop is what is dragging the transom to the left thus making the boat turn right, The rudder is what keeps the boat from turning right, so a larger rudder helps to keep the transom from being dragged by the prop. Maybe it is your rudder servo not having enough power to keep the rudder straight! This is especially noticeable when your boat comes out of a corner, you let off the rudder, and the boat continues to keep turning rather than straighten out. If that is what is happening you need a stronger servo. What boat, engine, prop, and servo combo are you using in this "could be a SAW boat if you got it to go straight?"

Thanks John, The servo is a Hitec 755MG (I think). Quarter scale, metal geared, and seems to be very torquey. It doesn't seem to have any trouble pulling the boat straight and upright (with the aid of left rudder), or even turning left. I did previously suspect linkage flex - especially since it's in "pull to go right" mode, but took measures to eliminate bends etc, and it's pretty rigid now. The hull is a big old bus of a Giant Apache clone, known as a Makara, powered by a CMB 90. Not exactly straightaway material, but probably does over 50 (guesstimate) - which isn't much on paper, but quite a lot for any of the Giant Apache clones. They also have quite a lot of lift, so it's running pretty light on the water at that kind of speed. Fastest props so far have been X462/2, and P260. The motor acts like it would pull more prop - even in that boat, but the issue seems to be speed related. Accelerating away, it will run relatively straight at first, but will gradually start to veer and lean right - increasing with increasing speed. It is worse with the above props than with smaller props, but I "think", partly because it is not going as fast. It seems like, as it airs out, and loses the support of the water, it is following what it wants to do. It has double trim tabs, and the outermost right tab is significantly further down than the left side tabs.

I know this is going to sound a bit crazy, but turn the boat upside down and run a small bead of cyanacrolate from the keel to the first inside trib tab right on the rear of the boat for one inch from the keel. Like drawing a line between the keel and tab right at the very last bit of the transom. ON THE LEFT side of the keel when the boat is right side up. I know this is opposite of what you do with trim tabs, but this will trip the boat to the left and push the bow down at the same time. This is reverse of trim tabs but only works within an inch from the keel going towards the tab. If the boat rides too wet then just sand a bit off the glue bead. Another thing.....you could check the very back of the boat bottom to see if maybe the right side has a hook in it close to the keel tripping the boat to the right. If it does you can sand it flat before trying the super glue bead trick. The area within one inch of the keel to the very rear of the boat controls the attidude of the hull greatly!

 

[ids987]

Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat.

Hi John, Something I've been pondering. The lift from the rudder helps to lift the right side of the boat, but doesn't the drag from the rudder also try to pull it right ?

Wondering what factors determine which force "wins", or the balance between the two forces.

Would deeper rudder immersion, for example, increase the tendency to pull right - by increasing drag, but not increasing, or possibly reducing lift ?

Presumably rounding the bottom corner of the rudder's leading edge should help to increase lift from the rudder, and rounding or "veeing" the bottom edge of the rudder ?

Hope you don't mind me asking. Thanks for any response.

Ian,

I have seen no difference in flat vs curved rudder bottoms myself, but others may have. I round all my rudder bottoms a bit and especially the leading edge where the leading edge meets the bottom of the rudder. For SAW my rudders are kicked back a tick so that they run perpendicular to the line of travel when the boat is at top speed and the bow is lifted. Just me. Having the rudder to the right does not make the boat turn right if you have a thin short rudder, which is what works best for SAW. The rudder will lift more if it is longer/ deeper in the water. If it lifts enough the boat will lean to the left which makes the boat turn left. So you can see the size, depth, location to centerline, and location from the transom all have to be in tune with the size of the prop, and boat. Keep in mind....this balance to get everything just right is for SAW. You can sometimes put a rudder just about anywhere on the transom of a heat racing boat and not make much change in the way the boat handles. It is when the boat is aired out at SAW speeds that the rudder position becomes highly apparent. If you have a very fast heat racing mono, say 65 mph or better, you will see the effects of rudder placement. Just last weekend a boater was at the pond trimming a sport hydro, I know it is not a mono, but same effect, and his boat was hoping. He cut 1/2 inch off the rudder and the boat ran smooth and fast. That is all it took. I think too many people ignore the rudder as a way to trim the boat and gain speed.

For heat racing you need a rudder long enough that you can finish all your heats even if it means a longer rudder than you would like to run. For SAW you give up consistency for speed. I usually keep shortening the rudder until the boat starts to veer to the right on the SAW pass. Then I cut a new rudder to the length that worked best.

Thanks John - for th detailed reply. I'm trying to figure a pulling right issue with a non SAW boat - though there's not always much of it in the water when it gets going. I didn't want to take the thread off topic, but figured that the effects of longer / shorter rudder would apply to both. It's already got offset strut (about 1/4"), and offset rudder (about 65mm). I've run strut up high, rudder further back, and tried shimming left too - all to little avail, so I wondered about aspects of rudder size and shape. I won't describe any further, because I don't want to hijack the thread.

Thanks again: Ian

The thing to keep in mind with SAW and heat racing boats is that without a rudder the boat would make a right hand turns because the prop is what is dragging the transom to the left thus making the boat turn right, The rudder is what keeps the boat from turning right, so a larger rudder helps to keep the transom from being dragged by the prop. Maybe it is your rudder servo not having enough power to keep the rudder straight! This is especially noticeable when your boat comes out of a corner, you let off the rudder, and the boat continues to keep turning rather than straighten out. If that is what is happening you need a stronger servo. What boat, engine, prop, and servo combo are you using in this "could be a SAW boat if you got it to go straight?"

Thanks John, The servo is a Hitec 755MG (I think). Quarter scale, metal geared, and seems to be very torquey. It doesn't seem to have any trouble pulling the boat straight and upright (with the aid of left rudder), or even turning left. I did previously suspect linkage flex - especially since it's in "pull to go right" mode, but took measures to eliminate bends etc, and it's pretty rigid now. The hull is a big old bus of a Giant Apache clone, known as a Makara, powered by a CMB 90. Not exactly straightaway material, but probably does over 50 (guesstimate) - which isn't much on paper, but quite a lot for any of the Giant Apache clones. They also have quite a lot of lift, so it's running pretty light on the water at that kind of speed. Fastest props so far have been X462/2, and P260. The motor acts like it would pull more prop - even in that boat, but the issue seems to be speed related. Accelerating away, it will run relatively straight at first, but will gradually start to veer and lean right - increasing with increasing speed. It is worse with the above props than with smaller props, but I "think", partly because it is not going as fast. It seems like, as it airs out, and loses the support of the water, it is following what it wants to do. It has double trim tabs, and the outermost right tab is significantly further down than the left side tabs.

I know this is going to sound a bit crazy, but turn the boat upside down and run a small bead of cyanacrolate from the keel to the first inside trib tab right on the rear of the boat for one inch from the keel. Like drawing a line between the keel and tab right at the very last bit of the transom. ON THE LEFT side of the keel when the boat is right side up. I know this is opposite of what you do with trim tabs, but this will trip the boat to the left and push the bow down at the same time. This is reverse of trim tabs but only works within an inch from the keel going towards the tab. If the boat rides too wet then just sand a bit off the glue bead. Another thing.....you could check the very back of the boat bottom to see if maybe the right side has a hook in it close to the keel tripping the boat to the right. If it does you can sand it flat before trying the super glue bead trick. The area within one inch of the keel to the very rear of the boat controls the attidude of the hull greatly!

Thanks John, I did previously flat that area of the hull - due to rockers just in front of the transom (long ago; this is a boat I keep shelving, then getting out again when I feel inspired to try something different). Even if that area appears truly flat, I guess the rockers, or the original cause of the rockers, may have affected things in other ways (some form of distortion). I will recheck it, and if it still looks good, I will definitely try the cyano trick. Not sure when I will get the chance to run it again, but I will post up the outcome when I do.

 

[John Finch]

Yea I know what you are saying about the put it up and then get an idea and pull in back down. After a while I started putting my boats through the bandsaw so I would quit doing that. Sounds like the hull bottom is the issue. Good luck with it and if you need more suggestions down the road feel free to write.

 

[Steven Bryant]

Hi Ian,

I have had 3 makara hulls over the years and have had similar problems with all of them, this was not really a problem for me as I was using them predominately for offshore racing. I did find that the bottom of the hull where slightly warped.

Steve

 

[John Finch]

Good point Steve. Sometimes you have to leave the hook in a boat because the hook is keeping the boat running true. Not recommended for SAW, but sometimes a good thing for heat racing.

 

[ids987]

Thanks Guys,

John, yes, the bandsaw treatment probably would have been the right treatment. I was disappointed when I noticed the rockers, as I was pretty sure they would affect the handling, but I built and tested the boat as received. The maiden went like this:



I sent the link to the maker, who told me that the lake was too small, and I was coming off the throttle too early. All I needed to do was to keep it at WOT, and the boat would settle down. He also said that Makaras are meant to have a hook (which mine didn't), and that if it had rockers, I should sand them out. After sanding, filling, re-sanding, and adding trim tabs, the boat ran much better, but was still left with the pull to the right (which was there from the start, and visible in the above video). I originally built it with the shaft offset, because I expected some natural tendency to roll right, but I guess, in this case, the biggest clue is maybe that it appears to be speed related rather than prop related. I may have been looking at the running surface wrong, as my thoughts were (based on "spoon in stream"), that - apart from an overall twist, bend etc, likely causes would either be a bulge / rocker on the right, sucking the right side down, or a hook on the left, pushing the left side up. I hadn't considered that a hook could slow the boat on the same side, making it veer in that direction.

It's almost raceable as it stands, and I kind of think a small counteracting force in the right place will have it running straight (ever the optimist. I don't have a bandsaw, but I do have a jigsaw). I've actually raced it twice (sort of long duration heat racing on a square course), using left rudder to hold a straight line when necessary, but it doesn't inspire me with confidence around other boats. Last time I raced it, it was rough and windy, and it also suffered a slight strut kickback. I had to retire after a few instances of hitting buoys. Not just hitting buoys, but hitting them whilst going sideways.

Steve, I have a 42" Delta Force, and a Greenhead CMB 67HR in my attic, which I think may once have been yours.....

 

[John Finch]

WoW! That boat is totally out of sorts. Needs trims tabs down or weight in the front or take out the rocker, or check the strut angle. Kind of looks like the strut might be kicked back. Put a ruler along the keel and extend it past the transom to see if the strut is level with the keel. Chances are it is kicked back. That would explain why it takes to the air when it turns on good.

John

 

[ids987]

WoW! That boat is totally out of sorts. Needs trims tabs down or weight in the front or take out the rocker, or check the strut angle. Kind of looks like the strut might be kicked back. Put a ruler along the keel and extend it past the transom to see if the strut is level with the keel. Chances are it is kicked back. That would explain why it takes to the air when it turns on good.

John

Hi John, That was the "before" video, of the maiden - from three years ago. Just included for entertainment value. The centre of balance was not too far back either. One of my boating buddies put a couple of pounds of concrete in the nose that day. It still nosed up, just slammed back down harder. I took the rockers out after that, and added tabs - plus the 1/4 scale servo. The combined effect of the first two give it a relatively good ride attitude now, and one which I can control with strut angle (or tab adjustments if I choose, but I put the tabs a couple of mm above the waterline, so that they don't cause excessive amounts of drag). Just the veering right issue remains really. I don't have any more recent video, but the piccy below is from a race in the early part of this year; boat on the left, coming through on the inside.

Second piccy, on its own, same day.

 

[ids987]

Sorry, just realised that my last comments about ride attitude, could appear to contradict my earlier comments about airing out. When it airs out now though, it doesn't nose up excessively. I think it may be effectively riding the keel at speed.

 

[David Bryant]

I'm curious, do the popular Seaducer hulls have a flat keel section at the transom?

 

[Steven Bryant]

Thanks Guys,

John, yes, the bandsaw treatment probably would have been the right treatment. I was disappointed when I noticed the rockers, as I was pretty sure they would affect the handling, but I built and tested the boat as received. The maiden went like this:

http://www.youtube.com/watch?v=6mdJRjX3xLo

I sent the link to the maker, who told me that the lake was too small, and I was coming off the throttle too early. All I needed to do was to keep it at WOT, and the boat would settle down. He also said that Makaras are meant to have a hook (which mine didn't), and that if it had rockers, I should sand them out. After sanding, filling, re-sanding, and adding trim tabs, the boat ran much better, but was still left with the pull to the right (which was there from the start, and visible in the above video). I originally built it with the shaft offset, because I expected some natural tendency to roll right, but I guess, in this case, the biggest clue is maybe that it appears to be speed related rather than prop related. I may have been looking at the running surface wrong, as my thoughts were (based on "spoon in stream"), that - apart from an overall twist, bend etc, likely causes would either be a bulge / rocker on the right, sucking the right side down, or a hook on the left, pushing the left side up. I hadn't considered that a hook could slow the boat on the same side, making it veer in that direction.

It's almost raceable as it stands, and I kind of think a small counteracting force in the right place will have it running straight (ever the optimist. I don't have a bandsaw, but I do have a jigsaw). I've actually raced it twice (sort of long duration heat racing on a square course), using left rudder to hold a straight line when necessary, but it doesn't inspire me with confidence around other boats. Last time I raced it, it was rough and windy, and it also suffered a slight strut kickback. I had to retire after a few instances of hitting buoys. Not just hitting buoys, but hitting them whilst going sideways.

Steve, I have a 42" Delta Force, and a Greenhead CMB 67HR in my attic, which I think may once have been yours.....

Hey Ian, you are absolutely right that was my boat and was my last boat that I sold when I quit racing 6 years ago. Do you still use the delta force? If so how's she running?

Steve