q about the design of a cat

[gavsgonefishing]

I will be adding pods onto the markham whaler in the near future to bring the back up around 150mm as the f50's are sitting a little low in the water.

I will be adding a new transom as well,which will include the various features that will make the whole rig a little more easier to fish on. The engine well will be removed and the transom raised to the hieght of the sides of the boat.

I noticed a couple of stress fractures between the pontoons ( not sure of its proper name) at the back, so I will have to rip up some of the floor again to address the problem.

The question is this model markham has a keel ( see photo) To my knowledge I have not seen this addition to any other cat including the markhams (This is an early 80's model). I can't see any benefit from it, and infact would slow the boat down. I am thinking about cutting it out. Can you think of any cons to this

[NQCairns]

Whats the bet the designers added the centre after testing the hull and finding out that the boat was a real dog at anything under 25 knots and just plain bad above that, these boats need lift and i would guess that is its reason, the lift would be both hydrolic and pneumatic ....or it could have simply been a way of strengthening the hull and adding underfloor space as much as the above. look forward to hearing what those who know these boats well have to say about your idea.nq

edit: Just noticed your boat has fins! you may want to consider adding to the centre to get rid of them instead of cutting it out. just a thought

[DR]

could it be they were experimenting with a single motor, like the Websters, & it is to break the water?

[Kerry]

back up around 150mm as the f50's are sitting a little low in the water.

In doing that how will that affect the relationship of the vent plate to the bottom of the hull. Really if the motors are now positioned with the vent (cav) plate level (or near enough) with the boottom of the hulls then how can you really lift them any higher?

Stress fractures

What's the rec HP and weight for that model.

The question is this model markham has a keel

I thought this was one of the selling points of these small cats in that they were able to befitted with a single engine, hence the bit in the centre. There's a few designed like this for that reason.

As for removing it? you would want to make sure it's not part of the overall strength in the tunnel. Somehow I don't see that you really want to remove that.

As for adding pods, all that might do is push the engine weight further to the rear and with the weight of 4S's could do all sorts of things.

I'd be talking with the guy that designed/built the thing before a major change like this one.

Cheers, Kerry.

[Smithy]

Gav,

try and sell it for good money and buy "Little Stooge"! Heard Jase is down to about high 20s without his big sounder and plotter.

[aido]

cats with outboards usually seem to have a problem
with motor height. maybe extra long drive legs are the
go. plenty of them also have remote air intakes, like
they are going to be sucking water and spray.

looking at your centre keel, a centre mounted outboard
would've solved all the problems of keeping the powerhead
high and dry. but i guess that would eliminate the main
reason for having a cat, engine redundancy.

btw, is your l/h engine loosing ptt oil?

[zoley]

Gav,
You need to talk to Mark Hookham on 65 823922 or
mob. 0408655627 before you alter your hull.
He will answer your queries on that hull, he built it. :)

cheers.

[gavsgonefishing]

Thanks for the replies,

I will be talking to Mark Hookham in the near future. Before I did I wanted more objective points of view, which I got.

When I first started this project I rang Markham Marine about the max size of motors I could put on the back ( as there was no plate on the boat), the reply being 2 x 50's ( I can't remember if I was in the 4 st phase at that stage). The whole idea was to built a small boat to be used for the game fishing. This included big fuel tanks, all the other stuff and sometimes crappy seas. The boat has proved itself, but now I am finding some problems which I hope to fix. The common sense part of me (the part that is never used) says it was never designed for what I am trying to do anyway.

When i first pulled the floor out, the hull was full of saturated foam fill. Apart from one bulkhead up high in the sponsons (spelling?) there was not any other structure under the floor. Even the original tanks where cradled in the foam. I thought this a little strange and have glassed in hardwood bearers etc to hold the hull together and giving the flooring some support, but the middle hull is still flexing. I was thinking of extending two of the bearers to the hull making 2 more bulkheads, hopefully slowing the flexing down a little. As you would of guessed I have already broken number one rule, don't over capitalise, but I figure its the boat I will keep for a while anyway.

Since I put these motors on I have had to extend the transom up, get rid of the flow through deck holes and push the tanks forward. I have had 2 people at different times with reputable backgrounds in the marine industry tell me I should put pods on to lift the motors out of the water (the intake is just above the waterline). I was told for every 100mm you go back the motors will be mounted 25mm higher ( or there abouts). Kerry, I don't want to go through this if what you say is correct. Have you heard of the this?

The motors are still a little low, but cannot be lifted without a new transom anyway.

Zoley, why do you ask? Both motors are new and do not leak any oil whatsoever.

Thanks for the ideas on the centre keel, its starting to make sense now, I will talk to Mark re the mods on that.

Smithy, little stooge's sister boat is also up for sale, but the name escapes me, he was also in the SCGFC up until last year, asking the same sort of money

[NQCairns]

To lift the motors up as much as 4 inches using the same transome holes you could try a couple of manual jack plates. Do a search on www.cabelas.com

[Sportfish_5]

How about one of these style brackets ? Should have something for a small cat

http://www.armstrongnautical.com/index.htm

[Kerry]

I was told for every 100mm you go back the motors will be mounted 25mm higher

The "rule of thumb" with pods is 1" per foot (25mm per 300mm) so you could pick up a couple of inches but certainly not what your looking for.

So those would be long (20") shaft motors? and about the only way to get the power heads higher on cats is to go longer in the shaft.

Cheers, Kerry.

[snappa]

Hi gav

I have a cat also and few years back I refitted my cat out with new floors transoms bearer’s bulkheads.
I used a 20 m floor because my cat was flexing due to the rotten timber.

I have put up some pics feel free to ring me about the cat.

My ideals on the keel are and I could be wrong and mostly likely is ???/
One a wave breaker to sop the slamming of the waves under
Two to break or change the water flow out the back so as to eliminate the mist being sucked into the cabin.
Three to give more buoyancy to the back at rest and when 3 fishos standing down the back.

I went through the pods on the back but went away from that ideal because of the way I fish deep tempest with the back into the waves. The motors dip into the water MORE
I had the same problem with my first motors being mounted too low and dipping onto the water so I opted at first to make aluminum brackets bolted onto the low transom and bought new LONG shaft motors.
Brackets finally cracked and then had the transoms fibre-glassed and raised.
I have snorkeled my motors from day one because of the spray at the back of boat.
The cal. Plate of motor has to be level to the bottom of hull or forget about any kind of performance out of the cat..

[snappa]

another pic ... bearers [stringers] go from one side to the other and floor sits on top of that ??

[snappa]

finished job .. cal. plates level with bottom of hull..

[zoley]

Gav,
It was Aido who mentioned the oil. He was prolly talking
about the marks on transom under port motor.

cheers.

[gavsgonefishing]

I'm going to have to have a good think about this. Kerry, I have been told that the Longshafts would be the go before. Might look into the price of a conversion ( that should be scarey)

Snappa good pics, The frame is basically the same except I have a lenght of hardwood running down the sides as well. The forward stringers are not glassed to the centre of the cat because of the floor height required. Its still looks like I require a little more rigidity so the bulkheads may be the go.

As for the raised transom, pods vs no pods, I'll speak to Mark Hookham and have a chat to Mr Kevlacat (Andrew) on Monday.

I love it when I resign myself to an ugly job, then after getting different points of few I'm back to square one. Will undate after monday.

[yockman]

Hiya Gav,
I once looked at a Markham nad was going to buy it till someone said they'd seen it a couple of years earlier at the local fibreglass repair shop. Rang Peter, the guy from th eglass shop and seem to remember him saying something about that being a wave breaker, added to later models coz earlier ones were splitting in the tunnel from the force of water slamming into it all day. strongly recommend you do not cut it out till you've spoken to Hookham.
Great boats.
Yockman

[Kerry]

Gav, looking at your orig pic if those are 20" motors (long shaft) then it would appear the transom isn't really made to handle UL (25") motors , which is probably what you are referring to as "Longshafts" ??

Somehow the hull simpy doesn't appear deep enough to handle 25" motors.

If those engines are wallowing then is that simply too much weight ??

Cheers, Kerry.

[gavsgonefishing]

Kerry I was afraid of that, should not of trusted the guy who sold/ fitted them. Then again I should of done a little more homework.

Waiting for Mark Hookham to call back, he may have a little more info on the boat.

I dont think I will be touching the keel, it sounds I have enough dramas without looking for more.

The other option is to look around a slightly bigger cat hull and transfer all the options across ???

[Smithy]

Stooge is looking better all the time ;D.

[gavsgonefishing]

The news so far has been pretty cruel. Basically the boat or any boat of that age is not designed for four strokes ( or the extra weight) the two F50s come in at 220kg plus the adaptors which would weigh approx 8kg for both.

The 2 x two stroke 50's and 40's come in at 176kg, no adaptor required.

The hull design cannot support this extra weight. The pod option does not seem to be the go as it shifts the problem further back, I think snappa had some experience in this.

The draw back with swapping back to the 2 st 50 or 40 is the economy, at WOT 7 ltr/ hr difference. Ok I rarely am going flat chat but I do spend a lot of time trolling ( Which is where the 4st come into their own.) I worked out conservatively there would be 5 ltr/ hr difference, say 8 hrs running time (very conservative), thats 40 ltrs per tank (80ltr /trip). Now thats going to hurt :'

Looking at other options, see how we go...

[ANYFISH]

have you seen the new e-tech results.
i saw them in queensland fishing monthly a few months back, and they seem really good. almost better than the four's....

if you look back there are a few blokes looking at them on here somewhere.

cheers