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Old 21 October 2013, 20:38   #161
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Thanks SIBRider. It may be that the large drain hole was drilled high, but I am certain that the floor is properly assembled in that picture; the rear floorboard is fitting "tongue in groove" with the ledge on the transom.

Hey, before you modified your transom to raise your motor, and your A/V plate was 2-3 inches below the bottom of the transom (as mine was before modifying the transom too), did you have severe bow steer at any trim angle, or just reduced performance and maybe some excess splashing?
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Old 22 October 2013, 02:23   #162
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I meant that tongue-and-grove ledge is possibly mounted too low. I'd suspect it's fitted later in process after boat been glued together. Hole is most likely drilled in a jig or with CNC at the same time when transom is shaped.

I only run about for about a week before building riser. Performance was abysmal. Lots of splashes. I didn't do much WOT testing since motor was new. Mostly run with my entire family on board. I remember once taking it up to WOT briefly with just me. It was wild ride. She got to 20-21 mph then she wanted to go each and every way barely controllable.
Reason why I got into this thread was I felt that your problems described at page 3-4 seemed similar.
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Old 22 October 2013, 02:25   #163
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Once on a plane boat rides pretty flat though even now.
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Old 22 October 2013, 13:40   #164
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Hi again Projectile

First...Im no expert on boat designs so take my words with a pinch of salt.

I do know my own inflatable boat pretty well though, so posted this to give some food for though with a view to try and help by comparisons, as there is obviously something wrong with your boat.. although I have no idea what ?

Earlier, some folks were suggesting pressure in the tubes and keel could be the problem. Im certainly not suggesting that is not the problem, but I know with my own inflatable ..it wouldn't be.

The reason I say that is... I like to keep a flabby SIB when its on land and even put it in the water that way.. as seen from this photo.




Then, when the boat is assembled with engine.. I clamber on board and pump it up with the hand pump. It is at the right pressure for me when I hit the tube with a clenched fist and it bounces off. I wouldn’t know a PSI from a metal bar ..so pressure in mine will vary depending in how hard I want to punch it on the day. Yet I still get a beautiful smooth wake with little turbulence from the prop part and with most turbulence streaming off the ends of the tubes as in this photo..no pressure gauge used...ever.



I also think that my wooden floor is designed to bend and flex at the section joints up at the bow end. I can tell this by the way the pieces slot together..one side is almost D shaped so it flexes or hinges in the slot on the other floor piece..if that makes sense. The whole bottom of my boat is also banana shaped..in a similar manner to your description of a hooked boat. Im pretty sure the bottom of my boat changes shape constantly as waves push and pull at the whole flexible bottom as I change speed or angle of attack to waves etc. But I dont have your problems.

I have a fish finder on my boat and keep my transducer on a DIY "slot" so I can slide the transducer up and down or even remove it to put it onto another boat. Im mentioning this..because when Im on the plane..if I slide that transducer even as little as 1/4 - 1/2 an inch too low ..I get a lovely rooser tail wake coming up from it.. it can easily reach the height of the transom. See photo of transducer and its sliding mount on my transom



Looking back at this photo you posted of the rear of your boat.. does that transom step not look very low compared to the rest of the bottom of your boat ? Almost as if it had slipped slightly when it was all glued together ? Could it act like the transducer on my boat when its a bit too low and throw up a rooster tail ..or if engine trimmed to combat it.. force the bow down and cause stearing problems ? I know my boat..although it is banana shaped underneath .. it does not have a pronounced step as shown in this photo of your boat.



Perhaps you could send that photo to the supplier you are dealing with..and ask them to send you a photo of another similar boats transom step ..to see if it is a problem on yours ? hey ... perhaps someone else who has the same boat as you and is reading this..could post a photo of their transom step..to eliminate my thoughts..


As mentioned at the start of this post..Im certainly no expert.. so take this posting as you will.. I do hope you get the problem resolved.
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Old 22 October 2013, 17:33   #165
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Gurnard,

The bow as shown on first picture, looks way under inflated, if you have invested so much money on that nice sib, do your Quicksilver a big favor, buy a pressure gauge. Using your fist to test your tube's pressure doesn't work as you expect. You will always be under inflated with fist check, worst when sib is floating on water after some time rest.-

If continue inflating and using that way expect transom ungluing issues shorty, worst scenario if boating heavily loaded and with max 4 strokes HP engine on choppy seas, jumping waves.-

Happy Boating
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Old 23 October 2013, 03:25   #166
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Many thanks for your concerns over a soft SIB Lucozodiac. As mentioned Im no expert and can only refer about my experiences with my inflatable boats.

I posted to show that my Quicksilver does not have bow steering problems, cavitation or water over the transom issues, even though.. as you appear to agree.. I probably run it under inflated. I think the Quicksilver has a similar type of bottom as the MK4 Zodiac ? so wondered if comparisons would help Projectile. I suspect he would be over the moon if his boat ran correctly..over or under pressurized.. then he could work that issue out.

While I appreciate that from a purist’s point of view .. trying to get maximum performance out of their SIB.. a pressure gauge is a must.. I do think there are lots of horror stories going around that if you don’t use one.. you will have bow steering issues, cavitation issues or worse still .. your transom will fall off. That is only my opinion though

The Quicksilver I now own and shown in the photos is a 2005 boat. It belonged to a friend before I swapped a hard shell boat for it. I admit that I have only had it since the summer and done around 500 miles...but my friend used it for diving for the rest of its life. I can assure you that a pressure gauge as been no where near it as the thump test suited him too. For an 8 year old boat with regular use.. I think it’s transom is as sound as the day she was made :-D

Perhaps it will fail a year or so before it would if a pressure gauge was used ..but I suspect that could be around the same time as the rest of the boat fails ? 10-15 years from a PVC boat is great value anyhoo..some fibre glass boats die of osmosis long before that L

I do respect your experience with boats Lucozodiac .. so what is your thoughts on the shape of Projectiles transom as shown in his photograph ? Do you see many like that and do they work as advertised ?
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Old 23 October 2013, 09:06   #167
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I agree with Loco's comments re. pressure gauge. Underinflation will ruin your boat and give you poor performance.
That pic of the hull and the wood makes me wonder if the inflatable keel was properly installed. It looks like it may have been folded over onto itself and not extending fully rearward to the transom.
Or it may be improperly installed in the hull by Avon, placed too far forward.
That wrinkly area of the hull should be taught and stretched downward and outward by the inflatable keel on the inside of the hull and under the floor.
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Old 23 October 2013, 12:34   #168
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Quote:
Originally Posted by Northern Pike View Post

That wrinkly area of the hull should be taught and stretched downward and outward by the inflatable keel on the inside of the hull and under the floor.
Yup.. that ties in with my thoughts.. is there something not quite right in that area just before the transom. ?
I have taken a liberty and adjusted the contrast in Projectile,s photo so the area is clearer to see ..to me ... it looks quite wrinkly there and I know my transducer throws up a lot of water if its a tad too low and disrupts the main water flow below the boat.


For a comparison.. here is a better photo of the rear, underneath area of my Quicksilver. I should mention that it is in winter storage now and the inflatable keel has very little air in it. I have the top covers tied down so don’t want to disturb it all to blow the keel up.. but even with little air..its still very smooth at the rear end of my boat.


I don’t know what all this proves.. but I do wonder if that wrinkly area is the cause..
I think Projectile will have made sure it is assembled properly.. so perhaps the transom was set and glued in the wrong position during construction..if that could be possible ?

Anyhoo..there is little more that I can add to this thread.. its just thoughts.. so take my thoughts or leave them as you choose
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Old 23 October 2013, 23:13   #169
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The Gurnard,

Thanks for your concern and your comments.

Underinflation is like religion. You can always believe in it while you can never prove it.

I've indicated in this thread that I did use a gauge and got proper pressure even after letting the boat sit in the water for 15 minutes, and still there are skeptics here! Maybe my gauge doesn't work, they offer!

Underinflation is unscientific: it seems that you can never falsify the hypothesis that underinflation is the problem.

Well, I don't buy any into religions, and I don't buy that underinflation is the problem with my boat either.

Thanks again for your input.
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Old 24 October 2013, 11:30   #170
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I'm certainly guilty of not re-inflating boat to spec pressure after temperature drop after sunset on occasion. My keel has a leak as well and gets soft after few hours. Returning home on somewhat flabby boat worst problems I've experienced was loosing 1-2 mph at the top. I'm sure floor shape at the time was far from perfect. No other ill effects such as bow steer or whatever.

Another data point though. Last weekend I took my boat out specifically to see how it will perform with my stock low pitch prop. I swapped for 13" prop and raised motor at the same time. Since all this discussion I decided to experiment. Mostly it was as expected: Easy to over-rev. Couldn't move past 2/3 of throttle once on plane. Good grip on 3rd hole. Bow steer at #2. #4 was biggest difference though. Intolerable cavitation/ventilation on anything but smooth straight line. Cresting even small wave it would loose grip over-rev instantly. Very different from 13" that I normally run. With later on 4th hole It feels at worst a bit loose but not much else. No over-revving, no major cavitation.
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