Join Us On Social Media!
|
|
|
Download The App!
Login To
Remove Ads
Remove Ads
Login To
Remove Ads
Remove Ads
Model Boats Website
Watercat M12 (Jurmo Class) landing craft
64 Posts · 12 Followers · 394 Photos · 198 Likes
Began 2 years ago by
United KingdomFollow This Thread
Not currently following
> Click to follow
> Click to follow
Latest Post 10 days ago by
| Oldest posts shown first (Show Newest First) | (Print Booklet) |
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 (
Commander)
Commander)✧ 128 Views · 2 Likes · 5 Comments
Flag
💬 Add Comment
Decided to have a go at building a Watercat M12 as I have recently brought a couple of 28mm jet drives, yet to arrive! and wanted a craft to fit them in.
The model will be semi- scale and I intend to modify the stern's deadrise to ensure both jet intakes keep in the water when turning a deep v stern may cause ventilation on turns.
upscaled the plans available to make a craft around 35.5in (90cm).
The model will be semi- scale and I intend to modify the stern's deadrise to ensure both jet intakes keep in the water when turning a deep v stern may cause ventilation on turns.
upscaled the plans available to make a craft around 35.5in (90cm).
▲
⟩⟩
GaryLC
Colin H
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 Colin H (
 Fleet Admiral)✧ 113 Views · 0 Likes
Flag
It's by my reading your answers that I am now understanding the problem.
Sorry if my thoughts put doubts in your mind. Thanks for taking the trouble to reply, I'm enjoying the flow of your work so far. Cheers Colin. ▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
|
Login To
Remove Ads 💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 (
Commander)✧ 115 Views · 0 Likes
Flag
Could you use a single water intake on the centre line.
Hi Colin, Another good original idea, but would need some complex implementation. The intake would need to be twice the area to feed two jets, extra tubing to route to each jet (more friction) Danger of fluid switching effect see link below: 
▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 Colin H (
Fleet Admiral)✧ 115 Views · 0 Likes
Flag
Roy, I didn't mean only one jet drive, but a single intake duct feeding both jet drives.
Cheers Colin. ▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 (
Commander)✧ 117 Views · 1 Like
Flag
Hi Colin,
You're quit right, but I wanted the boat to look scale, the original has 2 jet drives, also a single drive limits control a little, as with two you should be able to turn the boat in a standing position (spin) by putting one jet in forward and the other with reversing bucket down. similar to this on my CB90 which did not have water jets but duel props: 
▲
⟩⟩
Colin H
|
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 Colin H (
Fleet Admiral)✧ 126 Views · 0 Likes
Flag
Could you use a single water intake on the centre line.
Cheers Colin. ▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
Login To
Remove Ads
Remove Ads
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 129 Views · 3 Likes
Flag
💬 Add Comment
From the enlarged plan, I design the sections and cut them out,
please note, the deck appears to have no camber, but the deck does rise slightly from stern to bow.
please note, the deck appears to have no camber, but the deck does rise slightly from stern to bow.
▲
⟩⟩
Colin H
GaryLC
Norway
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 119 Views · 3 Likes · 2 Comments
Flag
💬 Add Comment
Hi There,
I thought I'd better mention the jet drives, they are relatively cheap, compare to the quality German products (loads of money). the output port is about 28mm and suitable for a 36mm diameter motor with 3.17mm shaft.
I have ordered two 4-Pole 3650-1500KV 2-4S inboard Brushless Motors to power them.
regards Roy
I thought I'd better mention the jet drives, they are relatively cheap, compare to the quality German products (loads of money). the output port is about 28mm and suitable for a 36mm diameter motor with 3.17mm shaft.
I have ordered two 4-Pole 3650-1500KV 2-4S inboard Brushless Motors to power them.
regards Roy
▲
⟩⟩
GaryLC
rolfman2000
Colin H
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 (
Commander)✧ 109 Views · 1 Like
Flag
I Built a CB 90 (note my handle)some years ago but made it a bit too big. My home made waterjets did not work they kept ventilating.
▲
⟩⟩
Muskrat
|
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇨🇦 Rowen (
 Captain)✧ 118 Views · 0 Likes
Flag
Hi Roy,
Very interested in your project. Am planning the Interceptor version of the Swedish CB90 as my winter project. My version will be about 30" long and already have purchased 2 x 20mm waterjets without reverse. Will make my own reversers as need the clamshell not bucket style. Which watch your endeavours with interest. Rowen ▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 104 Views · 1 Like
Flag
💬 Add Comment
Traced Frames from paper patterns to 4mm ply. the stringers will be 4.5mm square and the skins will be 0.8mm birch ply.
▲
⟩⟩
Colin H
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 106 Views · 1 Like
Flag
💬 Add Comment
The stern (frame) is a little more complex as had to reduce it's width to allow for the 2x 18mm quadrants to represent the curved stern corners.
Please note. There is a 1mm gap to insert a 0.8mm ply stern panel to support the jet drives output ring. as 4mm is likely to be too thick!
As with all scratch builds you have to make it up as you go along!
Slowly I will cut out the rest of the frames,
the middle frame will be solid as a watertight bulkhead and forward of that will most probably be foamed or filled with polystyrene blocks.
regards Roy
Please note. There is a 1mm gap to insert a 0.8mm ply stern panel to support the jet drives output ring. as 4mm is likely to be too thick!
As with all scratch builds you have to make it up as you go along!
Slowly I will cut out the rest of the frames,
the middle frame will be solid as a watertight bulkhead and forward of that will most probably be foamed or filled with polystyrene blocks.
regards Roy
▲
⟩⟩
Colin H
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 106 Views · 1 Like · 1 Comment
Flag
💬 Add Comment
Jet Drives Arrive today at 14:30.
I have added a pic with some measurements.
The solid coupling appears to be 4mm to 3.2mm and is 23mm long, this could be changed for a flexible one.
Also noticed a 2mm movement in the shaft this would put pressure on the motor bearings if not adjusted.
The impeller is a normal prop about 25mm if you wish to improve the unit this may be the one of the things to change, for a proper impeller.
Not bad for the money, £22.
regards Roy
I have added a pic with some measurements.
The solid coupling appears to be 4mm to 3.2mm and is 23mm long, this could be changed for a flexible one.
Also noticed a 2mm movement in the shaft this would put pressure on the motor bearings if not adjusted.
The impeller is a normal prop about 25mm if you wish to improve the unit this may be the one of the things to change, for a proper impeller.
Not bad for the money, £22.
regards Roy
▲
⟩⟩
Colin H
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇨🇦 Rowen (
Captain)✧ 110 Views · 1 Like
Flag
Roy,
Just noticed your remark on the 2mm end float. The jets I purchased have a spring on the shaft to ensure the movement is loaded in one direction, thus reducing the float. Rowen ▲
⟩⟩
Colin H
|
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 106 Views · 1 Like · 2 Comments
Flag
💬 Add Comment
First water Jet up-grade is a new coupling as a solid coupling transfers vibrations to the assembly, and I have found a review on Amazon where it has fractured the unit casing.
I looked at a suitable Impeller but it cost £25, more than the entire unit.
Regards
Roy
I looked at a suitable Impeller but it cost £25, more than the entire unit.
Regards
Roy
▲
⟩⟩
Colin H
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 (
Commander)✧ 103 Views · 0 Likes
Flag
The new couplings don't seem very flexible, may only reduce vibration.
They only seem to come in 4mm to 3.17mm, so may not fit your unit. Along way to go before this boat is finished. Regards Roy 
▲
⟩⟩
No likes yet
This member will receive 1 point for every like received |
|
💬 Re: Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇨🇦 Rowen (
Captain)✧ 111 Views · 1 Like
Flag
I have used 22 mm waterjets with solid drives on my Visby corvette. Had no issue with reliability so far.
The only issue is one of noise. Rather than sounding like a smooth gas turbine, it sounds like a high speed mangle. Have thought about trying a coupling as you propose, but it means removing the impellor to get the shaft out. That is not too daunting, but it will mean disturbing the outlet nozzle which has finally been sealed and is watertight. Would like to hear of your experiences and thoughts when completed. Rowen ▲
⟩⟩
Colin H
|
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 105 Views · 1 Like
Flag
💬 Add Comment
New couplings and motors arrived today!
Took out prop shaft and put the PTFE washer on the prop end, for some reason it was between the housing and the coupling the prop is a standard dog type.
Unfortunately the coupling could not be used without modifying the length of the Motor shaft, about 5mm needs to be removed from it.
No real problem as motors were cheap 3650 1500kv 2-3cells 7.4-11.1v.
Took out prop shaft and put the PTFE washer on the prop end, for some reason it was between the housing and the coupling the prop is a standard dog type.
Unfortunately the coupling could not be used without modifying the length of the Motor shaft, about 5mm needs to be removed from it.
No real problem as motors were cheap 3650 1500kv 2-3cells 7.4-11.1v.
▲
⟩⟩
Colin H
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 99 Views · 3 Likes
Flag
💬 Add Comment
Hi there,
One of my sources of info, was the Model boats Magazine website which has a Watercat M12 build of a commercial kit by Nautical Marine Models (Now out of Business)
One of my sources of info, was the Model boats Magazine website which has a Watercat M12 build of a commercial kit by Nautical Marine Models (Now out of Business)
▲
⟩⟩
jbkiwi
Rowen
Colin H
📝 Watercat M12 (Jurmo Class) landing craft
2 years ago by 🇬🇧 CB90 ( Commander)
Commander)✧ 102 Views · 2 Likes
Flag
💬 Add Comment
Hi Shipmates,
Work on transom, recess the waterjets in 4mm transom then add a 2mm outer skin over the transom
with circular 32mm hole to fix the the unit in place.
Regards Roy
Work on transom, recess the waterjets in 4mm transom then add a 2mm outer skin over the transom
with circular 32mm hole to fix the the unit in place.
Regards Roy
▲
⟩⟩
Colin H
Rowen
Login To
Remove Ads
Remove Ads
