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Liked Re: Aerokits Sea Commander. Strange Handling ? 46 minutes ago
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💬 Re: Aerokits Sea Commander. Strange Handling ?
34 minutes ago by 🇺🇸 Chum444 (
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I completely agree with Roy & Oxford Dave. I’m surprised it didn’t roll on its side & sink before. Again, one cannot ignore physics. The combination of the rudder’s force vector & the motor torque at higher speed is more than the hull was designed for.
As I mentioned in one of my early posts, one of my lobster boats when set up for racing exhibited extreme prop torque. It flipped onto its side and would have sunk had I not immediately killed the throttle when I saw it.
As I mentioned in one of my early posts, one of my lobster boats when set up for racing exhibited extreme prop torque. It flipped onto its side and would have sunk had I not immediately killed the throttle when I saw it.
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💬 Re: Roof, pilot, lights
3 hours ago by 🇺🇸 Chum444 ( Captain)
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Looking good Cash. You might want to consider moving the P & S nav lights quite a bit forward to create distance from the stern light. At least I think I am seeing a stern light in one photo.
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hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
4 hours ago by 🇺🇸 Chum444 ( Captain)
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A couple of questions & then some observations.
1. When turning right are you hard over to Stb’d with the rudder?
2. Are you making the turn with the throttle wide open?
A. In these videos your wake does not look proper. It should be flat when coming the stern without the white water (which are bubbles) showing. The white water is an indicator of prop cavitation. Said another way the prop cannot handle the RPM’s imposed on it.
B. The stern rising when you slow down is normal. It’s your stern wake catching up to the slowing boat. Your hull looks to be flat in the stern which accentuates the effect. Since one can’t defy the laws of physics, there is nothing that will stop this phenomena.
1. When turning right are you hard over to Stb’d with the rudder?
2. Are you making the turn with the throttle wide open?
A. In these videos your wake does not look proper. It should be flat when coming the stern without the white water (which are bubbles) showing. The white water is an indicator of prop cavitation. Said another way the prop cannot handle the RPM’s imposed on it.
B. The stern rising when you slow down is normal. It’s your stern wake catching up to the slowing boat. Your hull looks to be flat in the stern which accentuates the effect. Since one can’t defy the laws of physics, there is nothing that will stop this phenomena.
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hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
18 hours ago by 🇺🇸 Chum444 ( Captain)
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There could be an unintended benefit. When running ahead with neutral trim, the boat may, emphasis on may, drift to Stb’d due to the drag force created by the wedge. That would require some trim to port in order for the hull to track straight. The when turning to Stb’d the trim to port will reduce the rudder angle to Stb’d which may, again emphasis on may, reduce the diving.
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Madwelshman
hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
21 hours ago by 🇺🇸 Chum444 ( Captain)
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Well Bob, look at it this way: you won’t learn when you’re any younger. 😊
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hermank
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AlessandroSPQR
💬 Re: Aerokits Sea Commander. Strange Handling ?
6 days ago by 🇺🇸 Chum444 ( Captain)
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I wouldn’t remove the forward strakes. Doubt very seriously they contribute to the problem. The wedge might create just enough drag on the port side to greatly reduce the effect of the prop torque. Were it me, I would spend some time experimenting with size & location. A possible downside is that you will need to add starboard trim to get the hull to track straight.
Your comment that this a narrow hull jumps off the page at me. How narrow is the beam? A long hull with a narrow beam doesn’t have enough wetted hull surface to counter the prop torque.
Ain’t this fun?
Your comment that this a narrow hull jumps off the page at me. How narrow is the beam? A long hull with a narrow beam doesn’t have enough wetted hull surface to counter the prop torque.
Ain’t this fun?
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Madwelshman
💬 Re: Aerokits Sea Commander. Strange Handling ?
6 days ago by 🇺🇸 Chum444 ( Captain)
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Lift strakes that far forward do not enhance lift since they are not in the water when on plane. Cutting them back from the chine makes sense but it’s a drastic move at this point. I wonder why the hull doesn’t display the same diving behavior when turning to port; except for prop torque.
I don’t recall having seen a spray rail on the chine; usual location is somewhat above both in the bow & stern.
I don’t recall having seen a spray rail on the chine; usual location is somewhat above both in the bow & stern.
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hermank
DuncanP
💬 Re: Aerokits Sea Commander. Strange Handling ?
7 days ago by 🇺🇸 Chum444 ( Captain)
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“Before this dive the boat was seen to lean outwards slightly before digging in on the right hand side (as usual)”.
The textbook demonstration of prop torque. I think you are beginning to see the light at the end of the tunnel.
The textbook demonstration of prop torque. I think you are beginning to see the light at the end of the tunnel.
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💬 Re: Aerokits Sea Commander. Strange Handling ?
9 days ago by 🇺🇸 Chum444 ( Captain)
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Bob. I hope you do solve the problem if there is a solution & post the steps you proceeded through to determine what needed to be done. You’re absolutely right about changing one variable at a time. A person with two watches really doesn’t know what time it is! Your postings have elicited a lot of ideas & suggestions seemingly without you’re taking offense. At least we all hope you were not upset.
For my part it has started a very interesting discussion & generated widely varied solutions. I look forward to learning the solution(s) if you discover one or more. 👍
For my part it has started a very interesting discussion & generated widely varied solutions. I look forward to learning the solution(s) if you discover one or more. 👍
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hermank
Madwelshman
zooma
💬 Re: Aerokits Sea Commander. Strange Handling ?
11 days ago by 🇺🇸 Chum444 ( Captain)
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Ouch! My memory just kicked in & reminded me that the closer the shaft angle is to parallel with the bottom of the hull the less prop torque is an issue. Ugly thought to bring up now & essentially impossible with your Kommander given the shaft is firmly in place in the skeg. But, consider it with your next build.
Re my last post. If it looks like it might work, you’re right. The rudder will probably need to be trimmed on the AFT side. Rudder surface area is an important parameter.Too large, great maneuverability at slow speeds almost unmanageable at high. Too small, almost no maneuverability at low speeds, very stable when going fast.
Re my last post. If it looks like it might work, you’re right. The rudder will probably need to be trimmed on the AFT side. Rudder surface area is an important parameter.Too large, great maneuverability at slow speeds almost unmanageable at high. Too small, almost no maneuverability at low speeds, very stable when going fast.
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Madwelshman
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💬 Re: Aerokits Sea Commander. Strange Handling ?
11 days ago by 🇺🇸 Chum444 ( Captain)
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Bob,
My modification would be to temporarily extend the vertical length of the rudder you have in place so that it extends to just below the arc described by the prop rotation. Warning; start slow & increase speed in steps as this may make the problem worse. But it might improve handling by reducing the amount of rudder needed to initiate a turn to stb’d. Would be a great experiment.
My modification would be to temporarily extend the vertical length of the rudder you have in place so that it extends to just below the arc described by the prop rotation. Warning; start slow & increase speed in steps as this may make the problem worse. But it might improve handling by reducing the amount of rudder needed to initiate a turn to stb’d. Would be a great experiment.
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💬 Re: Aerokits Sea Commander. Strange Handling ?
12 days ago by 🇺🇸 Chum444 ( Captain)
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Re pmdevlin’s latest post. What you say is exactly true for real aircraft. Single engine propeller driven aircraft definitely require application of a bit of opposite rudder in a turn to eliminate effect of prop torque. You cannot make what’s known as a coordinated turn, maintaining needle, ball, & airspeed consistency, turning with ailerons only. Jet aircraft can be turned with ailerons only since there is no prop torque. No need to coordinate turn with rudder.
I’ve flown both of the real aircraft.
So, for Bob’s Commander issue the above aircraft analogy supports the idea of applying a touch of opposite rudder to eliminate the dive.
I’ve flown both of the real aircraft.
So, for Bob’s Commander issue the above aircraft analogy supports the idea of applying a touch of opposite rudder to eliminate the dive.
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💬 Re: Aerokits Sea Commander. Strange Handling ?
13 days ago by 🇺🇸 Chum444 ( Captain)
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Couple of thoughts.
I think you have solved your handling problem. When the bow starts to dive when turning to starboard just give it a bit of port rudder enabling the hull to recover. Eliminates need for further modification of rudder location or other potentially unsatisfactory results.
The rudder you describe on your boat is pretty much a standard & is known as an unbalanced design. More rudder aft of the rudder post lowers the turning radius. I wouldn’t change it. If anything I would deepen the rudder blade to get it below the tip of the prop blades. That may well cause you to have to back off on the throw of the rudder to prevent making matters worse. But not making such a sharp turn to starboard might help with the diving issue.
Not uncommon at all with models or 1:1’s to have to make small adjustments in the helm while maneuvering. Think of it as seamanship!
I think you have solved your handling problem. When the bow starts to dive when turning to starboard just give it a bit of port rudder enabling the hull to recover. Eliminates need for further modification of rudder location or other potentially unsatisfactory results.
The rudder you describe on your boat is pretty much a standard & is known as an unbalanced design. More rudder aft of the rudder post lowers the turning radius. I wouldn’t change it. If anything I would deepen the rudder blade to get it below the tip of the prop blades. That may well cause you to have to back off on the throw of the rudder to prevent making matters worse. But not making such a sharp turn to starboard might help with the diving issue.
Not uncommon at all with models or 1:1’s to have to make small adjustments in the helm while maneuvering. Think of it as seamanship!
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RodC
hermank
pmdevlin
💬 Re: Continuing progress
15 days ago by 🇺🇸 Chum444 ( Captain)
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Thank you Bob. The windscreen proved to be quite a challenge given that it took over 30 pieces to construct. Should have constructed a fixture…..oh well!
On another note I hope your offset rudder solves your Kommander handling issue. Watching your video I see you were not running as fast as I had assumed. The wake also looked flat as it should. Tells me that prop walk(torque) is the issue assuming your prop is a right hand prop.
Hopefully I’m wrong but offsetting the rudder will reduce/solve the diving problem in right turns but will show up somewhere else. The reduced & asymmetrical water pressure on the
rudder may make left turns a problem. Left turn radius could become impossibly large & tracking straight may be difficult.
Anyway I’ll be watching to see how you make out.🤞
On another note I hope your offset rudder solves your Kommander handling issue. Watching your video I see you were not running as fast as I had assumed. The wake also looked flat as it should. Tells me that prop walk(torque) is the issue assuming your prop is a right hand prop.
Hopefully I’m wrong but offsetting the rudder will reduce/solve the diving problem in right turns but will show up somewhere else. The reduced & asymmetrical water pressure on the
rudder may make left turns a problem. Left turn radius could become impossibly large & tracking straight may be difficult.
Anyway I’ll be watching to see how you make out.🤞
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hermank
📝 Continuing progress
16 days ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 19 Views · 2 Likes · 2 Comments
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I’ve been making the cockpit sole, etc removable to provide access to running gear & bilge. This all because the 26’s bottom has not yet been wetted so I have no idea what might be amiss & require fixing or replacement
Spray rails glued & pinned to hull.
Decided on a bit of color change for deck.
Cockpit details begun; the fun stuff.
Owner anxious for first boat ride.
Spray rails glued & pinned to hull.
Decided on a bit of color change for deck.
Cockpit details begun; the fun stuff.
Owner anxious for first boat ride.
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EdW
hermank
📝 Open the box, and you get pancakes!
17 days ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 50 Views · 2 Likes
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Will this be an RC or display build? Your documentation of a bread & butter build will be interesting for many folks. Many years ago I did a small lobster boat using that method.
I’ll be watching.👍
I’ll be watching.👍
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hermank
jumpugly
💬 Re: Aerokits Sea Commander. Strange Handling ?
18 days ago by 🇺🇸 Chum444 ( Captain)
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Duplicate post. Delete.
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hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
18 days ago by 🇺🇸 Chum444 ( Captain)
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Bob,
Scientific curiosity understood. What does the wake behind your boat look like when running straight at the speed you like? Is it flat?
Scientific curiosity understood. What does the wake behind your boat look like when running straight at the speed you like? Is it flat?
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Madwelshman
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EdW
💬 Re: Aerokits Sea Commander. Strange Handling ?
18 days ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 80 Views · 5 Likes
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My advice, even though you didn’t ask for it 😎, is to know that you are pushing the hull to do something (run at high speeds) it was not designed for.
The higher the speed the more pronounced prop walk becomes. I learned this lesson when I set up one of my lobster boats for racing. After getting soundly defeated in the boats first racing event I went to a higher KV in runner. MUCH faster at the expense of SEVERE prop walk. At WOT the boat could roll over completely on the starboard side& almost did. Asking it to do something it wasn’t designed for.
I mentioned earlier a speed of 15-20 kts for a 1:1 of this type. In reality the speed is much closer to 15 kts than 20. I humbly suggest you slow down the running speed & celebrate your skills for constructing a nice scale boat.
I have a bit of experience with offshore big game fishing. We were happy with a bit over 20 kts with twin outboards to run to & from the fishing grounds. Reasonable fuel consumption in a 23 ft boat. The larger the boat the more costly speed becomes. On one trip on a 47 ft twin diesel sport fisherman we returned at 25 kts. Fuel consumption? 75 gallons diesel fuel per hour. Attainable but why? Unless running from a storm.
I understand it might be quite boring for you to run at lower speeds given your vast experience with fast electrics. But try other things like docking maneuvers and precise steering with your scale build.
My boring long expression of my thoughts 🤣
The higher the speed the more pronounced prop walk becomes. I learned this lesson when I set up one of my lobster boats for racing. After getting soundly defeated in the boats first racing event I went to a higher KV in runner. MUCH faster at the expense of SEVERE prop walk. At WOT the boat could roll over completely on the starboard side& almost did. Asking it to do something it wasn’t designed for.
I mentioned earlier a speed of 15-20 kts for a 1:1 of this type. In reality the speed is much closer to 15 kts than 20. I humbly suggest you slow down the running speed & celebrate your skills for constructing a nice scale boat.
I have a bit of experience with offshore big game fishing. We were happy with a bit over 20 kts with twin outboards to run to & from the fishing grounds. Reasonable fuel consumption in a 23 ft boat. The larger the boat the more costly speed becomes. On one trip on a 47 ft twin diesel sport fisherman we returned at 25 kts. Fuel consumption? 75 gallons diesel fuel per hour. Attainable but why? Unless running from a storm.
I understand it might be quite boring for you to run at lower speeds given your vast experience with fast electrics. But try other things like docking maneuvers and precise steering with your scale build.
My boring long expression of my thoughts 🤣
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Madwelshman
EdW
Ronald
DWBrinkman
hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
20 days ago by 🇺🇸 Chum444 ( Captain)
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For what it’s worth, a 1:1boat like this would cruise somewhere around 15-20 knots.
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peterd
💬 Re: Aerokits Sea Commander. Strange Handling ?
21 days ago by 🇺🇸 Chum444 ( Captain)
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Is your prop right or left handed?
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RodC
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💬 Re: Aerokits Sea Commander. Strange Handling ?
21 days ago by 🇺🇸 Chum444 ( Captain)
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Beginning to seem to me that the boat is not intended for running at high speeds. If indeed that is the situation nothing will really solve the issue except running within the envelope intended for the hull’s geometry.
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Madwelshman
RodC
💬 Re: Aerokits Sea Commander. Strange Handling ?
23 days ago by 🇺🇸 Chum444 ( Captain)
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Re latest post by Chris F. When you slow down in a real boat the bow is pushed downward by the remnants of the boat’s wake. Happens when the wake, which is now faster than the hull’s speed, catches up to the stern. The flatter the hull’s deadrise is in the stern the more the bow will be forced downward. Analogous to slow running in a following sea.
Same thing happens with model boats.
Same thing happens with model boats.
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Madwelshman
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Colin H
💬 Re: Aerokits Sea Commander. Strange Handling ?
23 days ago by 🇺🇸 Chum444 ( Captain)
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From your post after the prop shipping cost post it’s beginning to sound like there might be a problem with the hull design. Hopefully not.
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Madwelshman
hermank
💬 Re: Aerokits Sea Commander. Strange Handling ?
24 days ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 101 Views · 2 Likes
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You might find this article & it’s reference to other similar articles useful.
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hermank
zooma
📝 Some progress
28 days ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 24 Views · 4 Likes
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Well, it’s been tack glue, marking fit pieces to fit, remove, cut, re-tack glue to check fit, & repeat! For next scratch build I need to improve cutting accuracy for bulkheads, gunnel support, etc. Same for applying epoxy sealer in hull interior. Kind of slopped epoxy blobs onto gluing surfaces. *#*”#!
Photos
Sprayed cockpit sides with ammonia based
window cleaner, clamped to gunnel, & left to sit
overnight. Will reduce tensile stress on joints
when finally glued in place.
Motor box fabricated. Servo will be hidden by
removable aft seat.
Owner is anxious for a boat ride but yard
schedule indicates that is in the distance.
Photos
Sprayed cockpit sides with ammonia based
window cleaner, clamped to gunnel, & left to sit
overnight. Will reduce tensile stress on joints
when finally glued in place.
Motor box fabricated. Servo will be hidden by
removable aft seat.
Owner is anxious for a boat ride but yard
schedule indicates that is in the distance.
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EdW
LeeA
thadlietz
hermank
📝 Falkirk Wheel
1 month ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 20 Views · 2 Likes
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Very informative. Thanks to all who provided information & videos.
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Steves-s
hermank
📝 Falkirk Wheel
1 month ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 43 Views · 2 Likes
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What is the Falkirk Wheel?
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RodC
📝 Historic ships on the Baltic coast.
1 month ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 30 Views · 2 Likes
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Thank you for posting these photos Wolle. Provides an encyclopedia of details for anyone building or contemplating building a similar vessel.
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hermank
Wolle
📝 Windscreen
1 month ago by 🇺🇸 Chum444 ( Captain)
Captain)✧ 34 Views · 8 Likes · 2 Comments
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Finally can see the light at the end of the tunnel! So far, excluding the windows, the windscreen required 34 pieces to construct. Maybe one more sanding with 500 grit paper & one more coat of gloss clear. Then the windows & figuring out how to attach the screen to the hull in a way that is removable with the trunk cabin.
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