Boat Builder Central - Builder Forums

Posted: **Thu Oct 28, 2021 6:17 am**

Hi Guys, a little help please. Maybe I can't see the wood for the trees!

Assembling my form for my TX18+10% build. All bulkheads side stingers and transom appear to align correctly. When it comes to the centre stringer it aligns at Bulkhead C then rises above D by 5mm and then above MW by 12mm, but flushes perfectly at the transom with both side stringers and the transom V. I searched the forum and found a post from 2011, but it seemed to result in no conclusion.

The plan diagram for Centre stringer shows a curved line below the straight line marker--- see pic. This looks like it should fit to the bulkheads and align to the transom, but there is no offset measurement. The diagram also shows notched where the stringer meets the bulkhead, but if I cut these to make the sole side match the bulheads then the stringer will be at least 12mm low on the transom.

: note curved line below top line and notched on bottom

I am worried about changing the angle of the hull incorrectly as the inverted V becomes a slight V at the stern and I assume the transition is important. Any help would be appreciated.

: transom aligns on side stringers and centre, MW 12mm low

Posted: **Thu Oct 28, 2021 8:35 am**

It must be straight. That is why I wrote "straight above that line. I don't know why there is second line with a camber superposed on it.
I will check my version of the drawing later today: I am on the road now.

Posted: **Thu Oct 28, 2021 8:43 am**

Point of clarity...

The transom cannot grow by 10%, yes or no? A 21.5" transom cannot be built to 23.65" high.

The waterline in a 10% bigger boat remains the same and the baseline at the transom remains the same, yes or no?

If you make the boat bigger by 10%, then there needs to be some way to resolve the transom back to the original height. (This is not done!!!)

Based on looking at your pictures, it looks like you are trying to scale the height and I believe this may be causing the issues?

Posted: **Thu Oct 28, 2021 8:50 am**

You cannot scale the height.

Doesn't this picture show you attempting to do just that?

You would create some hook or rocker in the hull as drawn and the boat would perform badly.

Posted: **Thu Oct 28, 2021 9:00 am**

jacquesmm wrote: ↑Thu Oct 28, 2021 8:35 am It must be straight. That is why I wrote "straight above that line. I don't know why there is second line with a camber superposed on it.
I will check my version of the drawing later today: I am on the road now.

See my comments. I see some notes on the pictures that concern me.

Posted: **Thu Oct 28, 2021 9:09 am**

Also, the boat should be getting built with the waterlines level to the world.

I am having a hard time believing your waterlines are level with all the variation going on...I could be wrong here...

...but I think the height scaling is throwing things off as well...

The good news is if you made everything too big; you should be able to repair them. Wait and see what JM has to say, but please post back what you did with the heights.

Posted: **Thu Oct 28, 2021 9:50 am**

fallguy1000 wrote: ↑Thu Oct 28, 2021 8:43 am Point of clarity...

The transom cannot grow by 10%, yes or no? A 21.5" transom cannot be built to 23.65" high.

The waterline in a 10% bigger boat remains the same and the baseline at the transom remains the same, yes or no?

If you make the boat bigger by 10%, then there needs to be some way to resolve the transom back to the original height. (This is not done!!!)

Based on looking at your pictures, it looks like you are trying to scale the height and I believe this may be causing the issues?

HI Fallguy, thanks for the input.

I am making the forms from MDF and the hull sides for half the hull from cheap crate plywood as I wait for the marine ply etc to arrive. I would rather modify and adjust cheaper easy to obtain materials till I get it right.

I have scaled all measurements by 10% and used the sole line as my base line as per the drawings. So I measured up and down from that baseline and left and right from the centre line. I increased all measurements by 10% so as to keep the scale correct. As I see it if I only increased the scale of the length of the stringers then all bow curves would be wrong. I cannot see how I can scale some components and not others.

I agree the transom height cannot be +10%. My plan was to rectify by measuring from the V of the transombottom up (down when inverted) to get the 20 inch finished transom height. As I wanted higher gunnels I was going to cut down for the transom forming a U, leaving the sides higher.

Posted: **Thu Oct 28, 2021 10:55 am**

Vundu wrote: ↑Thu Oct 28, 2021 9:50 am
fallguy1000 wrote: ↑Thu Oct 28, 2021 8:43 am Point of clarity...

The transom cannot grow by 10%, yes or no? A 21.5" transom cannot be built to 23.65" high.

The waterline in a 10% bigger boat remains the same and the baseline at the transom remains the same, yes or no?

If you make the boat bigger by 10%, then there needs to be some way to resolve the transom back to the original height. (This is not done!!!)

Based on looking at your pictures, it looks like you are trying to scale the height and I believe this may be causing the issues?
HI Fallguy, thanks for the input.

I am making the forms from MDF and the hull sides for half the hull from cheap crate plywood as I wait for the marine ply etc to arrive. I would rather modify and adjust cheaper easy to obtain materials till I get it right.

I have scaled all measurements by 10% and used the sole line as my base line as per the drawings. So I measured up and down from that baseline and left and right from the centre line. I increased all measurements by 10% so as to keep the scale correct. As I see it if I only increased the scale of the length of the stringers then all bow curves would be wrong. I cannot see how I can scale some components and not others.

I agree the transom height cannot be +10%. My plan was to rectify by measuring from the V of the transombottom up (down when inverted) to get the 20 inch finished transom height. As I wanted higher gunnels I was going to cut down for the transom forming a U, leaving the sides higher.

This is incorrect afaik.

Boats, (like this one) when scaled are only scaled in the beam and length. Consider your plan wrong until you hear from JM. If you want the sole 30mm higher; it is added straight as 30mm to all BH tops.

If you want a higher sheer; that is done with the hullsides; never bulkheads or stringers unless you were going to set the gunwhale on the edges of a bulkhead. And then you'd only adjust at the edge for the sole to remain same if sole is bh top.

I am very certain you have scaled wrong and I saw it on the drawing.

Posted: **Thu Oct 28, 2021 10:58 am**

Also, if you only scale beam and length; the inverted vee is only wider and longer as expected.

also, you would never scale in the height from the sole; the boat is drawn on the waterline usually

Wait for JM to get involved here. I am only book smart and the scaling tutorial here is not very good. Scaling an inverted vee is a serious adventure. Glad you brought up problems early.

Posted: **Thu Oct 28, 2021 11:45 am**

Another issue with scaling and this is just for you to think about while waiting for JM.

Suppose the stringer is not a uniform height and this one is not.

Part of the stringer is above dwl and part is below dwl. If the sole contacts the stringer, adding 10% to the entire stringer is a clerical error.

Use this stringer for an example.

2000mm long
Transom depth of stringer 100mm, top of stringer is sole.
Forward bulkhead depth of stringer 200mm, ""
Design waterline at transom 70mm from baseline, 30mm from 'sole'.
Design waterline at forward bulkhead 170mm from baseline, 30mm from 'sole'.

Scaling from dwl 10% (still an error because transom is affected)
Transom stringer height 77mm plus 30 to sole. Total 107mm
Forward BH 187 plus 30. Total 217mm

Scaling from sole (worse error because sole is affected and not level)
Transom 110. Less 70mm dwl to baseline, sole is 40mm above dwl.
Forward BH 220. Less 170mm dwl to baseline, sole is 50mm above dwl..??? Bad

Do you see how the waterline, also the sole, is no longer level in the height scaling from the sole?

The design waterline must he laid out on all your parts and shot with a laser or a level of some type.

Posted: **Thu Oct 28, 2021 1:42 pm**

fallguy1000 wrote: ↑Thu Oct 28, 2021 11:45 am Another issue with scaling and this is just for you to think about while waiting for JM.

Suppose the stringer is not a uniform height and this one is not.

Part of the stringer is above dwl and part is below dwl. If the sole contacts the stringer, adding 10% to the entire stringer is a clerical error.

Fallguy, I do appreciate your help. I am somewhat confused, maybe too long looking at this today.

I have made sure the bulkheads are aligned horizontally at sole level both by laser and water level. The vertical centreline is plumbed and aligned by laser.

I am obviously an amatuer and after reading the tutorial on scaling and mentioning in my foam core thread I wanted to scale all dimensions equally I decided to use 10%. I then increased every dimension on the plans by 10%, length, width and height and depth. So, for example, the slots in my bulkheads for my side stringers are 10% deeper and fit the side stringers perfectly. I then spread the bulkheads +10% on my form base, my plan is to add at least 1 additional bulkhead so as to keep the hull reinforcement correct.

I need to digest what your trying so hard to explain to me, I honestly throught that by altering every dimension by the same factor I would not change the hull characteristics / angles barring the transom height and static draft.

Hopefully by the time JM gets back to us I'll have 'clicked'

Posted: **Thu Oct 28, 2021 2:09 pm**

fallguy, Vandu did it correctly, all dimensions must be increased by the same percentage. That means every line on the plans. If he does not want the sides as tall as they come out he ccan reduce them. Vandu at only 10% you do not need to add an extra bulkhead, just spread them about 3.6" apart, this is well with in tolerances, This is why Jacques limits scaling to 10%. You will also need to cut down the center of transom for the length of the motor shaft.

Tom

Posted: **Thu Oct 28, 2021 8:33 pm**

TomW1 wrote: ↑Thu Oct 28, 2021 2:09 pm fallguy, Vandu did it correctly, all dimensions must be increased by the same percentage. That means every line on the plans. If he does not want the sides as tall as they come out he ccan reduce them. Vandu at only 10% you do not need to add an extra bulkhead, just spread them about 3.6" apart, this is well with in tolerances, This is why Jacques limits scaling to 10%. You will also need to cut down the center of transom for the length of the motor shaft.

Tom

You are mistaken Tom. He didn't scale CORRECTLY. Read what he did. He scaled from the sole. Boats are not drawn from the sole. The sole is usually a fixed dimension above the waterline. Think the constant K.

The hull dimension varies from the design waterline. Some variable X.

When the boat is scaled, the scaling needs to be done against variable dimensions; not constants. So the boat would be scaled 110% of x and no change to K.

Also...this boat would scale much easier length and beam only.

Posted: **Thu Oct 28, 2021 9:28 pm**

my understanding was that in a scaled boat the original design waterline needs to stay the same, but all dimensions are still scaled. otherwise the hull shape changes. so the risk is that additional weight may need to be added to bring the boat down to the correct waterline.

the displacement volume has changed, but the additional weight of the materials used for the +10% may not be enough to bring the boat to the correct line.

Posted: **Thu Oct 28, 2021 11:32 pm**

fallguy i guess I missed that. But all dimensions still need to be increased by 10%, the height of the stringers for stringers for strength, the same with the frames, only the sides can be cut down if he does not like the height of the height of them but 10% is not that much of an increase to have a good height from the deck to the rail.

Posted: **Fri Oct 29, 2021 12:56 am**

jonnymac wrote: ↑Thu Oct 28, 2021 9:28 pm my understanding was that in a scaled boat the original design waterline needs to stay the same, but all dimensions are still scaled. otherwise the hull shape changes. so the risk is that additional weight may need to be added to bring the boat down to the correct waterline.

the displacement volume has changed, but the additional weight of the materials used for the +10% may not be enough to bring the boat to the correct line.

jonnymac the waterline is set by Jacques as he designs the boat. If you add more weight that is the waterline, if you add less that is the waterline Jacques has set the static waterline at 5" at 1800lbs. The hull dry weight is 850 lbs. The draft PPI is 495lbs and increase/decrease the design water line by 1' if you add or remove that amount of weight from the 1800lbs. You need to add 950lbs to get to 1800lbs, you will never be exactly on that.

Regards, Tom

Posted: **Fri Oct 29, 2021 7:48 am**

what I meant by design water line for a +10% boat is if original was 5”, now it would be 5.5” for the boat to sit the way in the water Jacques designed it.

TomW1 wrote: ↑Fri Oct 29, 2021 12:56 am
jonnymac wrote: ↑Thu Oct 28, 2021 9:28 pm my understanding was that in a scaled boat the original design waterline needs to stay the same, but all dimensions are still scaled. otherwise the hull shape changes. so the risk is that additional weight may need to be added to bring the boat down to the correct waterline.

the displacement volume has changed, but the additional weight of the materials used for the +10% may not be enough to bring the boat to the correct line.
jonnymac the waterline is set by Jacques as he designs the boat. If you add more weight that is the waterline, if you add less that is the waterline Jacques has set the static waterline at 5" at 1800lbs. The hull dry weight is 850 lbs. The draft PPI is 495lbs and increase/decrease the design water line by 1' if you add or remove that amount of weight from the 1800lbs. You need to add 950lbs to get to 1800lbs, you will never be exactly on that.

Regards, Tom

Posted: **Fri Oct 29, 2021 7:50 am**

jonnymac wrote: ↑Fri Oct 29, 2021 7:48 am what I meant by design water line for a +10% boat is if original was 5”, now it would be 5.5” for the boat to sit the way in the water Jacques designed it.

PPI would also go up for +10% boat because the surface area of boat bottom went up

TomW1 wrote: ↑Fri Oct 29, 2021 12:56 am
jonnymac wrote: ↑Thu Oct 28, 2021 9:28 pm my understanding was that in a scaled boat the original design waterline needs to stay the same, but all dimensions are still scaled. otherwise the hull shape changes. so the risk is that additional weight may need to be added to bring the boat down to the correct waterline.

the displacement volume has changed, but the additional weight of the materials used for the +10% may not be enough to bring the boat to the correct line.
jonnymac the waterline is set by Jacques as he designs the boat. If you add more weight that is the waterline, if you add less that is the waterline Jacques has set the static waterline at 5" at 1800lbs. The hull dry weight is 850 lbs. The draft PPI is 495lbs and increase/decrease the design water line by 1' if you add or remove that amount of weight from the 1800lbs. You need to add 950lbs to get to 1800lbs, you will never be exactly on that.

Regards, Tom

Posted: **Fri Oct 29, 2021 7:52 am**

jonnymac wrote: ↑Fri Oct 29, 2021 7:48 am what I meant by design water line for a +10% boat is say original was 5”. now + 10% boat would be 5.5” for the boat to sit the way in the water Jacques designed it.

TomW1 wrote: ↑Fri Oct 29, 2021 12:56 am
jonnymac wrote: ↑Thu Oct 28, 2021 9:28 pm my understanding was that in a scaled boat the original design waterline needs to stay the same, but all dimensions are still scaled. otherwise the hull shape changes. so the risk is that additional weight may need to be added to bring the boat down to the correct waterline.

the displacement volume has changed, but the additional weight of the materials used for the +10% may not be enough to bring the boat to the correct line.
jonnymac the waterline is set by Jacques as he designs the boat. If you add more weight that is the waterline, if you add less that is the waterline Jacques has set the static waterline at 5" at 1800lbs. The hull dry weight is 850 lbs. The draft PPI is 495lbs and increase/decrease the design water line by 1' if you add or remove that amount of weight from the 1800lbs. You need to add 950lbs to get to 1800lbs, you will never be exactly on that.

Regards, Tom

Posted: **Fri Oct 29, 2021 10:36 am**

He needs to draw the waterlines on the crossmembers; especially the transom and he will see where he is messed up. Most likely the transom is incorrectly placed.

The sole should be a fixed dimension above dwl. Simple as that unless otherwise drawn.

Posted: **Fri Oct 29, 2021 10:39 am**

fallguy1000 wrote: ↑Fri Oct 29, 2021 10:36 am The sole should be a fixed dimension above dwl. Simple as that unless otherwise drawn.

why? I ask because I see so little details on this forum about the why and that is as important as doing it.

Posted: **Fri Oct 29, 2021 1:50 pm**

Good afternoon Guys.

I am just a layman, and appreciate all the comments and assistance. That being said I am trying to learn, and will be asking questions till I understand, so please be patient with me.

When I wanted to scale the TX18 I posted in the core material thread and mentioned scaling up in all directions. I also said I wanted to lift the sole a few inches (3-4) and the gunnels similarly. On this JM did not think there would be a problem as long as I stayed within 10%.
MY engine is heavier than standard, and I wanted to add livewell and 20-30 US gallon fuel tank, and cooler.

There are 2 issues as I see things:
1) I have scaled every dimension by 10%. The base line on the TX18 plans is also the underside of the sole. I now understand that I am being advised to scale only from the waterline, and to scale beam and length not depth below the sole. I have attached below a diagram showing Bulkhead C, A- standard (Purple), B- Green- adding 10% to beam only, and C- adding 10% on all dimensions (which is what I have done). I have not arbitrarily lifted the sole, or the gunnels, it is all part of the 10% increase.

Am I correct in saying I should scale the beam as per picture B?
Considering that the TX18 is designed to rise above the water when on the plane is the static draft an issue?

2) The curved line on the plans for the centre stringer, and the centre stringer lifting above Bulkhead D and MW but flush with the transom.
When I built my first TX18, which was not scaled I recall having the same problem, and instead of asking for help I cut out the offending material making a straight line from Transom to MW and then another from MW to Bulkhead D. This created somewhat of a ramp effect between MW and Transom, and I do not think this is good, especially with a larger engine planned for.

I have scaled my plans on the computer and compared them to what exists on the workshop floor. The straight line of the centre stringer sits 12mm above the bulkhead MW and 5mm above bulkhead D. When I compare the distance from the curve to the straight line on my computer I find they are 11 and 4.5mm respectively. So, if I created the curved line as per the plans I would not have the problem at hand. All this being said, the plans clearly state to follow a straight line. Hopefully JM will be able to shed some light when back from his break.

Posted: **Fri Oct 29, 2021 3:11 pm**

Vandu you are correct in scaling every direction by 10%, that means every line on the plans. It doesn't matter where the base line is just scale the lines by 10%, there will be a new base line for the scaled boat. The stingers and frames to support the extra weight of the sole aad the wider spacing of them. I don't know if you have read this but it definately says scale all dimensionss: https://boatbuilderceontral.com/support ... -plans.pdf Since the TX18 is such a specialized boat I would post a note for Jacques in the Questions Before *** above this about Scaling The TX18 10% you may get a faster answer that way. As for the transom yes scale it but cut down the motor well to the designed height probably 21 1/2", other wise the sides of the transom will not meet the height of the sides of the boat.

Good luck on your build, Tom

Posted: **Fri Oct 29, 2021 3:29 pm**

If you had this problem on the unscaled version; then there is something in the plans or your interpretation that is incorrect.

But not drawing the waterlines is not helping because you ought to be able to reference details.

The associative property of math allows multiplying each or combined by a common amount. Disregard my comment saying you cannot. However, if you want to maintain the same sole distance above dwl, then I am right.

So...

1.1 • (k + x) where k is the sole above dwl and x is the dimension from dwl to hull is same as 1.1 • k + 1.1• x,
but if you want k to remain the same, then scaling is done as 1.0•k + 1.1•x..... verstehen Sie?

Why would you want to raise the sole or change the depth of the bulkheads and stringers? They are within their limits at 10% and require no increases!

But if you know the error is 12mm at mw, then you ought to know the error at transom.

This is all for the designer, I have tried to help, but have not. If the issue was apparent in the unscaled version; it is either the same error repeated by the builder or in the plans.

Posted: **Fri Oct 29, 2021 7:49 pm**

There is no cabin , so wind is not much issue if you scale above the waterline , no real safety or performance downsides . I would go with C , and lift my sole if I wanted to , transom cut like Tom said would have to remain the same from waterline to top of cut . Waterline might change a little due to scaling , add an inch , put it in the water and trim as needed .

Posted: **Sat Oct 30, 2021 1:03 am**

Thanks guys for the input. I will keep going with the +10%. Once I figure our the centre stringer quandary.

Fallguy, To answer your question about why to raise the sole. I wanted to add some space for storage. Having seen whats available with the 10% increase I won't be adding any more to the sole.

I am going to find some scrap and cut bulkheads C, D and MW as well as the centre stringer without scaling and see what happens. I'll keep you posted.

I know JM is away for a short while yet, I'll try and get his input when he's back and settled.

Posted: **Sat Oct 30, 2021 1:46 am**

Vindu-you should be able to determine the following..

length of center stringer
Distance from sole to dwl all stations @ center stringer (transom,mw, etc).

Distance from dwl to hull all stations @ center stringer.

Then you should be able to graph the distances at each station and determine if they are indeed a straight line.

No need to cut anything.

Send me the numbers in a private message. I'm not splashing Jacques plans. I'll graph it out and tell you what I get/find.

Posted: **Sat Oct 30, 2021 1:48 am**

Sorry, Vundu...yours is not an American name and I am an American. Will work on spelling it right!

Posted: **Sat Oct 30, 2021 9:21 am**

fallguy1000 wrote: ↑Sat Oct 30, 2021 1:48 am Sorry, Vundu...yours is not an American name and I am an American. Will work on spelling it right!

No Worries Fallguy! Vundu is a type of large catfish we get out here

. I was gone before your kind offer to help came through.

I left home early today and and went off to my cave to see how much of a 'numpty' I really am. I drew out the centre stringer without any dimensional adjustments on MDF, extrapolated the curve on the plan, and cut a few pieces of MDF the exact size of the slots in the bulkheads and put it all together.....

Note, I used the .pdf drawings from BBC and a free online very basic drawing program to do it...... The results are below:

: full size mock up

The height of the slots in the bulkhead appear to follow the curve better than the straight line.

closeups std.docx: (8.86 MiB) Downloaded 5 times

I then drew the curve on the full size Stringer and obtained similar results:

Centre stinger to Bulkhead C and B fits perfectly. Stringer is proud to A by 8mm. I will check the curve and measurements monday.

I do not think the curve on the plans is a mistake.

Posted: **Sat Oct 30, 2021 11:28 am**

I'm thinking the curve is supposed to be there too. It is a twin V hull with a complicated center stringer to fit I suppose. Here's a pic of the bottom of the hull in construction before stringers from DaveTx's build. Scroll down to the bottom of the page for the pic:

viewtopic.php?t=15242

Dougster

Posted: **Sat Oct 30, 2021 11:57 am**

Thanks Dougster, at least 2 of us agree

. I think at this stage it's a case of waiting for JM to get back and see what he thinks. May need to open a new thread as the guys have advised, but would prefer to see if JM see's this first.

Posted: **Sat Oct 30, 2021 12:22 pm**

So, to simplify things, you are finding a detail in the plans it appears.

The way to correct this would be relatively simple. But this is all conjecture from me and a way for dialogue, not more.

You are 5mm big at one BH and 12mm big at MW, so you have a 7mm rise in the run from BH to MW. That rise extends to the transom and so what you could do as an option would be to calculate the error in the transom which will be on the order of say 15mm. Then you might be able to cut that 15mm vee into the transom and lower the stringer, retain the inverted shape, etc.

Just offered as an idea. The designer really is the one to decide. But you could calculate the amount needed to keep the stringer flat.

If the waterlines are marked on the parts, that would help as well to make sure the sole is a consistent amount above the waterline at all transverse members.

Posted: **Sat Oct 30, 2021 12:45 pm**

Hi Fallguy, Thanks for the input. I'll have another look monday. The transom fit is perfect though.

Been looking at your build, Fantastic! The build quality is excellent. I am going to be on a steep learning curve here.

Posted: **Sat Oct 30, 2021 1:26 pm**

Vundu wrote: ↑Sat Oct 30, 2021 12:45 pm The transom fit is perfect though.

Respectfully, just because the transom and stringer touch each other doesn't mean they are correct (at this point).

Ultimately, it sounds like some minor adjustment in the plans is needed. Don't build a vee!!!!

Posted: **Sat Oct 30, 2021 1:54 pm**

For some reasoon this post did not post. All dimensions must be increased by 10% 10% to maintain the strength of the boat. Since the stringers and frames are widened out there height must be increased to support more weight, just like in a hpuse the beams must increase height the longer they span.

Vandu did you read the Instructions on Scaling I posted, it should have answered all your questions as it was written by Jacques.

Also post a question to Question to Jacques in the section above this Questions Before **** with a title like Scaling the TX18 he watches that section closer than any other.

Tom

Posted: **Sat Oct 30, 2021 2:02 pm**

fallguy1000 wrote: ↑Sat Oct 30, 2021 12:22 pm So, to simplify things, you are finding a detail in the plans it appears.

The way to correct this would be relatively simple. But this is all conjecture from me and a way for dialogue, not more.

You are 5mm big at one BH and 12mm big at MW, so you have a 7mm rise in the run from BH to MW. That rise extends to the transom and so what you could do as an option would be to calculate the error in the transom which will be on the order of say 15mm. Then you might be able to cut that 15mm vee into the transom and lower the stringer, retain the inverted shape, etc.

Just offered as an idea. The designer really is the one to decide. But you could calculate the amount needed to keep the stringer flat.

If the waterlines are marked on the parts, that would help as well to make sure the sole is a consistent amount above the waterline at all transverse members.

fallguy quit talking about the waterline, please. He needs to use the baseline. Waterline varies by weight, baseline is a constant. That is why Jacques uses it to take all measurements from.

Tom

Posted: **Sat Oct 30, 2021 2:10 pm**

TomW1 wrote: ↑Sat Oct 30, 2021 1:54 pm For some reasoon this post did not post. All dimensions must be increased by 10% 10% to maintain the strength of the boat. Since the stringers and frames are widened out there height must be increased to support more weight, just like in a hpuse the beams must increase height the longer they span.

Vandu did you read the Instructions on Scaling I posted, it should have answered all your questions as it was written by Jacques.

Also post a question to Question to Jacques in the section above this Questions Before **** with a title like Scaling the TX18 he watches that section closer than any other.

Tom

Hi Tom,
Thanks for all the help. I did read the scaling tutorial thanks. Also, in the write up on the TX18 it says we can lift the sole. I understand JM is away on holiday for a few days yet. I'll repost as advised Monday/Tuesday.

Posted: **Sat Oct 30, 2021 2:17 pm**

(boat in its natural orientation) looking at the underhull form on the study plans, the center line of the bottom looks to be above the transom and as it goes aft it meets the transom. I would take a look back at the plans again and think about what straight means. It means several points are in the same line. it doesn’t mean parallel to another line, perpendicular to transom.

Also, the best way to get someone’s attention on the forum is to quote their user name like this. and ask you question. that way they get a notification. Otherwise you are relying on Jacques to just read through the forum.

Vundu wrote: ↑Sat Oct 30, 2021 2:02 pm

Posted: **Mon Nov 01, 2021 3:15 pm**

jacquesmm wrote: ↑Thu Oct 28, 2021 8:35 am It must be straight. That is why I wrote "straight above that line. I don't know why there is second line with a camber superposed on it.
I will check my version of the drawing later today: I am on the road now.

Hi Jacques, I've done some more work on my TX20 centre stringer glitch. I would be very grateful if I could have your thoughts on the curve line superimposed in the photos and the way I have scaled the 10%.

Thanks.

Posted: **Thu Nov 04, 2021 1:16 am**

jacquesmm wrote: ↑Thu Oct 28, 2021 8:35 am It must be straight. That is why I wrote "straight above that line. I don't know why there is second line with a camber superposed on it.
I will check my version of the drawing later today: I am on the road now.

HI Jaques, Please could you take a quick look at this thread and confirm if I am scaling right and maybe shed some more light on the centre stringer glitch I have. Thanks.

Posted: **Thu Nov 04, 2021 10:10 am**

The center stringer bottom side is straight where marked straight. It looks like you did that right.
The MW bulkhead is a little low but keep in mind that you will fine tune all the framing along the hull skin side to fit to the fiberglassed inside.
You will make it fit at that time: all frames and stringers will require adjustments to go over the multiple layers of glass.
At this point , focus on getting a straight bottom panel.

Posted: **Thu Nov 04, 2021 12:48 pm**

jacquesmm wrote: ↑Thu Nov 04, 2021 10:10 am The center stringer bottom side is straight where marked straight. It looks like you did that right.
The MW bulkhead is a little low but keep in mind that you will fine tune all the framing along the hull skin side to fit to the fiberglassed inside.
You will make it fit at that time: all frames and stringers will require adjustments to go over the multiple layers of glass.
At this point , focus on getting a straight bottom panel.

Great, thanks Jacques. Will do as advised. Materials arrive next week so will be ready.

Posted: **Thu Nov 04, 2021 7:06 pm**

Wouldn't an inverted vee bottom need to have the MW and transom veed?

Posted: **Thu Nov 04, 2021 9:50 pm**

fallguy1000 wrote: ↑Thu Nov 04, 2021 7:06 pm Wouldn't an inverted vee bottom need to have the MW and transom veed?

there is a stern picture in the study plan and the transom isn’t v’d.

Posted: **Thu Nov 04, 2021 9:54 pm**

jonnymac wrote: ↑Thu Nov 04, 2021 9:50 pm
fallguy1000 wrote: ↑Thu Nov 04, 2021 7:06 pm Wouldn't an inverted vee bottom need to have the MW and transom veed?
there is a stern picture in the study plan and the transom isn’t v’d.

Yeah, but his center stringer is 12mm too high at MW. How is he gonna get a straight panel and not vee the hull at MW? Isn't the proposal by JM to build the center stringer flat and the bottom flat impossible? I see a vee.

What am I missing?

: 135E07C3-9941-4491-84DA-00842F8A7A3E.jpeg (74.44 KiB) Viewed 539 times

Posted: **Fri Nov 05, 2021 1:09 am**

Some thing is not kosher to me also fallguy. MW may need to be cut higher or something like that.

Tom

Posted: **Fri Nov 05, 2021 11:31 am**

I agree something isn’t right. to me it looks like MW is closer to the shape its supposed to be than the center stringer. the center stringer is straight for that run as discussed ad nausea but not in the same plane as the chine. the chine and the center stringer should be different angles based on the hull shape I see. I’d like to see a picture more back(so the whole frame setup and looking from stern to bow and bow to stern. I’d guess the real problem is a few stations back from here.

Posted: **Fri Nov 05, 2021 11:51 am**

Vundu-how will you deal with it?

Posted: **Fri Nov 05, 2021 12:55 pm**

Transom is straight on the bottom. Scroll down on this link and see pic:
viewtopic.php?t=15242&start=90

Also use DaveTx's link to his blog to see more.

Dougster

Posted: **Fri Nov 05, 2021 1:28 pm**

fallguy1000 wrote: ↑Fri Nov 05, 2021 11:51 am Vundu-how will you deal with it?

Hi Fallguy.

The short answer is I am not sure yet. I have been inundated with work, so tomorrow is the day.
I will take a few more pics tomorrow and post them.

I have checked and double checked the bulkheads and cannot find any anomalies. This is not to say I haven't missed something.

It is not possible to draw a straight line from Bulkhead C to transom, or from D to transom, without leaving bulkhead bulkhead MW low. If I lower the transom and then the side stringers and centre stringer won't fit. If I raise bulkhead MW then then I have to deviate from the centreline by 12mm, and the sole will be out by the same amount.

I can can draw a straight line C-D-MW then from MW a 12mm incline to Transom (This is what I did on the first boat).

At present, the baseline for all bulkheads is correct. The alignment of the bulkheads and side stringers is also correct. Motorwell bulkhead MW is an inverted V, the transom is a very slight positive V.

It pains me to say it, but.... the curve that is incorrectly on the plans appears to be the best fit for now

I will know more tomorrow.

Posted: **Fri Nov 05, 2021 2:22 pm**

Okay, scaling a W is not easy.

The inverted bottom is indeed a W shape, and you can't just make all the tops higher and you can't scale from the baseline or the sole.

Consider the following picture.

Now consider how to scale it vertically.

Can you show us your mw drawing with the numbers? Since you used the sole, all your numbers might have been reductions, but the middle of mw (and all the BH) should be lower...not 10% higher. (On the upside down jig)

Friendly comments welcome. I think the scaling is perhaps wrong..

Posted: **Fri Nov 05, 2021 2:26 pm**

Dougster wrote: ↑Fri Nov 05, 2021 12:55 pm Transom is straight on the bottom. Scroll down on this link and see pic:
viewtopic.php?t=15242&start=90

Also use DaveTx's link to his blog to see more.

Dougster

I can't find the pic, but I trust you. The blog link is broken as well, but I trust you. I read the pages the other way, so it is 70 for me. Funny thing is, this is almost like the scaling issue I highlighted.

Posted: **Fri Nov 05, 2021 2:31 pm**

Here is a drawing showing how scaling from the sole would result in flattening the inverted shape.

Posted: **Sat Nov 06, 2021 9:48 am**

fallguy1000 wrote: ↑Fri Nov 05, 2021 2:26 pm
Dougster wrote: ↑Fri Nov 05, 2021 12:55 pm Transom is straight on the bottom. Scroll down on this link and see pic:
viewtopic.php?t=15242&start=90

Also use DaveTx's link to his blog to see more.

Dougster
I can't find the pic, but I trust you. The blog link is broken as well, but I trust you.

Click on my link and scroll down to the 10th post. At list it works for me. It's an old photoshop pic.

Dougster

Posted: **Sat Nov 06, 2021 3:24 pm**

Dougster wrote: ↑Sat Nov 06, 2021 9:48 am
fallguy1000 wrote: ↑Fri Nov 05, 2021 2:26 pm
Dougster wrote: ↑Fri Nov 05, 2021 12:55 pm Transom is straight on the bottom. Scroll down on this link and see pic:
viewtopic.php?t=15242&start=90

Also use DaveTx's link to his blog to see more.

Dougster
I can't find the pic, but I trust you. The blog link is broken as well, but I trust you.
Click on my link and scroll down to the 10th post. At list it works for me. It's an old photoshop pic.

Dougster

Hi, I have not been able to do any work on this, and will not be able to work on it for a week or so due to an unforseen emergency. I do, most sincerely, appreciate all input, thats why I am here!

Dougster, sorry if I have not read your posts correctly, I am somewhat pre occupied at the moment. I did not scale vertically, from the baseline, I scaled each leg of the W, \ / \ / and all the horizontal measurements (beam and length) on the plans by 10%, in otherwords, every single measurement on the plan was scaled 10%. That way I think all the angles would all remain the same.

I did look at the bulkheads briefly today. The chine panel sections of Bulkheads ( first \ and last / of the W) D, MW and Transom align perfectly.

I hope to be back with more information by next weekend.

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TX18 Centre stringer fit and modification

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