Performance difference slick bottom to poly

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
CypressHunter
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Performance difference slick bottom to poly

Postby CypressHunter » Sat May 06, 2017 10:06 am

I have tried to do a search but haven't really found the answers I am looking for.

I have only ever run slick bottom on my 13'6" cottonmouth. My hull is in need of some work but I have a serve lack of time to do it. ( baby at home ) I found a used 13'6" cottonmouth that has poly. Trying to weigh the pros and cons before pulling the trigger.

1) I know poly is stronger and holds up longer that slick bottom but how does it ride? My current hull is free in the water and does not porpoise a bit.

2) I don't beat on my boat or run a lot of dry ifni can avoid ( mainly because I want to prolong the life of my steelflex ) but when I do run dry it does pretty damn good. Will poly be as slick or will it be slicker?
13' 6'' Cotton Mouth 220 GPU 70'' signature series

CarMotorBarge
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Re: Performance difference slick bottom to poly

Postby CarMotorBarge » Sun May 07, 2017 6:48 am

The real advantage to poly is that it last a lot longer and provides much better protection to the bottom of the boat. Otherwise slick bottom is superior in every way. Slick bottom rides better and does better in the sticky green grass. Poly weighs about 150 lbs more when you consider the poly and the rivets/bolts to hold it on. Anybody serious about racing is using slick bottom. Also where do you normally ride? Slick bottom does good in certain areas such as Kissimmee and the glades.
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CypressHunter
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Re: Performance difference slick bottom to poly

Postby CypressHunter » Sun May 07, 2017 8:33 am

St. John's in Brevard County and Area 2A ( my old stomping grounds before moving to Melbourne)

I first got my boat when I was living in Broward and it had slick bottom and that's all I needed. Before moving up here I did frog spit which wore off pretty quick. Quick slick wore off even quicker. I went back to steelflex 2000 and that seems to be holding up the best but granted I don't get to ride nearly as much as I use to.
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terrible ted
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Re: Performance difference slick bottom to poly

Postby terrible ted » Sun May 07, 2017 9:15 am

For the St john from 192 to Monroe there a lot of roots and other crap. Scared up allot of poly riding here and hit some old dock stumps in the middle off when the f was there ever a dock here.

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Deano
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Re: Performance difference slick bottom to poly

Postby Deano » Sun May 07, 2017 9:48 am

I fundamentally agree with everything that's already been said. However, I will add a couple of clarifiers to help expand on a couple of points that are also relevant to the question(s) you propose and the situation you find yourself in.

First, and probably most important, is that you realize (and weigh) the fact that the installation of poly is NOT the main consideration of whether or not a boat porpoises. The inherent 'straightness and rigidity' of the stringers is the major concern here. A straight bottom will not porpoise, either with, or without poly installed. Conversely, a hooked or non-straight bottom will porpoise whether it has, or does not have poly installed.

The reason I point this out, is that you need to make darn sure that the bottom on the replacement hull is straight before you even consider that as an option. It could very well be less work in the end to redo the one you have than to start over with a hooked hull that porpoises (whether it has poly or not). :idea: I would not want to talk you into poly, and then have you acquire a hooked hull that porpoises and mistakenly think it was because of the poly. It would be because the bottom is not straight. Running a string line on the bottom before you buy it, may be the wisest thing you do during the week when that happens.

With that having been said, I, personally am partial to running polymer due to how and where I run. Around here in the water, there are rocks, stumps, pilings and things that go bump on the bottom. Out of the water there is more than plenty of sand. It kind of makes for an easy decision. Given that I'm not a racer anymore and the minimal performance difference, about the only time I wouldn't run poly would be if the weight factor severely hampered the ability to run dry.

Carmotorbarge is spot on when he says polymer lasts longer and affords better protection. There is also no disputing that polymer is not the preferred option where sticky green grass is concerned. This is, to me, the single biggest reason there would be to abandon the poly. There isn't that much around here for it to be an issue, in my case.

The one area where our views are different, is where the weight of the poly is concerned. While what was said may not be incorrect, I will point out that ~150 lbs. guesstimation only applies when you are running dry (and is also contingent on the thickness used). Polymer in and of itself is not that far from being neutrally buoyant, so when you are in the water the weight hit you're taking is little more than the bolts/fasteners, it is not like adding another person to the load. I've posted numbers here pertaining to this, but don't recall right now what they were. They are here though, if you want to search for them.

Lastly, I will add that if your signature is current, swapping to a medium hub and gaining 2" in diameter would offset any performance loss you would encounter by running the poly. My dd Caddy boat is two feet longer than your Cottonmouth and runs dry surprising well with 3/8" polymer and 72" Signature blades.
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terrible ted
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Re: Performance difference slick bottom to poly

Postby terrible ted » Sun May 07, 2017 10:09 am

I put on 1/4 inch poly on my Cottonmouth thick enough to do what it needs in my opinion.

CypressHunter
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Re: Performance difference slick bottom to poly

Postby CypressHunter » Sun May 07, 2017 10:15 am

Yeah I want a go to a 72" prop as well but have tight clearance in my prop well. Plenty at the top of my cage
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Prototype
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Re: Performance difference slick bottom to poly

Postby Prototype » Fri May 19, 2017 7:34 pm

Depends on how both are attached or applied!
I've seen quite a few rigs done on 4 saw horses with 2x supporting the sides only. A glass hull will sag being done that way. 2 saw horses on the stringers is a pain to work around but provides a non sagged hull to deal with.


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