Inflatable keel vs tubes

[jaymasta]

I am looking at getting a 9-11ft inflatable, I want to mount my 5hp honda engine to it and be able to plane the boat. I know it is possible as I have seen it done and there are a few youtube videos of people planing small inflatables with 5hp motors. Anyways I have found a few boats some with inflatable keels some without. The ones without are significantly cheaper. I am wondering if the inflatable keel helps plane the boat or if it just helps with stability or if an inflatable keel would even make a difference on such a small boat with small power. I have found a really nice zodiac in great shape and with comes with a bunch of extras that I am ready to purchase but it does not have an inflatable keel. Any help here is appreciated.

 

[deejaycee_2000]

Re: Inflatable keel vs tubes

Yes the inflatable keel does help in planing out .... you need a solid /sturdy floor to plane out and keep it stable, the smaller tenders with those perspex spines on the soft floor doesn't work well at all, so ideally you don't need an inflatable keel or one with solid floor, as long as the floor board itself is solid it should be good to go ....

 

[Sea Rider]

Re: Inflatable keel vs tubes

Generally small sibs with inflatable keel has wooden, aluminum or air mat floorboards, the ones without keel, are air mat sibs with flat hulls. Hard floorboars sibs performs much better than air mat sibs, which rocks outrageous if not correctly inflated to their working pressure.

Happy Boating

 

[jrs_diesel]

Re: Inflatable keel vs tubes

I have a Bombard 9 ft SIB, the Max 3+S, with the inflatable keel. It came with an interlocking wooden floor. Got it for $700 on a sale at Defender Marine. I have a 3.5 HP Nissan 2 stroke on it. The boat itself weighs about 85 lbs, the motor is 28 lbs, and I weigh 165, for a total weight of around 278 lbs.

That 3.5 HP Nissan has suprised me in that with just myself onboard, I can get on plane and achieve between 7-9 knots (depends on the tide).

The hard floor is awesome to have. I have been in a SIB that had an air floor, and I much prefer the hard floor, just feels much sturdier.

My winter project this year is rebuilding my 6 HP Johnson 2 stroke. I wonder how fast I will be able to go once I get that one running

 

[likalar]

Re: Inflatable keel vs tubes

The inflatable keel offers another advantage in that the keel helps any boat's tracking performance. A flat bottom boat on plane may have a tendency to "slide" in the turns (not necessarily a problem on flat water, or with the size boat you are setting up). The keel will help keep the boat going where you point it. This is even true with a rowboat. Notice that even most kayaks have a bit of keel molded in to help keep the boat from wiggling left and right too much with each stroke of the paddle.

Larry

 

[nightstalker]

Re: Inflatable keel vs tubes

If you are looking to buy one in the 9' to 11' length, you need the keel. You arn't going to be happy without one. It's not about getting on plane, it's about performance once you are on plane. The one's without a keel are made for putting around at slow speeds. If you want to get up and go, get one with a keel.
Nightstalker

 

[dlindeblad]

Re: Inflatable keel vs tubes

The inflatable keel offers another advantage in that the keel helps any boat's tracking performance. A flat bottom boat on plane may have a tendency to "slide" in the turns (not necessarily a problem on flat water, or with the size boat you are setting up). The keel will help keep the boat going where you point it. This is even true with a rowboat. Notice that even most kayaks have a bit of keel molded in to help keep the boat from wiggling left and right too much with each stroke of the paddle.

Larry

Completely agree w/ tracking. My Bombard C4 has a 50 HP engine and when my inflatable keel is not at the correct pressure it does slide considerably while turning. If I keep it tight she turns very well.

As far as planing easier, well sure. This is why hydrafoils plane and travel faster due to the smaller surface area in contact with the water.

 

[jaymasta]

Re: Inflatable keel vs tubes

Interesting, I think I will hold out and try to find one with a keel then, remember though I am only dealing with 5hp here, I don't expect much.

 

[dlindeblad]

Re: Inflatable keel vs tubes

Interesting, I think I will hold out and try to find one with a keel then, remember though I am only dealing with 5hp here, I don't expect much.

Maybe I should have been a little more specific in my hastily written post. The inflatable keel will help you plane better, but you really don't have to worry much about tracking with a 5hp motor. My 50hp will get really squirrely if the keel is not inflated, that's all I was pointing out. I always prefer a good keel to a slick bottom.

 

[livendive]

Re: Inflatable keel vs tubes

Interesting, I think I will hold out and try to find one with a keel then, remember though I am only dealing with 5hp here, I don't expect much.

I picked up a 9.5' nordik air deck and 5 hp merc a couple weeks ago. It's a silver marine 275AD with a different label on it. It does have an inflatable keel, and it gets me (235 lbs) and a couple gallons of gas up on a plane in short order...less than 4 seconds. My guess is full speed on a plane is somewhere around 18 mph...I'll check tonight with my gps if the weather holds up. Sometimes I have to lean forward for a second to get it to tip over onto the plane, but not normally. Once on a plane though, it's kinda sketchy in hard turns. I'm having to learn moderation on the steering/throttle, as full speed hard turns feel decidedly unstable, as if any second it's gonna dig in and flip. Fun though!

 

[jaymasta]

Re: Inflatable keel vs tubes

I picked up a 9.5' nordik air deck and 5 hp merc a couple weeks ago. It's a silver marine 275AD with a different label on it. It does have an inflatable keel, and it gets me (235 lbs) and a couple gallons of gas up on a plane in short order...less than 4 seconds. My guess is full speed on a plane is somewhere around 18 mph...I'll check tonight with my gps if the weather holds up. Sometimes I have to lean forward for a second to get it to tip over onto the plane, but not normally. Once on a plane though, it's kinda sketchy in hard turns. I'm having to learn moderation on the steering/throttle, as full speed hard turns feel decidedly unstable, as if any second it's gonna dig in and flip. Fun though!

So even with the inflatable keel your are having unstable and "slipping" issues?

 

[livendive]

Re: Inflatable keel vs tubes

So even with the inflatable keel your are having unstable and "slipping" issues?

I took it out Friday night for an hour or so, then for a couple hours and a dozen miles or so on Saturday, and in both cases I found it more stable. I had my dog with me on Friday, which might have helped, but not on Saturday, so I'm going with it being a combination of me getting to know the boat better and my having put a bit more air in each compartment.

Also GPS'd it at 15 mph with a wide open throttle.

 

[Sea Rider]

Re: Inflatable keel vs tubes

If wanting near best performance, you need to inflate all compartments and keel to their working pressure recommended by the manufacturer and not by finger touch, get yourself a pressure gauge, it's the way to go. Air mat must be inflated to a hard working pressure for the deck to rock less, don't make close turns, just wide turns with good throttle.

Happy Boating