FS17 Transom and Water line?

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silentneko
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FS17 Transom and Water line?

Post by silentneko »

Looking over the plans I have a few more questions, and I'm sure these won't be the last, lol.

Transom - looking at the plans and nestings it looks like the transom is only one sheet of 3/8" and the clamping board is an additional 3 layers of 3/8", is this right? If it is, even though I know it would be structurally fine, I'm not super comfortable with that. Any issues with doubling the full transom width to 3/4" and then a 2 Layer clamping board?

Transom - Second do I have to curve the transom top? Or can I cut it flush with a rear casting deck that will be gunnel height?

Stringers/Floor/Bail height - This might be an overly complicated question but bare with me. Before deciding to build again I was looking to buy, and quickly saw a pattern with some older hulls. I was looking at Aquasports, Key wests, Largos, Makos...... and they all had complaints of standing water and wet feet on the self bailing decks. The main issue was the weight of the 4-stroke motors that weren't around when these boats were put into production. That being said I may power this boat with a 50-60hp 4-stroke and want to make sure it will very much still be self bailing even when loaded down with my family and gear.

So the stringers are cut at 6 3/8" and add another 3/8" for the floor, I also assume you would gain height from the deadrise too. So figure floor height is about 7.5" ? Draft at the DWL is 7" at a Displacement of 1465lbs. So does that mean that the hull, motor, people......must add up to a max of 1465lbs to draft under 7" ? Or is the figure of 330lbs/per inch multiplied by 7" to get a swamping load of 2310lbs?

If not is raising the stringer height an inch an option? I know it will change the floor size and all. I also may want to put in an under deck fuel tank and might need the height for that too. I'm not asking to load the boat to an unsafe level, I'm just wondering about the math to keep us dry.

Thanks.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe, and an FS17.

TomW1
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Re: FS17 Transom and Water line?

Post by TomW1 »

silentneko wrote:Looking over the plans I have a few more questions, and I'm sure these won't be the last, lol.

Transom - looking at the plans and nestings it looks like the transom is only one sheet of 3/8" and the clamping board is an additional 3 layers of 3/8", is this right? If it is, even though I know it would be structurally fine, I'm not super comfortable with that. Any issues with doubling the full transom width to 3/4" and then a 2 Layer clamping board?

- No but you will probably need an extra sheet of plywood. Jacques nesting plans and design are very tight. On the other hand you can use the extra for part of your center console which will require extra plywood also. Your also adding extra weight to the back of the boat and there have been plenty of these boats built as is.

Transom - Second do I have to curve the transom top? Or can I cut it flush with a rear casting deck that will be gunnel height?

- You will need to keep a center portion 20" above the keel so as to have the right amount for the motor to mount properly.

Stringers/Floor/Bail height - This might be an overly complicated question but bare with me. Before deciding to build again I was looking to buy, and quickly saw a pattern with some older hulls. I was looking at Aquasports, Key wests, Largos, Makos...... and they all had complaints of standing water and wet feet on the self bailing decks. The main issue was the weight of the 4-stroke motors that weren't around when these boats were put into production. That being said I may power this boat with a 50-60hp 4-stroke and want to make sure it will very much still be self bailing even when loaded down with my family and gear.

So the stringers are cut at 6 3/8" and add another 3/8" for the floor, I also assume you would gain height from the deadrise too. So figure floor height is about 7.5" ? Draft at the DWL is 7" at a Displacement of 1465lbs. So does that mean that the hull, motor, people......must add up to a max of 1465lbs to draft under 7" ? Or is the figure of 330lbs/per inch multiplied by 7" to get a swamping load of 2310lbs?

- Displacement at DWL is 1465 the PPI is 330lbs, so apply the PPI the Displacement and you get a new Displacement of 1795lbs and increase draft to 8". PPi only applies at the DWL, it is 0 at the keel and increases with distance above the keel. A swamping load is a long way from 2310lbs, you'll just increase draft by a 3-4 inches.

If not is raising the stringer height an inch an option? I know it will change the floor size and all. I also may want to put in an under deck fuel tank and might need the height for that too. I'm not asking to load the boat to an unsafe level, I'm just wondering about the math to keep us dry.

- Yes people have raised the stringers and other parts. Just remember you are also raising the vertical center of buoyancy so she may be a little tippier. The FS17 is a small 17' boat compared to the C17 or the OB17.

Thanks.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: FS17 Transom and Water line?

Post by jacquesmm »

I"ll look at that tomorrow . . . but:
is this right? If it is, even though I know it would be structurally fine, I'm not super comfortable with that.
You can always add stuff, make it heavier.
As designed, it can take the specified HP and more.
Sole level:
you can raise it, this will raise the CG and make the boat less stable and less safe but you can raise it. I find the cockpit depth of some production boats dangerous but you can modify my design.

It's a small boat, you have to compromise.
If you want more capacity with a self bailing sole, you may need a bigger boat.
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Re: FS17 Transom and Water line?

Post by silentneko »

Jacques, I get the feeling you think I'm challenging your design, I'm not, I'm just asking questions. I'm sure it could take the HP, that's only part of my concern. I'd rather have more thickness below for the drain plug and I can't really screw any accessories into a 3/8" board, even 3/4" I'll need to be cautious. As far as weight goes, I'll just be extending one clamping board, it might add 4lbs or so, well worth it IMO.

With all due respect I think you read my question on capacity wrong, I'm not asking to raise the capacity, I'm asking if the capacity as designed is in line with modern heavier outboards? Or basically will the scuppers be under water at rest?

Tom thanks for the explanations, I'm ok with buying the extra ply, I think I've already figured where I can take it from on the nesting plans. So as long as the center cut out on the transom is in line with the 20" needed for the shaft I can shape the top as needed. When I said swamping, I was really referring to water flushing in the scuppers, not a total swamp. I hope I don't have to raise the sole as it would add more to the work and materials, I'll be exploring different fuel tank sizes and shapes to see what I can do.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe, and an FS17.

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Re: FS17 Transom and Water line?

Post by Cracker Larry »

I'd rather have more thickness below for the drain plug and I can't really screw any accessories into a 3/8" board, even 3/4"
No you can't. but where the drain plug goes you can glue in another small piece or 2 of plywood, maybe 2" square and an inch thick. If you use a standard brass flared in drain tube it takes at least an inch of thickness for the flaring tool to work. I prefer more. Same with any fittings. Back them up where you need to.
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Re: FS17 Transom and Water line?

Post by Browndog »

Good suggestion Larry!

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Re: FS17 Transom and Water line?

Post by jacquesmm »

For the transom, many builders make it the same thickness than the clamping board, The FS17 is designed to be relatively light and economical, what I show saves us a sheet or two of plywood. For the drain, you can build up thickness with scrap plywood but you can also build a full, thick transom.

The FS17 is small is a small boat for it's length because it has a small waterplane area. It makes the boat seaworthy but the FS17 has less capacity than for example, the OB17 or C17.

Sorry for the tone of my post, I did not mean to be aggressive.
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Re: FS17 Transom and Water line?

Post by silentneko »

Thanks Larry, I've actually been making my own drain tubes for the last few projects and it has worked out great. I take a deepwell socket or dowel rod closest to the size of the drain plug, then wrap it in a few layers of wax paper, and glass it with 3 or more layers of 6oz cloth. I then cut a hole and glass it in to the transom. Sand it flush and it is darn near fool proof and will never leak around it. But I need at least 1/2-3/4" for it to work best I think, so I'll build up that area.

Image

Image

Image


Jacques, I think adding a board of scrap to the bottom might be the ticket. I agree with you that a transom as thick as the clamping board would be heavy and overkill for this skiff.

I would rather sacrifice a little capacity for the extra seaworthyness. I know it is a smaller 17ft, but it's bigger then what I have now and I know will suit my needs well, I'm just concerned because the motor is more then twice the weight of my current one, plus I'll probably have a jackplate on top of it. I'll naturally balance the load as much as possible, so we will see how it works out.

No need to apologize, I just chocked it up to your accent getting things mixed in type, lol. Obviously I like your designs, I hope to start once the weather cools a bit.
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe, and an FS17.

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Re: FS17 Transom and Water line?

Post by remedy32 »

I stayed away from this until the dust settled a little. Here's a bit of real world FS17 info which I hope helps.

Took this side profile picture the other day. The boat is floating free in about 6-8" of water. The Yamaha 40 weighs about 150#. The battery is located 6" in front of the transom in a compartment to starboard and weighs about 50#. The fuel tank is full with about 8 gallons of gas and located under the console/seat area.
Image
The boat is floating just a bit stern down and the cockpit drains are about 2-1/2" above the water. The black graphite epoxy is a good reference at about 2" below the sole where it crosses the transom. Here's a close up.
Image

The battery could easily be moved under the console to compensate for a heavier engine. My transom is 4 layers of meranti to the top but a single layer in the bilge. I added a small area of extra glass at the low point and a 1" molded glass drain tube to drain any water collected in the center bays of the bilge which I did not fill with foam. BTW the outer bays are filled making the boat virtually unsinkable.

My splash well is removable but I am not recommending this as JM doesn't like the idea and I do see his point. We do get some water in through the scuppers when backing or when two fishermen decide to stand together in the back of the bus. Out solution has been to simply tape over the cheap poor sealing plastic scupper temporarily. Built to plan with a permanent splash well and tubes as other have suggested I would expect very little water and the tubes can easily be plugged from inside if you want.

My suggestions.......build the transom to plan or add that one extra layer above the clamping board. Keep it light especially if using meranti and a bigger motor. This is the second heaviest part in the build (sole is heavier) BTW. Watch the engine weight. The boat goes well with 40hp. If a 50 weighed the same...sure why not. But there's no need for 60 or more IMO. Unless the water is really flat you'll want to slow down a bit in chop. Evaluate the load you expect the boat to carry. We regularly leave the dock at about 1400# gross with 4 aboard who weigh around 650 total plus fuel and gear. At this weight the boat still will do about 30mph in flat water. AS JM said this is a small waterplane for a 17' hull. It's a trade off I was happy with but for others a bigger boat might make more sense. 6 years in and I'm still very happy with what I built though the FS19 plan is on the workbench. :lol:

OK, hope I've helped a bit. Good luck with the build.

Bill
CT

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Re: FS17 Transom and Water line?

Post by Jeff »

Bill, really nice looking boat and thank you for the details!! Jeff

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